HELP-PIPE SHOP SPOOL DRAWINGS 4

[abba7114]

Hi,
I have been a piping design engineer suddenly I found my self in construction, a contractor is is constructing some facilities we have designed, I issued them GA'S and isometrics anl all relevant documents. I am to check their shop spool drawings, what will I look out for? I want someone to help with some tips on checks and may be with a sample shop spool drawing and likely problems.
I can also do with some inspection tips becouse I am to inspect construction, I have asme B31.3, API 14-E and piping specifications only that this field is new to me.
Thanks in anticipation of your usual assistance.

Abba7114

 

[ARASH54]

A good guideline for checking of shop spool isometric drawings is project piping fabrication and erection specification .Some items that you should check in these drawings are : 1.Restrictions for size and shape of spools according to location,elevation and transportation 2.FFW(field fabricated welds)welds and 100 mm length added to pipe nipples(in three direction for rotaries) for spools connected to nozzles

 

[pennpiper]

Checking Shop Drawings

The prime motive for checking shop drawings is to eliminate (or reduce) field changes to shop fabricated spools. One person cannot be expected to check ALL of the shop drawings and still meet the construction schedule. So you must use your time wisely. You must have a plan. You should also talk to the piping foreman in the field and ask him/her what are some of the typical errors that cause them the most problems during installation.

A. First, sort the shop drawings by line number and “cost groups” i.e.: separate by material, wall schedule and line size. The reason you need to do this is that it will allow you to focus your effort on the high cost piping. The most costly piping is the large diameter, heavy wall carbon steel, any alloy materials and any material that requires post-weld-heat-treatment (PWHT). Start with the most costly lines and their shop drawings.
B. Next, review each line first for continuity. By this, I mean, do you have all the shop drawings to complete “that” specific line? If yes then proceed. If no then have someone connect the shop to find out when the missing drawings will be available. It is always possible that they forgot to draw one or to send one.
C. Next, check the drawings against the engineering drawings for configuration. By this I mean does the line turn when, where and in the right direction to match the design? If not then this will require a change in the shop (If the spool piece is not yet shipped) or a change in the field (if the spool piece has already been shipped). Shop errors can, in most cases be back-charged to the shop. However, any error can cause a delay to the schedule which adds cost to the project.
D. Next, review the material used against the piping line specification for the material that is required. If the shop used the wrong material, STOP. This line or spool will need to be refabricated.
E. Next, review the shop drawings against the design looking for places where a wrong dimension in a welded-out configuration would do the most harm. Don’t worry about fitting make-up such as flange-reducer-flange. These have a low possibility for error. Don’t worry about spools that terminate with a field weld. These have a built in opportunity to make a correction.
F. Next, look for any place where there is a requirement for or the possibility for odd flange bolt-hole rotations. Did the shop do it correctly? On the other hand, did the shop call for and fabricate an odd bolt-hole rotation that was not called for?
G. Next, spot check 10% of the dimensions within each “cost group.” If you do not find any error trends then you may want to consider backing off additional checking. However, if you do find an error trend within a specific cost group (material, wall schedule, size, etc.) then note the name of the person who did these high-error shop drawings. The next step is to notify the shop of your concerns and request that they launch their own investigation. In the meantime notify the construction manager and based on the “cost groups” look at all of this persons work.

This should give you some ideas to consider.

 

[unclesyd]

One thing in addition to the excellent post by pennpiper is in his section (A) is make sure the weld details are called out/transferred correctly. This is one of biggest problems that I've run across, especially in recent years. This is especially true with alloy piping.

I also like his section (F), just saw a 60" vessel flange, a replacement, that was "1 holed" while the existing head was "2 holed".

 

[abba7114]

pennpiper ,
Thanks for this wonderful posting, I will let you know how I am coping, infact must of the lines are CU-NI and 316L SS with some carbon steel.
Thanks once again.
abba7114