Rubber, Metal, PTFE, and Fabric Expansion Joints
Failure to follow the installation instructions may cause premature failure and/or rupture of the unit resulting in property damage, serious personal injury, or even death.
Ensure the expansion joint rating for temperature, pressure, vacuum and movements match the system requirements. Contact UIP International, Inc. for advice if system requirements exceed those of the expansion joint selected. Make sure the elastomer selected is chemically compatible with the process fluid or gas.
Expansion joints are not typically designed to compensate for piping misalignment errors. Piping should be lined up within 1/8”. Misalignment reduces the rated movements of the expansion joint and can induce severe stress and reduce service life. Pipe guides should be installed to keep the pipe aligned and to prevent undue displacement.
Solid anchoring is required wherever the pipeline changes direction, and expansion joints should be located as close as possible to anchor points. If anchors are not used, the pressure thrust may cause excessive movements and damage the expansion joints.
Piping must be supported so expansion joints do not carry any pipe.
Install the expansion joint against the mating pipe flanges and install bolts so that the bolt head and washer are against the retaining rings. If washers are not used, flange leakage can result–particularly at the split in the retaining rings. Flange-to-flange dimensions of the expansion joint must match the breech type opening. Make sure the mating flanges are clean and are flat-face type or no more than 1/16” raised face type. Never install expansion joints that utilized split retaining rings next to wafer type check or butterfly valves. Serious damage can result to a rubber joint of this type unless installed against full face flanges.
Tighten bolts in stages by alternating around the flange. If the joint has integral fabric and rubber flanges, the bolts should be tight enough to make the rubber flange O.D. bulge between the retaining rings and the mating flange. Torque bolts sufficiently to assure leak-free operation at hydrostatic test pressure. Bolt torquing values are available. If the joint has metal flanges, tighten bolts only enough to achieve a seal and never tighten to the point that there is metal-to-metal contact between the joint flange and the mating flange.
Ideal storage is a warehouse with a relatively dry, cool location. Store flange face down on a pallet or wooden platform. Do not store other heavy items on top of an expansion joint. Ten-year shelf life can be expected with ideal conditions. If storage must be outdoors, joints should be placed on wooden platforms and should not be in contact with the ground. Cover with a tarpaulin.
Large Joint Handling
Do not lift with ropes or bars through the bolt holes. If lifting through the bore, use padding or a saddle to distribute the weight. Make sure cables or forklift tines do not contact the rubber. Do not let expansion joints sit vertically on the edges of the flanges for any period of time.
Anchoring & Guiding the Piping System
It is generally stated that the proper location of rubber expansion joints is close to a main anchoring point. Following the joint in the line, a pipe guide or guides should be installed to keep the pipe in line and prevent undue displacement of this line. This is the simplest application of a joint, namely, to absorb the expansion and contraction of a pipeline between fixed anchor points.
Control Units Used in Restraining the Piping System Control units may be required to limit both extension and compression movements.
Control units must be used when it is not feasible in a given structure to provide adequate anchors in the proper location.
In such cases, the static pressure thrust of the system will cause the expansion joint to extend to the limit set by the control rods which will then preclude the possibility of further motion that would over-elongate the joint. Despite the limiting action that control rods have on the joint, they must be used when proper anchoring cannot be provided. It cannot be emphasized too strongly that rubber expansion joints, by virtue of their function, are not designed to take end thrusts and, in all cases where such are likely to occur, proper anchoring is essential. If this fact is ignored, premature failure of the expansion joint is a foregone conclusion.
Pipe sleeves or inside nuts can be installed on the control rods. The purpose of the sleeve is to prevent excessive compression in the expansion joint. The length of this pipe sleeve should be such that the expansion joint cannot be compressed beyond the maximum allowable compression.
The exact number of control rods should be selected on the basis of the actual design/test pressure of the system. Always specify the mating flange thickness when ordering control unit assemblies.
Control Unit Assemblies
When an elastomeric expansion joint with a control unit assembly is to be installed directly to a pump flange, special care must be taken. Make sure that there is sufficient clearance behind the pump flange not only for the plates, but also for the nuts, bolts and washers. In cases where there is not sufficient clearance, the control rod plates on the pump end can be mounted behind the expansion joint flange if the expansion joint flange has a metal flange. If the elastomer expansion joint has an integral flange with split retaining rings, this method is not usually recommended as the split retaining rings may not have enough strength to withstand the total force encountered.
Control Unit Installation
- Assemble expansion joint between pipe flanges to the manufactured face-to-face length of the expansion joint. Include the retaining rings furnished with the expansion joints.
- Assemble control rod plates behind pipe flanges. Flange bolts through the control rod plate must be longer to accommodate the plate. Control rod plates should be equally spaced around the flange. Depending upon the size and pressure rating of the system, 2, 3 or more control rods may be required.
- Insert rods through top plate holes. Steel washers are to be positioned at the outer plate surface. An optional rubber washer is positioned between the steel washer and the outer plate surface.
- If a single nut per unit is furnished, position this nut so that there is a gap between the nut and the steel washer. This gap is equal to the joint’s maximum extension (commencing with the nominal face-to-face length). Do not consider the thickness of the rubber washer. To lock this nut in position, either “stake” the thread in two places or tack weld the nut to the rod. If two jam nuts are furnished for each unit, tighten the two nuts together, so as to achieve a “jamming” effect to prevent loosening. Note: Consult UIP International, Inc. if there is any question as to the rated compression and elongation. These two dimensions are critical in setting the nuts and sizing the compression pipe sleeve.
- If there is a requirement of compression pipe sleeves, ordinary pipe may be used and sized in length to allow the joint to be compressed to its normal limit.
- For reducer installations, it is recommended that all control rod installations be parallel to the piping.
- Location: The expansion joint should always be installed in an accessible location to allow for future inspection or replacement.
Split Metal Rings
Retaining rings must be used to distribute the bolting load and assure a pressure tight seal. They are coated for corrosion resistance and drilled as specified.
The rings are installed directly against the back of the flanges of the joint and bolted through to the mating flange of the pipe. Steel washers are recommended under the bolt heads against the retaining rings; at a minimum at the splits. Rings are normally 3/8” (9mm) thick, but can vary due to conditions. The ring I.D. edge installed next to the rubber flange should be broken or beveled to prevent cutting of the rubber.
Additional Tips for Installation
- For elevated temperatures, do not insulate over a non-metallic expansion joint
- It is acceptable, but not necessary to lubricate the expansion joint flanges with a thin film of graphite dispersed in glycerin or water to ease disassembly at a later time
- Do not weld in the near vicinity of a non-metallic joint
- If expansion joints are to be installed underground, or will be submerged in water, contact UIP International, Inc. for specific recommendations
- If the expansion joint will be installed outdoors, make sure the cover material will withstand ozone, sunlight, etc. Materials such as EPDM and CSM are recommended. Materials painted with weather resistant paint will give additional ozone and sunlight protection
- Check the tightness of leak-free flanges two or three weeks after installation and re-tighten if necessary
- Inspect for damage during shipment, i.e. dents, broken hardware, water marks on carton, etc.
- Store in clean dry area where it will not be exposed to heavy traffic or damaging environment
- Use only designated lifting lugs
- Make the piping system fit the expansion joint by stretching, compressing or offsetting the joint to fit the piping, it may be overstressed when the system is in service
- It is good practice to leave one flange loose until the expansion joint has been fitted into position. Make necessary adjustments of loose flanges before welding.
- Install joint with arrow pointing in the direction of flow
- Install single Van Stone liners pointing in the direction of flow. Be sure to install a gasket between the metallic liner and Van Stone flange as well as between the mating flange and liner.
- With telescoping Van Stone liners, install the smallest I.D. liner pointing in the direction of flow
- Remove all shipping devices after the installation is complete and before any pressure test of the fully installed system
- Remove any foreign material that may have become lodged between the convolution
- Refer to EJMA standards for proper guides.
Expansion joints may operate in pipelines or equipment carrying units and/or gasses at elevated temperatures and pressures and may transport hazardous materials. Precautions should be taken to protect personnel in the event of leakage or splash.
Non-metallic joints should not be installed in inaccessible areas where inspection is impossible. Make sure proper drainage is available in the event of leakage when operating personnel are not available.
Flange Bolt Torque Specifications
When assembling flange connections, it is recommended that a full complement of clean, new and high-strength A193-B7 bolting is consistently utilized. When Stainless Steel bolting is used, it should consist of the following:
- A 320/A320M Class 2 B8 (304 SS)
- Class 2 B8M (316 SS) with A 194/A194M
- Grade 8 or 8A Nuts (for 304 SS)
- Grade 8M or 8MA (for 316 SS)
When other bolting materials are employed, user should ensure new bolting material strength properties exceed the calculated bolt stress values generated in establishing the piping connection.
The following practices are strongly recommended:
- Always utilized flat washers on both sides of the connection
- Ensure that the flange bolts are tightened with a calibrated torque wrench expressly for the specified bolt torques. Note: For anti-seize compounds, the torque values may vary. Please contact UIP International, Inc. for more information
- Firmly secure the flange bolts with a torque wrench utilizing a “criss-cross” pattern that alternately tightens the bolts located 180 degrees apart
- Employing the above mentioned pattern, tighten the bolts in 20% increments of the final bolt torque until 80% of the final bolt torque has been accomplished
- To tighten the final torque values, firmly tighten bolts sequentially clockwise one time around the flange. This procedure ensures the bolts have been evenly stressed
- Extreme caution should be taken to avoid over-torqueing which can result in damage to plastic sealing surfaces
NOTE: When bolting dissimilar materials, always tighten to the lowest recommended torque of the components in the joint. Employing higher torques may cause excessive deformation of the “softer” material contained in the joint. Position a ½” thick spacer between UIP International, Inc. PTFE-lined pipe or fittings and other plastic-lined components, particularly valves, should differences in the diameters of the raised plastic faces occur. *Belleville washers are not recommended for use with PTFE-lined products.
A retorque should be applied a minimum of 24 hours after the initial torque or after the first thermal cycle. Retorquing enables seating of the plastic and allows for the relaxation of the bolts. In the event that the system is intended to perform at elevated temperatures, hot water should be circulated at the maximum operating temperature of the process (if possible) for at least 24 hours. This process will allow the pipe system to experience one full thermal cycle.
After cool-down, retorquing of the system should be completed. Torqueing need only be completed on the system in the ambient, cooled state and never while the process is at an elevated temperature. This could cause excessive force to be exerted to the plastic faces. Never attempt to disassemble a flange joint in a hot system. Wait until the system has cooled to ambient temperature.
Typically after initial torque and retorque, a hydrotest should be carried out utilizing ANSI requirements. Experience has demonstrated that if the aforementioned procedure is adhered to, very few, if any flange joints will fail the hydrotest. If a flange joint leaks, first re-check the torque values and tighten in 10% increments over the specified bolt torques until completely sealed. If, however, 150% of the specified torque value has been reached and the flange joint continues to leak, stop the process and disassemble the flange joint. It is likely that something else is wrong, i.e, a scratched plastic face. The hydrotest must be successfully completed, and any existing leaks corrected before the pipeline can be approved and commissioned.
Regular inspection for leaks and periodic bolt tightening in accordance with good maintenance practice is recommended. Never attempt this process at an elevated temperature as damaging excessive force may be applied to the plastic faces.
Below are suggested Torque Values. The amount of torque required is different for all applications. They can change depending on media, temperature, pressure, material type, mating flange type and surface, specialty joints, if lubricant is used, installation offsets and environmental conditions.
Bolt Torque Values
Size = ft./lbs of torque
1″ to 2-1/2″ = 25 lbs. to 75 lbs.
3″ to 6″ = 40 lbs. to 85 lbs.
8″ to 12″ = 45 lbs. to 95 lbs.
14″ to 18″ = 50 lbs. to 110 lbs.
20″ to 28″ = 60 lbs. to 150 lbs.
30″ to 40″ = 75 lbs. to 200 lbs.
42″ to 48″ = 90 lbs. to 250 lbs.
Above 48″ to 144″ can vary greatly from 100 lbs to 500 lbs. depending on the application. See disclaimer above.
Additional Considerations for Metal Bellows Expansion Joints
Single | Double Metal Bellows Expansion Joints are designed to absorb a specified amount of movement by the flexing of the thin-gauge convolutions. If proper care is not taken during installation, it may reduce the cycle life and the pressure capacity of the expansion joints, which could result in a premature failure of the bellows element or damage to the piping system. The following recommendations are included to avoid the most common errors that occur during installation When in doubt about an installation procedure, contact the manufacturer for clarification before attempting to install the Expansion Joints.
Additional Considerations for PTFE Style Expansion Joints
- Do not remove flange covers (and spacer sleeves) until expansion joint is to be bolted into position or sealing forces may become warped or damaged.
- Limit bolts with elastic stop nuts are factory set at the maximum travel position to prevent over-extension. Severe damage or personal injury can result if the limit bolts and stop nuts are removed, replaced, or altered to exceed the factory setting, or if non-locking nuts are installed. Install expansion joint and nominal setting except, when used to handle hot material, the units should be installed at nearly extended length to permit compression when piping expands due to heat. If used in chilled line, install at nearly compressed length to permit piping to contract.
- Sealing faces of expansion joints and adjacent flanges must be clean and smooth. Sharp corners and burrs on adjacent flange faces, and any extended scratches in either face, should be removed with fine emery cloth. If surface irregularities cannot be completely removed, it may be necessary to install at 1/16” thick gasket to obtain adequate sealing. Gaskets are recommended when connecting to flanges of dissimilar materials.
- Do not install nuts or connecting bolt heads behind expansion joint flanges or accidental wrench damage may occur to the TFE element. Expansion joint flanges are tapped with thread sizes to accommodate ANSI class 150 or optionally glass pipe bolt sizes. At most, two bolt threads should extend behind expansion joint flanges to prevent interference and possible damage when expansion joint is compressed. Do not bore cut threads.
- Do not over tighten bolts
- Expansion joints should not be tested to more than 1-1/2 times the working pressure as indicated in the following pressure/temperature curves. Anchors must also be designed to withstand test pressure conditions and all anchors and guides must be installed and checked prior to testing.
Additional Considerations for Fabric Expansion Joints
There are a couple of fundamental considerations when deciding the type of expansion joint to be used:
Is it a new plant?
If this is the case, it is more easily possible to create an optimal solution with respect to economic and technological concerns.
Does the plant already exist?
If this is the case, your expansion joint may need to be designed to operate in less than optimal conditions.
Questions for consideration:
Is the location of installation easily accessible? Do you require scaffolding or other complex equipment to install the expansion joint? Is a crane or other heavy equipment necessary to lift the expansion joint into place?
It is imperative that these and other similar conditions be considered prior to selecting the expansion joint design. It is at this stage that determination should be made on whether the expansion joint should be supplied open, closed on site, or supplied as a pre-assembled unit.
The following movements, alone or in combinations, are compensated for by fabric expansion joints: Axial compression, axial elongation, lateral offset, angular offset and torsion.
The size and frequency of movements will affect the choice of expansion joint type. For large movements, convoluted and wave-form designs (moulded corners) or multi-layer expansion joints with scissor control guides should be used. They ensure that movements are controlled and help prevent damage to the fabric or heat pockets from occurring.
Fabric expansion joints can also compensate for vibrations and noise.
Consider the following when selecting an expansion joint: over stretching, abrasion by solid matter, hardened deposits and friction along the sleeve/baffle
Pressure affects the design (type of fabric and number of layers) of an expansion joint in the same way that temperature and medium do.
The following distinctions are made:
- Positive pressure (normal, peak)
- Negative pressure (normal, peak)
- Variations of pressure (pulsations)
- Pressure surges of design or operating pressure
To allow for greater flow efficiency, fitting a sleeve/baffle may be recommended. When flow rates exceed 10 m/sec., a sleeve/baffle construction can protect the expansion joint from flutter or pulsation. Elastomer expansion joints, however, do not require a sleeve/baffle even at flow rates of up to 40 m/sec.
The flow, or medium, is a major factor in the design of an expansion joint.
- Dust content (concentration, grain size)
- Chemical load by acids, solvents, etc. (type, concentration)
- Flue Gases
- From coal, oil, gas firing etc.
- Analysis of the flue gas (content of pollutants)
- Humidity (value below dew point)
- Contents of soot or fly ashes v. Flushing/washing of ducts
Varying temperatures play an important role in the design and construction of the expansion joint. The external covering materials are protected from thermal damage by the utilization of insulating layers; the thickness and number of layers depends upon the temperature.
The most important temperature values to consider are:
- Operating temperature
- Excursion temperature (duration, frequency)
- Variations in temperature (duration, frequency)
- Design temperature
- Ambient temperature
Expansion joint designs are typically dependent upon a given ambient temperature. Higher ambient temperatures can be tolerated by adjusting the thickness of the insulation accordingly.
Cover plates have been shown to provide an effective measure of protection against rain, snow, sand storms, and other forces of nature. They also protect the joint from falling objects and build-up of debris along the top of the joint.
Temperatures below dew point
When temperatures are below dew point, the resulting increase in humidity also increases the chemical load on the expansion joint, and the duct work. Temperatures may drop below dew point as a result of the process being utilized, the shut-down of the plant, or if the plant is at partial operating capacity.
When temperatures are below dew point, they will affect:
- Material choice for the purpose of chemical resistance
- Flange area design
Proper use of insulation inside the expansion joint, and around the joint frame’s external surfaces can be very effective in controlling the negative consequences of consistently cycling through dew point.
The manufacturer’s warranty may be void if improper installation procedures have been used.