PM plans for high pressure check valves and relief valves

[Reifleman2]

I am not expecting a definitive answer to the following question, I simply want some recommendations concerning preventative maintenance on high pressure oil skid fittings.

I am writing a recommendation for a customer concerning some fittings that see on average 1100 psi in a clean service. I have the following fittings that saw some form of failure after being run for an unknown number of years without any preventative maintenance:

Parker R10PF Relief Valve, 150-2000 psi
Parker C2000S Check Valve
Static-O-Ring 9LC-KK45 Pressure Switch, 200-1500 psi

My initial idea is to simply tell them to replace them all every 5 years, but that's not really based on any data or logic (other than my own). Anyone have experience with check/relief valve and pressure switch failures to know a good way to PM them? This oil skid is a critical part of a very large system and needs to be properly regulated.

I am also contacting Parker to see if they have any recommendations.

Thanks in advance

 

[LittleInch]

I have a few questions before I give my opinion on this to hopefully start a bit of a discussion.

What constitutes "failure"? Is is mechanical failure (cracking, breaking etc) or failure to perform or faiure to seal?
what were the settings vs normal operation?
Where there repeated shocks / reverse flow / transient events?

PM on items which don't move and are normally supposed to be non operational is difficult, but if specified and operated correctly should last the design life of the equipment.

You probably know all this so I apologies if it comes accross the wrong way, but it's the only way I can see to answer the point.

Relief valves tend to fail in terms of passing product due to operating very close to the set point (chattering) or short bursts of high pressure. In terms of PM, you could instigate a removal and strip down on say a 5 year basis and an annual presusre set point check in-situ using a dead weight tester, assuming you can isolate the valve and plug in a test connection.

Check valves should operate for ever unless they are subject to repeated sudden flow reversal when they can break or fail to seal or have dirty fluid or waxed up. There is no real alternative other than removal and repair or replace, but no time period is normally specified. Check valves should only ever be a back up to isoation valves and not relied on to seal (IMHO), but simply reduce reverse flow to a low amount.

Pressure switches are much the same as relief valves. They should work without issue unless thay have been abused. Most switches now are actually transmitters fitted with internal switches to provide a switch type contact (on/off) and again as with the relief valve, an annual check on calibration and switch set point accuracy is about all you can do. If the set-point is critical there are normally at least two or more to provide back-up and voting to stop spurios trips, but alos try and eliminate single point failure.

Hope you find this sueful, but would be good to know the answers to the questions at the top of this post.

LI




My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Reifleman2]

I am never insulted when I'm begging for information

To answer the questions:

What constitutes "failure"? Is is mechanical failure (cracking, breaking etc) or failure to perform or failure to seal?

The failure is in terms of the inability to function at a set-point. These parts are on a set of pumps regulating pressures down to ~1100psi. When the regulators and relief valves stop functioning properly (accurately), the whole system becomes unreliable and can cause bigger failures with the systems they are supporting. (Without disclosing too much, this is pipeline application support systems for mechanical seals)

What were the settings vs normal operation?

Settings are as described above. Approximately 1100psi, but the pumps are capable of running upwards of 1800psi. Hence the need for regulators, reliefs and pressure switches.

Where there repeated shocks / reverse flow / transient events?

As with any system, it can happen, but typically no. This is a self contained support system supporting other pieces of equipment. It draws from its own reservoir and should (USUALLY) see standard operating conditions.



I think the biggest question I'm trying to answer is this: For guaranteed (99%, we're all engineers and understand there's no guarantee ) operation, how often should these parts be replaced? I believe their version of PM on parts like this is simply replacement, they don't have the time to be rebuilding small valves etc.

My thoughts (based on my own knowledge and your comments):

5 years, replace: Parker R10PF Relief Valve, 150-2000 psi
Never: Parker C2000S Check Valve
5 years, replace: Static-O-Ring 9LC-KK45 Pressure Switch, 200-1500 psi