21 replies to this topic

[PME]

Hello !

Pl. answer this question .
How can one find the point of Piping Material Specification break in P &ID ?

Thanks
PME

[ashetty]

Hello !

Pl. answer this question .
How can one find the point of Piping Material Specification break in P &ID ?

Thanks
PME

It would be easier for u to check than for me to explain.Anyway ..generally look for spec breaks any place where you would expect pressure reduction or change in operating conditions (Control valve outlet..depressuring valves etc)

[djack77494]

Also, you should have a symbols/legend sheet(s) that accompany and a a part of the full set of your P&ID's. The symbology for depicting spec breaks should appear on this sheet(s).

[JoeWong]

As explained by Doug and ashetty, you can easily locate the spec break in P&ID. Check the legend sheet.

I am curious with your simple question...
Are you really looking answer for locating the spec break or determination of spec break location ?

[fallah]

Hello !

Pl. answer this question .
How can one find the point of Piping Material Specification break in P &ID ?

Thanks
PME

It would be easier for u to check than for me to explain.Anyway ..generally look for spec breaks any place where you would expect pressure reduction or change in operating conditions (Control valve outlet..depressuring valves etc)

Check valve could be added to items on which spec break would be occured.

[JoeWong]

Check valve could be added to items on which spec break would be occured.

What is the purpose of Check valve in regards to spec break ?

[ankur2061]

PME,

I prepared a company standard for a reputed Oil & Gas company in the middle east. The company standard was well researched in terms of its contents from various reputed sources, including API and other company standards. The same has now been accepted and approved by the client company. One of the topics covered in that company standard was "Piping Specification Breaks". I am attaching that portion as a file for the benefit of the forum members as well as inviting comments and a healthy discussion on the contents of this document.

Comments from stalwarts like Art, Joe, Zauberberg, Doug etc. would be most welcome.

Happy reading.

Regards,
Ankur.

Attached Files

•  PIPING_SPECIFICATION_BREAKS.doc   77.5KB   1242 downloads

[fallah]

Check valve could be added to items on which spec break would be occured.

What is the purpose of Check valve in regards to spec break ?

The cases such as:
a)High-pressure utility systems flowing into lower pressure process systems
b)Non-Corrosive material flowing into a corrosive system
that has been taken from previous post well described by Ankur

[JoeWong]

For (a) how check valve function from spec break aspect ?

For (b) It is subject to type of corrosive material. If continuous injection and weak acid i.e. acid carbonic cause by CO2 in water, then the arrangement is acceptable. If intermittent and present of H2S in water which possibly lead to stress cracking, do you really rely on a check valve as final safeguarding ?

[fallah]

For (a) how check valve function from spec break aspect ?

For ( It is subject to type of corrosive material. If continuous injection and weak acid i.e. acid carbonic cause by CO2 in water, then the arrangement is acceptable. If intermittent and present of H2S in water which possibly lead to stress cracking, do you really rely on a check valve as final safeguarding ?

a)Prevention back flowing from "process spec" section to "utility spec" section in the case of utility line pressure being failed.
b)Continuous injection was considered.

[JoeWong]

a) Can not rely on check valve as safeguarding.

b) Misleading statement... Again can not rely on check valve as safeguarding.

[ankur2061]

Joe,

Aren't we getting off the track. This post is not about the risk and reliability analysis of check valves. The discussion is about piping specification breaks.

Check valve reliability is a debatable issue and when in doubt I would provide two dissimilar check valves to address the supposed problem of reverse or back flow.

I would appreciate if we don't get diverted from the real topic which is "Piping Specification Breaks".

Regards,
Ankur.

[fallah]

Joe,

Aren't we getting off the track. This post is not about the risk and reliability analysis of check valves. The discussion is about piping specification breaks.

Check valve reliability is a debatable issue and when in doubt I would provide two dissimilar check valves to address the supposed problem of reverse or back flow.

I would appreciate if we don't get diverted from the real topic which is "Piping Specification Breaks".

Regards,
Ankur.

Good explanations.
Indeed,in current post we are not discussing about the ability of check valve as a safeguard for prevention of backflow.These type of discussions (Joe submitted) usually should be done in HAZOP study.

[JoeWong]

Please ignore my comment if it is out of track.

[JoeWong]

A piping spec relates to material and rating.
A piping spec break is not only rating break, it is also material break...

Can not rely on check valve !

[fallah]

A piping spec relates to material and rating.
A piping spec break is not only rating break, it is also material break...

Can not rely on check valve !

If you have to break the spec in a line,in your opinion what is the thing(s) you can rely on?!

[JoeWong]

A piping spec relates to material and rating.
A piping spec break is not only rating break, it is also material break...

Can not rely on check valve !

If you have to break the spec in a line,in your opinion what is the thing(s) you can rely on?!

Check with your material engineer. What is leakage rate. What leakage is acceptable ? then you know what you can rely on ?

Come back with your answer if you wnat to discuss further.

[JoeWong]

Joe,

Aren't we getting off the track. This post is not about the risk and reliability analysis of check valves. The discussion is about piping specification breaks.

Check valve reliability is a debatable issue and when in doubt I would provide two dissimilar check valves to address the supposed problem of reverse or back flow.

I would appreciate if we don't get diverted from the real topic which is "Piping Specification Breaks".

Regards,
Ankur.

Good explanations.
Indeed,in current post we are not discussing about the ability of check valve as a safeguard for prevention of backflow.These type of discussions (Joe submitted) usually should be done in HAZOP study.

You are deciding a piping class break and yet you leave the risk and reliability issue behind. What's the logic behind ?

[fallah]

Joe,

Aren't we getting off the track. This post is not about the risk and reliability analysis of check valves. The discussion is about piping specification breaks.

Check valve reliability is a debatable issue and when in doubt I would provide two dissimilar check valves to address the supposed problem of reverse or back flow.

I would appreciate if we don't get diverted from the real topic which is "Piping Specification Breaks".

Regards,
Ankur.

Good explanations.
Indeed,in current post we are not discussing about the ability of check valve as a safeguard for prevention of backflow.These type of discussions (Joe submitted) usually should be done in HAZOP study.

You are deciding a piping class break and yet you leave the risk and reliability issue behind. What's the logic behind ?

HAZOP study is an activity usually would be done during detail design stage (P&ID including piping class had been issued in FEED stage and many points left as hold items going to be finalized in detail stage) and all design points,such as piping class, subject to change in order to meet the HAZOP requirements.After that new Rev. of P&ID with implimenting HAZOP actions (may be including piping class change) should be issued.

[ankur2061]

Joe/Fallah,

I think the post is getting a little out of hand. Further discussion should be discontinued. I think everybody is entitled to his/her opinion.

I do tend to agree with fallah that during a HAZOP review of the P&IDs such issues as reliability of check valves, single valves, relief systems, drain systems etc. come up for discussion and suitable safeguards are incorporated in the P&IDs as recommended in the "HAZOP Closeout Report".

As a personal experience, during my long tenure (10 years) as a production engineer in polymer petrochemical plants where a variety of liquid petrochemicals such as Ethylene Glycol, Methanol, Molten Dimethyl Terpephthalate and hot oil (Dowtherm A) were pumped, I did not face a single instance of so called "check valve failure".

So I do believe that it is a matter of individual opinion about the kind of failures and operational problems that the individual has experienced.

A favorite quote of one of my distinguished colleagues who was a commissioning expert was:

"No two operational plants are alike".

What was meant was that even if two identical chemical process plants are built side by side, the chances that their output is 100% identical is very remote. And this has been my experience too when I was involved in commissioning for several plants.

So let us stop further discussion on the topic respecting each ohers individual opinion and experiences.

Regards,
Ankur.

[JoeWong]

Ankur / Fallah,
I am 100% agreed "repect each ohers individual opinion and experiences...".

I am a bit confuse when Fallah brought the HAZOP up. When we design a system, we determine the location of spec break. It can be at the check valve (i have never discarded the fact that check valve can not be the location of spec break). However, it shall be defendable and proper analysis has been conducted. System design will normally goes through the DESIGN review cycle and finally goes through the HAZOP review. The designer shall properly define (or defense) he/her design is safe and operable (before it is being REVIEWED). However, we do not let the HAZOP team to trace / identify the design fault and error that a designer made.

I am sure there are many spec break is located at the check valve and in fact i have many such experiences. Nevertheless, all these are defendable and has gone through a proper consideration. A lot of engineer take the advantage of "thing being done by others, thus they just followed". Spec break CAN BE but NOT ALWAYS at check valve. This is the only point that i would like to bring up...

[fallah]

Joe/Ankur,
Agree with your final conclusions in your latest posts.Also agree with stopping discussion.