Isolation valve on pressure vessel 1

[Alwynb]

Hi there,
The OHS act states that a pressure vessel shall have a relief device as well as a pressure gauge. I know it is not allowed to install a isolation valve upstream of the relief device unless rigorous lock out procedures are applied.

The question is, is it allowed to install a isolation valve upstream of the pressure gauge? Maintenance staff like it because they can remove the gauge for calibration while the vessel is under pressure. The Safety guys feel that an isolation valve may be closed during maintenance and be a safety risk when the vessel is under pressure and the gauge reads zero.

Any comments?

 

[gr2vessels]

The pressure gauge is installed for visual inspection of the pressure level in the vessel. As such, is normal that the inspection / maintenance personnel to investigate the cause of error pressure display of the gauge.
The isolation valve can be installed upstream the gauge in order to enable "in operation" removal of the gauge for checking, test, calibration or replacement. Obviously, the removal can only be done under strict controlled conditions, most likely a remote pressure transmitter is operating in parallel and is sending informations to the control room, or the gauge is not of critical importance to the process, etc...However, your safety guy should do a lot more to improve the operating manual;- he should propose an appropriate operating procedure for the opening and closing of the valve. Also, he could include a proposal to ensure anybody walking around the vessel will take a look at the gauge and report any fault, perhaps instate a regular patrolling team for that gauge and a logbook to record the isolation valve's handle position.
Howzat,
cheers,
gr2vessels

 

[dcasto]

The block valve between the vessel and PSV can be safe gaurded with administrative controls and not rigours engineering controls like 1/2" chain and pick proof locks. But that's another question.

Get real on the pressure gauge. Unless someone is paid to sit there and watch that gauge 24/7, what harm comes from removing it to begin with. Gr2 is right, your safety person needs to set a realist set of proceedures. I cannot even imagine a pressure gauge even being on a list of devices that is monitored for safety reasons, they are monitored for operational and production reasons.

On the other hand, there is a device somewhere that sets the pressure and monitors it. This can be a control valve a PSV a regualtor ect... These devices should have some controls to keep them secured, especially the sensing line to them (or the line and valve to the PSV). I'd recommend a Carsel system with plastic ties and tags that warn personel that the cannot be closed with out a permit that covers alternate proceedures when the valve is closed.

We even close the valves under PSV's for an hour or so to test and inspect relief valves. We supply humane intervention proceedures that act like the PSV. Pressure to high, open vent valve.