Can New Oil Cause Seal Leaks?
"We are investigating an issue encountered by the maintenance team. When they shifted to a newer and better oil, the seals started to leak. It was determined that the oil in the cylinder was contaminated with metallic debris. Is the new oil the culprit or has it identified an issue in the piston cylinder?"
The costs associated with unexpected leaks are often enough to make you reevaluate several elements of your operation. Based on the information provided, it appears the problem involves seals and piston cylinders of a hydraulic system or a large reciprocating compressor. The answer to the question is that both issues could be contributing to the leaking seals along with a list of other factors. In any case, root cause analysis should be performed to help determine the source of the problem.
To help mitigate the issue of seal leakage and select the best solution, you must first consider the type of seals being used. There are four basic seal types: static seals (gaskets and O-rings), dynamic rotating contact seals (lip seals and mechanical end-face seals), dynamic rotating non-contact seals (labyrinth seals), and dynamic reciprocating contact seals (piston rings and rod packings), which are the type of seals discussed here.
The purpose of a seal is to keep contaminants out while keeping lubricants in. Dynamic reciprocating seals attempt to seal against a sliding metal surface. With every stroke, oil will leave the system, and contaminants will be pulled back in, so determining the cause of a seal failure can often be difficult and even harder to eliminate.
There are many factors that can affect sealing including the lubricant, temperature, pressure, shaft speed and misalignment. Most conventional oil seals are designed for low-pressure applications. Seals must also be continuously lubricated with a high-performing lubricant that has the correct viscosity and that is compatible with the seal material. Both the temperature of the oil and the environment should be assessed, as the temperature range cannot exceed the range of the seal elastomer. In addition, if the shaft and bore are misaligned, it will cause wear to be centered on one side of the seal. However, when selecting a seal, shaft speed is one of the most important factors and governs all the other factors.
What Are the Causes of Oil Seal Failure?
Running the engine consistently with a low oil level can make the seal too hot or dry it out so that it warps and starts leaking. Driving with an overheated engine may have the same result. Adding too much fluid can "blow out" a seal, especially on a transmission.
Seals are rather fragile and easily ruined by a ham-handed mechanic. It is essential to mount seals flush in the recess made for it and for it to be free of dirt or burrs. It's easy to destroy a seal by an errant slip of a tool when working on something else. A gouged, dirty or dented seal will probably leak.
Improper installation or removal of a seal might damage the seal "seat," causing the new seal to leak after installation. Use the proper seal puller and installation tools for any operation involving seal replacement.
Oil Seal Failure Checklist - Symptoms / Cause / Reccommended Action
A guide to why your oil seal / Rotary Shaft Seal may fail
The below Oil Seal Failure Checklist provides information about seals leakage to those involved in the application and maintenance of Rotary Shaft Seals. Identifying and correcting the cause of leakage will assist the trouble-free, efficient and extended operation.
There are two parts an Oil Seal / Rotary Shaft Seal where leakage can occur:
- The interface between housing bore and seal O.D
- Between the seal lip and shaft
The following Oil Seal Failure Checklist shows the causes of failure and the means of prevention. A poster version can be downloaded here
SYMPTOM: Oil Seal rotates with shaft
CAUSE: Seal O.D smaller than bore I.D
RECOMMENDED ACTION: Select correct size seal and replace
SYMPTOM: Oil Seal moves in axial direction along the shaft
CAUSE: Seal O.D smaller than bore I.D and caused by the rotating of shaft or the internal pressure
RECOMMENDED ACTION: Select correct size seal and replace
SYMPTOM: Seal installed in declining condition
CAUSE: The I.D of housing bore is undersized, incorrect means of installation causing the seal to be misaligned
RECOMMENDED ACTION: Ensure housing bore is correct size
SYMPTOM: The deformation of the metal case
CAUSE: Use of incorrect tool to install the seal
RECOMMENDED ACTION: Use correct installation tool
SYMPTOM: The damage on the case O.D
CAUSE: The finish of housing is not correct and / or incorrect means of installation
Dirt adhering to the seal O.D or the housing I.D
RECOMMENDED ACTION: Ensuring housing size is correct
Use correct installation tool
SYMPTOM: Lip worn seriously
CAUSE: Insufficient lubrication
Application design restricts lubricant access to seal lip
RECOMMENDED ACTION: Ensure sufficient lubricant
Change design to ensure seal lip is accessible to lubricant
SYMPTOM: Lip worn seriously
CAUSE: Inner pressure too high
RECOMMENDED ACTION: Change seal design to pressure type
SYMPTOM: Lip partially worn
CAUSE: Seal partially installed
T.I.R of I.D and O.D are too big
RECOMMENDED ACTION: Select seal which T.I.R is suitable
SYMPTOM: Lip partially worn
CAUSE: Seal misaligned in housing
RECOMMENDED ACTION: Ensure housing bore is correct
Use correct installation tool
SYMPTOM: Lip hardened worn and cracked
CAUSE: High temperature / shaft rotation speed / pressure
RECOMMENDED ACTION: Select a suitable compound type
Supply sufficient lubricant
SYMPTOM: Lip material swollen
CAUSE: Incorrect compound selection
RECOMMENDED ACTION: Select the correct compound
SYMPTOM: Lip scratched
CAUSE: The shaft surface is not smooth
Scratch caused by incorrect installation tool
RECOMMENDED ACTION: Let all the lip configuration clear Install seal correctly
SYMPTOM: Lip turning out
CAUSE: Incorrect installation
Inner pressure too high
RECOMMENDED ACTION: Lubricate the lip and shaft before installation
Use pressure type seal
SYMPTOM: Crack on the base of flex section
CAUSE: Inner pressure too high
Sudden pressure strike on the flex section
RECOMMENDED ACTION: Use high-pressure type seals
SYMPTOM: Spring dislodged from spring groove
CAUSE: Shaft chamfer is incorrect
Incorrect installation
The retainer lip is too short
RECOMMENDED ACTION: Finish the shaft chamfer and lubricate the shaft before installation
Be careful while installing
Change the seal design
(Oil-Seals-Failure-Checklist-Poster.pdf)
M Barnwell Service is one of the UK’s most trusted Manufacturer, Stockist and Distributor of Oil Seals / Rotary Shaft Seals. For more information about our range and to talk to an expert contact the team today.
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