Hot Oil System Rating 1

[Angsi]

I came across an article by a Heating Oil Supplier (Therminol) saying that if the supply temperature exceeds 175 deg C, it is prudent to have the piping pressure class in 300# minimum (even if the design pressure/temperature rating allows the applciation of 150#) to ensure "leak tightness" of flanges.

Can someone please comment? What is the theory behind this? Is there a concern over bolt extensions due to thermal heating? But surely we have many applications where temp is above 175 deg C and yet 150# is used.

 

[25362]

http://www.process-heating.com/ph/c...pcoverstoryitem/0,,19380,00+en-uss_01dbc.html

 

[Ashereng]

25362,

Great article.

Angsi,

If your process conditions can be suitably met by 150#, then going to 300# is sort of "overkill".

That said, going to 300# will allow you in the future to go up in temp/press.

Some sites standardize in a various ANSI flanges (my current client will only use 600# and up). This reduces the number of spares. The field services guy is less likely to show up without the correct part.

One other reason may be flanging to stainless steel. As you know, stainless has a lower rating than carbon for the same ANSI rating. For Class 150, at 400°F, A105 CS is rated to 200 psi and 316SS is only rated to 195 psi. For the whole line to be rated to the full 150#, you would need to use 300# flanges for the 316SS instrument/valve. Otherwise, the line would need to be de-rated.

 

[NozzleTwister]

Angsi,

Ashereng is right, "If your process conditions can be suitably met by 150#, then going to 300# is sort of "overkill".

But, Hot Oil Systems are notorious for leaking flanges, the piping is hot and 150# flanges are very weak to bending moments. 300# flanges will provide a significant increase in reliability which is why the supplier is pushing for them.


NozzleTwister
Houston, Texas

 

[Angsi]

Thanks guys. Appreciated. Great article too.