Construction sequence in general--Is it Pipe first or the Pipe Supports first? 3

[cjabhijit]

Hello Dear experts,

May I get some clarity on the construction sequence in a typical oil & gas plant facilities?

Especially I am curious to know if the Pipe Supports comes first or the Piping above these supports first or is it like doing this together to avoid mismatches?

I think Pipe supports first but not really sure....pls help me understand.



Thanks & Regards,
Abhijit

 

[Dhurjati Sen]

Dear cjabhijit,

With time and experience you would understand that is it the chicken or the egg that came first.

Regards.

DHURJATI SEN

 

[cjabhijit]

Thanks for your reply Dhurjati...so is it the Pipe or the Supports?

Thanks & Regards,
Abhijit

 

[pennpiper]

It depends.

If you are developing the total design of new Plant or Unit you will develop the main Pipe Rack first. Later if you have one single line to route (off the main Pipe Rack) then you consider the route and then think about the support. You will consider and choose the best from many possible types and designs of pipe supports.
Single leg "T" supports and multiple leg "Pipe Racks" are considered Primary Pipe Supports.
Pipe Hangers, Base Supports, Shoes and many other devises are considered Secondary Pipe Supports.





Sometimes its possible to do all the right things and still get bad results

 

[MJCronin]

pennpiper, as always, is spot-on ...

The problem, of course, lies with management. MBAs ALWAYS want a simple answer that fits all cases.

The worst case (and i have seen this on multiple occasions) is where the piping is installed by one contractor and pipe supports are installed by another. Only by having both the pipe supports AND the piping installed by the same people is success even possible

In my humble opinion:

- If there is a rack, it must go in first. Piping must be installed from the rack outward.

- Below a certain pipe diameter (say 3"NPS) temporary supports may be necessary and permitted. Temporary fabricated steel supports may be necessary.... but must be approved by the site construction engineer.

- Temporary pipe supports may also be required for larger diameter piping undergoing hydrostatic testing. These specific systems shall be defined by the engineer before the systems are constructed and supported.



MJCronin
Sr. Process Engineer

 

[bimr]

Agree that it depends. As a general practice, appropriate adjustment, modification, and addition of piping supports are made by the construction contractor according to the actual field conditions, especially for small diameter piping. It is generally preferred that piping supports should be fabricated and installed prior to the piping installation, and the use of temporary supports is minimized. In the case that the use of temporary piping supports are necessary, the piping support arrangements should be made such that there will be sufficient bearing strength and stable supporting of the piping system.

However, it is not practical in all cases to install piping supports first.

 

[cjabhijit]

Thank you all for your valuable insights.

So what I understood is as below,

- It is not hard & fast rule (as always in Piping) that what comes first. It depends on various factors like revamp
project or a completely new grass root project have different way of handling the sequence.

- Cost drivers says that in bigger projects it is best to put the supports in Civil scope as much as possible as that
makes the Pipe support steel cost together with the main steel very efficient. Here in our organization Civil gives
a cut-off date to include the pipe supports & Piping try to transfer as many supports possible to Civil (however,
this may cause issues later in terms of scope per point below).

- It is best to put Pipe Supports + Piping to the same contractor so as he manages the mismatches the best way
possible instead of having a blame game in between the 2 different contractor. (As I am in a Revamp jobs
environment, we do this more often as well).

- Also, I understood of a concept of building the plant Bottom-Up from my senior here. Bottom-Up means all the earth work, Piling,
Foundations,Trenches first (bottom items), moving up then build the steel above those foundations, equipment on those foundations built,
support steel above foundations & later Piping, cable trays etc. etc.. ..Sounds very logical to me.

Pls provide your feedback on my understanding to be more clear on this....

Have a great weekend.

Thanks & Regards,
Abhijit