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#14970 - 05/21/15 02:44 AM Pressure Reducing Valve HELP
ktmtragic Offline
MBN member
Registered: 07/04/10
Posts: 233
Loc: Sydney Australia
I have a customer that has 4 ovens for cooking various types/varieties of meats. The system comprises of the four ovens having 2 inlets each of low and high pressure steam. My problem is the pressure reducing valves are failing frequently and the REP is saying "The installation is wrong" He is saying the pressure reducing valve on each oven should be AFTER the pneumatically controlled angle seat control valve. To my mind this would be worse as the high side pressure would go from nothing to max (on the inlet of the PRV) every time the control valve opened and it would fail sooner. I have searched the web but no luck.
Can you help?
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#14971 - 05/21/15 06:34 AM Re: Pressure Reducing Valve HELP [Re: ktmtragic]
Lu47Dan Offline
MBN Old hand
Registered: 02/14/10
Posts: 1108
Loc: N/W Pa. ****
Originally Posted By: ktmtragic
I have a customer that has 4 ovens for cooking various types/varieties of meats. The system comprises of the four ovens having 2 inlets each of low and high pressure steam. My problem is the pressure reducing valves are failing frequently and the REP is saying "The installation is wrong" He is saying the pressure reducing valve on each oven should be AFTER the pneumatically controlled angle seat control valve. To my mind this would be worse as the high side pressure would go from nothing to max (on the inlet of the PRV) every time the control valve opened and it would fail sooner. I have searched the web but no luck.
Can you help?

Couple of questions.
What are the pressures involved, it makes a difference.
Line or system.........
High pressure......
Low Pressure.......
Does the system bypass steam when the ovens are not operating?
If it is not bypassing steam does it have a drip before the PRV's?
Condensate setting in them can damage them.
Now then on to the Control Valve, does it "snap" open or is it a soft opening valve?
Opening steam valve too quickly can damage the system.
Spring driven closing on a control valve tends to soften the opening of the valve, but if it is pressure driven both ways than it can snap open.
Now if the rep is saying that the PRV's should be mounted after the Control Valve than get it in writing and change the location.
Going from zero to max pressure on the PRV's might not sound right but they might handle that better than being held at operating pressure all the time.
Just some ideas.


Dan.
_________________________
Tools are to Men as Shoes are to Women, you can never have too many!
Used diesel engines are an adventure anyway you look at them!
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#14983 - 05/25/15 12:39 AM Re: Pressure Reducing Valve HELP [Re: Lu47Dan]
ktmtragic Offline
MBN member
Registered: 07/04/10
Posts: 233
Loc: Sydney Australia
Hi Dan
Thanks for the response it is appreciated.
The line pressure is 5 Bar (72.5 psi)
The reduced pressure is 1-1 1/2 bar (14.5 -21.75 psi)
The low pressure lines are open to atmosphere in the cooking chamber.
All take offs from the main line run vertically and then horizontally
There is a condensate drain on the end of the main line.
The control valves are single acting spring return.(I might try installing speed controllers on the control valves (Pneumatic)
Your thoughts would be appreciated.
Thanks
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#14984 - 05/25/15 06:58 AM Re: Pressure Reducing Valve HELP [Re: ktmtragic]
Lu47Dan Offline
MBN Old hand
Registered: 02/14/10
Posts: 1108
Loc: N/W Pa. ****
KTM, You are welcome.
Now, it does not sound as if there is a condensate problem, so we will dismiss that.
I had a discussion with a friend of mine who was a Plant Engineer (boiler) before he retired, he is thinking the the PRV's would be better off on the controlled side of the angle valve. The act of opening and closing would exercise them, this would allow the everything to relax, also it would prevent them from taking a set over time.
One thing we also discussed was that the PRV's might not be big enough to stand the work load. With today's design mentality, the operating specifications might look good on paper but not survive in actual operation.
Since the existing valves are spring return, I would say that the speed controls are not all that necessary as they provide a softer opening than powered return would. But you could try it and see if it makes a difference.
None of your pressures are are very high so a good quality PRV should handle them.
If all else fails than swap the angle valve position into the PRVs place and vise-a-verse.
Good luck, hope this helps.
Dan.
_________________________
Tools are to Men as Shoes are to Women, you can never have too many!
Used diesel engines are an adventure anyway you look at them!
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#14985 - 05/25/15 04:26 PM Re: Pressure Reducing Valve HELP [Re: Lu47Dan]
ktmtragic Offline
MBN member
Registered: 07/04/10
Posts: 233
Loc: Sydney Australia
Hi Dan

Thanks for the info. You have mentioned something I had not considered,fatigue In the PRV I have had the stainless spring collapse and there are stainless steel bellows these have also failed regularly.
I think I will double the throughput specs on the next one I replace and see how we go.
Thanks again
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#14986 - 05/25/15 05:26 PM Re: Pressure Reducing Valve HELP [Re: ktmtragic]
Lu47Dan Offline
MBN Old hand
Registered: 02/14/10
Posts: 1108
Loc: N/W Pa. ****
We had to change to a bigger PRV on a paint curing oven, it kept failing. We went from 2" up to 3" with higher operating pressures to keep the pressure setting in the middle of its operating range.
Dan.


Edited by Lu47Dan (05/25/15 05:27 PM)
_________________________
Tools are to Men as Shoes are to Women, you can never have too many!
Used diesel engines are an adventure anyway you look at them!
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#14991 - 05/27/15 02:02 AM Re: Pressure Reducing Valve HELP [Re: Lu47Dan]
ktmtragic Offline
MBN member
Registered: 07/04/10
Posts: 233
Loc: Sydney Australia
Thanks for the info Dan! Talked to the steam component rep today and we both agree go bigger on the next failure.
Thanks for your input it was valuable to both of us!
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