CEJ Glossary of Terms

Active length (live length): The portion of the flexible part of the joint that is free to move.

Anchor: Terminal point or fixed point from which directional movement occurs.

Angles: L-shaped steel member used either as a duct flange or as the fastening member of an expansion joint used for bolting or welding the joint to the mating flange surface of the ductwork or adjacent equipment

Angular movement: The movement which occurs when one flange of the expansion joint is moved to an out of parallel position with the other flange. Such movement being measured in degrees.

Assembled splice: a splice that is constructed of multi-layers of materials and connected by mechanical means such as adhesives, stitching, and lacing hooks.

Axial compression: The dimensional shortening of an expansion joint parallel to its longitudinal axis. Such movement being measure in inches or millimeters and usually caused by thermal expansion of the ducting system.

Axial extension: The dimensional lengthening of an expansion joint parallel to its longitudinal axis. Such movement being measured in inches or millimeters.

Back-up bars: metal bars used for the purpose of clamping the expansion joint to mating ductwork flanges or clampig the fabric portion of a belted type joint to the metal adapter flanges

Baffle liner: A metal shield that is designed to protect the epansion joint from the abrasive particles in the gas stream and to reduce the flutter caused by the air turbulence in the gas stream and in some cases may be part of the overall thermal protection system.

Bellows: That portion of an expansion joint which accommodates the movement of the joint. Can be either convoluted or flat.

Belt type expansion joint: An expansion joint in which the flexibe bellows portion of the joint is made like a flat belt and is bolted or clamped to metal adaptor flanges or frame.

Bolt hole pattern or drill pattern: The systemati location of bolt holes in the duct flanges and expansion joint flanges where joint is to be bolted to ducting flanges.

Bolt-In baffle: A baffle that is designed to be bolted to the breach flange. This design can be either single or double acting and requires the use of a seal gasket.

Boot or belt: The flexible element of an expansion joint usually consisting of elastomer coated fabric.

Breach flange or duct flange: The portion of the duct system, usually an angel or a channel that interfaces witht he flange of the expansion joint.

Breach opening or Duct Face-to-Face distance: The portion of the duct system, usually an angle or a channel that interfaces with the flange of the expansion joint

Clamp bars: see Back-Up Bars

Composite Type Expansion Joint: A expansion joint in which the various plies are of different material that are not integrally binded together. Normally made up of an inside liner, thermal insulating barrier and an outer over. Other special plies can be included.

Concurrent movements: Combination of two or more types (axial or lateral) of movements

Corners: molded, formed, or radiused belt corners of rectangular expansion joint.

Design temperature: the maximum or most severe temperature expected during normal operation, not including periods of abnormal operation caused by equipment failure. (See excursion temperature.)

Design pressure/vacuum: The pressure or vacuum condition that exists during system start-up and/or shutdown operations. During this cclic phase in the system, both pressure and vacuum donitions may occur.

Drill pattern: The systematic location of bolt holes on the breach flange to which the expansion joint will be attached.

Duct ID: The insided dimension of the ductwork measured from the duct walls prior to any form of coating.

Dust shield: A flexible element that is attached between the baffle plates and/or duct wall to restict the buildup of fly ash between the baffle and joint body. This element is not gas-tight.

Excursion temperature: The temperature the system could reach during an equipment failure, such as an air heater failure. Excursion temperature should be defined by maximum temperatures and time duration of excursion.

External arch corner: An expansion joint corner with the arch formed outwardly that is designed primarily for the pressure service. General used in conjunction with a molded joint.

Field assembly: a joint that is assembled at the job site due to its size (too large to ship) or the location of the breach opening makes it more practical to install in sections.

Flanges: That par of an expansion join tused for fastening the joint into the system. can be either metal or same material as the bellows.

Flexible element: The part of the expansion joint that accepts the movement.

Flow direction: Direction of the gas movement through the system.

Flutter: the action that occurs on the jont body caused by the turbulence of the system gases or vibration set up in the ducting system.

Frame: the complete angle iron or plate frames to which elt or bellows protion of the expansion joint is attached.

Gas seal: The specific ply in the expansion joint that is designed to stop gas penetration through the expansion joint body: this ply can be the tube, cover, or a special ply depeding on the specific temerature requirements.

Internal Arch Corner: An expansion joint corner with the arch formed inwardly that is designed primarily for vacuum service. Generally used in conjunction with a molded joints.

Inner Ply (inner cover): The ga side of a composite elastomeric type joint

Installed face-to-face distance: The distance between the expansion joint flanges after installation when the system is in the cold position

Integrally flanged type expansion joint: An expansion joint in which the joint flanges are made of the same fabric as the body of the joint, as in “U” type joints.

Joint framing or picture framing: Metallic frame to which belted or integrally flanged joints are attached before installing.

Lateral deflection or lateral movement: the relating displacement of the two ends or the expansion joint perpendicular to its longitudinal axis. The displacement movement usually caused by the thermal expansion of the ducting system and measured in inches or millimeters.

Lateral Offset: The offset distance between two adjacent duct flanges or faces. Can be due to misalignment or, by design, to compensate for excessive displacement in the opposite direction during cycling.

Lifting lugs: A lifting device that is attached to the metal portion of the expansion joint for field handling and erection.

Liner (Baffle): A metal shield that is designed to protect the expansion joint from the abrasive particles in the gas stream and to reduce the flutter caused by the air turbulence in the gas stream and in some cases may be part of the overall thermal protection system.

Manufactured F/F or expansion joint: The manufactured width of the joint measured from joint flage face to flange face. The joint may be set into a breach opening that is less than the manufacturing F/f of the joint to allow for axial extension.

Maximium design temperature: The maximum temperature that the system may reach during normal operating conditions. Not to be confused with excursion temperature.

Misalignment: The out of line condition that exists between the adjacent faces of the breach or duct flanges during dctwork assembly

Molded type expansion joint: An expansion joint in which the entire wall of the joint is molded into a “U” or a convoluted configuration. The joint is manufactured y a moldling process

Movements: The dimensional changes which the expansion joint is required to absorb, such as those resulting fromthermal expasion or contraction.

Non-metallic expansion joint: expansion joint: expansion joint which utilizes flexible non-metallic boot or bellows material to accommodate joint movements.

Operating pressure/vacuum: The pressure or vacuum condition which occurs during normal performance. This should be pressure or vacuum, not both.

Operating temperature: The gas temperature at which the system generally will operate during normal conditions.

Outer cover: The external side of a composite or elastomeric type joint.

Pre-assemble joint: the combination of the metal framework and a bellows, factory assembled into a singe assembly.

Pre-compression: Compressing the expansion joint (shortening the F/F) so that in the cold position the joint has a given amount of compression set into the joint. The purpse of pre-compression is to allow the unexpected or additional axial extension.

Pre-Set: Dimensions that joints are deflected to insure tha desired movements will take place. See lateral offset and manufactured F/F.

Protective shipping cover: outer cover material used to protect expansion joint during shipment and installation.

Protective strip or rub tape: Fabric material or tadpole tape sometimes used between boot and metal member or expansion joint to protect boot from heat transfer or abrasion.

Resultant movement: The net effect of concurrent movements

Seal Gasket: A gasket that is placed between two adjacent metal parts to make a gas tight connection.

Set Back (Stand off height): The distance the expansion joint is set back from gas stream to allow for lateral movements and to prevent the joint from protruding into the gas stream or rubbing on the baffle when operating under negative pressure. Set back also reduces the heat input and prevents abrasion from particles in gas stream.

Shipping straps or bars: Braces that re located between the two expansion joint flanges to prevent over-compression or distortion during shipment and joint assembly.

Splices: Procedure for making endless boot or bellows from open ended material. splicing may be accomplished by one or more of the following: cementing, bonding, heat sealing, stitching, vulcanizing or mechanical fasteners.

Stand off height (set back): The distance the expansion joint is set back from gas stream to allow for lateral movements and the prevent the joint from proctoring into the gas stream or rubbing on the baffle when operating under negative pressure. Set back also reduces the heat input and prevents abrasion from particles in gas stream.

Thermal barrier: A layer of insulating material designed to reduce the surface temperature at the gas sealing layer to a level compatible with its heat resistance capability.

Thermal movements: Movements created within the duct system by thermal expansion. Can be axial lateral or torsional.

Torsional rotation: The twisting of one end of an expansion joint with respect ot the other end about its longitudinal axis. Such movement being measured in degrees same as angular rotation.

Vulcanized splice: A splice that is bonded with heat and pressure.

Welding blanket: A fire resistant blanket that is placed over the expansion joint to protect it from weld splatter during field welding operations.

Weld in baffle: A baffle that is designed to be welded to the duct wall. This design can be either signal or double acting type.

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