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Well that is how how understood it but I am in a bit of an argument as to whether the liquid protection figure always means higher is better.

I am getting mixed responses regarding whether higher IP ratings automatically qualify for the lower ratings, for example is a IP68 rated device always suitable for an IP56 application? The first figure relating to ingress of foreign objects logically seems higher is better but what about...

ScottyUK thanks for your replies, it turns out the item in question is triple certified IS, Exd, Exn for the North American FM/CSA models but the ATEX models we have are individually certified. So even though they are physically the same devices new Exn models have been ordered to ensure the...

They have no IS equipment in the installation area, no barriers etc. they do not want an IS system but just maintain the existing Exn system, I suppose the question is can you introduce an IS instrument into a Exn system.

We are replacing some old equipment, client simply requested Exn suitable for zone 2 IIB T3. We have plenty of stock of intrinsically safe instruments, it was suggested this is good for zones 0,1,2 so would be OK but I thought there may be more to it than that.

Can equipment certified EEx ia suitable for zones 0, 1, 2 be safely installed and used in an installation requireing Ex n zone 2 certification?

OK thanks for the replies. Relief valve required.

To be more specific we are regulating instrument air, the regulator is rated for 16 bar maximum, if someone was to send say 25 bar into this regulator and it broke, does this 25 bar end up down stream or in the atmosphere? Or are there different types available?

I am just looking for confirmation of the difference between self relieving and non-relieving filter regulators. I need to convince our client there is no risk to a diaphragm actuator downstream of a regulator which accidently gets over pressured. Pressumably in a fail situation one type vents...

It looks like a new larger air lock, thank you for your input.

Scrap what I said above, the operating speed does increase but the air fail position is the problem. With the booster positioned after the air lock as soon as air pressure drops to below the setpoint the actuator is vented via the booster. So to answer my own question, the air lock needs to be...

The booster/relay amlifies the air out of the positioner, the booster is a relatively large Cv compared to the air lock. We have swapped the airlock and booster around and operating speed is vastly increased. We are happy with the performance and on air failure the actuator stays put but...

Consider a pneumatic actuator with a positioner, air lock and volume booster on. I can understand the reasoning for putting the air lock last (ie next to the actuator) so when air is locked in there is less potential leakage path. The problem we are having is the airlock is restricting the...

Following on from a previous topic (thread330-184673) It was suggested NORSOK applies to higher grade(is this the correct term?)metals for example Duplex but not ASTM A352 LCC but the thread was ended. Our metal man at work is looking in to it but I thought an alternative opinion would be useful.

Is it normal to have Butt weld end connections on lower class valves. Specifically an ANSI class 150 300mm valve. I was lead to believe the point of welding them in was for higher pressure thicker pipelines.

I would say "containing" parts are vessels, bodies, tube etc. And "retaining" parts are the bolting, studs, nuts, clamps etc. holding the containing parts together.