Sticking PML Valves due to excess oil in system (Ammonia & Mineral Oil)

[Grizzly]

Hi Guys.
Long story cut short.
A customers plant was due to have been shutdown 2 weeks ago. When his new plant was due to go online.
Therefore probably for the last couple of years "We" have been fire fighting only, with an absolute minimum of maintenance being paid for!

Anyway his plant has 6 sets of plates which have hot gas injected into them at the end of a freeze cycle, using Pm valves.
These in the past have clagged up with mineral oil and started malfunctioning.
Resulting in them having to either be replaced or latterly stripped and cleaned before being put back online.
Has anyone come across some form of cleaner we could wash these valves in situ with?
We literally only have to keep the plant going short term.
So there is no hassle with the long term contamination.
Parts are subject to say -15c to + 30c approx.

Thanks Grizzly
PS. An oil drain is not an option!

[RANGER1]

Grizzly,
Lately have been using a couple or product in a spray can from auto spares shop.
Brake cleaner or degreaser.
Both seem to work well & degreaser very cheap, good for all cleaning of parts in & out of system.
Brake cleaner evaporates easily, so "if you spray it goes away".

We also use light scouring pad like for doing the dishes, to assist with removing "stubborn build up".

[Tycho]

I've had problems with oil in PM valves before, the solution that has worked for me is to drill a bigger "equalizing" hole in the actuator piston that opens the valve. from the factory it comes with a 1mm hole, and the problem have been that this hole gets "clogged" with oil, causing the valve to not close properly after a hotgas cycle. I find that a 2 or 3 mm hole in the actuator piston gives me a faster response time when the valve needs to close.

the is also a problem with the equalizing hole in the plug on the bottom of the valve which might keep it from opening properly, this is also remedied by drilling a bigger hole in the plug.

You don't say anything about what your specific problem is so I'm just going out on a limb here :)

[Tycho]

Maybe this explains it better :)
11517

[Grizzly]

Thanks Guys.
Brilliant suggestions,
Ranger, I was thinking of using wd40 however yours seems a better idea.

Tyco. You have cracked it in my opinion, I will let you know how I get on. A clever and practical solution to sticking pm valves.
Incidentally what program did you use to create the graphics?
They are very impressive, particularly the indicator arrows and comments.
I cannot give you any rep points yet, got to spread the love some more first!

Once again thanks guys, between the two sets of options. I should be able to help a genuinely nice customer keep his aged plant going.
Grizzly

[RANGER1]

Grizzly just to clarify, have you got a PM or PML.
As TYCO suggest pay particular attention to guide in bottom plug, as they can build up with junk as well as little vent roll pin.

[Grizzly]

A PML my friend.
I with My colleague are onsite from tomorrow for 2/3days.
I will let you know how we get on.
Grizzly

[Magoo]

Hi Grizzly
had a similar problem with an old PML that only partially opened, cleaning everything aggravated the problem. Came down to wear in piston barrel and piston ring with too must bypass, until I could a piston kit for it I actually blocked off the bleed hole in the piston and got it work in a fashion.

[Grizzly]

Hi Magoo.
A good point made, only knowing the history of this plant leads me to believe it is indeed Bleed holes.
Which is the crux of the problem.
We have swapped out all the aged Valves over the last couple of years.
I will remember your point though as it still could be relevant.!
Thanks.
Grizzly

[josef]

Dear colleagues, everyone has the right, but my experience is consistent with Magoo, drill a larger hole, Ok, you believe that the proper function of the system in the future, right?, Clean the spray-yes, but complete disassembly and cleaning piece by piece and many times repeat, mineral oil will float around for a long time in the pipeline, I think that Grizzly for you in the long run.

[RANGER1]

Interesting, does a
PML actually have a bleed hole in piston.
A PM yes PML & PMLX EVM is the bleed & usually hot gas to open through an EVM with restricting orifice.
Correct me if I'm wrong of course :)

[Tycho]

Thanks Guys.
Brilliant suggestions,
Ranger, I was thinking of using wd40 however yours seems a better idea.

Tyco. You have cracked it in my opinion, I will let you know how I get on. A clever and practical solution to sticking pm valves.
Incidentally what program did you use to create the graphics?
They are very impressive, particularly the indicator arrows and comments.
I cannot give you any rep points yet, got to spread the love some more first!

Once again thanks guys, between the two sets of options. I should be able to help a genuinely nice customer keep his aged plant going.
Grizzly

Hope it works out for you :)

The cutout of the valve I got from the danfoss web page, they have drawings similar to this for all their stuff on there, the arrows and text I added in a simple editing program :)

[Tycho]

Interesting, does a
PML actually have a bleed hole in piston.
A PM yes PML & PMLX EVM is the bleed & usually hot gas to open through an EVM with restricting orifice.
Correct me if I'm wrong of course :)

I think they all have a bleed hole through the piston as it's the only way to bleed the gas from the top of the piston back to the LP side so the valve can close.

The reason I started drilling out the bleed holes in the first place is because of the older systems we had, with a danfoss sv1 float valve on the pilot receiver, sometimes you would get liquid in the pilot pipe to the PM valve and it would take a long time to bleed off, causing the valve to stay open for too long and emptying the pilot receiver.

the hole on the bottom was because the dowel pin would sometimes get gunked up and after some experimenting I found that with a bigger hole the gunk would get flushed out somehow, or at least the valves didn't get gunked up anymore :)


one word of caution though, if you drill the hole too big, in some cases where the EVM is mounted on the valve, you might start an uncontrolled hammer.
This because when the evm closes and the main valve closes, the main valve gets slammed shut, this in turn jolts the EVM and it starts an ever worsening cycle of the valve machinegunning :)

[Grizzly]

Hi Guys.
I can confirm the bleed hole through the roll pin is totally relevant!
I can indeed also confirm that Rangers caution is valid.
As a PML does not have a bleed hole in the crown / periphery of the piston.
With the info posted last week, the restoration of all the plant was achieved and the customer was left producing Ice from all 6 plates.

Thanks Guys!
Grizzly