Definition – Rubber Expansion Joint
A rubber expansion joint is a flexible connector fabricated of natural or synthetic elastomers and fabrics and, if necessary, metallic reinforce-
A rubber expansion joint is a flexible connector fabricated of natural or synthetic elastomers and fabrics and, if necessary, metallic reinforce- ments to provide stress relief in piping systems due to thermal and mechanical vibration and/or movements. Noteworthy performance features include flexibility and concurrent move- ments in either single or multiple arch type construction, isolation of vibration and noise resistance to abrasion and chemical erosion.
Engineering can solve anticipated problems of vibration, noise, shock, corrosion, abrasion, stresses and space by incorporating rubber expan- sion joints into designed piping systems.
Rubber expansion joints isolate or reduce vibration caused by equipment. Some equipment requires more vibration control than others. Reciprocating pumps and compressors, for example, generate greater unbalanced forces than centrifugal equipment. However, rubber pipe and expansion joints dampen undesirable disturbances including harmonic overtones and vibrations caused by centrifugal pump and fan blade frequency.
This is based on actual tests conducted by a nationally recognized independent testing laboratory. Rubber expansion joints reduce transmission of vibration and protect equipment from the adverse effects of vibration.
Dampen sound transmission
Subsequent to going on stream, normal wear, corrosion, abrasion and erosion eventually bring about imbalance in motive equipment, generating undesirable noises transmitted to occupied areas. Rubber expansion joints tend to dampen transmission of sound because of the steel-rubber interface of joints and mating flanges. Thick-wall rubber expansion joints, compared with their metallic counterparts, reduce considerably the transmission of sound.
Compensate lateral, torsional and angular movements
Pumps, compressors, fans, piping and related equipment move out of alignment due to wear, load stresses, relaxation and settling of supporting foundations. Rubber expansion joints compensate la- teral, torsional and angular movements-preventing damage and undue downtime of plant operations.
Compensate axial movements
Expansion and contraction movements due to thermal changes or hydraulic surge effects are compensated with strategically located rubber expansion joints.
They act as helix springs, compensating for axial movements.
BBV Tech is able to design and manufacture rubber expansion joints strictly in accordance with actual specification. Cooperation with qualified pro- ducers of textile fabrics and rubber compounds allow BBV Tech to keep a high standard level of quality and reliability.
Minimal face-to-face dimensions
Minimal face-to-face dimensions in rubber expansion joints offer untold economies compared with costly expansion bends or loops. The relative cost of the pipe itself may be less or no more than a rubber expansion joints; however, total costs are higher when considering plant space, installation labor, supports and pressure drops.
Rubber expansion joints are relatively light in weight, requiring non special handling equipment to position, contributing to lower installation labor costs.
Low movement forces requied
The inherent flexibility of rubber expansion joints allows almost unlimited flexing to recover from imposed movements, requiring relatively less force to move, thus preventing damage to motive equipment.
Reduced fatigue factor
The inherent characteristics of natural and synthetic elastomers are not subject to fatigue breakdown or brittleness and prevent any electrolytic action because of the steel-rubber interface of joints and mating flanges.
Reduced heat loss
Rubber expansion joints reduce heat loss, giving long maintenance free service. The added piping required for loops contribute to higher operating costs after going on stream due to increase in heat losses.
Corrosion, erosion resistant
A wide variety of natural, synthetic and special purpose elastomers and fabrics are available to the industry. Materials are treated and combined to meet a wide range of practical pressure-temperature operating conditions, corrosive attack, abrasion and erosion. Standard and special sizes of rubber expansion joints are available with TFE/FEP liners, fabricated to the configurations of the joint body, as added insurance against corrosive attack. Teflon possesses unusual and unique characteristics of thermal stability, non sticking surface, extremely low coefficient of friction and resistance to practically all corrosive fluids and forms of chemical attack.
Elastomeric expansion joints are supplied with flanges of vulcanized rubber and fabric integrated with the tube, making the use of gaskets unnecessary. The sealing surfaces of the expansion joint equalize uneven surfaces of the pipe flange to provide a fluid and gas-tight seal. A steel ring spacer may be required for raised face flanges.
Elastomeric expansion joints significantly reduce noise transmission in piping systems because the elastomeric composition of the joint acts as a dampener that absorbs the greatest percentage of noise and vibration.
Greater shock resistance
The elastomeric type expansion joints provide good resistance against shock stress from excessive hydraulic surge, water hammer or pump cavitation.