×
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

Adjustments for flow meters

Adjustments for flow meters

Adjustments for flow meters

(OP)
thread124-194412: flow compensation from flow meters

I read through this thread and am having difficulty understanding where the square root function enters in.

I am looking at a Variable Area Flowmeter, specifically Swagelok VAF-M3

Neglecting density and temperatures ratios, (comparing nitrogen and air at ambient conditions), shouldn't P1 x V1 = P2 x V2 where the V's stand for volumetric flow rates at different pressures such as standard (P1) vs system pressure (P2). I don't think I need to consider compressibility factors and I do not think this varies much from the ideal gas law.

Given a 90 psig (104.7 psia) piping system and a flow meter calibrated at standard condition 0 psig(14.7 psia), using the sqrt[P2/P1] gives a different correction factor (2.669) than P2/P1 (7.122).

What am I missing?

RE: Adjustments for flow meters

The square root factor comes into play for meters measuring differential pressure to obtain flow.

A variable area meter may or may not be based on differential pressure.

See attached brochure for one that is based on dP.

There are other meters that would be called "rotameters" that will be true "volumetric" flow meters.

And also follow the compensation rules cited:

http://www.tokyokeiso.co.jp/english/technology/tec...

RE: Adjustments for flow meters

(OP)
The information from the Swagelok installation isnstructions indicates using the a field adjustment factor using square roots - so I am assuming it is because the flow meter uses differential pressure.

It just seemed strange to me.

I would like to see the math behind it, but it might not be readily available.

RE: Adjustments for flow meters

Refer to the factors in the Tokyoeiso guidelines also.

The "rotameter" is really a "force balanced" meter and does involve some square root funtions.

Perhaps Perry or some other reference can guide you. McCabe and Smith has some formulas also, and show how they are derived.

Good luck.

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