"severe cyclic service" ?

[alleyesandears]

Given the following would ASME B31.3 consider the piping to subjected to "severe cyclic service"?

300 plus feet of schedule 80 2" seamless line pipe in 10 foot joints using 2" fig 200 hammer unions delivering air to drill rig at 700 to 3,000 cfm with flucuating pressures of 500 to 2,200 psi while subjected to all sorts of outside weather and tempuratures?

 

[JohnBreen]

There is no "severe cyclic service" defined by B31.3

Severe cyclic conditions are defined in paragraph 300.2 as applying to specific piping components or joints in which Se computed in paragraph 319.4.4 exceeds 0.80 Sa as defined in paragraph 302.3.5 and the equivalent number of cycles exceeds 7,000. The cited paragraphs speak to DISPLACEMENT STRESSES and these do not necessarily vary (cycle) with internal pressure.

While B31.3 requires that the engineer consider fatigue due to pressure cycling in the piping design (Paragraph 300.10) there is no specific guidance provided. Reference is made to the fatigue evaluation described in paragraph K304.8.3 (high pressure).

If the conditions described (high displacement stresses combined with many displacement stress cycles) are shown to be present by stress analysis, the B31.3 Code limits the materials that can be used in paragraph 305.2.3. There are some API line piping materials listed in this paragraph.

Regards, John

 

[Ballbearing1]

JohnBreen,
I am somewhat astounded by the statement
"There is no "severe cyclic service" defined by B31.3"

There are three main classes of piping in B31.3 (I am not including Cat M and Chapter IX)and these are Severe Cyclic, Normal Fluid Service and Category D

Even in the index there are 22 references to Severe Cyclic Conditions.
I will not attempt to answer the original posters question as I am not a piping engineer, there will be gentlemen much more qualified than me that can give a response,
Regards,
BB

 

[JohnBreen]

Ballbearing1

I "spoke" the truth.

In B31.3 we define several "Fluid SERVICES" and these include Normal Fluid Service, Category D Fluid Service, Category M Fluid Service (the project manager for developing the "fluid service" concept was Dave Moody - therefore the D and the M) and High Pressure Fluid Service. If you look at paragraph 300.2 under "fluid Service" you will see that we define only four Fluid SERVICES.

Severe Cyclic CONDITIONS can occur in any of these Fluid Services (but it may disqualify the design by B31.3 standards). However, Severe Cyclic Conditions is NOT a Fluid Service. We added "boxes" to Appendix M to have Severe Cyclic Service considered by the owner and the piping engineer while determining the appropriate Fluid Service to be designated by the owner. Fluid Services, with appropriate designed safeguarding (when indicated) are not adverse conditions, severe cyclic conditions are to be avoided by proper design. Note that by reducing the level of displacement stress range (by design) to below 0.80 Se, cycles beyond 7,000 will not necessarily bring the design to a severe cyclic condition (see paragraph302.3.5(d)).

We carefully worded the definitions of "Fluid SERVICES" and included the consideration of Severe Cyclic CONDITIONS in the rearrangement of Figure M300 in an effort to avoid confusion between Fluid Services and other design considerations.

Regards, John.

 

[Ballbearing1]

John,
My apologies.
Thank you for the response and explanation.
However I am still a little confused,I am a CWI and have regularly worked on piping projects where the inspections are conducted in accordance with Severe Cyclic requirements.
That is what I thought the original question was about, was the piping he described required to comply with Severe Cyclic requirements ?
I always presumed that the design and fabrication were done in accordance with Severe Cyclic Conditions as well. Based on your explanation above it appears I was wrong.
Never too old to learn which is what makes these forums so educational

Thanks again,
BB

 

[JohnBreen]

BB

was the piping he described required to comply with Severe Cyclic requirements ?

Not necessarily. Again, it would take a stress analysis to determine if the Displacement Stress Range at any component exceeded 0.80 times the allowable stress range (Se). And then the system would have to exceed 7,000 cycles. All the current rules address for severe cyclic conditions are the displacement stress range (that could be driven by temperature excursions or by wave motion or other exciters). You can see our problem: we do not have rules in the base Code to address cycling pressure.

He doesn't give us the temperature or the material but if we assume it is API 5L grade B he will be OK for static (steady state) pressure up through 400 degrees F. But depending upon the compressor characteristics he might eventually have a fatigue failure at one of the unions (stress riser). That is why the reference to paragraph K304.8.3 in Chapter IX - that might be the only way to address the pressure excursions using B31.3 rules.

Regards, John.

Regards, John

 

[JohnBreen]

All,

Are you ready for "Elevated Temperature Fluid Service"? Stay tuned.

Regards, John.