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Hoon
28-03-2016, 12:11 AM
Tanks watching this question.

First I'm sorry my English uncomfortable.

I saw that "The refrigerant relief valve must be connected in the discharge line between the
compressor and the shut-off valve." as Fuller rotary compressor.

In my common sense, Relief valve can not working flow low pressure to high pressure side.

How can work that relief valve?

Or Has some different suitable relief valve?

Newbie Grateful waiting for your answer.

14049

RANGER1
28-03-2016, 07:51 AM
Hoon,
I think it is OK, as CHECK ARROWS on pipework indicate suction & discharge.
The pressure readings on suction & discharge is incorrect.
Suction normally 0psi or vacuum & discharge no higher than 45psi.
On picture suction is 250psi & discharge 75psi.
Relief valve is in correct position, but should now be special type balanced port or down stream pressure not effecting relief valve set point pressure or relieving pressure.

Hoon
28-03-2016, 03:43 PM
Ranger, I Really appreciate it.
Yes, as you said, when that machine running, It usually suction side is 0 psi.
I have got some wrong inform.

NH3LVR
28-03-2016, 07:04 PM
The drawing is labeled with the pressures reversed as Ranger noticed.
However the relief valve function is a bit different here.
As I remember the maximum pressure differential is 45 psi across the machine.
In order to prevent a high pressure differential the relief valve is installed. It does not need, nor should it be, the type which references ambient pressures.
The differential pressure is the only thing we are concerned with in this case.

RANGER1
28-03-2016, 09:34 PM
The drawing is labeled with the pressures reversed as Ranger noticed.
However the relief valve function is a bit different here.
As I remember the maximum pressure differential is 45 psi across the machine.
In order to prevent a high pressure differential the relief valve is installed. It does not need, nor should it be, the type which references ambient pressures.
The differential pressure is the only thing we are concerned with in this case.

Not sure I agree, will get back to you on that one.

NH3LVR
28-03-2016, 10:08 PM
Always up for a technical debate! Us retired guys are like that.
Think the internal relief on a Vilter compressor.
Hope all goes well down under!

Magoo
29-03-2016, 12:27 AM
I have found that generally the non return / check valve creates most issues with Fuller boosters if not removed and serviced regularly. Just a thought.

RANGER1
29-03-2016, 10:05 PM
NH3LVR,
Checked Fuller manual & come up with the following.

Differential pressure across machine maximum 45psi
Relief valve from discharge to suction 75psi

If differential pressure, high pressure or high interstage pressure switch failed or was started with discharge valve restricted or closed, then relief might work.

If compressor isolated it has no relief valve to protect it against over pressure.

No real description of relief valve function, but states if differential exceeds 45psi problems will occur.

Relief valve would probably never go off until you potentially damage blades.

If machine was isolated it would not protect compressor or jacketing as it returns downstream of suction stop valve.

A relief that vents back into system that is protecting something at a predetermined pressure should be not downstream pressure affected in any case otherwise setting is a moving target.

These machines were built in a era where they were monitored very regularly by operator checking plant pressures & lubricator oil levels.

As for Vilter internal relief it's no better or effective than the Fuller set up, but what can you do except make sure all safety switches are set correctly & work!