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Holds In P&ids In Detail Engineering Phase (Or End Of Basic Engine


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#1 PhilippM


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Posted 10 July 2019 - 02:31 PM

Hello everyone,

I was wondering how HOLDS on a P&ID are usually used:


I regard the HOLDS as a To-Do List that gets smaller until the P&IDs can be issued for construction, so basically all pieces of information conveyed by the P&ID which still need to be confirmed (e.g. by vendor documentation, or a hydraulic calculation, input by another engineering discipline, decision by the client etc.) are marked with a cloud and a short explanation is given (stating what information is required and who is expected to provide it)


I’m always suspicious when I start a Detail Engineering Phase with a set of P&IDs that do not have HOLDS on them, as I know that the Process Engineer who prepared them in the Basic Engineering could not have been certain that all of the information conveyed in the P&ID are final (otherwise there would be no point in working on the P&IDs in the Detail Engineering Phase anymore at all) but chose not to write down what pieces of information are still missing, or to quote Donald Rumsfeld: “We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know.”

In my opinion by not using HOLDs, we create those “unknown unknowns”, which is a real problem, as the P&ID then suggests a stage of completion of the project that does not reflect reality, with the respective effects on the schedule and the necessary man hours.


Does this philosophy make sense in your opinion/experience?


Kind regards



#2 Bobby Strain

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Posted 10 July 2019 - 03:04 PM

Most projects progress from Basic Engineering to FEED then Detail Engineering. Never have I seen holds on P&IDs issued from Basic Engineering.

#3 Chemitofreak


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Posted 12 July 2019 - 01:01 AM



My two cents.


Even at the start of the Detail Engineering one does not have all the data, vendor starts to provide concrete data, once the order is placed. So holds will always be there.


Even if the engineer in FEED does not provide holds on his documents, as a Detail Engineer, it is your responsibility to correct his mistakes or make necessary changes in the documents. One has to always challenge the FEED engineer's basis and value specified in his documents.



#4 PingPong


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Posted 12 July 2019 - 01:22 PM

It all depends on the company culture.


In the old days in my design company process engineers (like me) would put holds on P&ID's to indicate that something was preliminary and could only be final after receipt of vendor info for specialised equipment and packages, or after receipt of missing info from client.


As the years went by experienced project managers left or retired and we got more and more ignorent project managers who did not like holds and wanted to freeze the design as soon as possible, preferably already yesterday.

So no holds allowed on P&ID's anymore with the result that piping engineers are later surprised that what was on the P&ID has to be changed after receiving info from selected vendor and they have to redo part of their work. This then leads to irritation in progress meetings.

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