Tag Archives: expansion joints

Coal-Fired Power Vacuum – The Importance of Flexible Piping Products

It’s no news that coal-fired generation is going by the way-side.  Despite a recent resurgence in political support, coal is fighting an uphill battle on two major fronts: economically and environmentally.  After the shale gas boom in the 2000’s, plummeting natural gas prices and rising environmental concerns have continued to make operating aging coal-fired plants less and less attractive – for owners and consumers alike. The recent slowdown issues with the pandemic are only exacerbating the conditions – as industrial and commercial sectors are the greatest consumers of electricity.  With only the cleanest and most efficient plants left in operation (in 2010 coal generated 45% of the nation’s electricity, compared to 24% by the end of 2019) and the rest quickly moving towards eventual closure, we are witnessing a tremendous shift take place.  So how is this shift going to resolve and what should we expect?

picture of cooling towers

Long-Term Changes

Fortunately for us in 2020 – the shift away from coal has been happening long enough that new generation capacity has already been under construction and is coming online just in time to replace the retiring coal plants.  The economic downturn effecting industry has showed an acceleration in these trends – but natural gas and renewable outputs have been rising to pick up the slack for over a decade.  In fact, the U.S. has been somewhat lagging behind in terms of progress towards renewables with some European countries already shutting down the last of their coal-fired plants.  Though domestic renewables are indeed growing significantly – having nearly doubled in power production in the past ten years, and are expected to double-over again and overtake natural gas by 2050. Continue reading Coal-Fired Power Vacuum – The Importance of Flexible Piping Products

Case Study: Water Treatment Style 206 Expansion Joint

picture of style 206 expansion jointFacility Issue:

In a brine concentrator, an original competitor’s expansion joint failed upon start up.


Water Treatment

Background of the Facility:

This facility is a Zero Liquid Discharge (ZLD) power plant. Water is initially pumped from a well, pre-treated, used as process water, then reclaimed and retreated with a Brine Concentrator for use in their cooling towers. No city water is used and no waste water is disposed of from the site.

Brine concentrators use thermal energy to evaporate water, which is subsequently condensed and discharged as clean distilled water.

Brine Concentrators are also used in water treatment facilities in desalination plants, mining operations and well drilling operations in the oil & gas industry.

  1. Size: 24 “x 10” FF
  2. Temperature: 221° F
  3. Media: Brine Slurry
  4. Pressure: 30 psi


The original expansion joint unfortunately failed catastrophically without warning on start up. After consultation with the OEM of the Brine Concentrator, the recommendation was that only Garlock Expansion Joints be used for this aggressive application. The original expansion joints were replaced with Style 206 expansion joints which are built with a 4 to 1 safety factor.

Value Proposition:

Upon start up, Garlock Style 206 expansion joints offered superior performance, reliability and service life. This in turn improved plant safety, increased the mechanical integrity of equipment, and allowed Garlock’s customer to gain a competitive advantage in the market place.

The original article was featured on Garlock’s website and can be found here.

Gallagher Fluid Seals is an authorized distributor of Garlock gaskets, packing, expansion joints, and more.

For more information, contact Gallagher Fluid Seals today.


Case Study: Style 204 Expansion Joint w/ GUARDIAN® FEP Liner – Paper Mill

Garlock Style 204 Rubber Expansion Joint

picture of style 204The Style 204 family of spool-type expansion joints are manufactured with the industry standard narrow arch design. This style is intended to be used in dynamic conditions where both pressure and vacuum concerns are present.

Features and Benefits

  • Fully laboratory and field tested for long life and exceptional reliability
  • High pressure and vacuum resistance offer increased safety and ensure suitability for a wide range of applications
  • Single and multi-arch designs are available for a range of movement capabilities
  • Concentric and eccentric reducing configurations can be provided to join piping of unequal diameters
  • Available in a variety of elastomers and fabric combinations to meet the varied demands of temperature, pressure, and media

picture of paper mill


Pulp and Paper


Large South Eastern Paper Mill


A U.S. paper mill experienced multiple failures of expansion joints on the knotter screen pumps in the fiber area of the plant. The failures caused significant downtime and posed a safety hazard to employees working in the area.


  • Size- 24”ID (DN600)
  • Temperature- Less than 250°F (120°C)
  • Application- Knotter screen feed pump
  • Media- Black liquor with wood fiber
  • Pressure- Less than 65 psi (4.5bar)


A field survey determined that the expansion joints were experiencing significant elongation during installation. It was also evident that the pump and pipe flanges were not in parallel, creating angular misalignment. Additionally, the expansion joints were handling an aggressive media of black liquor and wood fibers, which collectively contributed to the failure.


Through on-site troubleshooting and surveying of the expansion joints, engineers were able to recommend and design an adapter plate for the pump flanges to realign the pump to the piping. This allowed the plant to standardize the replacement expansion joints to Style 204 with GUARDIAN® FEP liner to be used in multiple locations. In addition, the mechanical bond of the GUARDIAN® FEP liner provided greater reliability than the adhesive bond of competitive PTFE lined expansion joints. Replacement cost and frequency has been significantly reduced as a result of this engineered solution.

The original case study can be found on Garlock’s website here.

Gallagher Fluid Seals is an authorized distributor of Garlock. For questions about products or to learn more about rubber expansion joints, contact our engineering department.

Incorrect Uses for a Rubber Expansion Joint

Pay careful attention to these possible rubber expansion joint issues

What’s wrong with this picture?

A rubber expansion joint is likely the least understood and most abused component in a piping system. They are flexible, stretchy, and easily forced into lots of places despite what the installation instructions say. Most of the time, rubber expansion joints are merely an afterthought in a multimillion-dollar piping systems – until things go awry.

The rubber expansion joint is unmatched for vibration isolation. If properly installed, a rubber joint can greatly reduce equipment nozzle loads. Its resilience allows it to be installed in many different systems under a range of temperatures, pressures, and media. What could possibly go wrong?

Blame Murphy’s Law if you want, the fates, or the alignment of planets. The reality of most failures is more straightforward. Most of the time, it is installation. More specifically, not following the manufacturer’s instructions. See Images 1 to 7 illustrating the ugly aftermath of ignored installation instructions and unforeseen operating conditions.

Learn these lessons well so your piping system does not become the subject of another article.

Respect the Dimensions

picture of joint being compressed
Image 2

Sometimes flexibility is a disadvantage. Why? Because it is easy to compress a joint into a space that is too small, which is exactly the problem in this example. The bead was damaged as the joint was forced into a gap between flanges, resulting in a seal failure. Spherical expansion joints rely on this bead to form a seal between flanges. If the bead is damaged, the building engineer will curse your name for eternity. Do not violate the face-to-face dimensions of an expansion joint.

Alignment is Still Necessary

picture of joint between misaligned flanges
Image 3

Pipes misaligned? Think a bendy, stretchy rubber expansion joint will fix the situation? Thank again. This joint was installed between two misaligned flanges. A typical scenario may look like this:

  1. Joint installed between two misaligned flanges
  2. Joint begins leaking at the flange-to-flang seal in a week (or month, or several months)
  3. Bolts tightened, leak stops. In the meantime, the rubber bead takes a compression set, becoming less resilient
  4. Repeat steps 2 and 3 several times
  5. Bead is compressed to about 1/16th inch, rips apart from the body, pump room is now  a water park

Do not turn your pump room into a water park  or, even worse, a sewage tank. Align those flanges before installing expansion joints.

Consider Steam Generation

picture of failed expansion joint
Image 4

Did you know water pumps can generate steam? This operator did not. In this unfortunate scenario (Image 4), the operator closed the pump isolation valves with the pump operating, dead-heading the pump. This situation is fine for a short duration, but eventually all that mechanical energy added to the water has to go somewhere. It went into heat. The water contained in the pump and pipe up to the isolation valves had so much energy added, that it flashed to steam. The expansion joint was the first component to fail, which was fortunate for the pump. The temperatures and pressures exceeded the rubber performance limits and the joint failed, nobly sacrificing itself for the greater good of the pump and piping. Continue reading Incorrect Uses for a 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

Continue reading Custom Expansion Joints – Rubber

A User’s Guide to Expansion Joint Control Units

Expansion Joint Control Units

Elongation settings are a vital factor to assembly effectiveness.

Diagram of Control Unit and Control Rod Components

It is no secret that one of the greatest demands for an expansion joint is the expectation to serve a long, leak-free life with little-to-no maintenance. Once installed, these flexible rubber connectors should require little attention. The preservation of this investment (and one’s sanity) can be maximized with an in-depth overview of how control units can prevent a new expansion joint from being overstressed.

The purpose of a control unit is to act as a safety device against excessive movement resulting from pressure thrust. A typical control unit assembly is comprised of threaded rods, steel gusset plates, nuts and washers (see Images 1 and 2).Diagram of Effects of Pressure Thrust

The usage of control units with an expansion joint is always beneficial; pressure spikes during a system upset can cause uncontrolled surges through the expansion joint. This is a prime example of how valuable it is to have control units installed to protect these rubber assets from damage.

Methods to the Madness

A common misconception about control units  is that they are designed to support the weight of pipe members or act as a substitute for adequate mounting. They are not. The sole purpose of a control unit is to allow the expansion joint to move freely within a specific range of movement while preventing the joint from being overstretched from pressure thrust forces.

The control units in no way impede the joint from performing its other duties beyond movement  (vibration absorption, cycling or compensation for misalignment). The few extra steps needed to install the control units with the expansion joint could pay notable dividends in the long run.

Pressure thrust plays a huge role in how an expansion joint functions. While under pressure, the forces acting on the inside walls of the expansion joint actually cause the joint to swell and elongate. In the real world, an expansion joint is held comfortably between two pipe flanges, which in most cases are restrained by a pump lagged to the floor or mounted to a structural beam. Although it may not be apparent to the naked eye, once the expansion joint sees pressure, it produces a thrust force that acts axially on both pipe flanges.

Theoretically, what would be the result if the expansion joint was unrestrained on each end while pressurized?

Without fixed ends, the pressure thrust would force the joint to elongate without bounds.

Most useful in high pressure applications, the control rods will  engage with the gusset plates once a pre-specified amount of growth for the expansion joint has been reached, restricting the joint from stretching any further. At this point, the control rods are absorbing any additional thrust  acting on the pipe flange, thus limiting the amount of stress that is exerted onto adjoining equipment.

The design theory for sizing control unit hardware is based on the pressure thrust. Nominal inside diameter (ID) and arch geometry of the expansion joint are key drivers for calculating the thrust force that will be applied to the pipe at maximum line pressure. Per

Arch Diameter Diagram

industry standards set by the Fluid Sealing Association (FSA), both control rods and gusset plates are designed to withstand no more than 65 percent of the yield strength of the material.

Magnitude of the pressure thrust can be calculated by knowing the internal pressure and the effective area of the expansion joint. Effective area is found using the arch diameter of the expansion joint, which takes into account the size of the arch.

For example, we can calculate the resulting pressure thrust for a 10-inch ID expansion joint using an arch height of 1.5 inches that is rated for a maximum pressure of 250 pounds per square inch (psi).

The equation for pressure thrust “T” is:

Equation for pressure thrust

These design limitations based around yield stress are the reasons why some control units made from lower yield strength stainless steel contain thicker components or more rods per set than the standard carbon steel control units.

Installation & Inspection

For a control unit assembly to be effective, rod positioning and elongation settings are critical during installation. Each control rod should be evenly spaced around the flange to best distribute the load. Elongation settings (see Image 5) are often overlooked, yet are a vital factor to ensure the control units fulfill their intended use.

Every expansion joint comes with movement ratings based on arch size, configuration and number. These movement design ratings of the expansion joint are critical pieces of information that are absolutely required during the installation of control units. The general rule of thumb is the gap between the gusset plate and the nut should be adjusted to match the joint’s elongation rating.

Having this information at hand during installation is great, but what about the existing control units currently in operation? Visual inspections of these components are a basic task that goes a long way toward extending the life of the joint.

Here are the top 4 anomalies to look for when performing a field inspection: Continue reading A User’s Guide to Expansion Joint Control Units

Expansion Joint Failure Analysis

Failure Analysis - Rubber Expansion JointsGallagher 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.

Below is an except from the white paper, discussing failure analysis of rubber expansion joints, and what it can tell you about the overall health of your piping system.

Failure Analysis

There are perceptible warning signs when an expansion joint is failing:

  • Arch inversion indicating a system vacuum that has exceeded the joint’s specified expansion value.
  • Cracking at the base of the arch, which indicates the joint has been over-elongated and should be replaced with one of the proper length.
  • Ply separation on the outside of the cover. This is an indication the joint has been subjected to excessive movement.
  • Leakage due to over-expansion, mating flange surface issues, or poor installation practices, especially (but not limited to) bolt tightness.
  • Ballooning of arch, which indicates excessive system pressure.

Continue reading Expansion Joint Failure Analysis

How Important are Expansion Joint Surveys?

Expansion Joint SurveysGallagher 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.

Below is an except from the white paper, discussing design and maintenance of rubber expansion joints, as well as the importance of expansion joint surveys.

Elastomeric expansion joints are fabricated from natural or synthetic rubber and fabric, normally consisting of an inner elastomeric tube fused to a metal-reinforced fabric body and an elastomeric cover. These expansion joints accomodate greater pipe movement and provide greater abrasion resistance than metal expansion joints.

Expansion Joint SurveysThe proper design and maintenance of rubber (or elastomeric) expansion joints plays a major role in the overall preservation and lifespan of a piping system. They absorb movement, relieve system strain due to thermal change, stress, pumping surges, wear, or settling, reduce mechanical noise, compensate for misalignment, and/or eliminate electrolysis between dissimilar metals. Poorly functioning joints can lead to major deterioration of the piping system’s integrity, creating safety and environmental issues in your plant and processes. Visible signs of wear and fatigue – including exterior surface cracking, blistering, deformation and delamination, exposure to metal or fabric reinforcement, ply separation of the cover, rubber deterioration, and leakage – can alert observant users to potential failure.

Continue reading How Important are Expansion Joint Surveys?

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.

Metal Expansion Joints for High Temperature/Pressure

Expansion Joint Design Guide - Metal Expansion JointsGallagher 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 a section of our Expansion Joint Design Guide focusing on types of metal expansion joints.  To download the entire guide, visit our Resources Page, or click on the image to the right.

Much like elastomeric expansion joints, metal expansion joints are used to preserve the integrity of a piping system where the piping is subject to changes in temperature, pressure, vibration, compression, extension, cyclical movements or movements required by usage.

Oftentimes, metal expansion joints are used when an elastomeric joint simply cannot handle the extreme conditions – applications where high temperature, large temperature range, or high pressure exists. Generally, metal expansion joints can be used from -450°F to +2000°F, depending on the metallurgy, and can also handle pressures from full vacuum to 3,000psi.

Metal Expansion Joint Components

Though customized and intricate expansion joints can be manufactured for a variety of specialized applications, there are four basic designs that are most commonly used:

Metal Expansion Joints - Basic BellowsBasic Bellows

A bellows can be supplied without end fittings for field installation. The skirt, or straight portion at each end of the bellows, can be sized to fit a flange or pipe. Skirt length can vary depending on your needs and should be specified when ordered.

Metal Expansion Joints - Unrestrained SingleUnrestrained Single

An unrestrained single expansion joint is best used by piping systems which are equipped with proper guides and anchors to absorb axial, angular, and a small amount of lateral movement.

Continue reading Metal Expansion Joints for High Temperature/Pressure