×
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

Metallic Flex hoses in ASME B31.3

Metallic Flex hoses in ASME B31.3

Metallic Flex hoses in ASME B31.3

(OP)
Hello,

Can anyone tell me in which section of ASME B31.3 says that metallic flex hoses can not be used for permanent process piping?

Thanks in advance,

Corgas

RE: Metallic Flex hoses in ASME B31.3

Refer to table 326.1 for details on standards for flex hoses

RE: Metallic Flex hoses in ASME B31.3

There is nothing in B31.3 which prevents the use of flexible metal hoses in normal fluid service for permanent piping. Certain types of joining methods require "safeguarding". The table XL83NL gives lists the standards to which components such as flex hoses must comply.

RE: Metallic Flex hoses in ASME B31.3

(OP)
Thanks XL83NL & moltenmetal,

In our company, we don't have an in-house standard that covers use of flex metallic pipe. I checked two (US) oil & gas major companies and both prohibit the use of flex metallic hoses for permanent process piping.

Yes, I did look at table 326.1 and they list BS 6501, Part 1 as reference standard for flex hoses. In another post here I found : "When flex lines are used in critical or hazardous service, the owner should have a high-integrity maintenance system that ensures the flex line is always in good mechanical condition. Flex hoses are more likely to experience catastrophic failure as compared to hard-pipe, and that's one reason it's generally unacceptable from a risk perspective to simply run-until-failure. it's very difficult to implement any type of preventative maintenance testing that will accurately predict the life expectancy of a flex line. Consequently, good maintenance integrity programs typically call for a fixed time period at which the hose needs to be replaced."

Next question will be : How often should these hoses be replaced? If you tell me to follow manufacturers recommendation, I'll be changing them every 3 months!!!!

Corgas

RE: Metallic Flex hoses in ASME B31.3

Oil and gas companies prohibit lots of things, some for good reasons related to the LONG design life of their projects, and others for not-so-good reasons. But that's not the question you asked: you asked whether there were CODE rules preventing their application, and in B31.3 there are not.

Flex hoses, properly implemented, can be real problem solvers and can make piping systems safer. Compare the implementation risk of these against expansion joints of various kinds...But hoses too are often mis-applied, in particular when they are used improperly to replace an axial expansion joint. A hose where the overbraid has been slackened by axial compression is little more than an under-designed expansion joint.

Service life depends greatly on service conditions. Hoses contain thin parts which are highly worked, which makes them vulnerable to corrosion and corrosion-related embrittlement in particular. The nature, direction, magnitude and frequency of flexing is also important.

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