Common Rubber Expansion Compensation Types and Their Uses.

Rubber expansion compensators are rubber expansion joints installed in piping systems to absorb thermal expansion and contraction. When temperatures are changed, pipes expand or contract and if not controlled this movement will create high pressure, deformation and failure of piping system. Rubber expansion compensators permit movement of piping system without compromising the leak-proof seal. These include also handling of lateral misalignment and change in angle of piping system. These rubber expansion compensators are used in HVAC / plumbing / power generation / marine applications, among others.

Different rubber expansion compensators types found in different fields will be compared and their uses investigated.

Bellows/cylindrical style compensators.

These bellows style rubber expansion compensators resemble a series of convolutions or molded rings. They are oriented along a system axis and can bear thermal expansion and contraction with linear motion relative to the piping system. They’re very nimble and can expand or contract to accommodate huge expansion or contraction.

Bellows typically contain rubber but can also contain other materials such as PTFE or other plastics. They may also be strengthened with metal cords or with plies embedded.

Tied Rubber Expansion Joints

Tied rubber expansion joints absorb lateral/angular offsets on piping systems. Such compensators may take the form of rubber bellows or a sleeve with two reinforced tie ends made of reinforced rubber or fabric. Such compensators are very common where pipes are out of alignment/crooked due to thermal expansion, sinking of support, sinking of ground, etc.

Tied compensators have advantages of lateral and angular movement without axial debris on the piping system. – Rubber Expansion Joints with Metal Reinforcement.

The compensators are usually operated in hot or very pressured pipes, pipes having abrasive medium, or other undesirable conditions. These involve rubber compensators with metal reinforced. Rubber expansion compensators have a tight sleeve/bellow shape and directional reinforcement in rubber form of metal cords, rings, plies etc.

The rubber expansion compensators are very versatile in application and effective in absorbing thermal expansion and contraction of pipes. Major applications include:

For steam and liquidsMiscellaneous

Rubber expansion compensators are used in residential and commercial heating ventilation air conditioning and plumbing systems where long runs of piping are subject to high temperature variations. Expansion compensators are necessary so that such long pipes will not be torn from the device to which they are connected due to the expansion and contraction stopping of the flow causing it to break. Cylindrical bellows-style compensators are usually supplied for HVAC applications, and tied rubber expansion compensators are more typical for plumbing systems where the rubber must be able to flex and otherwise accommodate other angular or lateral offsets.

As with HVAC and plumbing, the power generation industry including fossil fuel and nuclear power stations can not operate without rubber expansion compensators. They must be able to tolerate the thermal expansion of high temperature and high pressure piping, so these expansion compensators are often reinforced and, where necessary, combined with metal cords even when several plies of rubber are used. Rubber expansion compensators are applicable to all kinds of materials carried by pipes and are used in any industrial process including chemical processing, petrochemical plants and manufacturing.

The rubber expansion compensators are an important component of marine and offshore piping systems, as they accommodate the constant motion and vibration of ships, oil rigs and other similar structures. In addition the compensators are corrosion resistant and suitable for harsh saltwater application. Tied rubber expansion joints are preferred for marine applications as they allow for angular and lateral movement acceptance whereas high pressure and temperature resistant reefing rubber expansion compensators are preferred for the less specific offshore oil and gas installations. Neither type of compensators is applicable to the marine / offshore industries for externally resistant piping systems of weapons delivery systems, desalination / marine sewage treatment and fire safety management systems.

In selecting a suitable rubber expansion compensator for a given piping application the following factors must be considered:

Temperature ranges. There are different rubber types and therefore the compensators are manufactured for temperatures related to the rubber they are made from. What this means is the compensator must be selected based upon the expected temperature variations of the pipe to which it is connected, so the margin of errors should be small so as to stop temperature excursions outside the range of the expansion compensator.

Pressure rating. Different rubber compensators can tolerate different internal pressures, expressed as constant maximal internal pressure against rubber. More reinforced rubber compensators are suitable for high internal pressure applications such as power generation or mixed chemical process.

Movement Accommodation. Various expansion compensators are designed for movement within some parameter range, for example axial compression or extension, lateral offset or angular misalignment. Hence selecting the right type implies selecting the type suitable for the compensator type of choice and of the right size considering the parameters.

Which rubber materials are appropriate depends on the media (gas, liquid or mixed media) passing through the piping system.

Some media are incompatible with some rubber compounds and may degrade or fail the compensator over time.

Manufacturers specify specifications and ratings for rubber expansion compensators’.

They may include temperature ranges & pressure ratings, maximum allowable movement capacities and recommended applications for a given compensator.

Follow and consult those specifications throughout your work.

Proper sizing of compensator according to piping system dimensions and required movement is necessary.

Finally the compensator should be installed properly – alignment, anchoring and support. The compensator may fail prematurely or excessively stress the system.

All these factors taken together with advice from experienced professionals or manufacturers should allow facility operators to select a suitable and long lasting rubber expansion compensator.

Proper inspection and maintenance are the keys to safe and effective work of rubber expansion compensators.

A good maintenance program and prompt replacement can extend the service life of these compensators many times over and prevent a costly failure or downtime of the facility.

Inspection schedule

A schedule should be prepared based on the manufacturer specifications and knowledge of the operation of a given piping system.

Signs of wear, cracking, deformation or other damage to the rubber bellows or sleeve should be visually checked periodically.

Leak, misalignment or excessive or inadequate movement of the compensator should be interpreted as a warning.

O the service life of rubber expansion compensator is dependent on operating conditions, material choice and maintenance techniques. For example, in normal operation most rubber compensators last between 5 and 10 years and more than 50% fail within this period. Due to the variability of operation condition and external stress of the hose, temperature, pressure and movement cycles most manufacturers provide expectations regarding service life of their product.

Preventive storage and handling of rubber compensators are necessary for their damage free installation.

Storage – cool dry place away from direct sunlight/ozone.

Replacement: follow manufacturer’s guidelines to avoid damaging surrounding equipment; usually done by professionals

Following these practices, inspections, maintenance and replacement efforts will reduce downhill events and extend the life of rubber expansion compensators for years of safe operation.

Flexible rubber expansion compensators are useful devices to account for thermal expansion or contraction in a piping system. For optimal use of these devices, types, application areas and selection factors need to be understood. The proper compensator reduces risk and liability of stressed or deformed piping. Besides, proper maintenance/inspection and replacement of the rubber expansion compensator is very important to ensure a long-term performance and the value of a solution. Whether bellows style compensators for HVAC or tied-rubber joint for plumbing or heavy duty metal compensateators in industrial applications – selecting the right one and following best practices will ensure trouble free operation.

Signs of stress/wear should be checked regularly.

Maintenance where necessary to assure that supports are engineered and installed correctly supporting the pipes network.

Operations should follow best practices for making repairs and following recommendations from the manufacturer or other qualified personnel.

Also the support of each compensator should be the right size and load matched.

Pick the right compensator type for the application.