AMCA_850-02_(R2011)

The International Authority on Air System ComponentsAIR MOVEMENT AND CONTROL ASSOCIATION INTERNATIONAL, INC. AMCA Publication 850-02 Industrial Process/Power Generation: Heavy Duty Dampers for Isolation and Control (R2011) AMCA PUBLICATION 850-02 (R2011) Industrial Process/Power Generation: Heavy Duty Dampers for Isolation and Control Air Movement and Control Association International, Inc. 30 West University Drive Arlington Heights, IL 60004-1893 © 2011 by Air Movement and Control Association International, Inc. All rights reserved. Reproduction or translation of any part of this work beyond that permitted by Sections 107 and 108 of the United States Copyright Act without the permission of the copyright owner is unlawful. Requests for permission or further information should be addressed to the Chief Staff Executive, Air Movement and Control Association International, Inc. at 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A. Authority AMCA International Publication 850-02 was adopted by the membership of the Air Movement and Control Association International, Inc. on May 16, 2002. It was reaffirmed by the membership of the Air Movement and Control Association International, Inc. on July 28, 2007, and on May 1, 2011. Foreword The Air Movement and Control Association International, Inc. (AMCA) is an international trade association representing manufacturers of industrial and commercial fans, airflow control devices such as backdraft dampers, louvers and dampers, airflow measurement stations, and acoustic attenuation devices. This publication covers dampers such as are used in industrial process systems, and power generation facilities, where flue gas or air is the primary medium. This publication contains base-line information on applications and provides specification guidelines that may be supplemented by designers, specifiers and users to encompass their specific needs. Disclaimer This manual has been prepared by the Air Movement and Control Association International, Inc. (AMCA). The information contained in this manual has been derived from many sources and is believed to be accurate. Please note that the recommendations contained herein do not necessarily represent the only methods or procedures appropriate for the situation discussed, but rather are intended to present consensus opinions and practices of the air movement and control industry which may be helpful, or of interest to those who design, test, install, operate or maintain fan-duct systems. Thus, AMCA disclaims any and all warranties, expressed or implied, regarding the accuracy of the information contained in this manual and further disclaims any liability for the use or misuse of this information. AMCA does not guarantee, certify or assure the performance of any fan-duct system designed, tested, installed, operated or maintained on the basis of the information provided in this manual. Objections to AMCA Standards and Certifications Programs Air Movement and Control Association International, Inc. will consider and decide all written complaints regarding its standards, certification programs, or interpretations thereof. For information on procedures for submitting and handling complaints, write to: Air Movement and Control Association International 30 West University Drive Arlington Heights, IL 60004-1893 U.S.A. or AMCA International, Incorporated c/o Federation of Environmental Trade Associations 2 Waltham Court, Milley Lane, Hare Hatch Reading, Berkshire RG10 9TH United Kingdom RELATED AMCA STANDARDS For Air Performance: ANSI/AMCA Standard 210 Laboratory Method of Testing Fans for Aerodynamic Performance Rating AMCA Standard 803 Industrial Process/Power Generation Fans: Site Performance Test Standard For Sound: AMCA Standard 300 Reverberant Room Method for Sound Testing of Fans AMCA Standard 301 Methods for Calculating Fan Sound Ratings from Laboratory Test Data For Balance and Vibration: ANSI/AMCA Standard 204 Balance Quality and Vibration Levels for Fans Industrial Process / Power Generation Series: AMCA Publication 801 Industrial Process/Power Generation Fans: Specification Guidelines AMCA Publication 802 Industrial Process/Power Generation Fans: Establishing Performance Using Laboratory Models AMCA Standard 803 Industrial Process/Power Generation Fans: Site Performance Test Standard Fan Application Manual: AMCA Publication 200 Air Systems AMCA Publication 201 Fans and Systems AMCA Publication 202 Troubleshooting AMCA Publication 203 Field Performance Measurement of Fan Systems TABLE OF CONTENTS 1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 3. Terms And Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 4. Types Of Dampers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 4.1 Control Damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 4.2 Isolation Damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 5. Damper Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 5.1 Leakage Containment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 5.2 Leakage Path And Leakage Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 5.3 Factors Affecting Actual Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 5.4 Selecting A Damper To Meet Low To Zero Leakage Requirements . . . . . . . . . . . . . . . . . . . . .10 6. Thermal Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 6.1 Normal Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 6.2 Thermal Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 6.3 Leakage Operating Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 6.4 Damper Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 6.5 Thermal Differential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 7. System Gas Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 7.2 System Gas Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 8. Corrosion And Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 9. Control Range (See Figure 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 10. Pressure Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 10.1 Pressure Drop Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 10.2 Pressure Drop Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 10.3 System Effect On Damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 11. Damper Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 11.1 Mechanical/Thermal Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 11.2 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 11.3 Deflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 11.4 Wind Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 11.5 Seismic Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 11.6 Connection To Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 12. Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 12.1 Pneumatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 12.2 Electric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 12.3 Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 12.4 Options And Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 13. Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 13.1 Location Of And Schedule For Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 13.2 Functional Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 13.3 Simulation Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 13.4 Test Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 14. Recommended Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 14.1 Louver Damper Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 14.2 Guillotine Damper Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 15. Sample Specification Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 16. Installation Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 1 Industrial Process/Power Generation: Heavy Duty Dampers for Isolation and Control 1. Purpose The purpose of this publication is to provide basic pertinent information in order to simplify communications between damper manufacturers and designers, specifiers and users of such equipment. 2. Scope The scope of the products covered in this application guide includes dampers that are used to control a flow of gas (be it a specific gas, a mixture of gas and air, or air alone), or to isolate one section of a duct system from another section of that system. The scope narrows to those dampers generally described as "heavy duty" or "severe service", because such dampers are normally used in applications where extreme temperature, erosion and/or corrosion conditions exist. 3. Terms and Definitions This section defines terms that have special meaning or significance in damper applications and within the damper industry. Most are specific to the dampers under discussion in this publication. For the reader’s convenience, terms that are defined in this section are shown in capital letters when used in the definition of a related term. 3.1 Accessory. An accessory is an item purchased by the damper manufacturer and either mounted on the DAMPER at the factory or supplied with the damper for field installation by others. An accessory is generally an item used to enhance or improve the performance of a damper. An accessory may be an ACTUATOR, a SEAL AIR system, a PURGE AIR system, a limit switch, a flow sensor (or system), positioning equipment, or some other item associated with powering, sensing or signaling. 3.2 Actuator. A mechanical accessory item attached to a DAMPER for the purpose of moving the damper BLADES(s) to either the open position, the closed position, or to an intermediate position to achieve low modulation. An actuator may be manually, electrically, pneumatically or hydraulically powered. The output force of an actuator is delivered in either a linear or a rotary direction. 3.3 Actuator torque. The rated torque capability of an actuator. 3.4 Airfoil (blade). A double-skinned damper BLADE, the blade skins meeting at the leading and trailing edges of the blade with no substantial protrusions external to either blade skin. 3.5 Area of restriction. The total cross-sectional area of DAMPER components that are permanently located within the gross FREE AREA provided for gas flow through the DAMPER frame. The restrictive cross-sectional area of each component is determined by its position when the damper is fully open. Generally, in the full open position, a component will present the smallest frontal area to the direction of the gas flow. 3.6 Blade. In strict terms, the moveable component within the DAMPER frame. The purpose of a blade is to restrict a gas flow for modulation (control), or for closure (isolation). 3.7 Blade entry seal. In a GUILLOTINE DAMPER, the sealing arrangement through which the damper BLADE passes. 3.8 Blade support. A structural member inside the frame of a GUILLOTINE DAMPER. The member supports a portion of the BLADE when the damper BLADE is in the closed position. 3.9 Bonnet, open. The portion of a GUILLOTINE DAMPER frame that supports the BLADE when the damper BLADE is in the open position. An OPEN BONNET does not have an enclosed blade. 3.10 Bonnet, fully enclosed (or sealed). The enclosed portion of a GUILLOTINE DAMPER frame that supports the BLADE when the damper blade is in the fully open position. 3.11 Butterfly damper. A LOUVER DAMPER having a round single BLADE. 3.12 Control damper. A DAMPER which has the purpose of modulating or regulating one or more gas flow parameters such as PRESSURE DROP, rate of gas flow, or airflow distribution. AMCA INTERNATIONAL, INC. AMCA 850-02 (R2011) 2 3.13 Chain drive. An arrangement of chain and sprockets for the purpose of bi-directional transmission of torque to the BLADE(s) of a damper. 3.14 Damper. A self-contained device for the control and/or regulation of gas flow from one portion of a duct system to another portion of that system; consisting of a frame and one or more linked moveable BLADE sections. 3.15 Drive. See ACTUATOR; DRIVE SYSTEM. 3.16 Drive lifting force. Of a GUILLOTINE DAMPER; the tensile force required to move the damper BLADE under specified conditions. 3.17 Drive system. The ACTUATOR and all components through which force is transmitted to the damper BLADE(s) for the purpose of positioning the BLADE(s). 3.18 Flow distribution. The pattern of gas flow variation in a duct, usually expressed in terms of gas velocity across a representative cross-section area of the duct. 3.19 Frame. Of a DAMPER, the external portion of the assembly that supports the BLADE(s), the means of attachment to the duct and provides the means of attaching other specified ACCESSORIES. 3.20 Free area. Of a DAMPER, the internal cross- section area of the DAMPER less the INTERNAL RESTRICTION. 3.21 Goggle damper. A DAMPER having a single sliding BLADE in which there is a cut-out area matching the inside dimensions of the duct. The damper is open when the cut-out area is moved to a position in line with the duct, and closed when the solid portion of the BLADE is positioned in line with the duct. The overall construction is similar to that of the GUILLOTINE DAMPER. (Note: The name "goggle" originated with the first application of this type of damper to a round duct.) 3.22 Guillotine damper. A DAMPER, also known as a GATE damper, having a single, solid, sliding BLADE. The DAMPER is closed when the BLADE slides completely into position over the duct cross- section area; it is open when the BLADE slides completely out of the duct area and into the BONNET. 3.23 Guillotine damper, double blade. A GUILLOTINE DAMPER having two parallel blades which operate in tandem, and a separating air space (AIR CHAMBER) which may be pressurized by a SEAL AIR SYSTEM to prevent LEAKAGE of high pressure upstream system gas when the damper is closed. 3.24 Height. A dimensional reference to DAMPER size. In a GUILLOTINE DAMPER, height is the inside duct dimension parallel to the direction of the BLADE movement (draw). In a LOUVER DAMPER, height is the inside duct dimension perpendicular to the axis of the BLADE(s). See Figures 4 and 2, respectively. 3.25 Isolation. The restriction of system gas flow across the DAMPER. The extent of ISOLATION provided by a damper varies greatly with application requirements and the nature and type of DAMPER. The extent of ISOLATION is usually expressed as LEAKAGE. 3.26 Isolation damper. A DAMPER having the primary function of ISOLATION. 3.27 Leakage. The volume of system gas that can pass through the various flow paths around the components of a closed DAMPER under a given set of conditions. LEAKAGE may be expressed in terms of Actual Cubic Meters per Second (ACMS) (Actual Cubic Feet per Minute (ACFM)), kilograms (of gas) per hour (pounds per hour), Percentage of Normal Airflow rate, or Percentage of Maximum Airflow rate. 3.28 Leakage area. The total area of the various flow paths between the component parts of a fully closed DAMPER. 3.29 Leakage zero. A condition in which no system gas passes from the upstream side of a duct system through a closed DAMPER to the downstream side of the duct system. 3.30 Linkage. Of a DAMPER, includes the blade shaft lever arms and connecting bar assemblies between blades, which accept operating force transmitted from an ACTUATOR. 3.31 Load bar. See BLADE SUPPORT. 3.32 Louver damper. A DAMPER having one or more BLADE(s) permanently in the gas stream; said BLADE(s) may be rotated between the open and closed position or to some intermediate position. See Figures 1 and 2. 3.33 Modulate. In a DAMPER, to vary the gas flow rate or pressure drop, or both, across a DAMPER by changing the restrictive effect of the BLADE(s). This change is brought about by altering the position of the BLADE(s) within the damper frame. Also, the effect of damper closure positioning to vary the AMCA 850-02 (R2011) 3 system gas flow rate, flow velocity, or pressure; the action of the damper, damper controls and ACTUATOR to maintain a predetermined set of flow parameters such as pressure or temperature. 3.34 Normal operating conditions. Of a damper installation, the specific (or range of) pressure and temperature at the damper when the system is functioning within the planned productive operating range and conditions. 3.35 Operator. See ACTUATOR. 3.36 Packing. Sealing material used to minimize or eliminate LEAKAGE at a shaft penetration through a damper frame. It is contained in a STUFFING BOX and retained by a packing gland that may be bolted to or threaded into the body of the stuffing box. 3.37 Perimeter air sealed damper. A GUILLOTINE DAMPER having a frame design which includes a chamber around the duct and the BONNET. The chamber must be pressurized by a SEAL AIR SYSTEM. 3.38 Pressure drop. The static pressure loss across a damper due to airflow resistance. Damper pressure drop must be added to other system pressure losses to obtain total pressure drop in the system. For more complete information on pressure drop, see AMCA Publications 200 and 201. 3.39 Purge air. As compared to SEAL AIR that is used for sealing, PURGE AIR is generally used to scavenge or displace gases from enclosed spaces formed within the damper or within isolated spaces in a duct or system. 3.40 Quarter-turn damper. One that moves from fully open to fully closed (or vice versa) with a 90° rotation of the damper shaft. 3.41 Rack and pinion. A damper DRIVE SYSTEM in which rotary effort applied to a toothed wheel causes linear motion of a mating bar having a compatible tooth form. See Figure 5. 3.42 Racking. The twisting of a DAMPER frame out of its intended planar arrangement. 3.43 Screwjack. A GUILLOTINE DAMPER DRIVE SYSTEM that uses the principle of the screw to change rotary motion into linear motion in applying opening/closing force. 3.44 Seals. In a DAMPER; any component located on a DAMPER BLADE or FRAME and having the purpose of limiting the amount of LEAKAGE AREA between the mating surfaces of a closed damper. 3.45 Seal air. Air introduced into the AIR CHAMBER of a DAMPER at a pressure higher than that of the upstream system gas. SEAL AIR thus provides a barrier to the passage of system gas from upstream of the damper to the downstream side. See Figure 6. 3.46 Shaft. In a LOUVER DAMPER, the supporting structural element of the blade; also the component about which the BLADE rotates and changes the BLADE attitude toward the gas stream. In a GUILLOTINE DAMPER, the round bar or tube through which actuation force is transmitted between components of the DRIVE SYSTEM. 3.47 Shut-off damper. A DAMPER that is not intended/used at any intermediate position between fully open or fully closed; sometimes referred to as "on-off" service. Note: Neither the name nor the expression denotes ISOLATION. 3.48 Stub shaft. A short, non-continuous shaft that extends through, as applicable: the LINKAGE, bearing, STUFFING BOX, or DAMPER frame and into the BLADE of a LOUVER or BUTTERFLY DAMPER. 3.49 Stuffing box. A chamber surrounding a shaft penetration through a DAMPER frame and into which PACKING may be installed to provide a leakage- resistant seal around the SHAFT. 3.50 Sprocket. A gear-like disk having teeth shaped to engage a drive chain for the purpose of converting actuator force to tensile force on the drive chain of a GUILLOTINE DAMPER. 3.51 Throat seal. See BLADE ENTRY SEAL. 3.52 Upset conditions. Those recognized potential excursions of pressure or temperature beyond the NORMAL OPERATING CONDITIONS and usually of short duration. A DAMPER subjected to upset conditions is usually required to sustain the upset conditions and perform thereafter without inhibition of normal function, or to specified functions under upset conditions. 3.53 Width. A dimensional reference to DAMPER size; in a GUILLOTINE DAMPER, the duct inside dimension that is perpendicular to the direction of BLADE movement. In a LOUVER DAMPER, it is the duct inside dimension parallel to the SHAFT axis. See Figures 4 and 2, respectively. 3.54 Wire cable. In a GUILLOTINE DAMPER, a tensile force component consisting of woven strands AMCA 850-02 (R2011) 4 of metal wire that are used to position the damper blade. 3.55 Wire cable sheave. In a GUILLOTINE DAMPER, a grooved wheel over which a WIRE CABLE passes. 4. Types of Dampers Dampers used in industrial process/power generation (IP/PG) service are, as mentioned above, of heavy construction to meet heavy service needs. This publication assumes that the reader is basically familiar with dampers for HVAC or light industrial service and the general construction of such dampers, so only terms and definitions unique to IP/PG service will be fully explained. Basic terminology and general damper construction is given in AMCA Publication 502, Application Manual for Louvers, Dampers and Shutters, and other special dampers are covered in AMCA Publication 503, Fire, Smoke and Ceiling Damper Application Manual. Dampers used in Industrial Process or Power Generation service are classified under two headings: control or isolation. 4.1 Control damper A control damper is one that is used to vary the flow rate of gas through a system. Variation of flow rate through the damper is achieved by changing the position of the damper blades, which physically restrict the gas flow. From the foregoing, one can tell that "control damper" is the functional name of a multi-blade louver damper. The damper blades may be arranged to act in parallel or opposition, depending on system needs. (See Figures 1, 2, AND 3) It should be noted that gate or guillotine dampers (See Figures 4 and 5) are NOT recommended for control purposes. There are several different varieties of control damper. 4.1.1 Balancing damper. A balancing (control) damper is used to balance the flow of gas in one duct of a system of ducts. Balancing in this sense does not always mean equal flow rate, but rather an apportioning of the total flow rate so that each duct conveys the correct percentage of the total flow. Once the correct percentage of flow is determined, a balancing damper is usually permanently "set", i.e., the damper blades are locked in position. 4.1.2 Pre-set position damper. A pre-set position (control) damper is normally open (NO) or normally closed (NC). Through the use of a signal-and- actuation system, the damper blades move from their normal position to a pre-set position, which is determined by the needs of the process being served. The pre-set position may be adjustable. This variety of damper is also called a two-position damper. 4.1.3 Modulating damper. A modulating (control) damper is one that is capable of attaining and holding any position from full-open to full-closed. Actuation of this damper depends on the needs of the process. It may be manually operated, or it may be operated with a signal-and-actuation system, in which case it also requires a positioner with feedback capability. For a modulating damper, opposed blades provide a better opportunity of achieving a near-linear relationship between signal and flow rate. 4.2 Isolation damper In a very real sense, an isolation damper is a special kind of control damper. The name originates with its application: to restrict gas flow across the damper to a specified maximum amount, compatible with the requirements of the process it serves. Many isolation dampers are used for isolation only, but there are many cases where an isolation damper also performs a control function. A damper that is intended for dual use is almost always a multi- blade louver damper with opposed blades. For isolation purposes only, a multi-blade louver damper with parallel blades, or a guillotine damper is used. A guillotine damper is generally of heavy construction and has one or two blades. Each blade slides through a heavy track in the damper frame, literally slicing through the gas stream as the blade moves from the open position to the closed position. The degree of isolation attained by a given damper is determined by its inherent physical ability to restrict flow and by additional measures that may be taken to enhance its flow-restricting ability. Thus isolation dampers are further classified as follows: 4.2.1 Shutoff damper. A shutoff (isolation) damper restricts flow to some specified amount of leakage, which can approach zero. The actual amount of leakage allowed is determined by the needs of the customer's process. The amount of leakage is then specified to the damper manufacturer, and the damper is designed accordingly. 4.2.2 Zero leakage damper. A zero leakage (isolation) damper is not used for control purposes and thus is either in the open position (for full flow) or the closed position (zero leakage). AMCA 850-02 (R2011) 5 AMCA 850-02 (R2011) OPPOSED BLADE ARRANGEMENT MODULATING PARALLEL BLADE ARRANGEMENT ON-OFF Figure 1 - Parallel Blade and Opposed Blade Arrangements and Operation 6 AMCA 850-02 (R2011) WIDTH BLADE EDGE SEAL BEARING AND PACKING GLAND BLADE END SEAL BOLT HOLES FOR ATTACHMENT TO DUCT FLANGE BLADE FRAME LINKAGE STUB SHAFT DRIVE SHAFT H E I G H T Figure 2 - Louver Damper Details 7 AMCA 850-02 (R2011) FLOW RATE vs. DAMPER OPENING DEGREES OPEN OPPOSED BLADES PARALLEL BLADES P E R C E N T O F F L O W R A T E 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 90 Figure 3 - Graphic Performance of Parallel vs. Opposed Blade Dampers Note: This figure is typical, only. The relative blade open angle versus percent of flow rate will vary with system pressure. 8 AMCA 850-02 (R2011) BONNET BRACING TORQUE TUBE BLADE ENTRY SEAL H E I G H T SEAT WIDTH BOLT HOLES FOR ATTACHMENT TO DUCT FLANGE BLADE SUPPORT BLADE ACTUATOR FRAME HANDWHEEL CHAIN BEARING SPROCKET LIFTING HOLE BONNET Figure 4 - Guillotine Damper Details 9 AMCA 850-02 (R2011) BLADE PINION (EXTERNALLY DRIVEN) RACK ELEMENTS (ENGAGED BY PINION TEETH) Figure 5 - Guillotine Damper Rack-and-Pinion Drive Details OPPOSTED BLADES (IF REQUIRED) FOR MODULATION PARALLEL BLADES ON-OFF SHUTOFF VALVE (BUBBLE TIGHT SHUTOFF OR AIR URGED ZERO LEAKAGE VALVE) SEAL AIR (P 2 = P 1 + 500 Pa (2 in. wg) MINIMUM P 3 P 2 P 1 Figure 6 - Seal Air System 10 The typical damper used in such applications almost always requires that the damper seals be pressurized to a level higher than that of the gas that is to be restricted. This pressurization is accomplished by a seal air system that consists of a fan and an isolation valve as the minimum components. (See Figure 6) The damper seals are enclosed in a cavity and seal air from a fan is fed through an isolation valve into the cavity around the seals. It is usually the case that some seal air does leak through to the downstream side of the damper. There are certain cases that do NOT require the use of seal air (or purge air) but instead require, in some combination: a. A goggle damper having a blade that extends outside the damper frame. This damper would be applicable if leakage of system gas to the atmosphere is acceptable. b. A vacuum-breaking chamber or draft-interrupting device for the isolation of negative pressure. c. The availability of a nearby induced draft fan, to the inlet of which a connection may be made for the evacuation of the area around the seals. 5. Damper Leakage Damper leakage is a flow of gas past the closed damper blade(s). The extent to which leakage becomes a consideration in a damper application depends on the nature and temperature of the gas being handled through the system, and sometimes it depends on the application itself. Once it is determined that leakage is a major consideration, it is then necessary to consider containment. 5.1 Leakage containment If it is decided that leakage is a major consideration, it is next necessary to determine whether it is necessary to address system leakage, ambient leakage, or both of these types. 5.1.1 System leakage. System leakage is leakage across the closed damper blade(s) that remains within the system ductwork. The extent to which system leakage is allowed is defined in actual cubic meters per second (Am 3 /s) or actual cubic feet per minute (ACFM), at a given temperature and pressure. An alternate definition of leakage may be the specification of an allowable percentage of some specified flow rate, such as design flow, normal flow, or maximum flow, in addition to giving the temperature and pressure. If no reference flow rate is given, the assumed flow rate is the normal flow. 5.1.2 Ambient leakage. Ambient leakage is leakage either into or from the system. In a louver damper, ambient leakage can occur though openings that allow damper blade shafts to pass through the frame. This leakage can be controlled through the use of packing glands or stuffing boxes around the blade shafts at those points. A guillotine damper is less susceptible to ambient leakage, but high positive pressure can result in ambient leakage. 5.2 Leakage path and leakage rate In the above, references were made to a leakage flow through an opening of some kind. Effective design and careful manufacturing will minimize the total leak path area. Any calculation for estimating the leakage rate should include pressure differential across the closed damper, the temperature of the gas, and the leak path area. 5.3 Factors affecting actual leakage The operating parameters of the system will dictate actual leakage. Variations in pressure, temperature, erosive/corrosive conditions, and normal wear and tear can all cause changes in the leakage rate, usually an increase. Physical deformation due to an upset condition or some other cause can also result in an increase in the leakage rate. 5.4 Selecting a damper to meet low to zero leakage requirements It is important to choose the right damper for the application. The choice is often directly affected by considerations of safety, system requirements, and economics. In choosing a damper for low-to-zero leakage service, several options are available. 5.4.1 Low leakage damper. A low leakage damper is usually required to meet allowable system and ambient leakage conditions as described above. A low leakage damper may be a multi-blade louver damper, or as allowable leakage rates approach zero, a guillotine damper may be more suitable. Much of the choice depends upon the suitability of materials for the application. 5.4.2 Zero leakage damper. In order to provide an isolated condition at some downstream location, two dampers and a seal air chamber are used. As shown in Figure 1, the personnel -safe system consist of: a. A louver damper on the upstream side. If this AMCA 850-02 (R2011) 11 damper is also used for flow modulation, an opposed blade damper is used, and seal air may leak to the upstream duct. b. A seal air chamber into which pressurized air is introduced. Pressurization is generally 500 Pa (2 in. wg) higher than the upstream pressure, at operating temperature. c. A louver damper on the downstream side. This damper is generally a parallel blade two-position louver damper. 5.4.3 Seal air. Seal air is used to provide a pressurized barrier of clean air so that work may be done in the ductwork downstream of the seal air chamber. The pressure of the seal air system relative to the upstream system pressure is critical. The volume of seal air must be such that it can overcome any leakage out of the seal air chamber. The sizing of the seal air source requires that the system temperature and pressure be fully accounted for. When a motor is involved, it must be properly sized to account for possible system abnormalities. For these reasons, seal air source sizing is usually left up to the damper manufacturer. In those cases where multiple dampers or seal air chamber are involved, a single source might be utilized. There are two general approaches to seal air: ambient and heated. 5.4.3.1 Ambient seal air. Ambient seal air is provided as produced by the seal air source, at a pressure consistent with the system requirements. Ambient seal air is generally provided at a temperature that ensures that isolation conditions are provided down-stream of the seal air chamber. It should be noted that ambient seal air may be below the dew point of the upstream system gas and could have an accelerating effect on system corrosion. When a guillotine damper requires seal air, ambient air is used. It is recommended that the user specify whether an intermittent or continuous supply of seal air is required. Such requirements may be discussed with the damper manufacturer. Consideration should be given to requirements for the needed frequency of isolation, power consumption of the seal air source, and the effect of ambient air leakage into the upstream system. It may be advantageous to operate the seal air system continuously to aid in minimizing both condensation and duct accumulation around the seals and in the bonnet. Ambient seal air is generally recommended unless there is a compelling technical reason why it should not be used. 5.4.3.2 Heated seal air. Heated seal air may be required in those cases where it is necessary or very desirable that any seal air leakage upstream be at or above the dew point temperature of the upstream system gas to minimize the acceleration of corrosion. Among the important factors to be considered in determining whether heated seal air is to be used: a. Heated seal air may restrict or severely delay entry of personnel into the downstream section for work b. The capital cost of a heated seal air system is greater c. Operating costs for such a system are higher d. The needed equipment is larger and requires additional space e. Additional controls are required f. Additional instrumentation is required to monitor the output of the heated seal air system 6. Thermal Considerations In industrial process/power generation damper applications, temperature plays a very important role, as indicated by the following. 6.1 Normal operating conditions The normal operating temperature range must be defined, as well as any upset temperature range over which the damper must operate. Peak temperatures, rates of temperature change, frequency and duration of upsets must be defined if the manufacturer is to design the equipment properly. For upset conditions, it should also be stated whether the damper is expected to operate properly once the system has returned to the normal operating range. 6.2 Thermal stresses It should be noted that damper equipment components are designed to withstand the thermal stresses of the specified conditions as well as the mechanical stresses, exclusive of external load. 6.3 Leakage operating temperature When leakage criteria are specified, the temperature or range of temperatures over which the leakage criteria must be met must also be specified. AMCA 850-02 (R2011) 12 6.4 Damper insulation If the damper is to be insulated after installation, that fact must be made known to the damper manufacturer, along with the following: a. Type and thickness of insulation to be applied to the mating ductwork b. Type and thickness of insulation to be applied to the damper by others 6.5 Thermal differential If the purchaser has cause to be concerned that thermal differentials may affect the damper or the duct structure, the thermal differential across the damper frame and closed blade must be specified. 7. System Gas Analysis 7.1 General The composition of the gas being conveyed through the duct system is important to two aspects of the damper. It affects the kind of damper selected or chosen, and it has a strong influence on the materials selected to construct the damper. It is also necessary to define any transient elements that the damper may be subjected to. The composition of the system gas and transients, as well as any other system parameters, is the responsibility of the specifier, and this information must be included with the damper specifications. While much of this information is available from the designers of the system process, similar existing systems may also provide valuable operational information that will aid in developing equipment that will provide satisfactory service. When actual system information is not available, estimated values should be established for expected areas of concern. 7.2 System gas characteristics An analysis of system gas analysis typically includes the following: a) Chemical composition b) Pressure, temperature and density c) Entrained particulate matter, if any d) Dispersed liquids, if any e) Flow rate f) Condensate chemicals and their dew point temperatures It should be noted that damper pressure drop calculations must necessarily be based on the actual system gas. If a gas other than the actual system gas is used for pressure drop calculations, this fact must be so stated in the equipment specification. 8. Corrosion and Erosion The damper specification should include the following with respect to corrosion and erosion: a) Minimum materials of damper construction b) Corrosion rates for the specified materials at normal operating conditions, and also at the operating condition that produces the highest rate of corrosion c) Erosion rates at the normal system gas velocity, and at 1.5 times the normal system gas velocity d) Estimated percent operation at other than normal operating conditions e) Desired damper life in years A damper design can include specified allowances for corrosion. Where the corrosion rate is not specified, the damper vendor makes a reasonable estimate of the corrosion rate, but cannot be held responsible for their accuracy. Damper components subject to corrosive/erosive attack are designed to include known or estimated allowances above what is required for mechanical strength alone. Typical design considerations are discussed in Section 11. 9. Control Range (See Figure 3) The range over which a damper can provide effective flow control or isolation cannot be determined solely from flow conditions and damper configuration. Control range is also a function of the duct system configuration and other variables that come into play when the damper is operated. In general, it is usually the case that the best control is ensured when damper size is minimized by designing for the highest allowable pressure drop. It is important to understand that the relationship of flow to damper openings is a function of many parameters, and a model of the complete system is usually necessary to determine such a relationship. AMCA 850-02 (R2011) 13 The choice of damper type may be influenced by the type of control needed or desired. An opposed-blade louver damper has a broader, more linear control range that can be effectively utilized with appropriate controllers. This characteristic makes the opposed- blade louver damper a good choice for flow modulation applications, since the flow profile remains essentially parallel to the axis of the duct. A parallel-blade louver damper, through which gas flow is directionally diverted by the operating damper blades and has higher pressure drop loss, is more suitable for on-off damper applications. Note: A damper used in close proximity to a fan is always a special case subjected to varying pressure and effect on fan performance that influence fan control. A control damper for such an application should be coordinated with the fan manufacturer. Flow stability will also affect the control range. A model test is usually required to determine the effects of stability on control range. Response time of the controls is important when flow conditions fluctuate rapidly. 10. Pressure Drop As system gas passes through a damper, there is a system pressure loss, or drop, due to the resistance of the damper itself. Pressure drop has its least effect on system performance when the damper is wide open. It is therefore necessary to establish some standard conditions for determining damper pressure drop so that system designers obtain accurate information on the equipment, and for the fair evaluation of equipment proposed by vendors. The first standard condition is that pressure drop is to be based on the damper being in the wide-open position. In the case of a guillotine damper, this means that the blade, as designed, will be fully retracted from the gas flow. 10.1 Pressure drop calculations A calculated pressure drop is often the first step in determining the actual duct system pressure drop that is due to the presence of the damper. When gas flow is not uniformly distributed, has eddy currents, has an angle of attack greater than zero or contains material in two phases (i.e., entrained fly ash or dispersed liquids), the calculated pressure drop may not be equivalent to the actual pressure drop. The following material should make the reader aware of not only the calculation steps involved, but also some of the assumptions attendant in damper pressure drop calculations so that pressure drop information can be reviewed in the proper perspective. 10.1.1 Initial assumptions. In order to set a starting point for damper pressure drop, the following initial assumptions are made: a. System gas flow is uniformly distributed across the cross-section of the duct (fully developed turbulent flow), and there is sufficient length of straight duct before and after the damper to ensure that the damper pressure drop is not magnified. The magnification of resistance, or performance loss, due to poor inlet and outlet conditions is known as system effect. System effect detracts from the performance of any component in a duct system. For further information on System Effect and how it detracts from fan performance, see AMCA Publication 201. b. The direction of system gas flow entering and exiting the damper is normal to the true cross- section of the duct at any point in the system gas stream. c. Incompressible flow conditions exist; i.e., adiabatic and isentropic. The reader should note once again that these assumptions might not reflect the actual conditions in a system. It is recommended, however, that the system be designed to ensure that the above assumptions are valid. See also Section 10.3 below. 10.2 Pressure drop equation The general form of the equation used to calculate damper pressure drop will be a modified form of the Bernoulli equation: Where: ∆P = Pressure loss in Pa (in. wg) K = Loss coefficient relative to the specific damper design sample, a non-dimensional number ρ = Density of the flowing system gas in kg/m 3 (lbm/ft 3 ) V = Average velocity across the entrance to the damper in m/s (ft/min) g = Gravitational constant, m/s 2 (ft/s 2 ) The value of K is dependent upon a number of geometric factors including the entrance and exit coefficients, skin friction, and reduction or enlargement of flow area. The value of K should be determined by test per AMCA Standard 500-D, and ∆P K V g = ×       ρ 2 2 AMCA 850-02 (R2011) 14 determined to be valid for a certain range of flow rate, temperature and pressure. In the absence of a K factor determined by test, the value of K is taken as the appropriate value for a square-edged orifice for the arithmetic average of the actual flow area. The general pressure drop equation above is used to determine only that loss due to the addition of the damper into the duct system and does not include the loss due to ductwork upstream or downstream of the damper. 10.3 System effect on damper The physical orientation of upstream and downstream ductwork relative to the damper can seriously affect the flow pattern into and out of the damper. If the orientation of a system is not as described under the assumptions made above, the actual pressure drop across the damper can be much greater than would normally be expected. Some of the variations that can cause a magnification of pressure drop include: a. Sudden reduction or enlargement in cross- section area b. Duct turns immediately adjacent to the damper c. Secondary flow of system gas into the ductwork immediately adjacent to the damper Again, these variations are not covered by the pressure drop equation given in Section 10.2. See also Section 11.2 for mechanical effects. 11. Damper Design Considerations A custom-engineered damper is designed to meet the parameters given in the equipment specification according to design guidelines which may vary slightly among manufacturers, but which are generally as follows: 11.1 Mechanical / thermal stresses 11.1.1 Damper 11.1.1.1 General. Damper components should be designed so that no load-bearing component stress calculated by conventional analysis shall exceed the yield strength of the selected material, given an appropriate factor of safety. 11.1.1.2 Safety factors. Unless more conservative values are specified, the appropriate safety factors to be used are: a. Bending: 60% of the material yield strength b. Torsion: 35% of the material yield strength c. Shear: 50% of the material yield strength 11.1.1.3 Creep. The effects of creep shall be considered in the design when operating temperature exceeds 427°C (800°F). 11.1.1.4 Distortion. Each component shall be designed to avoid function-limiting distortion during specified normal operating conditions or upset condition. 11.1.1.5 Specific function during upset. When the equipment specification requires that the damper perform a specific function during an upset condition, the design of the damper shall accommodate the requirement. 11.1.1.6 Compressive loads. A component subject to a compressive load shall be designed for the capability to transmit that load without exceeding the allowable buckling strength of the member using appropriate safety factors. 11.1.2 Drive system. 11.1.2.1 Basis of size. The drive system shall be sized to operate at the normal operating conditions, or at conditions as required in the equipment specification. 11.1.2.2 Actuator size. The drive system demand at the specified normal operating condition shall be specified by the damper manufacturer. The actuator must be sized so that its rated output exceeds the calculated damper demand by at least 50%. 11.1.2.3 Drive train design. The drive train shall be designed to accept the maximum actuator output stall torque without component failure. CAUTIONARY NOTE: There is the potential for field operating personnel to apply input force on a hand wheel such that components in the gear train and other drive components can be permanently damaged. Care must be exercised that the maximum recommended input force recommended by the damper manufacturer not be exceeded. 11.1.3 Allowable stress on material. The allowable stress on a material shall be determined based on material yield strength at the specified normal operating temperature unless otherwise specified. AMCA 850-02 (R2011) 15 11.2 Stability There is an additional result of System Effect when a damper is involved. Uneven flow characteristics have the potential to cause excessive localized loading on damper components. Therefore, the location of the damper in the system should be chosen carefully by the system designer. If uneven flow characteristics are anticipated, the location of a damper should be reviewed with the damper manufacturer so that the design of the equipment may account for potential instability or allow the damper manufacturer to recommend beneficial modifications to the duct system. 11.3 Deflection The damper manufacturer shall determine limits of deflection in damper components so as to ensure reliable free operation of the assembled damper and performance with respect to leakage. 11.4 Wind load Unless otherwise agreed to or specified, the damper design shall include and allowance for a wind load of 1.44 kPa/m 2 (30lbf/ft 2 ). For horizontal projections, the live load shall be as given in the equipment specifications. 11.5 Seismic loading Most dampers are analyzed as part of the duct system in which they are installed. Where seismic analysis is required, upon award of the damper contract the damper manufacturer shall supply detail drawings and bills of material to the purchaser to aid in seismic analysis of the damper by others. 11.6 Connection to ductwork 11.6.1 Dimensional requirements. The damper shall be designed to mate with ductwork that is square within 1/1000 of the diagonal and flat within the allowable compression range of the selected damper/ductwork gasket. It should be noted that a racked (distorted) duct will cause the damper frame to be non-planar when attached to the ductwork with the possible result of excessive leakage or binding during operation. Out- of-square ductwork may also produce the same results. Ductwork quality should ensure alignment such that no forces are imposed on the damper as the result of attachment. 11.6.2 Transmitted loads and damper support. Where possible, no external loads should be transmitted through the damper. Any external load to be imposed on the damper shall be given in the equipment specifications. A guillotine damper requires special consideration, as the damper flanges adjacent to the blade entry side are non-load bearing. Moment loads are of the greatest concern. It is preferable that a damper be supported from a duct flange on or near a duct support, with expansion joints installed to minimize wind load, thermal expansion loading, and vibration. When a damper is to be installed at the base of a stack, the design shall account for the stack load and bending moment as given in the equipment specifications. 11.6.3 Blade protrusion. The purchaser shall specify when it is or is not allowable for the damper blade(s) to extend beyond the damper frame. 12. Actuators The type of actuator to be supplied with the damper is defined in the equipment specification by the type of power source the actuator shall utilize. The three types of power source most commonly used are: manual, electric, or pneumatic. The choice of power source should take into consideration the operating time, failure mode, frequency of damper operation, availability of the power source at the damper location, the size of actuator required, and the amount of force and/or speed required. The choice of power source may require the trading off of some features for others which are more desirable in the specific application. Selection of an actuator may depend on the failure mode requirements (the desired reaction of the damper upon loss of control signal or power): a. Damper to stop in last position on loss of control signal or loss of power to actuator; b. Damper to open (or close) on loss of power to actuator; c. Damper to open (or close) on loss of control signal to actuator. AMCA 850-02 (R2011) 16 12.1 Pneumatic 12.1.1 Rotary. Rotary vane actuators provide double-acting motion and are directly coupled to the main drive shaft of the damper for operation at a 90° angle. Cylindrical actuators are directly coupled to the main drive shaft of the damper and provide double-acting motion through a lever crank, a Scotch yoke, or a rack-and-pinion connection. 12.1.2 Linear. Suitable for quarter-turn dampers, a double-acting linear actuator may be used to operate at a 90° angle via a crank and clevis. Guillotine or slide-gate dampers may use a direct cylinder drive or a rotary actuator with a screw drive or an intermediate chain drive. 12.2 Electric An electric actuator consists of a reversible electric motor that applies actuation force through a drive system. 12.2.1 Rotary. Rotary actuation force is applied through the drive system's self-locking gears. When used with a quarter-turn damper, the actuator is ordinarily shaft mounted. On a guillotine damper, the actuator delivers actuation force through a screw or chain drive. 12.2.2 Linear. Linear actuation force is supplied through a drive system consisting of a screw, intermediate chain drive, or gears. The output is self-locking. The output can be direct- coupled to the main drive shaft of the damper, or at a 90° angle through a crank or clevis. 12.3 Manual A manual actuator may be either the hand lever type or the hand lever-geared type. Frequently used with a guillotine or slide gate damper, actuation force is applied through arrangements of winch-and-chain, winch-and-wire rope, rack-and-pinion, or revolving screw with captive nut. 12.4 Options and accessories 12.4.1 Electric actuator. Options include the following: Limit switch(es), located outside the damper or inside the actuator, to indicate the position of the blade(s) or to control power. Torque overload device, to disconnect power if an excessive motor demand occurs. Positioner, to provide control of the drive shaft in response to a signal from a remote control device. Manual override for emergency operation of dampers. 12.4.2 Pneumatic actuator. Options include the following: Limit switches, to indicate the position of the damper blade(s) or to activate/deactivate indicator signals; Positioner, to satisfy which require that the drive shaft be moved to a position called for by a remote control device. The control signal may be 2.068 to 10.342 kPa (3 to 15 psi) instrument air, or a conventional electric control signal of 4 to 20 ma, or 1 to 5 V dc converted to 2.068 to 10.342 kPa (3 to 15 psi) by a transducer. Fail-safe features, to return the damper to a position upon loss of power air or control signal. This feature may be accomplished via a spring return to create resistance inside an air cylinder, or by providing an accumulator tank to store enough air pressure for one additional cycle of operation. Manual override for emergency stop of actuator; not available on all pneumatic actuators. 13. Testing Tests of prototype or production units may be requested for design proof or product acceptance. The nature of the tests, location of tests, test procedures to be followed, remedies, and acceptance criteria should all be established beforehand with the damper manufacturer in order to ensure that tests are satisfactory. It should be noted at the outset that tests that involve the simulation of service conditions are expensive. Since these tests are conducted at the customer's expense, they should be carried out on a selective basis. 13.1 Location of and schedule for testing A damper test is normally conducted at the damper manufacturer's premises, and scheduling is usually optimized to minimize delays between damper production and shipment. The manufacturer has the necessary test facility and test personnel. No shipment cost or time is involved, all of which minimize the cost to the purchaser. Testing at another location or to a schedule that involves delays usually AMCA 850-02 (R2011) 17 result in additional cost to the purchaser. When the physical size of the equipment precludes testing at the manufacturer's facility, a mutually acceptable test location should be agreed upon. 13.2 Functional tests These tests are normally conducted by the manufacturer as a standard procedure. Since there is wide variation in the information obtained, the damper manufacturer should be consulted to determine whether the manufacturer's standard tests provide sufficient information for the job, or whether additional tests are required. Functional tests are usually performed on a simulation basis, wherein the equipment is positioned with respect to flow and gravity just as it will be installed, or with those factors taken into consideration. Functional tests are intended to prove satisfactory operation of a damper in the "as-built" condition unless special arrangements are made to subject the damper to simulated temperature, pressure, contamination, or other special conditions during the test. Satisfactory functional testing does not relieve the damper manufacturer of responsibility for satisfactory operation when it is installed and subjected to service conditions. 13.3 Simulation test If it is determined that a simulation test is required, such testing should be discussed with the damper manufacturer. The results of most of such tests, if performed, require interpretation because they do not duplicate all the conditions to which the damper is to be subjected in service. The following is a list of damper candidates for simulation testing, and the performance parameters that may be included in such testing: 13.3.1 Louver damper without seal air system. a) Leakage b) Pressure Drop at design flow c) Operating Time (Cycle time, open-to-close, or close-to-open) d) Loose Material Obstruction e) Rigid Material Obstruction f) Deflection ______ mm (in.) 13.3.2 Louver damper with seal air system. a) Leakage b) Pressure Drop at design flow c) Operating Time (Cycle time, open-to-close, or close-to-open) d) Loose Material Obstruction e) Rigid Material Obstruction f) Deflection ______ mm (in.) g) Seal Air Cavity Required? h) Seal Air Cavity Pressure 13.3.3 Guillotine damper with seal air system. a) Leakage b) Pressure Drop at 100% open c) Operating Time (Cycle time, open-to-close, or close-to-open) d) Loose Material Obstruction e) Rigid Material Obstruction f) Deflection g) Seal Air Cavity Required? h) Seal Air Cavity Pressure 13.4 Test detail The details for testing the performance parameters listed above should be in accordance with the outlines given below. The data to be recorded during the test, the presentation of results, and criteria for acceptance should be agreed upon before any test commences: 13.4.1 Leakage. Leakage volume through the damper shall be measured when subjected to the operating pressure differential and the damper is closed by the actuator mechanism. The observed leakage volume shall be adjusted for service conditions of temperature and pressure. 13.4.2 Pressure drop. Pressure drop tests shall be conducted on the damper, size permitting. When equipment size precludes such a test, a model test per AMCA Standard 500-D shall be the preferred alternate test. 13.4.3 Operating time. The damper shall be cycled from open-to-close, and close-to-open, and the time in seconds for each recorded. 13.4.4 Loose material obstruction. A material shall be selected which resembles the anticipated duct deposit conditions. The material shall be placed in the damper and the damper shall be cycled. 13.4.5 Rigid obstruction. A mutually acceptable, reasonably solid obstruction shall be selected for the test. The obstruction shall be placed in the path of the damper blades and the damper shall then be cycled from open to closed in advance of pre-set shutoff switches to confirm the capacity of the drive mechanism and the strength of damper components when subjected to a solid obstruction. AMCA 850-02 (R2011) 18 13.4.6 Seal air cavity pressure. The seal air cavity pressure test shall be conducted with the damper in the "as-built" condition and without differential pressure across the damper. 13.4.7 Seal air cavity volume. The manufacturer shall provide calculations to seal air volume and pressure tests to actual operating conditions. 13.4.8 Deflection. The damper shall be subjected to loading to simulate loading as given in the equipment specification. The load shall be applied to the damper blade(s) or other damper components (as applicable) designated, and the deflection measured and recorded. 14. Recommended Specifications A clear and detailed specification of the damper equipment to be supplied is an important first step in ensuring that the desired equipment can be properly quoted, built, tested, installed and operated to the satisfaction of all concerned. The specification should ensure that the responses received will be from companies with sufficient resources and experience to manufacture, test and deliver equipment which will meet the equipment specifications. 14.1 Louver damper specification This recommended specification is intended to serve as a guide for the design and manufacture of heavy duty louver dampers for industrial process or power generation applications. 14.1.1 Scope 14.1.1.1 This specification covers the supply of a heavy duty louver damper for the Specified Service Conditions. 14.1.1.2 The damper shall be manufactured as specified under Construction and shall be supplied with an actuator and necessary limit switches and other components as required. Unless otherwise specified, the damper shall undergo functional testing by the manufacturer prior to shipment. 14.1.2 Quality program 14.1.2.1 All work, including design engineering, material procurement, fabrication and shipment shall be as agreed upon between the purchaser and the manufacturer. 14.1.2.2 The supplier's plant shall be accessible during all phases of manufacture of the equipment. The purchaser shall be notified at least ten (10) days prior to the manufacturer's final inspection and cycling of the equipment. 14.1.3 Submittal drawings. Upon award of the contract, complete detailed submittal drawings shall be prepared and submitted by the manufacturer, per an agreed upon schedule, to the purchaser for approval. Submittal drawings must be approved before the start of fabrication. The drawings shall exhibit system design parameters, interface dimensions, and performance data on accessories such as limit switches and actuators, et al. The submittal drawings shall include or have attached a bill of materials identifying the major components of the equipment. 14.1.4 Welding. All welding to be done shall be based on applicable sections of the American Welding Society codes or the ASME Section IX welding code. 14.1.5 Construction 14.1.5.1 The louver damper shall be constructed of materials which meet the minimum requirements given in the Specified Service Conditions. 14.1.5.2 The stress level in any component subjected to structural design loads shall not exceed the following percentage values of the yield strength of the selected material at the temperature given in the Specified Service Conditions: a) Bending: 60% b) Torsion: 35% c) Shear: 50% 14.1.5.3 Creep shall be considered in the design of the damper when operating temperature exceeds 427°C (800°F). Creep rate shall be based upon 1% at 100,000 hours. The allowable percentage of stress based on creep shall not exceed the allowable percentages given for yield strength. 14.1.5.4 The damper frame shall be rolled/formed structural channel. The frame shall be designed to meet the mechanical requirements resulting from the Specified Service Conditions and also for transportation and installation. The unit shall be self- supporting, with no external support or bracing required. The damper frame shall be designed with sufficient stiffness to preclude binding in induced- draft applications and to prevent excessive leakage across the damper under the pressure/temperature given in the Specified Service Conditions. 14.1.5.5 The blade structure shall not be permanently distorted by exposure to the maximum temperature given in the Specified Service Conditions. Allowances AMCA 850-02 (R2011) 19 shall be made for thermal expansion/contraction of the blade/axle assembly. Thermal expansion/contraction shall be controlled and directed away from the side of the damper where the drive system is located. 14.1.5.6 The damper blades shall be linked external to the damper frame. Linkage between blades shall be designed so that no blade may operate independently of the others. The linkage shall be completed, tested and fixed in position at the manufacturer's facility. 14.1.5.7 Bearings used in the damper shall be (ball/sleeve/roller) type. Bearing selection shall take into account jobsite ambient conditions and also heat conduction from the damper shaft to the bearing. 14.1.5.8 Stuffing boxes are (required/preferred/ optional) shall be secured to the damper frame at each shaft clearance hole in the frame and shall be filled with material which is stable under exposure to both the system gas and to the ambient conditions. The stuffing box shall be designed and constructed so that packing may be renewed without the removal of linkage or other drive system components. 14.1.5.9 Seals at the blade edges and the blade ends are (required/not required/optional). The material shall be suitable to withstand the Specified Service Conditions. 14.1.5.10 The actuator and all drive system components shall be sized with a minimum safety factor of 50%, based upon the Power required to operate the damper under the normal operating conditions given in the Specified Service Conditions. 14.1.5.11 The actuator mounts shall be furnished and installed on the damper frame by the damper manufacturer. 14.2 Guillotine damper specification This recommended specification is intended to serve as a guide for the design and manufacture of heavy duty (personnel-safe) guillotine dampers for industrial process and power generation applications. 14.2.1 Scope 14.2.1.1 This specification covers the supply of a heavy duty (personnel-safe) guillotine damper for the Specified Service Conditions. Note: If the personnel-safe features are not required, the [bracketed] phrases may be omitted. They are included to provide the most comprehensive sample specification. 14.2.1.2 The damper shall be manufactured as specified under Construction and shall be supplied with an actuator and blade drive mechanism [and complete seal air system] as required. Unless otherwise specified, the damper shall undergo functional testing by the manufacturer prior to shipment. 14.2.2 Quality Program 14.2.2.1 All work, including design engineering, material procurement, fabrication and shipment shall be as agreed upon between the purchaser and the manufacturer. 14.2.2.2 The supplier's plant shall be accessible during all phases of manufacture of the equipment. The purchaser shall be notified at least ten (10) days prior to the manufacturer's final inspection and cycling of the equipment. 14.2.3 Submittal drawings. Upon award of the contract, complete detailed submittal drawings shall be prepared and submitted by the manufacturer, per an agreed upon schedule, to the purchaser for approval. Submittal drawings must be approved before the start of fabrication. The drawings shall exhibit system design parameters, interface dimensions, and performance data on accessories such as limit switches and actuators, et al. The submittal drawings shall include or have attached a bill of materials identifying the major components of the equipment. 14.2.4 Welding. All welding to be done shall be based on applicable sections of the American Welding Society codes or the ASME Section IX welding code. 14.2.5 Construction. 14.2.5.1 The guillotine damper shall be constructed of materials which meet the minimum requirements given in the Specified Service Conditions. 14.2.5.2 The stress level in any component subjected to structural loads shall not exceed the following percentage values of the yield strength of the selected material at the temperature given in the specified service conditions: a) Bending: 60% b) Torsion: 35% 14.2.5.3 The damper frame shall be rolled or formed structural steel. The frame shall be designed to meet the mechanical requirements resulting from the Specified Service Conditions and also for transport AMCA 850-02 (R2011) 20 and installation. The unit shall be self-supporting, with no external bracing or support required. The damper frame shall be designed to support the extended blade, and to withstand the loads of the drive system, and wind/snow loads. 14.2.5.4 If blade support(s) is(are) required to restrain the closed blade, it(they) shall be designed to minimize pressure drop through the damper. 14.2.5.5 The blade shall be of single-thickness plate or an equivalent thermally-compatible structure. Blade deflection under any specified operating condition (blade extended, retracted, or partially open) shall not exceed the lesser of one-half the thickness of the blade material or 1/360th of the blade width. 14.2.5.6 The damper blade shall withdraw clear of the duct when in the open position. 14.2.5.7 The bonnet shall be of the (open/closed) type. 14.2.5.8 Seals shall be designed and located on the damper to allow replacement without the need for removing the damper from the duct. 14.2.5.9 Flexible seals shall be of such design and material to ensure proper spring retention and memory through the entire operating range from ambient to Specified Service Conditions. 14.2.5.10 A seal air blower shall be provided and sized to provide 500 Pa (2 in. wg) pressure more than the differential pressure across the closed damper at the Specified Service Conditions. 14.2.5.11 A shut-off device with a suitable actuator shall be located between the seal air blower and the damper to prevent reverse flow of flue gas through an idle blower. 14.2.5.12 The damper blade shall be operated either by chain-and-sprocket(s), lifting screws, or rack-and- pinion. 14.2.5.13 The damper operating drive system shall consist of a suitable power drive motor, sized for a minimum safety factor or 50% based on the maximum power required to operate the damper under the Specified Service Conditions. 14.2.5.14 Each component in the drive system shall accept the running-stall output of the power drive motor without failure. 15. Sample Specification Checklist The final purchase specifications for a damper are often an accumulation of diverse sets of documents. The accumulation will consist of purchase order forms and related contractual papers. Each purchaser has its own set of special forms, standards, and operating procedures that might be included as contractual papers. The information in these documents will include a technical description of the damper and details of the specific requirements of the installation. The information developed should be the result of a dialogue between the purchaser and the damper manufacturer, initiated by a Request for Proposal or Invitation to Bid (see sample form Section 15.1). The manufacturer will respond (see sample form Section 15.2), often with comments and suggestions for alternative equipment or options. This section is intended to assist in that dialogue. Form Section 15.1 may be copied and filled in, or may be used as a checklist against a form preferred by the purchaser. When completing form Section 15.1, the purchaser should refer to and include copies of any proprietary specifications covering motors, actuators, surface preparation, painting, and accessories, as applicable. Providing a completed form Section 15.1 (or its equivalent) together with all the applicable data will give the manufacturer the information he needs to develop a complete, competitive and responsive proposal. Form Section 15.2 may be used as a checklist to ensure that the manufacturer's proposal is complete and responsive to the user's requirements. 16. Installation Instructions To ensure that industrial process / power generation dampers operate satisfactorily it is essential that they be properly installed. Before starting work on ANY installation, the manufacturer's instructions should be carefully reviewed and thoroughly understood. The manufacturer should be contacted and any difficulties resolved before the installation work is started. AMCA 850-02 (R2011) 21 AMCA 850-02 (R2011) Figure 15.1 - Request for Quotation or Invitation to Bid (Page 1) GENERAL INFORMATION Request prepared by: Project Name or Code: Date: ____________________ ________________________ ______________________ Req’d submittal date: _______________________ Plant location: ______________________________ Proposal valid until: ________________________ Designated FOB point: _______________________ Return proposal to: Est. date of contract award: ___________________ ________________________________________ Est. shipping start date: ______________________ ________________________________________ Est. shipping end date: _______________________ ________________________________________ Est. date for completion: ______________________ Available specifications (motor, accessory & paint specs, etc.): _____________________________________ _______________________________________________________________________________________ INSTALLATION AND SITE CONDITIONS Barometric pressure: ______ (Pa/in. Hg) Maximum temperature: ______ (°C/°F) Wind load: ______ (N/m 2 ) or altitude: ______________ (m/ft) Minimum temperature: ______ (°C/°F) _______________(lbf/ft 2 ) DATA REQUIRED FOR EACH ITEM Item identification: _____________ _____________ _____________ _____________ Quantity req’d: _____________ _____________ _____________ _____________ Type of damper: _____________ _____________ _____________ _____________ Width inside frame: _____________ _____________ _____________ _____________ Height inside frame: _____________ _____________ _____________ _____________ Maximum frame, face-to-face: _____________ _____________ _____________ _____________ DAMPER ORIENTATION (Horizontal, vertical or stated angle from horizontal) Width orientation: _____________ _____________ _____________ _____________ Height orientation: _____________ _____________ _____________ _____________ 22 AMCA 850-02 (R2011) Figure 15.1 - Request for Quotation or Invitation to Bid (Page 2) DAMPER ORIENTATION (Horizontal, vertical or stated angle from horizontal) (continued) Top or bottom entry for non-horizontal guillotines: _____________ _____________ _____________ _____________ Item identification: _____________ _____________ _____________ _____________ Sealing direction (same as or opposite to flow direction): _____________ _____________ _____________ _____________ MATERIAL MINIMUMS Frame: _____________ _____________ _____________ _____________ Bonnet: _____________ _____________ _____________ _____________ Blade: _____________ _____________ _____________ _____________ Shaft: _____________ _____________ _____________ _____________ Seals: _____________ _____________ _____________ _____________ Type of bearings: _____________ _____________ _____________ _____________ DESIGN FLOW & LEAKAGE Maximum flow rate, ACMS or kg/hr; ACFM or lbm/hr: _____________ _____________ _____________ _____________ Allowed gas leakage, ACMS or ACFM at normal differential pressure and temp: _____________ _____________ _____________ _____________ Allowed gas leakage, ACMS or ACFM to atmosphere at normal operating temperature and pressure: _____________ _____________ _____________ _____________ TEMPERATURE AND PRESSURE SERVICE CONDITIONS Maximum operating temperature, (°C/°F) _____________ _____________ _____________ _____________ Normal operating temperature, (°C/°F) _____________ _____________ _____________ _____________ Upset transient temperature, (°C/°F) _____________ _____________ _____________ _____________ 23 AMCA 850-02 (R2011) Figure 15.1 - Request for Quotation or Invitation to Bid (Page 3) TEMPERATURE AND PRESSURE SERVICE CONDITIONS (Continued) Duration and frequency of upset transient: _____________ _____________ _____________ _____________ Normal operating pressure, (Pa/in. wg) _____________ _____________ _____________ _____________ Normal closed differen- tial pressure, (Pa/in. wg)_____________ _____________ _____________ _____________ Item identification: _____________ _____________ _____________ _____________ GAS & DEPOSIT CONDITIONS Gas analysis: _____________ _____________ _____________ _____________ Gas dew point temp- erature, (°C/°F) _____________ _____________ _____________ _____________ Gas dust load, (kg/m 3 /grains/ft 3 ) _____________ _____________ _____________ _____________ Estimated depth of duct deposit: _____________ _____________ _____________ _____________ Estimated tensile strength of duct deposit: _____________ _____________ _____________ _____________ Estimated shear strength of duct deposit: _____________ _____________ _____________ _____________ ACTUATOR AND ACCESSORY REQUIREMENTS Type of actuator: _____________ _____________ _____________ _____________ Required operating time (max or min): _____________ _____________ _____________ _____________ Limit switches (Y/N): _____________ _____________ _____________ _____________ Torque overload protection: _____________ _____________ _____________ _____________ Manual override (Y/N): _____________ _____________ _____________ _____________ Heaters in motors or Limit switch housing (Y/N): _____________ _____________ _____________ _____________ 24 AMCA 850-02 (R2011) ACTUATOR AND ACCESSORY REQUIREMENTS (Continued) Remote position Indicator (Y/M): _____________ _____________ _____________ _____________ POWER SUPPLIES, ELECTRIC AND COMPRESSED AIR Electric: Volts, Phase, Hz. _____________ _____________ _____________ _____________ Plant air: (Pa/psi) _____________ _____________ _____________ _____________ Instrument air, (Pa, psi) _____________ _____________ _____________ _____________ Modulating control _____________ _____________ _____________ _____________ Figure 15.1 - Request for Quotation or Invitation to Bid (Page 4) 25 AMCA 850-02 (R2011) GENERAL AND CONTRACTUAL INFORMATION • Damper manufacturer • Reference to quotation request • Quotation submitted by • Quote sent to attention of: • Issue date • Validity date limit of quote • Manufacturer’s job reference • Purchaser’s reference • FOB point & shipping terms • Surface finishes & paint specs • Contract terms • Price per item • Statement of manufacturer’s compliance to quote request / invitation to bid TECHNICAL DATA MAJOR COMPONENT & MATERIAL SIZE ACTUATOR DATA • Frame • Bonnet • Actuator make & model • Motor power • Blade • Shaft • Maximum stall torque • Maximum stall torque • Seals • Type of drive • Required torque including safety factors • Operating times, seconds, from full closed • Type of bearings to full open SEAL AIR SYSTEM (if required) ACCESSORY ITEMS (if required) • Fan make & model • Installed power • Limit switches: --- Number & type • Operating power: damper open, --- External mount or in actuator damper closed and sealed • Motor heaters • Positioners • Seal air isolation device • Remote position indicators • Seal air parameters: --- Pressure at fan outlet --- Required volume, including safety factor SIZE AND WEIGHT OF ASSEMBLY PERFORMANCE INFORMATION • Dimensions inside frame • Pressure drop (Pa/in. wg) added to system by full-open damper at maximum flow rate • Estimated overall dimensions including accessories: • Guaranteed leakage rate at operating --- Across closed damper • Assembled weight --- To (or from) atmosphere • Number of shipping pieces per damper, including accessories Figure 15.2 - Quotation Response Checklist AIR MOVEMENT AND CONTROL ASSOCIATION INTERNATIONAL, INC. 30 West University Drive Arlington Heights, IL 60004-1893 U.S.A. E-Mail : [email protected] Web: www.amca.org Tel: (847) 394-0150 Fax: (847) 253-0088 The Air Movement and control Association International, Inc. is a not-for-profit international association of the world’s manufacturers of related air system equipment primarily, but limited to: fans, louvers, dampers, air curtains, airflow measurement stations, acoustic attenuators, and other air system components for the industrial, commercial and residential markets.