Valves in Pistons, and Floating Piston design

[sms]

I have been looking at the floating piston design from Thomasson for recip compressors, and while it is certainly a different purpose it kind of reminds me of the Dresser VIP piston.

There were a few negative comments about the VIP in another thread, so I guess my question is, has anyone used the floating piston technology? If so how did it work out, and were there any problems with the valves in the piston failing? What about plugging off of ports?

BTW if you are not familiar with the technology, basically there are ports on the bottom of the piston, and gas is pressurized inside the piston using what looks like a standard compressor valve mounted in the piston face. The gas then flows out of the ports in the bottom to support the piston in the cylinder, making rider rings unnecessary. Sort of like air hockey...

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[tgmcg]

Wow, that sounds like a bloody awful idea.

The consequences of valve failure are a wrecked piston & liner. It's either working or tearing itself up...not much in between. Whereas conventional rider bands wear at a predictable rate and can be replaced before metal to metal contact occurs between piston and liner.

Stick with API designs and you'll be on much more solid ground.

I've dealt with Thomassen many times during my days as a machinery specialist with Shell in the Hague....25 years ago. They're a good company and make a good recip compressor.

 

[tgmcg]

My main objection to the FFP design is that most gas streams contain solid contaminants. Any design that involves the internal distribution of gas via small flow passages is prone to blockage. The design is non-lubricated nor does it appear to incorporate a standard wear bands as back-up or a fall-back option. So whaddya do if you discover that contamination is a problem....scrap the cylinder and start over??

Thomassen claims the design is "fail-safe" without explaining how....in view of the above, I have no idea how they can claim this.

They also claim the FFP design obviates the need for a spare machine. They completely ignore the need to repair/replace valves and rod packing, which the FFP design does nothing to address.

Such exaggerated claims detract from their credibility.

Better to let somebody else do Thomassen's R&D than risk your clients/employers operational reliability.



Best regards,

Tom McGuinness, PE
Turbosystems Engineering

http://www.turbosynthesis.com

 

[sms]

Yeah, and the application I am looking at is a gas stream with catalyst fines that wear out rider bands pretty quickly.

This design would be attractive, unless the ports plug up..

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[tgmcg]

Catalyst fines...hmmm...challenging application for a recip. I'd be concerned about solids accumulating inside the cylinder until such point that all end clearance is lost...and then something has to give. Valve life would be another issue.

I think I'd investigate installing some kind of liquid scrubber or hydrocyclone upstream to clean up the gas first.

Best regards,

Tom McGuinness, PE
Turbosystems Engineering

http://www.turbosynthesis.com