Solid Inconel 625 Pipe Vs CS + Clad Inconel 625 Pipe 1

[gvn]

We have significant amount of Inconel 625 piping being specified for an offshore facility containing sour service Gas with wet H2S, CO2 and Chlorides (aggressive service). Is there a cut-off with respect to diameter of pipes and thickness for deciding between Solid Inconel pipes Vs CS + Clad Inconel 625 pipes? Also, is there any cut-off for solid Inconel valves Vs clad Valves?

 

[metengr]

None that I am aware of with regards to clad or co-extruded pipe. For boiler, pressure vessel and piping construction codes in the US, you cannot take credit for cladding as part of the pressure boundary. So, if you are designing piping or pressure retaining items you need to design as if the cladding was not present.

The question of using cladding versus solid or integral pressure retaining items comes down to two factors; service conditions (temperature and pressure, and corrosion)and cost. IF you are working with service temperatures and pressures that allow the use of carbon or low alloy steel material, cladding or co-extruded components makes good economic sense. However, you will still need to determine if HIC resistant carbon steel plate is required beneath the cladding.

If service temperatures and pressures are such that carbon or low alloy steel cannot survive because of creep deformation, than you need to use higher performance alloys that could result in the use of Inconel.

The same concept should apply to valves with the exception that for small valves access limitations may require you to purchase an Inconel or other comparable alloy grade valve

 

[sadra]

dear sir
According to my experience from 6" and above wall THK. more than 10.7 possible to use CLAD pipe.but before applying this you have to check piping material specification.
regards,
Sadra

 

[MJCronin]

gvn,

I have never heard of "clad valves"..... (This does not mean that they do not exist)

Are these castings ??

Who makes them ?

Regards,

MJC

 

[gvn]

MJC,

I believe clad valves are CS valve body with weld overlay. For example, for soild Inconel 625 body specified to B564 (UNS N06625), the body can be say A350LF2 + 3mm Inconel 625 weld overlay. I understand that most of the reputable valve suppliers do supply clad valves, but these are not off the shelf, but engineered for a particular application.

Regards,
GVN

 

[unclesyd]

Check out the following thread as there is considerable discussion on problems with Clad Inconel 625.

thread330-65042