Stainless steel insead of carbon steel

[torque]

Hi guys
Can anyone tell me more about the use of s/s and the welding requirements (standards ) of s/s used for suction and liquid line on a NH3 installation.
The contractor I work for is getting qoutes from sub contractors and one welding firm have suggested using stainless instead of carbon steel.
thanks for your time.

[Andy]

Hi torque
stainless steel would not normally be used for NH3, as the welding has to be TIG root, fill and cap. This can be quite slow on pipe work above 2"n.b, as sizes above this are usually TIG root and filled out and capped with manual metal arc. Also stainless steel pipe needs to be specialy painted with a corrosion inhibitor to stop the insulation from eating the pipe. Personally I would stick with API5L Sch 40 piping (106 grade B). If this is properly installed and more importantly properly insulated it will last a minimun of twenty years.
Regards. Andy.

[amar]

Torque,

We have installed stainless steel pipework on some NH3 and HFC systems.

In my experience the total cost of installation is slightly higher than that when using the standard API-5L. However if the system a low temperature unit, where stress relieved carbon steel is required, then the costs are comparable.

We tend to use 316 grade S/S, with either Nilflam or Foamglass insulation. (These are chloride free so the pipe does not need to be foil wrapped or coated).

Regards,

Amar.