NACE Exposed NUTS 1

[bmoorthy]

The Fluid handled Mixed phase (Gas + Liquid and particulate Sulfurs)Sour Fluid.

Pressures close to 100 Bars.

HIC and SSCC requirements are specified by the user for all material that are exposed to fluid.

Now the question

AES type heat exchanger (Shell, Bonnet, Channel, Floating head type construction)Both side are sour fluid

I know that the bolting that fastens the floating head is exposed bolting. Material specified in A 193 B 7m and A 194 2 HM.

Now is the bolting between channel and end cover and bonnet and shell considered exposed (In NACE MR 0175/ISO 15156 parlance) and is it necesasary that B7M and 2 HM only have to be used (Assuming all the design requirements and allowable stresses etc are taken care of) in place of A 193 B& and A 194 2H?


Is the bolting between Nozzle flange and the connecting piping flange exposed bolting?

 

[jehan17718]

Bmoorthy,

As per ,my understanding only the "wetted" bolting as per NACE has to conform to specifications SA-193 B7M and SA-194 2HM. For "non-wetted" bolting example nozzle flanges connected to piping, SA-193 B7 and SA-194 GR 2H can be used.

However, to aid interchangability between the internal and external bolting SOME project specifications set both the internal and external bolting to SA-193 B7M and SA-194 2HM if the equipment is in NACE/Sour service. Due to this, plant inventory is smaller and the potential for mixup of the internal and external bolting maintenance/ post-maintenace is averted.

SA-193 B7M is having lower allowables than SA-193 B7 and thus for the same size of bolting and flange geometry, more number of bolts will be required for SA-193 B&M grade.

Hope this helps.

-Jehan

 

[strider6]

If i have understand your question you want to know if bolts and nuts not directly exposed to the sour fluid shall be sour service grade?
If the bolts are under insulation the answer is yes, if the bolts and nuts are directly exposed to the atmospher the answer in no.

S.

http://www.corrosionist.com

 

[chrysa1975]

Stud bolts per ASTM A193 B7M with nuts to A194 2HM shall be used when they are in direct exposure to sour environments or when the bolting will be buried or insulated or equipped with flange protectors, or they are deprived of direct atmospheric exposure.

 

[SJones]

Don't forget to allow for leaks!

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[TomEun]

I believe you got all answers from the sound experts above.

As Jehan mentioned, you may have to confirm the strength calculation (per ASME Sec VIII, Div.1, App.2 or EQ.) for new fabrication. However the flanges were already made, the next choice is to select the other material (i.e. higher Cr-Mo steel).