Ammonia relief valves question

[RANGER1]

If for example you instal a system that has thermosyphon oil coolers,is there any
particular type of relief valve that should be installed on refrigerant side of oil cooler?

We have a particular safety officer in the industry that is obsessed with standard relief valves only designed to vent gas not liquid.

Any thoughts?

PS He only picks on thermosyphon oil coolers not oil drain pots, work that out.

[Sandro Baptista]

I use to use the BSV 8 from DANFOSS. It discharge to the return line from the oil coolers. The relief is independent of the back pressure

[Grizzly]

I must admit you have me confused ranger.
Here in the U.K. it is normal to have the thermosyphon free venting back into the receiver.
Therefore the PRV'S on the receiver form the safety for either vessel. Plus either the liquid feed or the saturated vapour return.
Who says PRV'S are only for venting gas not liquid?
True where most are sited, it would be reasonable to assume that system pressure.
Would dictate that they would normally only vent vapour but i have never heard a preference being expressed. (If you understand what I am trying to say?)
Or am I being thick and missing the obvious here?

Grizzly

[Sandro Baptista]

Therefore the PRV'S on the receiver form the safety for either vessel.
Grizzly

Not if you isolate the oil cooler. In that case you would need a safety valve.

[RANGER1]

Not if you isolate the oil cooler. In that case you would need a safety valve.



Yes thats what I am trying to say as oil coolers can be isolated.

A Danfoss BSV 8 is a good method.

This guy has a bee in his bonnet about relief valves not designed for this.
If you ask him he cannot suggest a brand/type that is designed to relieve liquid.

Instead of a balanced port relief like BSV8 we just vent (liquid) to atmosphere.
Must admit never seen it happen, as you would have to be doing something stupid for it to happen.
-Relief valve set to 1700kpa
-compressor BSV8 POV set 1600kpa
-High pressure cutout 1550kpa

If you isolate liquid side of thermosyphon oil cooler without pumping out then you get what you ask for if relief goes off.

You can get hydrostatic reliefs but are the same thing as a standard relief to my understanding.

This safety guy see's only black & white so we can only win with common sense.

[Magoo]

Hi ranger 1
we both work on GB units and all of mine vent to atmosphere from liquid side of thermo oil coolers, 1.7 mpa. The oil side back to discharge.
I actually had a HPR go off for no apparent reason on the liquid side of a thermo oil cooler. Once sorted out the seat in the valve appeared to have gone pear shaped. it was a Valvco [ spell check ] the teflon seat grew/ swelled, possibly a low grade material option.
Your inspector may be onto something that we don't to know

[RANGER1]

Magoo,
There was one in Brisbane that released , not sure why.
If it was because of faulty seat on valco valve then what can you do?
Valco is main supplier in Aus & they are everywhere.
We would use Danfoss BSV8 but are twice the price compared to other brands.

Its never happened to us (that I know of)but I have heard that valves sometimes do not reseat.

This safety guy would have looked at it but he was on about relief valves only vent gas a long time before that.
It says on Hansen & Valco tech info that they are designed to vent gas only , so he grabbed hold of that, but with no real alternative.

Thats why I asked the question as to what other's do.

[Grizzly]

If the valve lifted would it vent liquid?
Thanks for the clarification by the way (re- vessel isolation).
Over here our Pressure vessel regs are applied as far as i know based upon vessel size.
At 250 bar/ Ltrs I think it is.
Otherwise as you say even a oil pot would have to be Relief valved.
Have you not got any design spec regs you can refer to to get the guy off your back.
Is this guy picking on you or has he others that he is questioning?

I take it that this is not a new install and therefore was built to the relevant specs at the time?

I wish you well with this guy I had similar earlier in the year which is another long story.

Where He was insisting NDT testing of a Surge drum to High side standards despite being a LP Drum.
Because the PRV'S were set to 13.5 bar.
Grizzly

[RANGER1]

Grizzly,
Its a lot to do with the Australian codes & how you interpret them.

He is not picking on us directly as everyone is doing the same thing as us.

For example as you say a pressure vessel which holds (in our case ) 200 litres of refrigerant has to have
duel relief valves.
So he then interprets this so compressor oil seperators have to have dual relief valves as they
are over 200 litres.
We only instal a single relief as oil seperators are just oil seperators, not liquid recievers.
Maybe we are wrong, depends on what side of the fence you want to sit.

[Grizzly]

Thanks for the explanation.
I hope someone from your side of the world can Help you.
Good Luck, Grizzly.

[RANGER1]

So Grizzly as far as your part of the world , are you doing it with a standard relief valve like we are ?


Thanks RANGER

[Grizzly]

Yep.
We tend to use Danfoss or Henry with a smattering of Hanson if I remember correctly?
I can send you details if you wish?
Cheers Grizzly

[RANGER1]

Grizzly thanks , no details required as I think we are on the same page.

[Mark Selby]

I use Parker A2 pressure regulators that vent around the isolation valves

[Magoo]

Hi Ranger1.
Maybe, the gas only use factor relates to the designed certified free air/ flow rate ratings. Which would be totally different with oil and liquids.
magoo

[Superfridge]

Hi Ranger1
The PRV's we use are Hansen, Henry ect and if you read the instuction it states gas only. I'm sure I read something about problems venting liquid, like valves not re-seating or icing up or the low temps at expansion point or something like that. Sorry to be so vague but i'll have a scout around to see if I can find the info.

We have just had recent decussions at work regarding PRV's on the oil side of oil coolers that tee into NH3 vent lines and into cooling towers. I like the sound of pressure regulators venting back into the system.

[RANGER1]

Thanks Superfridge any info welcome. Also sounds like a good resoning behind it as well.
On the oil side we vent from shell of oil cooler , oil side into discharge line with a standard relief valve set at 600kpa.
This is calculated with vessel max design pressure in mind as std reliefs are back pressure effected unlike a balanced port BSV8.
A Danfoss BSV8 pilot is good but probably to small unless utilized with a POV main valve

[Superfridge]

Ranger1
I hav'nt found the info I was looking for but did find that releving liquid would exceed the design temperature rating of some of the valves I have looked at regarding this issue.

I sent Hansen a e-mail and the out come is below.

Hello
Please explain to me why Hansen pressure relief valves and three-way dual shut-off
valves are only for refrigerant gas relief and cannot be used for liquid relief.

Thank you for contacting us.
Pressure Relief Valve:
Our pressure relief valves are only for gas.
They can’t be use on liquid because it doesn’t comply/not conform with Boilers and Pressure Vessels
3-way Relief Valve:
It could either we use on liquid or gas:
Use on gas when use with our relief valves.
Use on liquid when use along without relief valve attach.
Hope this helps answering your questions if you have additional questions let me know.

Hello again
What pressure relief device should be used on the liquid side of a thermosyphon oil cooler to relieve liquid pressure and how is it connected into the system?

At this moment we don’t carry relief valves for liquid.
The main difference between liquid and gas:
Liquid Relief Valves are connect to another vessel. (they have a additional port for draining)
Gas relief valves are connect to the atmosphere. (no additional ports)
Let me know if you still have additional questions.

Google searched this
http://www.refrigeration-engineer.com/forums/archive/index.php/t-13934.html

[RANGER1]

I see Tyco have a number of liquid relief valves but not sure on design difference.
I guess it does'nt matter except to say it is suitable for liquid.

Will contact Tyco in near future to check them out.

[Superfridge]

A company called CYRUS SHANK make a range of refrigeration relief valves including liquid.

http://www.cyrusshank.com/

[McFranklin]

Cyrus Shank has two liquid rated valves the 803LQ (75# or 100#) and the 805LQ 100#. These are the only liquid rated ASME approved relief valve that I know of that are available from the traditional ammonia valve manufacturers. I have used Anderson-Greenwood valves and Kunckle. These are from the chemical industry and are significantly more expensive.

[RANGER1]

Thanks Superfridge & McFranklin

I wonder why such low pressure settings?

Is it because they recommend to pipe outlet of relief back into
suitable location in system ?

I'd admit I would'nt want to be anywhere near the vent if it went off to
atmosphere & get showered in it.