9 replies to this topic

[manchester]

Hi,

Which one is the correct sequence to locate piping spec break??

pipe with spec A - flange - valve - flange - pipe with spec A - spec break - pipe with spec B
or

pipe with spec A - flange - valve - flange - spec break - pipe with spec B

And what is the reasons?
Because I've seen some P&IDs with both spec break location.

Thanks for your kind help.

[ankur2061]

Manchester,

Have a look at the following earlier post where I had provided an attachment for piping specification breaks. This should help you.

http://www.cheresour...3151#entry23151

Regards,
Ankur.

[fallah]

Second sequence is correct,because normally the point for spec break should be such that keeping the uniformity of the pipe class between two isolation valves (or isolation valve and equipment).

Edited by Art Montemayor, 01 December 2010 - 10:32 AM.

[manchester]

@ Fallah: if that so, why does API put some sketch in API 14J page 19 that indicates the break is in the pipe?

Any explanation regarding to this drawing? (I attached the snapshot drawing from API 14 J)

Attached Files

•  Pressure break.JPG   34.99KB   169 downloads

[fallah]

@ Fallah: if that so, why does API put some sketch in API 14J page 19 that indicates the break is in the pipe?

Any explanation regarding to this drawing? (I attached the snapshot drawing from API 14 J)

IMO,the mentioned Dwg is just a schematic diagram and actually (e.g. an as built PID) you would see the breaking point to be started from the adjacent valve flange.

[djack77494]

I agree with fallah that the drawing is a rough schematic and can't be taken too literally. However, I also counted 3 spec breaks in the schematic. The spec break in the line coming from the HP Separator is the most interesting. Unlike in almost every other case you're likely to come across, here the further downstream segment could operate at the higher pressure, for example if the HP Separator is bypassed. Though you don't state it, in your original post I take spec B to be a lower pressure spec than spec A since, if the flow is from left to right, it is the further downstream. BTW, did you notice the many assumptions needed to provide any answer at all? Engineering requires precise and accurate communications, a fact all too often omited.

[Zauberberg]

I have never seen in the field that the piping spec break is located somewhere in the middle of line. What does it mean? To weld two different pipes together, or to suddenly have a wall thickness reduction in pipe of the same material? It doesn's sound logical nor practical. It's always at the flane point, as per my experience.

[sheiko]

Manchester,

Have a look at the following earlier post where I had provided an attachment for piping specification breaks. This should help you.

http://www.cheresour...3151#entry23151

Regards,
Ankur.

Dear Ankur,

I have two quick questions on your (very useful) doc:

1/ Section 10.1: Why is the low temperature spec break located at the inlet flange of control valve on the scheme?

2/ Section 10.2: Why is the low temperature spec break shown at the outlet flange of the block valve upstream the control valve?

Regards

Edited by sheiko, 01 December 2010 - 07:12 PM.

[ankur2061]

Dear Ankur,

I have two quick questions on your (very useful) doc:

1/ Section 10.1: Why is the low temperature spec break located at the inlet flange of control valve on the scheme?

2/ Section 10.2: Why is the low temperature spec break shown at the outlet flange of the block valve upstream the control valve?

Regards

Sheiko,

1. The first case 10.1 if handling a high pressure stream has a drain valve between the upstream block valve and the control valve.
This allows the draining of the trapped fluid (condensed gas or liquid) between the block valve and the control valve in case the upstream system is isolated. Any chances of trapped material attaining lower temperatures due to the downstream low temperature stream is discounted considering that it can be drained. Hence the spec break is shown at the inlet flange of the control valve.


2. The second case 10.2 does not have any drain valve to remove trapped fluid. Fluid can remain trapped and attain lower temperature in equilibrium conditions due to pipe conduction and hence the spec break shown at the outlet flange of the upstream block valve and also a minimum distance of 600 mm shown from the bypass isolation valve to the bypass throttling valve.

Hope this helps.

Regards,
Ankur.

Edited by ankur2061, 01 December 2010 - 10:52 PM.

[sheiko]

Thanks but,
Item 2/ Section 10.2: the text is saying "spec break at inlet flange of control valve"...might be an error?
Regards.

Edited by sheiko, 04 December 2010 - 05:54 AM.