Gas Main 16" Weld Cap (Y52) - ASTM A516? 1

[EZasPieEngineer]

I have a spec. calling for 16" welded cap (grade Y52) to be installed on the end of a gas main. Most cases the MSS-SP-75 and ASTM A234 is called for but in this case there is an additional requirement of ASTM A516 added. Whats the added benefit of using A516 besides improved notch toughness?

 

[BigInch]

ERROR

ASTM A694, is for high pressure service, or A420 for low temperatures, but you don't mention design temperatures.
If you want 52 yield, then Grade F52 should be specified.
I think you probably want A694. It is the standard specification that covers carbon and alloy steel forgings for pipe flanges, fittings, valves, and parts for high-pressure transmission service. Several grades of material based on the minimum yield strength requirements are covered under that spec. Specify the grade as F52 when you need the 52,000 psi yield strength, F60 for 60,000 psi, etc.

Note that for WPHY-52 the TENSILE STRENGTH REQIREMENT = 66ksi

ASTM A694 is listed in MSS SP-75 Specification for High Test, Wrought, Butt Welded, Fittings
The MSS SP-75 Grade you want is designated using "WPHY" prefix and the grade, 52
As ASTM A694 is referenced within MSS SP-75, as are others, and all other things are the responsibility of the mfgr, so I would specify this fitting simply as,

16" CAP, WALL THICKNESS = XXXX, BUTT WELD FITTING, MSS SP-75 GR WPHY-52, ASTM A694
Specify supplementary Notch Toughness requirements as applicable to your situation.


MSS SP-75 does not list A516
A516 is for Pressure Vessel Plate for Moderate Service
There is no intrinsic notch toughness requirement for this material.
Notch toughness requirement must be specified as a supplementary requirement in the P.O.
Here's the killer!
A516 Gr 70 has a tensile strength of 70ksi, but has a yield strength of 38ksi

 

[BigInch]

PS in the general notes, or cover sheet of your purchase order, or somewhere, you should also mention the Pipe Design Code, B31.1, .3, .4 or .8, and/or CFR 49 Part 192 or 194, etc. Tell the mfgr the design pressure, the product, natural gas, or hydrocarbon liquids, refined products, etc. as well and area class designation, and other information as may be applicable.

 

[EZasPieEngineer]

Thanks, that was very helpful.

You said, "516 Gr 70 has a tensile strength of 70ksi, but has a yield strength of 38ksi". Is the yield strength information provided in 516 specification?

 

[EZasPieEngineer]

BigInch, thanks for your help. I was able to find a copy of 516 specifications on IHS. You are correct, the yield stregth is lower then expected. Thanks again!

 

[BigInch]

When I checked the A516 spec I was actually surprised to see the grades defining the tensile strengths, instead of specifying yield strengths. I obviously do not prefer that convention. I believe most engineers are more accustomed to working with yield strengths.

 

[weldstan]

Per ASME BPVC design allowable stress is based on a reducing factor of tensile strength.

 

[BigInch]

Pipeline and structural design codes are different in that way.

Using the same grade terminology to represent the two was almost dangerous in this case.

 

[weldstan]

I agree that mixing materials and design codes can be quite dangerous.

One seldom finds X-52 pipe / Y-52 fittings over 1" thick. It is much more common in pressure vessels. The lower yield strength of A-516 is based on the capability of the material to meet the mechanical properties in a full range of thicknesses up to more than 8". In normal pipeline thicknesses, the yield strength of A-516 is almost always > 52 ksi.

 

[BigInch]

We prefer highest yield strengths, thinnest walls, fastest welding speeds, lightest weights and the smallest diameters, w/o PWHT. Keeps costs down when there's lots of material moving and being fabricated outdoors, over long distances. Occasionally even the pipe diameters are less than your 8" thickness.

So back when they invented that tensile strength criteria, they weren't worried about bulging boilers, as long as they didn't explode???

 

[Duwe6]

"So back when they invented that tensile strength criteria, they weren't worried about bulging boilers, as long as they didn't explode??? "

Apples and strawberries; totally different design philosophies. For SA516 Gr.70, the max allowable design stress is 20ksi; so we never get close to YS. To a Boiler & PV guy, u/g pipe looks mighty thin and flimsy. But both design philosophies work just fine if NEVER mixed together.

 

[BigInch]

Yes. I understood that. It's always to do with setting appropriate safety factors for the equipment, expected mode of failure, expected risk and the analysis and design method used.

Lesson here is read the specs carefully before making designs and ordering materials.

 

[weldstan]

From an economic standpoint, it's one thing when manufacturing a 100 ft long vessel, totally different when installing a 1000 mile pipeline.

 

[rconner]

Right after the Civil War I understand the near football field long "Sultana" steamship was dispatched from down South up the mighty Mississippi River, fighting against spring floods​ and by all accounts carrying way too many former Union soldier prisoners home from captivity. The boilers of this ship reportedly exploded north of Memphis, TN, ​with intolerable conflagration as well, and per some ghastly reports near 1,800 (and many doubly unfortunate Yankee) folks didn't make it any further.
While I guess it is true there is a whole lot of difference in boilers and a thousand mile pipeline, I can't imagine the potential costs/liability if a disaster comparable to the Sultana were to happen today! While there were apparently a whole lot of nefarious reasons for what happened, in the end it was reported no one was ever held accountable for the still greatest maritime disaster in United States history (incredibly even more lives lost than from the Titanic!)
Despite its scope and human interest this event flew sort of under the historical radar, as the day before one John Wilkes Booth had shot President Abraham Lincoln at Ford's Theater.
I believe however the American Society of Mechanical Engineers (ASME), as well as the boiler and pressure vessel "codes" applied to pressure vessels and piping, all had roots at least partially the result of this unfortunate history.

 

[BigInch]

Grover Shoe Factory

http://en.wikipedia.org/wiki/Grover_Shoe_Factory_disaster

Remember the Maine.