Conversion of RF to RTJ 2

[jimmcmahon]

I am wondering if it is accepted practice to cut a RTJ into a RF flange. I have 2 only 6 inch 1500 ANSI RF pipeline valves for NACE 0175 applicable service. Are there accepted practices that maintain ASME compliance? Or is this strictly within the domain of the manufacturer to certify and re-issue.

 

[jmiles]

You want to cut the flanges to make them mate up?

I would recommend against that, particularly since you should be able to just buy gaskets that will allow the two to mate, ive been told that pikotek gaskets will mate between RF and RTJ flanges, though you would want to confirm that with the manufacturer.

Of course you could jsut put RF flanges on your pipeline to match your valves.

I would also state that i dont think any valve manufacturer would want you cutting into the flanges that are an integral part of their valve.

In short dont cut, use the right flanges or buy gaskets that will mate.

 

[JimCasey]

RTJ flanges are a lot thicker than RF flanges, to allow for acceptable thickness at the bottom of the ring-groove.

It can be done. You can weld on more metal onto the face, machine it to RTJ profile. It ptobably will no longer have code face-to-face dimensions, and it will likely have huge heat-affected areas of the body that may lose properties, and I'm pretty sure (without being able to quote chapter and verse), that it won't be acceptable to your code inspector or insurance company. And the manufacturer DEFINIELY won't honor the warranty or accept any liability on the valve.

 

[jmiles]

Jim I think thats is one of the biggest Yes... BUT answers ive seen in a while

 

[jimmcmahon]

I have been reading API 6DR which provides for the refurbishment and remanufacture of valves, given owner approval, ie. if the flange thickness at bottom of RTJ groove, meets ANSI B16.5 specifications and welding procedures meet appropriate code and one can demonstrate hardness testing that this practice can and does take place. I am wondering if there are valve repair houses out there doing this type of conversion? I agree that refacing a flange by applying weldments to build up the raised RTJ portion would cause heat affected zones in the flange facing but are there procedures being applied that are considered acceptable? I am being told this is being doen on sour gas valves in Edmonton service shops.

I appreciate the response to this thread.

 

[jmiles]

Jimmcmahon,

Im sure it is being done, and im sure you can do a ton of testing to make sure its all up to code, but the fact still remains that jsut because you can do it does not mean you should.

Its basically a colossal waste of money, you can get gaskets (albiet expensive ones) that will let you mate the two flanges, or you can change the connecting flanges on the pipe side, both options should be much cheaper than modifying the valves to meet the pipe flanges, and then testing those valves extensively to ensure they still work.

Plus the big question is what happens later on down the road if something goes wrong with that valve, if the ERCB asks why that valve blew out or started leaking like a paper bag well thats going to be a rougher conversation when yuo are talking about modifications to the valve, as opposed to just using the correct mating flanges on the pipeline.

And just for the record, it is ok to use RF on 1500#, i know alot of specs call for RTJ, but ive worked with clients that use RF, and it has worked out fine. you might need a deviation from the specs witht he client, but once you explain the situation to them im sure they will agree.

 

[jimmcmahon]

I have just spoken with a company in Edmonton that manufactures parts for TK, Cameron, Grove and apparently builds up an RF face dimension both radially and axially to comply with the RTJ dimensions. They have taken all their welding procedures and registered them with the Alberta Boilers branch which have accepted them for application to valves on Sour gas applications. They can weld up tp 8" thick valves of low temp material, such as A-350 LF2 without post heat treatment. This includes welding with the valve body in a water bath. They can be found at

http://www.umcorp.com/valveservice.html

This may not apply in state side business.

Cost for a 6 inch ANSI 1500 valve is $1333.00 1 to 2 week delivery.

My take is there are some clients that will not accept anything but a RTJ on anything above a 600 class on sour service.

I would like to thank all for their help.

 

[jte]

The conversion of Ring Joint to Raised Face flanges is not unusual. I’ve seen it done on vessels and piping at ratings as high as CL-1500, though I have not seen such a conversion performed on a flanged valve. A review of B16.5 indicates that the flange thickness, tf is the same regardless of flange finish. Ref: B16.5 2009 6.4.2.1 and 6.4.2.2 on page 10. Thus, provided that no “cleanup” needs to be made on the bottom of the groove, the added weld metal will consist solely of material above the minimum flange thickness as required to bring the RF up to B16.5 dimensions. In some cases alloy flanges are converted using stainless weld buildup in order to avoid a PWHT. Clearly, weld procedures relative to the service environment must be clearly thought out.

ASME PCC-2 2008 Repair of Pressure Equipment and Piping has an article (3.5) titled Flange Repair and Conversion which deals with flange repair and has a placeholder for the conversion part. The next edition (2010 or 2011) will include a section dealing with converting RJ to RF flanges.

As noted in some posts above, “conversion gaskets” exist and can be used on RJ flanges without the need for converting the flanges to RF style. The use of such gaskets not clearly within the intent of B16.5. Note that with the change in gasket reaction diameter, moments within the flanges are changed. Thus, the overall stress distribution within the flanges should be considered by folks who are evaluating the use of “conversion gaskets” on RJ flanges vs converting the flanges to RF dimensions vs replacement.

jt