rubber expansion joints
- May 07, 2021
During an initial expansion joint Preventative Maintenance and Reliability (PMR) Service performed at the paper mill, it was determined that several competitor joints required replacement. These pipelines carry water, pulp, black/white liquor, bleach, and CIO2.
Though recommended for replacement on the Garlock Preventative Maintenance and Reliability (PMR) report, the mill postponed purchase. To date, four of those items flagged for replacement have failed - with the most recent failure resulting in an administration building filling with 4 feet of pulp.
OPERATING CONDITIONS AT CUSTOMER FACILITY
- Size: Pipe- 1.5” - 48” ID
- Temperature: 70° - 250°F
- Application: Various throughout mill
- Media: Various throughout mill
- Pressure: Vacuum to 200psi
- January 21, 2020
Garlock Style 204 Rubber Expansion Joint
The 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
- January 10, 2020
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
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
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:
- Joint installed between two misaligned flanges
- Joint begins leaking at the flange-to-flang seal in a week (or month, or several months)
- Bolts tightened, leak stops. In the meantime, the rubber bead takes a compression set, becoming less resilient
- Repeat steps 2 and 3 several times
- 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
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.
- November 06, 2018
Gallagher 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.