DESIGN & MATERIAL CONSTRUCTION
Our VBU type flanged Expansion Joints are designed to absorb vibration and reduce noise on pipelines connected to the vibration producing equipment such as pumps, compressors, turbines etc. They provide solutions for many problems related to mechanical vibration and have a higher pressure and temperature capacity than rubber bellows. Double ply bellows provide remarkable vibration absorption as well as axial and lateral (combined) deflection compensation capability and lower stiffness.
Stainless steel bellows (membranes) are designed according to EJMA coding system and manufactured according to European Standard EN:14917:A1.
VBU type Expansion Joints are finished with nickel plated carbon steel flanges (EN:1092/1-PN16 or BS4504-PN16). Stainless steel flanged version provides high corrosion and temperature resistance up to 550°C. Van Stone end configuration for swivel flanges provides complete stainless steel surface which is in contact with the fluid.
- Pump connections, vibration producing systems
- Low, medium & high temperature heating systems
- HVAC-R mechanical piping systems
- Industrial process & applications
- Steam & condensate pipelines
- All VBU type expansion joints are produced by fully penetrated TIG welding method according to Whitehouse’s approved weld procedures.
- VBU is type approved by hydrostatic pressure test at 1.5 times of the design pressure.
- PED 2014/68/EU approval and material certificates according to EN 10204 is available for all sizes on request.
- Tie rods are used for pressure thrust forces from the pump are not transferred to the piping.
- They have a compact design that reduces the waste of space.
- Performance reliability and increased service life of the pipe system and connected equipment.
- Unlike rubber expansion joints, the vibration absorbers are resistant against ageing, high temperatures and UV-radiation.
We strongly advise not to use expansion joints to manage pipe misalignments. Torsion (twisting) on bellows parts is undesirable and should be eliminated.
IMPORTANT TYPE DESIGNATION
INSTALLATION INSTRUCTIONS FOR AXIAL EXPANSION JOINTS
- Store in a clean dry area where it will not be exposed to heavy traffic or damaging environment.
- Care should be exercised to prevent any damage to the thin bellows section, such as dents, scores, arc strikes and weld splatter.
- No movement of the expansion joint (compression, extension, lateral offset, rotation) due to piping misalignment should be imposed.
- Any field pre-positioning should be performed in accordance with specific instructions which include both the direction and magnitude of movement.
- It is good practice to leave one flange loose until the expansion joint has been fitted into position. Make necessary adjustment of loose flange before welding.
- Anchors, guides, and pipe supports should be installed in strict accordance with the piping system drawings.
- The expansion joint, if provided with internal sleeves, should be installed with the proper orientation in respect of flow direction.
- Once the pipeline anchors or other fixed points are in place and the piping is properly supported and guided the expansion joint can be properly installed. At this point the shipping devices should be removed in order to allow the expansion joint to compensate for changes in ambient temperature during the remainder of the installation phase.
- Do not use chains or any lifting device directly on the bellows or bellows cover.
- Do not force-rotate one end of an expansion joint for alignment of bolt holes. Ordinary bellows are not capable of absorbing torque.
- Do not use cleaning agents that contain chlorides.
- Do not use steel wool or wire brushes on bellows.
No more than one expansion joint should be installed between two main anchors. If the thermal expansion of the pipeline is too big for a single expansion joint, the pipeline should be divided into sections with additional intermediate anchors.
ALLOCATING THE EXPANSION JOINTS
Where possible, expansion joints should be located as close as possible to one of the anchors to prevent the risk of buckling. Sliding guides & anchor allocations should be completed as shown below.
CONNECTING THE EXPANSION JOINTS
The attachment edges of the pipe should be smooth, clean and parallel to each other. Don`t use bellows to correct misalignment of pipes unless this has been considered in the design of the expansion joint.
Counter flanges should be placed vertically to the pipe axis.
Using the proper electrode, weld the expansion joint to adjacent piping. Damages caused by arc sparks through welding process should be prevented. Bellows must be protected by a wet towel or cloth during the welding.
Orient expansion joint flanges so that the bolt holes are aligned with the mating flanges.
Do not torque the expansion joint to match the bolt holes of the mating flange. This causes torsion on the bellows and will severely reduce the bellows capability during operation and may lead to premature failure of the expansion joint.
INSTALLATION INSTRUCTIONS FOR AXIAL EXPANSION JOINTS
Standard axial expansion joints are unrestrained expansion joints. Fixed points should be created so as to withstand pressure thrust and springing force.
CALCULATION OF ANCHOR (FIXED POINT) LOADS
Pressure thrust is the most important force encountered in pressurised pipe systems and if ignored or incorrectly calculated, it can have a major impact on the pipe systems and the anchors. Pressure thrust can`t be eliminated as long as the axial bellows movement exist in the pipeline, and it must be calculated very carefully. Bellows usually have a cross-sectional area, which is slightly larger than the pipe diameter due to the height of the convolutions.
This is very important as it should be taken into consideration when designing the fixed points. The effective cross section is given by the sketch below. Pressure thrust force is calculated by bellows mean diameter multiplied by the maximum system pressure as follows: always use maximum pressure that occurs, usually the test pressure.
Fp = P x A
Fp = Pressure thrust force [N]
P = Pressure [bar]
A = Bellows mean diameter area [mm2]
Flexible bellows can be compared to a steel spring in its flexible motion. The spring rate is an expression of the force required to compress or extend the bellows, or alternately its resistance to deflect, which is another factor to take into account when calculating loads on fixed points.
The amount of the spring force is dependent on the bellows spring rate and the amount of the bellows movement, which is calculated as follows:
F = K x X
F = Force [N]
K = Spring rate [N/mm]
X = Movement [mm]
POST INSTALLATION INSPECTION PRIOR TO SYSTEM PRESSURE TEST
A careful inspection of the entire piping system should be made with particular emphasis on the following:
- Are anchors, guides and supports properly installed in accordance with the system drawings?
- Is the correct expansion joint installed in the right location?
- Is the expansion joint flow direction and pre-positioning correct?
- Have all of the expansion joint shipping devices been removed?
- If the system has been designed for gas and is to be tested with water, has provision been made for proper support of the additional dead weight load on the piping and expansion joint? (Some water may remain in the bellows convolutions after the test. If this is detrimental to the bellows or system operation, means can be provided to remove such water.)
- Are all guides, pipe supports and expansion joints free to permit pipe movement?
- Has the expansion joint been damaged during handling and installation?
- Is the expansion joint misaligned? This can be determined by measuring the joints overall length, inspection of the convolution geometry and checking clearances at critical points on the expansion joint and at other points in the system.
- Are the bellows and other movable portions of the expansion joint free of foreign material?