900# WN RTJ flange connection with WNRF 900# flange 2

[surekhaajay]

We hade a tie-in with existing 900# globe valve, the piping class for the existing line was not available and also during site visit the face of the flange was not recognized. Hence I assumed that the 900# flange could be WNRF in line with the other flanges and ordered accordingly. The flange welded with pipe was ready to be installed on the site but the problem arised when we opened the existing flange only to find that the existing flange has RTJ face. This is a shut down job and I don't know how to proceed with limited time in my hand. Also this kind of flange may not be easily available with the vendor. This new 4", 900# WNRF is connected with 4" 40SCH pipe whereas the existing pipe thickness is 120Sch. What can be done in this case?

 

[georgeverghese]

If you can show the right color of money, you'll probably get this 900lb RTJ flange to this location quicker than you can imagine.

 

[LittleInch]

surekhaajay,

Unfortunately very little can be done. You probably need to pay someone NOW to hand carry a 4" WNRTJ flange or find one you don't need and cut it off and re-weld in place of the RF flange.

Unfortunately SH1T sometimes happens - I had the same thing a few years back but the other way around RTF flange, RF valve, but was saved by one of the store rooms having one lying around as they had some spares from an earlier piece of work.

Ask around the local fab shops, vendors, operating companies, anyone who looks like they might have one and ask very nicely.

Put it down to experience and the next time it's not confirmed or even for any tie-in which is time critical, order both types - you will save someone else next time as it's not always easy to confirm the type of flange.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Gator]

Nobody has mentioned yet that the new piping assembly to be installed ( flange plus pipe segment) is also the wrong wall thickness. Old piping = Sch 120, New piping = Sch 40.

Piping Design Central

 

[LittleInch]

Gator,

The OP didn't say it was the wrong thickness, only different.

I don't know what code or material the OP is talking about, but assuming 31.3 and basic steel, I still get an design pressure of ~ 170 barg, > #900 rating. exact Design Pressure will vary by material and temperature etc, but certainly sch40 looks like it is close.

Who knows why sch 120 was used or what the design conditions were / are now?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[donf]

Check with your local gasket supplier for a spiral wound style that's dimensioned/designed for use with RTJ facings. One major manufacturer calls it their CGI-RJ style.

I've used them with success to install RF valves between RTJ flanges. One key point is to verify that gasket contact area on the existing RTJ flange face is suitable.

donf

 

[jte]

surekhaajay-

You could consider machining the existing RTJ to a flat face. Keep in mind that the B16.5 required thickness starts at the bottom of the groove, so you are free to remove any steel above it without impacting the required thickness of the flange. If you do this, then at this point you have two options:

1) Bolt it up to the RF flange and specify a torque value and observe the torqueing operation to ensure that the flange pair is not torqued to the extent that the OD's of the flanges are brought together. Recognize that this has the effect of shortening the assembly, so you'll have to have a bit of flexibility somewhere to allow for this. Using a thicker than average gasket (e.g. a nominally 1/4" thick kammprofile type) will reduce this dimensional issue.

2) Prior to machining, weld build the groove to add ~0.30" to the bottom. PWHT if necessary (remember, the thickness of the weld, not the flange thickness governs for thickness based criteria). Machine to RF dimensions.

This type of issue is covered in ASME PCC-2 Repair of Pressure Equipment and Piping Article 3.5, Flange Repair and Conversion. In this article, recognize that the limit in 3.1 for RF height is specifically that: A limit if you wish to continue to call it a RF flange. If you accept that you may have a flat face to RF connection - and the hazard is that the OD's will touch thus limiting effective seating pressure - then this criteria need not be met. For the general weld repair (presuming the common groove bottom cracking) and conversion to RF, see Fig. 1.

 

[LittleInch]

Well I learnt something. Didn't realise these things existed.

http://www.lamons.com/products/kammpro.php

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[surekhaajay]

Thanks all for ur suggestions.

Thanks LittleInch, the main line is 20" sour gas line tapped with 4" line with double isolation and RO and then connected to flare header which is designed for 18 bar. This 900#WNRF is special flange with thickness sch 40 to match the downstream pipe.

Thanks donf & jte for ur valuable suggestions. I will definite check that out and let u know.

 

[surekhaajay]

@ jte I don't have ASME PCC 2, how can I get it. If u have it can u share please.

 

[jte]

surekhaajay-

You can get PCC-2 from ASME.

It is also available on IHS provided that your subscription covers it or you purchase thru them.

I do not condone theft of intellectual property, and as copyrighted material it would be illegal and unethical of me to share my copy with you or anybody else.