Ground smooth on capping

Date 07-05-2009 13:03 Edited 07-08-2009 05:44

Project specs call for socket weld and branch weld for small branch connections such as vent, drains and bleeder SHALL BE GROUND SMOOTH for the following service piping; ACOUSTIC INDUCED VIBRATION SERVICE and SEVERE CYCLIC CONDITION SERVICE.

The above subject reqt's was overlook in fabrication and erection. If the line is already completed checking and hydro testing is already approved and the company allowing the contractor not to ground smooth on capping or waive this requirements for it may cause delay on the project since its too many small branches/lines involve on this subject. What is the effect or is there any effect on WELDING during commissioning, start-up and operations if the weld cap allow NOT to ground smooth?

By michael kniolek (***)

Date 07-05-2009 22:57 Edited 07-05-2009 23:01

What ever happens get it in writing , signed sealed and delivered.
I would guess the reason for gringing smooth is crack prevention so id agree with cracks.
They do want smooth and not flush right.

By Joey

Date 07-06-2009 02:00 Edited 07-06-2009 02:02

Richman,

The main reason is to remove those sharp notches which may initiate Cracks.

Nevertheless, you have to consider that the fillet weld size before and after grinding will not be the same.
Final measurement should be performed after grinding smoothly.

So before you think of Crack, the weld size is to consider first if grinding smoothly is the requirement.

Regards
Joey

By CWI555

Date 07-06-2009 02:40

They'll be wanting smooth if they specified acoustic vibration service. Rough surfaces can create uncontrolled constructive interference. It's been known to take a joint out within hours of operation. They'll likely have very tight fit up tolerance's as well. I would also go so far to say a spec like that is usually related to a pressure relief system.

I would advise getting the surface finish specification from them in writing as well.

There are a lot of things that happen when it's smoothed out, but it would take a book to explain it. suffice to say I get real edgy when I see a spec like that as it's usually a harbinger of bad news.

By Richman (**)

Date 07-06-2009 06:17

Thanks for all the response on my query on the above topic. However, in your best opinion as a client or owner’s inspector or as a client's Piping and Welding engineer are you agreed to waive this requirements of the contractor for any Gas Plant project or not?

By CWI555

Date 07-06-2009 11:39

If I had FEED documents requiring any given specific order of build or process of constructing, I would not approve an RFR without putting the FEED engineers in the loop. Especially one like this.

It is almost like a game to some contractors now, to read the FEED, understand that it will take more time, and bid it on the lesser time anyway.
When it comes time to build, they wait until they have schedule pressure on their side, then hit the owner with a request for relief and a sad tale about how ridiculous and onerous a given requirement is.
This leaves the owner exposed. Those FEED documents are typically what they received their initial approval from (governmental, corporate, etc). It's not a good idea to be changing them on your own.

I strongly advise you to send this to your FEED engineers before approving.