×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Help with standards that govern welding valves to gas pipelines

Help with standards that govern welding valves to gas pipelines

Help with standards that govern welding valves to gas pipelines

(OP)
Does anyone know what industry standards are commonly used to govern the design and procedures used to determine the wall thickness of butt weld adapters used on ball valves for the gas pipeline market?  Also, does anyone know what standards govern when it is necessary to use a transition piece when welding two sections of pipe together with different wall thickness?


Background To The Questions:

On large diameter ball valves used in the construction of gas pipelines, we are seeing different valve manufacturers offer valves of the same size, type, and pressure class but with with large differences in the ID of the butt weld adpater flanges that are used to connect these valves into the pipeline.

Some have told us that ANSI B31.3 and/or B16.34 standards are typically used for formulas, allowable wall thickness or allowable material stress to determine required wall thickness of a valve's buttweld end.  These are conservative standards that tend to lead to very thick wall sections that are in some cases 2-2.5 times thicker the the wall thinkness of the actual pipeline (when high stregnth X60 pipe is used).  Others don't provide that much detail about what drives their standards, but provide much thinner adapter sections and state that there valves meet all design standard.

Who is right?  It all comes down to cost, as some of our engineers feel that there is no way to weld a valve with say a 1" wall thickness to a gas pipeline that has a .375" wall without the use of a transition piece.  Those components add lots of extra expense that I want to avoid if possible.

RE: Help with standards that govern welding valves to gas pipelines

I can only try to answer part of your post as follows:
a.) API Specification 6D - Specification for Pipeline Valves (Gate, Plug, Ball, and Check Vlaves)
b.) API Standard 1104 - Welding of Pipelines and Related Facilities

I'm not sure if any one standard covers specific component thickness(es) of materials, this would be material/service/pressure-specific information. The 6D specification provides standard dimensional properties of certain elements of valves such as bore sizes, flange properties, etc., and operating pressures (class specific).

Can the theoretical valve (1"T) be machined to accomodate the thinner wall pipe (0.375"T) eliminating a pup piece reducer?

RE: Help with standards that govern welding valves to gas pipelines

Refer to ASME B31.8 Fig. 15 for acceptable designs for unequal wall thickness. Please note that gas pipeline design is based on Specified Minimum Yield Strength (SMYS)- not on Specified Minimum Tensile Strength as for B31.3 and the minimum wall thicknes of your low strength valves may be less than that required for B31.3 designs.   

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources