Parker EPR noise ----> help.

[mspanky]

Here's the situation:

Walkin cooler that is 1.5 years old running off a Parker, internally piloted, suction stop EPR.

Starting approx. 2 weeks ago, the valve began emitting a very loud, very annoying shreek as it modulates. Adjusting the pressure setting higher or lower stops the noise temporarily. The problem is the pressure range that causes the noise is 10psi covering the acceptable box temp.

Has anyone found a cure for something like this? I've heard the same noise elsewhere, but brief enough to not be a problem.

I would rather not guess a fix for this rather pricey valve. The evap. superheat is normal and stable. If the port size was too small / large, the noise would have started when the box was new.

Any suggestions??

[juneair]

I have found that the o-rings can stick slightly, causing the valves to shreek or whistle. An 0-ring kit is a cheap approach to try.

[mccool]

Call the Parker Reps at Refrigeration Components in B.C., they are usually very helpful.

[jjnelso1]

Hey, first post! You successfully dragged me out of lurk mode. I'm part of the engineering group with the Parker division that manufactures the valve in question.

Whistling or howling is a uncommon occurance for (S)Port EPRs in my experience. Usually noises like this are present only in high load/pressure drop situations. The fact that the noise started suddently without a change in operating conditions is also a bit curious. What are the suction and evap pressures? Is the noise intermittant or continuous?

Juneair- I'd like to hear which o-ring you replaced. Would it be the diaphragm o-ring? I think my first attempt at a fix would be a complete diaphragm kit.

McCool- You're right. The guys at RCC are very knowledgeable.

[R12rules]

Originally posted by jjnelso1
Hey, first post! You successfully dragged me out of lurk mode.

I bet your not Irish!
No Irishman could resist speaking up in that length of time ... even if he was promised free drink for the duration of his life!!!:D

[icemeister]

Welcome to the group....albeit belatedly. We hope to see a lot more of your input around here now that we know you're out there. ;)

Question:
Now that Parker and Sporlan are married, does that make you and Andy in-laws? :D

[icemeister]

If the pressure drop across the valve is substantial (like over 40-50#), I've been told that the noise is actually caused by the gas velocity through the valve exceeding Mach1.....essentially a sonic boom. I recall an equation regarding the maximum velocity for an orifice flow involving the speed of sound and square roots and such.

Lay some techno-stuff on us. ;)

[Andy Schoen]

Originally posted by icemeister
Welcome to the group....albeit belatedly. We hope to see a lot more of your input around here now that we know you're out there. ;)

Question:
Now that Parker and Sporlan are married, does that make you and Andy in-laws? :D

Probably... but I'm the better looking one :D

We are currently transitioning the Sporlan ammonia product line to Joe and his group, and I need to get better acquainted with the Flo Con PRVs.

When Joe reaches my age (well after I've retired), he may well become the Sporlan answer guy here :)

[jjnelso1]

Originally posted by icemeister
If the pressure drop across the valve is substantial (like over 40-50#), I've been told that the noise is actually caused by the gas velocity through the valve exceeding Mach1.....essentially a sonic boom. I recall an equation regarding the maximum velocity for an orifice flow involving the speed of sound and square roots and such.

I'm like Andy's long lost cousin that only comes around when he needs money. We only speak when I need help and it happens altogether far too often.

Ice- I'm no fluid dynamics expert, but I'm fairly certain that we're dealing with flows that are subsonic. Valves do have a critical pressure ratio (outlet/inlet ~.5) where vapor flows will become "choked", presumably reaching sonic velocity at the vena contracta (how's that for techno-stuff). Liquid flows (near saturation) are a bit more complicated, but that's Andy's territory. Supersonic flows can be acheived using converging/diverging nozzles, but I've never heard of this phenomenon in valves.

Sometimes noises are emitted from valves for very mysterious reasons. We've addressed this a few times before. Perhaps it has something to do with the frequency of the vortices shed by the flow as it passes through the valve trim. I think in this particular case that we may have excited the natural frequency of the diaphragm. Just a guess.

[Edited by jjnelso1 on 08-24-2005 at 12:34 AM]

[Andy Schoen]

Originally posted by jjnelso1
Sometimes noises are emitted from valves for very mysterious reasons.

That's a fact. :)

I agree with Joe. You're likely fighting either a sonic flow condition or resonance within the valve, the latter case probably more likely. I would check the valve sizing. If the valve can be downsized, I would do so, as it could resolve either of these problems. I believe internal parts kits are readily available for this purpose.


[Edited by Andy Schoen on 08-24-2005 at 02:01 PM]

[mspanky]

Well, here's some more info.

The SPORT II is now set to 62psi with the suction line staying mostly between 45-55 psi. I ended up increasing the TxV superheat in the range of 15-20F (was at 10) and lowered the EPR setting by a few pounds.

It hasn't made any noise in a few days whereas prior adjustments only lasted minutes. If it happens again, I will rebuild the valve.

Question: Can the mounting position of the valve possibly affect its noise? I'm guessing no, but I thought I would ask anyway.

The valve was sized for 14.0 MBH at +20F. I can't remember if the port size is on the valve or not, but I will find out.

[Edited by mspanky on 08-25-2005 at 08:01 PM]

[Andy Schoen]

Your scenario makes sense. Lowering the pressure drop across the SPORT II valve solves the problem, which means either the sonic flow or the resonance condition could apply. I suspect the latter, which would argue for downsizing the valve, but I would not suggest until all the facts are known. I doubt a sonic condition could occur at say a 20 psi drop across the SPORT II at your conditions. Joe and I will get around to comparing our flow equations for this valve... :D


Originally posted by mspanky

Question: Can the mounting position of the valve possibly affect its noise? I'm guessing no, but I thought I would ask anyway.

I would put it low on my suspect list, but a resonance problem can be a funny sort of problem... :)

[mspanky]

Actually, lowering the suction drop across the valve, alone, did not cure the noise. The valve was still problematic until I increased the TxV superheat above what I would normally like to see.

I'm guessing the reduced mass flow is what did the trick.

[mccool]

Spankowski,
Is this a walkin on a rack or protocol?
Possible that the temp. control method has been altered to full temp. control vs. EPR style, this could potentially control the SPORT II solenoid if so and have influenced it's life cycle?. I am guessing rack, but field installed valve on multi circuited loop system/or not.:D

[jjnelso1]

This one is still a mystery to me. The changes you made altered both the vapor velocity and mass flow. I would have thought that changing the vapor velocity alone would have been sufficient.

I'm assuming R-404a based on the pressures you mentioned, but I don't think it has been explicity stated. If this is the case, you should have an 05 cartridge size. An oversized valve is one possible reason for the problem as Andy mentioned.

The reason I suspect the diaphragm as the noise source is that you mentioned that the condition occured after a period of time. The motion of the diaphragm is damped by a pair of o-rings and a gasket. I'm guessing that these could be wearing.

It sounds like you've solved the problem, at least temporarily. If you would like try a few things to rectify it completely, shoot me an email at jjnelson@parker.com