×
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

Pressure rating on a tank return manifold
2

Pressure rating on a tank return manifold

Pressure rating on a tank return manifold

(OP)
Good afternoon everyone,

There is a welded manifold fabricated from 1.5" square ERW tubing and half couplings, it is a collector of a number of case drain lines from some hydraulic pumps. The hoses come together to the manifold because there is a temperature gauge on each line for monitoring the condition of each pump, the manifold brings the gauges together so a person could monitor all the pumps easily from one place. The case drain lines all collect into the manifold which then dumps into the supply tank via a return filter. There is a steady stream of flow that keeps the manifold full, and the manifold is flooded anyway because it is mounted a couple feet below the level of the tank.

The problem is that one of this manifold had developed a pinhole leak, and in the resulting investigation it was determined that the manifold had not been given a pressure rating and therefore had no pressure test instruction. As I say this is a low flow-rate application mounted just a couple feet below fluid level, so while the collector is exposed to a constant pressure, it isn't exposed to much pressure.

I'm thinking of giving the collector a working pressure limit of say 100 psi and ask for a pressure test at time of fabrication of 1.5x working pressure (150 psi). It is a weldment constructed of 1.5" square HSS tubing and end caps with numerous in and out ports, the ports are just half couplings welded on. It doesn't lend itself to any standard pressure rating calculation, would FEA be appropriate for this?

What is your suggestion?

Thanks in advance.

RE: Pressure rating on a tank return manifold

Are you kidding????
Your using square tubing in a Pressure Piping situation, Are you NUTS!!!

Where is this facility? I want to make sure I don't pass it when I drive around.

prognosis: Lead or Lag

RE: Pressure rating on a tank return manifold

(OP)
Hi, yes that would be bad. But seriously it is just a collector manifold that dumps into the supply tank, forgive me if I wasn't clear enough, the supply tank is at ambient pressure conditions.

If I was to make a guess what the collector manifold is pressurized up to, it might be as high as 10 psi or so.

RE: Pressure rating on a tank return manifold

ASME VIII Div 1 allows Proof Testing. Just do that, using a 4:1 safety factor. Hydro to 160 psig, and rate this 'problem child' at 40 psig, based on the proof load. Or 200# and 50#. And if anybody is afraid to hydro it to these pressures, scrap it and make one from SA-53 pressure piping material.

1.5 x hydro's are ONLY for items designed within the rules of ASME, and built using approved materials. A500 tube-steel is really 'nice' stuff to build with, but it has NEVER been allowed for pressure-retaining members of ASME or API boiler, vessel, tank, pipeline, etc.

RE: Pressure rating on a tank return manifold

If you treat the flat side of that tubing as a fixed-fixed beam, calculate the moment and then the stress, that should be a pretty reasonable approximation. There are various grades of square tubing available, I think the most common is A500 Grade B, which has a yield stress of 42,000 or 46,000 or so- a little higher than A36, at any rate. If the calculated pressure comes up high, I'd probably lower it considerably anyway, just to allow for uncertainties in the grade and the construction. If it's subject to just a couple of psi, there's no real reason to rate it higher than 15 psi or so.

ASME Section VIII does have design data for rectangular vessels in one of the appendices, but that'd probably be overkill. They may also assume stiffeners at regular intervals.

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