Happy new YEAR. Slight question about piping again please 1

[gravitate]

If we have a system with stainless austenitic pipe work and it is catagory M asme B31,3. It will be low pressure like 2 bar. 3- 4 inch stainless. Must it have a welded connection or is it acceptable for others like grey lock etc?

I dont have my copy of ASME to refer to I am afraid.

 

[LittleInch]

There is no requirement for all welded construction in B 31.3.

Some company specific standards might require it though and it would seem to be a good idea, if feasible.

It is not permitted to be a system with severe cyclic stresses.

This section may be useful

M308 FLANGES, BLANKS, FLANGE FACINGS, AND
GASKETS
Paragraph 308.1 applies in its entirety.
M308.2 Specific Requirements for Metallic Flanges
Paragraph 308.2.4 does not apply [see para. M300(e)].
The following shall not be used:
(a) single-welded slip-on flanges
(b) expanded-joint flanges
(c) slip-on flanges used as lapped flanges unless the
requirements in para. 308.2.1(c) are met
(d) threaded metallic flanges, except those employing
lens rings or similar gaskets and those used in lined
pipe where the liner extends over the gasket face

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

 

[BigInch]

Maybe you should have a quick review of Cat M requirements and decide if you really want to use..

High temp differences

 

[gravitate]

Thanks very much so these grey lock joints here could be used.

But I have been told that the joints with 3 clamps are easier to take off than the ones with 2 clamps. Does anyone know why that is please or can you think of any other fittings that could be used rather than these I cant really think of anything else.

http://www.oceaneering.com/oceandocuments/brochures/subseaproducts/GRLC - Grayloc Connectors.pdf

 

[MickMc]

You mention welding and Graylock Clamps which implies that instead of welding you are using clamps which does not make sense to me as the clamp secures the 2 welded hubs together instead of 2 welded flanges with bolts therefore you have the same butt welded connections. Hubs with clamps are predominately used in offshore applications where they have space and weight savings and normally in high pressure systems, it seems to me that weld neck raised face flanges are suitable for your low pressure system where flange type connections are required even in Category M.

 

[europipe]

Why should you use graylocks?(1500#), you said it was design 2 barg.
Maybe victaulic (or equal) system is much more economic.

 

[gravitate]

Hey thanks for the ANswer! I thought Victaulic had rubber seals in? Cat M States non metalic components are not allowed.

I have worked with Victaulic a lot on a biofuel plant but didnt think it would be of use in this situation. Tell me if I am totally wrong though please Can you use them Cat M?

 

[europipe]

gravitate, the piping should be metallic, but not gaskets or other sealings,

K308.4 Gaskets
Gaskets shall be selected so that the required seating
load is compatible with the flange rating and facing, the
strength of the flange, and its bolting. Materials shall
be suitable for the service conditions. Mode of gasket
failure shall be considered in gasket selection and joint
design.

 

[gravitate]

OK great thank you very much for all the replies.

 

[XL83NL]

graviate, in your second last post you mention I thought Victaulic had rubber seals in?. Now, do you wish to use greyloc connectors, or victaulic joints? The 2 are totally different in design and application, and Im starting to believe that you meant to say Victaulic for your application, but instead mentioned greyloc.

 

[moltenmetal]

You absolutely, positively should NOT use Victaulic piping in category M (lethal) service, even at 2 barg pressure! Most people shy away from using Victaulic in anything other than Category D (nonhazardous fluid) services. The main concern is fire safety of the design, given the huge amount of rubber gasket material in each joint, but there are other concerns. It is widely used for Category D services such as potable and fire suppression water, compressed air and nitrogen etc. It has a very limited upper service temperature due to the performance of the rubber gasketing and is not recommended for steam or condensate at any pressure above atmospheric.

Grayloc is a replacement for something like a metallic ring-type joint flange at classes 1500# and above. It offers very significant fire safety, but it can be leakage prone at low pressures and merely tightening the clamp bolts may not stop the leakage. The sealing ring in Grayloc is energized by internal pressure, rather like an o-ring. Using it at 2 barg is a bit like swatting a fly with a sledgehammer, but it is allowed in category M. You'd be served better by using 150# ASME B16.5 flanges with a suitable gasket material in my opinion. If you use a spiral wound gasket with graphite filler, assuming it is acceptable for your service conditions, the resulting joint will likely be more than adequate from a fire safety perspective.

 

[BigInch]

Thanks moltenmetal.

Just because you can do something, doesn't mean it's a good idea.