Rupture Disc Gauge Problems?

[Jenson Storm]

We have been annoyed with PRV vent alarms but we can't determine which relief vent is the source. I would like to install rupture disks on the PRVs. I have heard a rumor the gauges mounted on the rupture disks are problematic. Anybody have any experience with these gauges?

[Grizzly]

We have been annoyed with PRV vent alarms but we can't determine which relief vent is the source. I would like to install rupture disks on the PRVs. I have heard a rumor the gauges mounted on the rupture disks are problematic. Anybody have any experience with these gauges?

Hi Jenson.
Yes you are correct all PRV and their joints can be a pain.
Extra care is needed when assembling them and you must pay due consideration to what refrigerant they are monitoring.

Henry (There are other manufacturers also available) do as nice type with indicator gauges.
So at least with these you will know which one has lifted?
Follow the link.
Cheers Grizzly.
http://www.henrytech.com/catalog/2010/h20-h21.pdf

[frank]

We have been annoyed with PRV vent alarms but we can't determine which relief vent is the source. ?

Tape a small clear polythene bag over all of the PRV's. The next time one blows, it will burst (read - destroy) the poly bag over the valve outlet.

[Grizzly]

Good tip Frank.
I have also used a grease plug as an indicator.
Only when the valves are piped away to atmosphere the bagging or plugging can get quite difficult.
Cheers Grizzly

[Jenson Storm]

I am going to buy rupture disks this week and i need to know if the indicator gauges are adequate. The refrigerant is NH3 and i have heard from a couple guys in the industry that the gauges are faulty. The gauge is located after the rupture disk, so there shouldn't be any pressure on them unless the disk ruptures.

Anybody have any problems or experience with these gauges?

Thanks

[Grizzly]

Hi Jenson.

The gauge is located after the rupture disk, so there shouldn't be any pressure on them unless the disk ruptures.

As far as I understand if the gauge is showing pressure or has moved off its standstill peg.
Then it is indicating a leak has occurred.
I am not sure if you can reset them?

Most PRV'S can be re-calibrated so I assume the "telltale" can be reset.

You need to specify these relief valves are for ammonia and they will be of steel construction not non ferrous.
Grizzly

[NH3LVR]

I have installed rupture discs in plants that had problems with the monitors on the PRV piping leaking (NH3). Even if you change the valves out for new ones you may have a small leak. Eventually it rises to the level where it will ring an alarm. Some people put in a air fitting to blow the lines clear.
Rupture discs simply prevent the valve from leaking. The gauge only shows that the discs have ruptured. If they have you have had a serious problem.
They are not a bad idea on ***** systems either. You can lose a lot of expensive refrigerant from a PRV on the condensor and never know it until it is too late.

[Jenson Storm]

Some people put in a air fitting to blow the lines clear.

NH3LVR,

I have blown the lines clear half a dozen times in the last month.

[Grizzly]

NH3LVR,

I have blown the lines clear half a dozen times in the last month.

Then back to what you said in the first place! You need to change them there valves!
Grizzly

[NH3LVR]

NH3LVR,

I have blown the lines clear half a dozen times in the last month.

This leakage from relief valves had probably gone on for years and we did not know about it. The rupture discs solve the problem. New valves can leak a bit and it takes so little to set of the alarms.
I would not hesitate to install them. You will have to recalibrate your sensors after you put them in. They will probably have been zeroed with some NH3 in the lines.

[Grizzly]

Wise words NH3LVR!

Grizzly