MTBR for Dry Gas Seals

[RGRAJANI]

What is good value for MTBR of DGS ? 3 yrs ? 5 yrs ? 10 yrs ?

Do any one have MTBR records for DGS in Refinery/Gas plant/Petrochemical plant compressors ?

 

[JRLAKE]

Ten years is good but so is 1 year in a very difficult application.

Can you give more information?

 

[RGRAJANI]

JRLAKE, Application is for various centrifugal compressors - 5 to 30 MW rating, 3000 - 14000 rpm, 1 to 30 Bar sealing pressure, 4" to 10" seal size, fitted with Carbon type barrier seals.

 

[JJPellin]

I would never expect to see a failure of those seals. If the support system was properly designed and instrumented, the seal should last longer than the overhaul cycle of the compressor. At the compressor overhauls, the seals would be replaced just because they were removed for the overhaul. We don't have very many gas seals in multi-stage compressors, but we have never had a failure except when the seal support system failed (loss of buffer gas pressure).

Johnny Pellin

 

[JRLAKE]

I have seen many vibration failures of these seals. Mostly from improper balance. I have also seen a lot of these fail due to improper installation. If you have had excessive failures I would save a failed seal and show it to a good seal vendor. A good mechanical seal vendor can usually determine the cause.

 

[longeron]

In a centrifugal compressor some OEMs will recommend service after about 5 years (usually time for a T/A anyhow). That is not due to face wear... that is due to limitations of elastomers. That limit also applies to storage. If you've got a compressor seal that has been sitting around for a while it is worth it to send the seal back to the mfg and have them refresh the O-rings. If your seal uses polymer rings/U-cups this may not apply. I am not certain what conservative shelf lives are for them. Your vendor should be able to help with that. But- you should check with your vendor anyhow. As much as these cost, they should be happy to find out for you.

 

[flexibox]

This may be a late posting but did you know that most dry Gas Seals failures are due to contamination! The first thing to do is to provide your seal vendor a Gas composition so that they can carry out a Gas Analysis to determine if any liquid will drop out during settle out conditions. Once this is established and the Gas panel is suitably designed to provide continious DRY CLEAN GAS these seals can run for many years trouble free. I have recently seen a seal that has been installed for 16years. Generally the shelf life of the elastomers is about 10 years however if you had a seal on the shelf for 6 years and had 5-8 years between T/A then you should have a health check which will include Oring change and Dynamic test. So providing that you create the right environment for the primary seal and the secondary seal the seals should provide trouble free operation before any overhauls. You must not forget the tertiary seals. if you contaminate the seals with lube oil then the seals will fail pre-maturely another form of contamination. Oil comming from the bearing is a common root cause of seal failures on some machines because of the lack of instrumention in the panel.

trust this helps a little.