Tag Archives: rubber expansion joint

Custom Expansion Joints – Rubber

A flexible choice can adapt to permanent misalignment, preventing future damage.

Keeping aging facilities and equipment maintained is an ever-changing task that can jeopardize the goal of maximizing uptime. Years of thermal cycling, vibration or foundation settling can disorient piping or pumps. Piping engineers will use rubber expansion joints to account for these types of challenges in a rigid piping system. Permanent misalignment can set in after years of operation. The original-size expansion joint could no longer be the best fit when it comes time to replace.

Replacing a permanently misaligned expansion joint connection with the original part could lead to reduced service life and/or missed expectations of the new expansion joint. Determining the best way to accommodate this when it comes time to replace the existing expansion joint can have long-term effects on reliability. Since the original components may not fit in the newly disoriented flange connection, they are limited in their reliability.

Types of Customization & Benefits

Expansion joints are designed to withstand the pressure retention of rigid pipes, yet be flexible and absorb misalignment induced in these systems. However, there are limits to exactly how much flexibility can be absorbed before damage occurs. Using this flexibility to connect two misaligned pipe flanges will take away from how much movement can be absorbed during the actual operational period when the system is running.

Attempting to retrofit a standard-size expansion joint to connect a misaligned pipe connection can put excessive stress on the component and could lead to a shorter operational service life. For this reason, the Fluid Sealing Association (FSA) recommends no greater than ±1/8-inch misalignment of the pipe flanges during installation. Depending on the severity of misalignment, it can be advantageous to implement  custom expansion joints to minimize the stresses that cause these joints to fail or become damaged during installation.

Maintenance crews can also benefit by having a component that will fit precisely. Concerns for safety are present when attempting to put enormous pressure to compress, elongate or offset the joint so it will fit in place.

Face-to-Face Tailoring

Stress area stretched axially
Image 1. Stress area stretched axially during installation

Years of cycling, wear and other factors can contribute to the disorientation of a particular pipe connection. The length of an expansion joint, a dimension commonly referred to as face-to-face, bridges the gap between two parallel pipe flanges. A common industry problem is created when foundations settle and piping support structures transition lower than where it was originally constructed (Image 1). Expansion joints are designed to account for this, but choosing the correct replacement will make the difference between continued reliable service life or system failure.

Stretching an expansion joint to fit the changed flange connection often results in immediate damage that is only sometimes visual to the naked eye. A stress point on the outer cover of the expansion joint will usually become visible at the transition corner between the flat portion and the base of the arch in the form of a crack. The severity of cracking, elongation and settling will be aggravated when pressure in the pipeline is turned on.

Depending on nominal pipe size, industry standards will include standard face-to-face sizes of 6, 8, 10 or 12 inches, according to the FSA. When a standard 6-inch face-to-face joint is removed, the length between flanges could have been elongated to 7 inches or more. Many expansion joint consumers are not aware of the capability to build the expansion joint to the required nonstandard 7-inch face-to-face since it is not a standard offering. Building the replacement expansion joint to the nonstandard 7-inch face-to-face will eliminate any initial stress imposed on the joint.

picture of lateral expansion joint
Lateral offset expansion joint. and Angular offset expansion

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NEW! Expansion Joint Surveys & Failure Analysis White Paper

Rubber Expansion Joint Surveys & Failure Analysis White PaperGallagher Fluid Seals recently added the Rubber Expansion Joint Surveys & Failure Analysis white paper to our Resources page. This white paper discusses the importance of inspecting your plant’s expansion joints.  Proper design and maintenance of rubber expansion joints plays a major role in the overall preservation and lifespan of a piping system.

It will also discuss failure analysis of rubber expansion joints and some of the leading causes of joint failure.

Download your copy today, and contact our engineering department if you need assistance choosing the right expansion joints for your processes.

Rubber vs. Metal Expansion Joints

An expansion joint can relieve stress in piping systems and prevent flange gaskets from being crushed.  But which expansion joint is best for your specific application?  Let us first describe the two types of expansion joints:

Rubber — a flexible connector fabricated of natural and/or synthetic elastomers and fabric and, if necessary, internal metallic reinforcements designed to provide stress relief in piping systems due to thermal movements and mechanical vibration.

Metal — a flexible element (bellows) constructed of relatively thin gauge material (generally stainless steel) designed to absorb mechanical and thermal movements expected in service.

Advantages: Metal Expansion Joints

Expansion Joints - Metal
Typical Metal Expansion Joint

Temperature
Rubber joints with standard construction and materials have an upper range to 230°F. Most manufacturers, however, can offer special constructions up to 400°F. Metal expansion joints do offer a far greater range, from -420°F to +1800°F. However, working pressures are reduced at elevated temperatures.

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Now Available: Expansion Joint Design Guide

Expansion Joint Design GuideGallagher recently released its Expansion Joint Design Guide, now available for download on our site.  This design guide takes an in-depth look at elastomeric, metal, and flue duct expansion joints.  The excerpt below is the first section of our Expansion Joint Design Guide, diving into elastomeric expansion joints, and what to consider when selecting which joint is right for your application.  To download the entire guide, visit our Resources Page, or click on the image to the right.


What is an Expansion Joint?

Elastomeric Expansion JointAn expansion joint is a specially engineered product inserted in a rigid piping system to achieve one or more of the following:

  • Absorb movement
  • Relieve system strain due to thermal change
  • Reduce mechanical noise
  • Compensate for misalignment
  • Eliminate electrolysis between dissimilar metals (metal expansion joints)

They are built to expand, contract, and adjust without straining or breaking the piping or ducting on either side.  Essentially, an expansion joint is meant to protect the piping system from damage.

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