Chemical / Petrochemical

A Guide to Choosing Expansion Joints for Chemical Processes.

Why are expansion joints important?

Expansion joints are critical components of chemical processing industry (CPI) piping systems to assist the safe transportation of chemicals at elevated temperatures and pressure. A piping system requires flexibility and compensation for thermal expansion and contraction, as well as absorbing vibrations.

Selecting the correct expansion joint will maximize production efficiency, joint lifespan, and operational uptime as well as maximising safety by avoiding wasteful leaks of process fluids. An Expansion Joint Survey can provide a detailed report with suggestions for optimum specification, better performance and longer joint life.

Placing Expansion Joints in Chemical Systems

Chemical piping expansion joints rely on good positioning and adequate support to ensure that the joints are working within design parameters for both safety and extending the periods between maintenance.

It is recommended that expansion joints should have anchor points as close as possible noting that even regular straight pipelines require anchors. Anchor points are particularly important where there is a turn or directional change. Good anchoring guides and supports ensure that the pipeline weight is supported to avoid additional stresses being carried by the expansion joint. If systems are unanchored, expansion joints must be supplied with limit / control rods to keep from over compression or elongation.

Here are three items to check when choosing expansion joints for chemical processes:

Anchoring System for Pipework

It is crucial to use high-quality, dependable anchors capable of withstanding expansion joint pressure thrust and pipe motion forces. The use of full thrust anchors will ensure that expansion joint function is maintained without overextending.

Chemical Pressure and Temperature

Pressure and temperature are the initial factors to assess when selecting expansion joint material type / CPI piping systems. There is a relationship between pressure and temperature, please consult our product manuals.

When pressures and/or temperature become too high, stainless steel or PTFE lined stainless steel is the preferred choice, which is ideal for steam applications. An exception to the rule is when caustic or acid materials are being transported, these may require stainless steel or PTFE expansion joints based on temperature and pressure.

Fluid type and concentration

When selecting an expansion joint, Proco Products, Inc. advises users to refer to the relevant Material Safety Data Sheets (MSDS) for the materials being transported before making a choice. After identifying the issues around pressure and temperature, consider concentration levels. For instance, an elastomer may tolerate a 5% concentration of a caustic substance but could degrade when exposed to a 20% concentration of the same substance. In such scenarios, stainless steel expansion joints may be necessary. Stainless steel expansion joints are the more appropriate choice for processes involving gases, as rubber expansion joints can be permeable.

Types of expansion joints

Rubber Expansion Joints:

Rubber expansion joints are made from elastomers like EPDM, nitrile, and neoprene, each offering varying degrees of resistance to chemicals, temperatures, and pressures. Rubber expansion joints are particularly useful in handling diluted acids, alkalis, and aqueous solutions. Key features are high flexibility, cost effectiveness, corrosion resistance, low or no maintenance and easy installation. Find out more about choosing rubber expansion joints by application.

PTFE Expansion Joints:

Within environments that require a non-reactive material, moulded PTFE or PTFE lined rubber expansion joints can withstand extreme temperatures, ranging from -20°F to +250°F to 400°F. With low permeability, PTFE also helps prevent leakage. PTFE is non-reactive making it valuable in areas where corrosive fluid is carried. Examples of use are in acid piping, effluent, chemical waste and areas such as brine piping.

Braided Pipe Connectors:

Braided metal hose pipe connectors are used to relieve stress and vibration, control noise and are an excellent choice to deal with pipeline misalignment. They can stand high operational pressure and temperature and are used with compressors, pumps and other heavy process equipment. They may also be made of other metals other than stainless steel, such as copper. Proco Products, Inc. design and manufacture leading Braided pipe connectors which support the internal hose to withstand pressure whilst allowing necessary movement.

Pipe Penetration Seals:

Pipe penetration seals provide a robust, watertight seal for pipes passing through walls, floors, or tanks, ensuring efficient system performance helping to protect against air leakage, water ingress and they can also support fire control. 

Fabric Expansion Joints

Fabric expansion joints are suitable for lower pressure applications and can handle large amounts of thermal movement. They are constructed from layers of heat and chemical-resistant fabrics and can be designed to suit a wide range of chemical environments. These joints are particularly effective in handling exhaust gases and are commonly used in ducting systems of power plants and other industrial settings.

Life expectancy

By taking care to properly specify a chemical process expansion joint you can extend its lifetime, reducing maintenance and avoiding premature failure by factors such as pressure, temperature, aggressive or abrasive materials flow, weather exposure or extensive movement outside of design capabilities.

Whilst a rubber expansion joint has an average lifespan of 7-10 years, depending on the application, incorrect specification or extreme use can reduce this to a matter of months, whilst other joints might function well for 25 years or more.

Using the “STAMPED” Method for Selecting Expansion Joints

When selecting expansion joints for the chemical process, the STAMPED method provides a thorough checklist for specifying the expansion joint required:

Size – the diameter and pipe thickness of the pipes under consideration.

Temperature – the process temperature, variability, rate of change and maximum temperature.

Application – the equipment connected and environmental consideration where the joint is placed. Assess the pH of the chemicals being transported whether acidic, basic, or neutral.

Movement – assess the support needed and the magnitude and type of movement of the expansion joint and its effect on the surrounding pipework and equipment, for example, compression, expansion, level of vibration, lateral movement and other motion.

Pressure – assess the range of pressure variance.

End fittings – check how the pipes are capped.

Delivery – confirm how the expansion joints will be installed.

Guide to Rubber Expansion Joints and Use

Here is a helpful guide to selecting rubber expansion joints by application: 

Molded PTFE Expansion Joints

Convoluted PTFE expansion joints are used where there is a need to resist corrosion or chemicals whilst accommodating movement in a pipe

Series  231/ET Lined Expansion Joints

Lined expansion joints are designed for tough, demanding, corrosive chemical applications such as chemical and petrochemical process facilities and highly corrosive industrial piping and pollution control systems.

Wide Arch Spool Type Expansion Joints

Wide-arch expansion joints are specifically constructed to reduce or eliminate common occurrences such as noise and vibration, misalignment/offset, or turbulence. 

 

Chemical Process Application	440 Convoluted PTFE	231/ET PTFE Lined Rubber	230 Rubber Expansion Joints	230, 271, 260, Reducing Expansion Joints	260 Rubber Expansion Joints
Acid Piping Expansion Joints	x	x
Brine Piping Expansion Joints		x		x
Carbon Graphite Expansion Joints	x
Caustic Piping Expansion Joints	x	x
Chemical Piping Expansion Joints	x	x	x
Chemical Waste Piping Expansion Joints	x	x
Chlorine Membrane Expansion Joints	x	x
Co-Gen Expansion Joints				x
Final Effluent Process (FEP) Expansion Joints	x	x		x
FRP Piping Expansion Joints	x	x		x
FRP Tank Connection Expansion Joints	x			x
Glass Lined Expansion Joints	x
Graphite Heat Exchanger Expansion Joints	x
GRE Piping Expansion Joints	x	x		x
Lined Steel Expansion Joints		x		x
Mag Drive Pump Expansion Joints	x	x		x
Non-Metallic Expansion Joints Chlor Alkali Expansion Joints	x
Pump Discharge Expansion Joints	x	x		x
Pump Suction Expansion Joints	x	x		x
PVC Piping Expansion Joints	x				x
VCM Piping Expansion Joints	x
Wastewater Plant Expansion Joints	x	x		x

 

Tips For Storing and Protecting Rubber Expansion Joints

• Store your expansion joint in a cool, dry location, face down on a pallet or wooden platform without any other boxes on top of the expansion joint or expansion joint box.
• Beware of welding splatter that can damage rubber material and use a welding blanket to protect against damage.
• Whilst it recommended not to insulate a non-metallic expansion joint, ensure that any insulation is removable for inspection of the expansion joint material and connection. Be aware that insulation must not restrict movement or allow heat to build up that would cause the joint material to exceed its rated capability.
• Inspect the mating flanges to ensure that they are clean before installing the rubber expansion joint.

Proco Products, Inc. understands the unique needs and demands that companies in chemical process industries face. Proco Products, Inc. operates worldwide and maintains one of the largest product inventories in North America.

For more information on expansion joints and check valves from Proco Products, Inc. and to check pricing and availability, contact us today or use our interactive PDF applications form.