A faulty gasket is often blamed as the cause of a leaking joint. To verify this conclusion, the gasket in question should be withdrawn from service and subjected to a systematic physical examination. Thoroughly examining the gasket taken from a leaking joint can often uncover whether the gasket is truly at fault and, if so, what may be causing the gasket to fail. In this blog, we present some of the observations that are typically made when examining a leaking gasket.
Troubleshooting leaking gaskets: examining the physical evidence
When physically examining a gasket taken from a leaking joint, one should focus on the following aspects of the gasket:
The condition of the material.
The physical shape, circumference and dimensions of the gasket.
The cross-section and thickness of the gasket.
A good examination of the gasket can often reveal the cause of the leak. Below we describe some of the observations that are typically made when examining a leaking gasket that has been withdrawn from service.
Troubleshooting leaking gaskets: physical observations
When examining the condition of the gasket material, look for evidence of corrosion or other signs of degradation. Corrosion or material degradation is prima facie evidence that the gasket is not withstanding chemical attack from the application media. The remedy in this case is to choose a gasket material that can withstand the chemical attack and provide a leak-free seal.
Examining the physical shape and dimensions of a leaking gasket can often be instructive. Checking the overall gasket shape, to see if it is misshapen or “extruded” beyond its original dimensions, can indicate that the gasket has insufficient load-bearing capability and is being unduly deformed under load. To address this, choose a denser gasket material which can better handle the load-bearing force being applied.
Similarly, a gasket which has an irregular circumference or shape can indicate that mechanical load is not being evenly applied across the flange, causing shape distortion. It can also indicate an uneven or warped flange face. The corrective action is to check the flange face for evenness and to ensure that mounting bolts are evenly torqued around the flange.
Checking gasket compression is also important. In some cases, a gasket may be insufficiently compressed by the mechanical load applied to it, resulting in a poor seal. This can occur if the gasket is either too thick or is made from too dense a material. The remedy in this case is to select either a thinner gasket or one made from a less dense material.
Alternatively, a gasket may be unevenly compressed, indicating that an improper bolting-up procedure was performed at installation. The remedy is to ensure that the proper bolting-up sequence is followed when a new gasket is installed.
Check the thickness of the gasket to see if it varies around the circumference or exhibits evidence of being crushed. A crushed gasket indicates that the gasket has insufficient load-bearing capability. To correct this, choose a gasket material with a greater load-bearing capability.
A gasket whose thickness varies around the circumference can be indicative of a warped or misaligned flange face. Consider using a softer gasket material or examining the flange faces to see if they require machining or correction to bring the faces parallel.
While these observations are not exhaustive, they highlight some of the findings that can often be made when examining a leaking gasket. These observations can point the way towards the root cause of the leak and lead to an effective corrective action.
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