4 replies to this topic

[martin_h]

Hello,

I am looking for some advice on specifying a large, welded, low-pressure storage tank to store a chemical heavy end residue. I am not sure if this is the correct forum, but it seems to be on topic.

The feed temperature will be 60 C ( 140 F) or less and we propose to use a maximum positive gauge pressure of 1 barg (14.5 psig). These conditions are within the range specified in API-620 which gives a maximum operating temperature of 250 F (clause 5.2) and a maximum nominal pressure rating of 15 lbf/in2g.


However, when examining the fire relief case using API 2000, I find that the temperature of the residues when boiling is 200 C, and clearly the relief valve would be specifed for this temperature.

As far as I can see API 620 makes no mention of a design temperature during relief conditions, but only refers to operating temperature defined in terms of ambient conditions or feed temperature.

So should the tank have a design temperature of 60 C or 200 C?

The question is important to us because 200 C is clearly outside the scope of API 620, and if this is what is requred there doesn't appear to be a tank standrd that we could use. API 650 will handle the temperature, but for this pressure appendix F bounces us straight back to API 620.

Any thoughts on the above will be more than welcome.

[proinwv]

I have requested that this post be moved to a forum more in line with your question.

[Art Montemayor]

Martin:

I think this thread belongs in another Forum. But please help me out; I don't know what your question(s) are.

You state that you are "looking for some advice on specifying a large, welded, low-pressure storage tank to store a chemical heavy end residue"; but then you ask about the relief temperature of a PSV on the storage tank.

I am going to take a chance and move this thread to the Relief Devices Forum.

[fallah]

martin_h,

In low pressure storage tanks as well as pressure vessels the releiving temperature of the fire case not to be considered in mechanical design of the equipment. Hence it might even be more than equipment design temperature.

Fallah

[martin_h]

Thanks Fallah,

That clears it up.

martin_h