Material for high pressure sealing in reciprocating service

[luizventura]

All

I am looking for an alternative material for a tri-ring seal used in a high pressure reciprocating equipment.
The equipment is an intensifier that works with 1800psi ethylene @-32°C (liquid) during suction stroke and 35000psi @50~60°C during discharge stroke.
The rings of the tri-ring seal design are:
- Solid ring- during discharge stroke seals against plunger and axially against a spacer, and during suction stroke seals axially against a spacer
- M'Ring - seals against plunger during suction stroke and remains under hydrostatic pressure during discharge stroke.
- Radial ring - it does not seal; it is just a ring to maintain the radial and M'Ring in their position.
The material of construction of the rings is a 80Cu/7Sn/12Pb alloy. This is the original (end of 70's) alloy and does not have a good performance regarding wear resistance and also has a low mechanical strength. The lubricant used is the UCON-PE-320 and the lubrication conditions are very severe, specially for M'Ring that operates under boundary to dry lubrication however it is never exposed to a bearing pressure of more than 7000psi and operates most of the time at near 2000psi. The radial ring operates under quasi-hydrodynamic lubrication.

 

[unclesyd]

UHP seals are considered an expendable component of intensifiers and the only way we have achieved an incremental increased in the life of some seals is by material changes. We have never achieved a quantum leap in seal life as we still use a riding mechanic on the intensifiers.

I would get with your intensifier manufacturer and see if he has anything new to offer. I would also checkout what is new with the waterjet industry as the machines are really proliferating.

Here is a breakdown of a seal similar to ours. There are several slight variations on this arrangement.

http://www.h2ojetcorp.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=302004-1&Category_Code=OSP

Here is another company that supplies PAG’s for compressors and intensifiers that we have used.

http://www.cpieng.com/

Anecdotal:
Most of the UHP sealing strategies , static and dynamic, have been around for many years starting in the 10's by P. W. Bridgman.

 

[EdDanzer]

Any seal becomes a dry bearing at the actual point of zero leakage. To solve your problem you will need a material with a yield strength higher than the lowest working pressure, design the shape to reduce contact pressure, and use materials that have a P/V value that matches the operating speed and seal contact pressure.
This is difficult and there may not be any materials that will work well. There is a material called ToughMet that might work.

http://www.brushwellman.com/alloy/products/copper_nickel_tin/copper_nickel_tin.asp