How Long will my Gasket Last?
Whenever our team visits a client, we are always asked the same perennial question "How Long will this Gasket last?" The inconsequential gasket has long been a reason for frequent maintenance, unscheduled shutdowns and jugaad engineering. In this analysis, we try to identify exactly how long does a Gasket survive the application conditions.
Shelf Life or Service Life- The difference
Shelf Life is storage life of the Gasket in your stock. Service Life is the application or performance based life of the Gasket once installed. It is important not to confuse or use these terms interchangeably. Maintenance Heads care about Service Life as a longer performance gaskets can reduce their headaches. Procurement Managers prefer longer Storage Life so there is value derived from stocking on Spares. Usually, the Gasket life is a balance between the two.
Original Equipment Manufactures (OEMs) prefer longer service life in order to improve the reliability of their machinery. Maintenance Repair and Operations (MROs) prefer longer shelf life so there is always a backup option whenever there is a requirement. The lack of service expectancy is compensated by adding frequent replacements to their maintenance scheduled.
The ISO 2230 "Rubber Products: Guidelines for Storage" is a great reference point for Shelf Life that identifies the storage life based on the polymer used. Under appropriate storage conditions, the storage life is as follows:
- Natural Rubber / Synthetic Rubber: 2years.
- Nitrile / Hypalon (CSM): 3 years
- EPDM: 4years.
Do note the fine print: "appropriate storage conditions" which are practically extremely difficult to adhere in India. Storage Temperature <25 Deg C. No direct Sunlight or left in the open. Dry Atmosphere, max 65%. Stored in UV Protective Packaging. Stored Flat and not in rolls. Very few or none of these conditions are available at a Storage level.
Failure to adhere to these "appropriate storage conditions" would mean a reduction by 50% to 75% in the overall shelf life of these products. This is why Rubber Gaskets kept on the shelf for long periods become brittle and hard and why they require just frequent replacements.
How to Increase the Life of the Gasket
There are Gaskets that require no maintenance for years (Engines, Compressors etc) and there are Gaskets that require replacements every 6months (Pipe Lines, Process Lines). One of the most overlooked factor affecting Gasket Life is Installation.
Gasket Installation is considered #1 key factor affecting performance. This involves ensuring lubrication of the load bearing surfaces but also calculating the actual torque required and using a torque wrench. Manual Torquing the bolt is going to initially seal but it wont offer the long life you require. Remember the torque required changes based on multitude of factors.
Selecting the right Material is also important. Using a Pure Rubber or an Elastomer Gasket require frequent maintenance. PTFE materials suffer from Creep and Flow hence you are restricted to their usage as Envelopes or in very thin thickness. Modified PTFE or ePTFE are better alternatives than Virgin PTFE especially in Sealing environments. Fiber Reinforced Gaskets (Aramid, Carbon, Mineral etc) offer a more balanced alternative to Rubber and PTFE Based Gaskets assuming it is within the application parameters.
Graphite Gaskets require metal Reinforcement and work but cannot be used due everywhere due to contamination fear and flange corrosion from leechable acids. Similarly using a Spiral Wound Gaskets in a Flange designed for Rubber will also result in frequent leaks since the Flange was not designed for heavy torque.
Correct Partner. Ensure you have the correct technical partner in place to help with Gasket Selection, Design Calculations, Thickness Selection and material development. It is not possible for your R&D department, or Maintenance Head to be briefed about every technological development in every equipment. It is usually your vendor or partner who must work to upgrade the overall life of the Gasket and as a result, the overall reliability of the Equipment.
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PILOT Gaskets and Engineers is a technical partner for Donit Tesnit (www.donit.eu) Europe.