×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Orifice Plate Measuring Flow Away From Calculated Value!

Orifice Plate Measuring Flow Away From Calculated Value!

Orifice Plate Measuring Flow Away From Calculated Value!

(OP)
Hi,



I need ur support to point out our current issue with one of orifice plates at Refinery site. It is measuring LPG produced from Overhead of Platformer Stabilizer Column. The issue is unclear for us until this moment;

The orifice was calculated and its transmitter was calibrated for a full range of 222 TPD of LPG for delta pressure of 0.5 barg. The calculation was checked through software and confirmed that the data is suitable for orifice plate with bore size 27 mm. The current issue is; the transmitter of this orifice plate is reading over range "IOP" lively and DP was checked at site to be found 0.7 bar which makes sense for having "IOP" reading at DCS. However, the actual flow based on other downstream transmitters are showing around 70 TPD coming from this line ! and it goes to the sphere as a final destination. So we are sure this flow should be lesser than what the transmitter is showing (>222 TPD) ! The high DP 0.7 bar around this orifice at site is making us without a clue!

We took plenty of actions trying to understand why we have a high DP where; the impulse lines were changed, the transmitter was changed with a new one, a live pressure gauge was installed at site to measure DP around impulse line. With all of these actions, yet the DP is high "~0.7" bar.

What is missed here? Please advise,

I attached the calc sheet for this orifice.

RE: Orifice Plate Measuring Flow Away From Calculated Value!

Temperature and pressure at the orifice are reading what? Temp and pressure at the downstream transmitters are what? What is the chemical composition of the gas, any water in the mix?

RE: Orifice Plate Measuring Flow Away From Calculated Value!

The vapor pressure of your propane component is 13 BarA, chances are, the vapor pressure of the actual fluid is even greater.

You may be dealing with two phase flow though your meter.

RE: Orifice Plate Measuring Flow Away From Calculated Value!

Reviewing your documents, the meter calc specifies "liquid" service with a density of 508 kg/m3

when I run my calc's, I get density of 38.5 kg/m3 with SG relative to air of 1.584
Haven't used those calcs in ages and may have some units a bit off, but food for thought

Good luck

RE: Orifice Plate Measuring Flow Away From Calculated Value!

What hacksaw says...you've got significant amounts of ethane and methane as well, so you are likely having 2-phase (gas bubbles in liquid) flow.

RE: Orifice Plate Measuring Flow Away From Calculated Value!

and possible liquid buildup unless mounted vertically,

but fundamental questions regarding his "fluid" claimed as overhead gas, with liquid properties

RE: Orifice Plate Measuring Flow Away From Calculated Value!

The pid sketch suggest the flow meter is in a pump discharge
The overhead gas is passed through a water cooled HEX

RE: Orifice Plate Measuring Flow Away From Calculated Value!

What the process owner didn't tell you was that a you were asked to install a failed design!
Good luck.

RE: Orifice Plate Measuring Flow Away From Calculated Value!

Without knowing more, would suggest that, in volatile LPG service, the impulse lines should be remote sealed.
Looking at your PFD, presume water is decanted at the ovhd reflux drum ?? Is there LPG dehydration further down the line before the other FT near the sphere which is reading 70TPD?
Assuming this is in Oman, the impulse line temp could be as high as 65degC, so is your max normal LPG bubble point temp > 65degC at the min operating pumping pressure from P8212/13/27 ? If LPG bubble point temp is less than 65degC, the impulse lines must be remote sealed.

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close