Carbon Steel for Instrument Air Pipe 1

[norzul]

Hi,

Is it common to have API 5L B (without galvanised) for the instrument piping material?

Based on my previous experience it should be pre-galvanised, however on my current project it is specified as API 5L B without galvanised?

Any advise

Thanks

norzul

 

[Ashereng]

rmw,

Would you classify "bottled" air as "clean dry air" - the ones used in breathing apparatuses?

 

[tc002]

I've been associated with the petrochemical, chemical and metallurgical industries for almost 40 years. Stainless, copper and in some cases even poly is used for instrument air since it can be field fitted more easily than cs and since it has thinner walls, but other than cs being a dirty steel as compared to the other materials there is no reason not to use cs. If you look at the price of all I'm sure you will see why they selected cs.
In any case I have never seen inst air used that is not dried and of course filtered. What are people thinking if they are not using dried air for sensative instruments and electronic operators.
Most instrument suppliers will also specify the type of connections and types of gases acceptable for instrument operation. If they haven't then ask them to do so such as to comply with their guarantees.
tcinc002@aol.com

 

[Ashereng]

For most valves that I spec, I also include a filter and regulator with the pneumatic actuator that I purchase.

 

[tc002]

Yes I agree. The filter will take out any debris and the regulator is required for any Pneumatic actuator, but the filter will not take out any liquids.
As an afterthought, the design that we mostly employ for the instrumentation air is cs from the air reservoir and/or compressor to the vicinity of the instrument then SS or copper, depending on the duty, to the instrument, with of course vibration resistent mounts. We also like to use swagalock fittings (quick disconnects) and sometimes flex couplings or fittings directly on the instrument to reduce any potential leaks from vibration.
The selection of copper vs. SS depends on the duty. Mostly in petrochemical we stick with SS due to the atmospheric corrosion potential and higher pressure requirements of safety items, valve actuators. We also recommend strict compliance to maintenance for the filters, dryers, and periodic soap tests on connections. Dryers are also checked for dew point on a regular basis if not on-line moisture analyser.
tcinc002@aol.com

 

[Ashereng]

tc002,

Yes, tubing from the instrument air header/piping system to the instrument is usually SS. You won't find much CS tubing.

However, the original thread was about instrument air piping, not the tubing to the instrument.