pipe material for high pressure hydraulic application 2

[ktxmarco]

We need to have some hard pipe runs fabricated for use in a large mobile machinery application.

Normal operating pressure 320 Bar. Relief valves set 380 Bar. Highly cyclic > 1,000,000 cycles per annum.

I can use XXS thickness ASTM A106B/C but would prefer to use a stronger alloy steel with less wall thickness.

Is ASTM A335 CrMo suitable for this application ??

If so, what grade is recommended. It is max 80 degC.

Can anyone advise the UTS and yield strength for the different A335 grades ? and what max pressure under the above conditions wold be for 1-1/2" and 2" pipe ?

Thanks

 

[MJCronin]

ktx,

As I understand, you are looking for "a stronger alloy steel with less wall thickness" than the common A106 B/C.

As you consider other high UTS materials, you must recognize that you are selecting from a group that will be of either much higher cost/difficult to weld or both..!!

Although it will not be your code of construction, ASME B31.1 provides relative allowable stress values between various materials as described in the Appendices.

The A335 alloy piping materials are commonly available in P11 and P22 flavors, but have about the same strength as A106 B/C at low tempertures ( <500F). The P91 subset of A335 has significant additional strength at low temperatures(about 25-30%), but is notoriously more difficult to weld.

You may want to consider A312 stainless steel piping

On another related topic, how do you plan to make elbows and piping joints ? Butt welds ? Socket joints ??

The B31.1/B31.3 codes caution against use of socket welded joints in high pressure cyclic duty... (like you would find in a hydraulic system)

Hope that this helps...


-MJC

 

[cbrn]

Hi,
also keep in extreme attention the fact that high-strength alloys are generally much more sensitive to fatigue than common carbon steels.
Moreover, carefully examine weldability. In the industry field in which I work, a disaster with 3 human beings' cost happened because a buried penstock pipe was made in high-resistance steel and the weldings prooved, in the end, difficult...

For the chronicle: one penstock exploded in service due to failure of a shop-made longitudinal welding. The water, at a pressure of about 140 bars, perfored 13 meters of rock and destroyed a control house on the surface, where the 3 men were working...

Regards

 

[ktxmarco]

Thanks guys.

I think we will go with the A106B/C as it will do the job and the cost/benefit of the CrMo isn't there, plus the weldability and fatigue is a downside that we don't want.

Cheers,
Mark

 

[DavidMc]

As a pipefitter I have used common seemless schedule 80 Carbon on alot of high pressure hydrolic systems. The one thing that I may offer to you is that the engeneer always used Socket Weld type fittings. Allowing the pipe to adjust to the different operating tempatures. Hope I was of any help.

 

[monofm4m]

Hello,

The high strength grades of API 5L such as Grade X42, X60 seems to be more close to A106-B or C rather than A335 (low alloy steel).

Of course, X grades of API 5L is also required to think about weldability more careful than 35 ksi like A106-B. I think, however, still P No.1 is S1 so that it is more easier for you to manage.

Only what you need to add for consideration is corresponding material specification of fittings and flanges.