Previous in Forum: SMC IP801   Next in Forum: Magnetic Flow
Close
Close
Close
11 comments
Active Contributor

Join Date: Aug 2014
Location: CAIRO
Posts: 14

Electromagnetic Flow Meter Installation Issue

12/02/2014 3:10 AM

Dears ,

I have Siemense Magflow 5100W , DN750 , the required Straight length upstream is 5D and downstream is 3D , which means i need a straight length of 6 Meters , this is not available in the existing installation , i just have around 4 meters of straight length , is there any solution by which i can get acceptable reading ? ,

Login to Reply
Interested in this discussion?
You can "subscribe" to this discussion to be notified of new comments.
Click on the Subscribe menu at the top of the page.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 76
#1

Re: Electromagnetic Flow meter Installation Issue

12/02/2014 3:12 AM

Define "acceptable".

__________________
Good moaning!
Login to Reply Score 1 for Good Answer
Active Contributor

Join Date: Aug 2014
Location: CAIRO
Posts: 14
#2
In reply to #1

Re: Electromagnetic Flow meter Installation Issue

12/02/2014 3:21 AM

I mean low error %

Login to Reply
Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 76
#4
In reply to #2

Re: Electromagnetic Flow meter Installation Issue

12/02/2014 11:52 AM

Define "low error %"!

__________________
Good moaning!
Login to Reply
Guru

Join Date: Feb 2011
Posts: 1120
Good Answers: 11
#3

Re: Electromagnetic Flow meter Installation Issue

12/02/2014 5:40 AM

Follow the manufacturer's manual, you need a laminar flow on the line to have acceptable & reliable reading. Bends and elbow distorts stream line which could affect transducer reading.

What fluid are you measuring? Please consider having the pipes reduce to some smaller diameter so 5D and 3D could be achieve, but take note, fluid velocity at this reduced pipe will be greater than the original size and by this gather information on the manual if it recommends allowable fluid velocities.

Reducing Pipe lines also constricts flow, so better check if pumping is not on a critical issue to consider.

__________________
" To infinity and beyond" - Buzz Lightyear
Login to Reply
Guru

Join Date: Jul 2007
Location: Commissariat de Police, Nouvions, occupied France, 1942.
Posts: 2599
Good Answers: 76
#5
In reply to #3

Re: Electromagnetic Flow meter Installation Issue

12/02/2014 12:03 PM

No, you don't need laminar flow in a "Reynolds number less than 2300" sense in a magmeter. Magmeters are routinely used in >2300 situations in municipal water supply.

The diameters are needed for flow straightening before and after bends. As fluid takes the outside of the bend it archives a different velocity compared to the inside, and it takes a few diameters of straight pipe for this effect to normalise, creating the correct velocity profile across the pipe. Installers ignore the manufacturer's recommendations at their peril.

__________________
Good moaning!
Login to Reply
Guru
New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
Posts: 8777
Good Answers: 376
#6

Re: Electromagnetic Flow Meter Installation Issue

12/02/2014 1:38 PM

Siemens are generally pretty good when it comes to application notes, all I can suggest is looking in the manual and on-line application notes and see if there are accuracy derating factors. You may find that the error is negligible and Siemens are just being cautious, but again it may depend on your flow rates, the material flowing and pipe diameter.

If all else fails and Siemens are no help you could calculate the flow rate manually and check the real error that way, after all what goes in must come out.

__________________
jack of all trades
Login to Reply
2
Guru

Join Date: Jul 2010
Posts: 664
Good Answers: 175
#7

Re: Electromagnetic Flow Meter Installation Issue

12/02/2014 2:15 PM

I have sacrificed downstream length to get as much upstream as possible for a magmeter. No way to tell what the error was, it was the only flow meter.

This article on piping requirements for flow meters is interesting.

In case it can't be read due to image molestation, I'll quote the significant part, "Magmeters are relatively insensitive to errors caused by nonsymmetrical velocity patterns or swirl. The general rule of thumb for straight piping is a five-diameter length of piping upstream and three diameters downstream from the meter (measured from the center of the tube).

Independent testing has shown that magmeters may be affected by piping effects when the length of upstream straight pipe is less than three pipe diameters. Errors from piping effects generally run between 0.1 percent and 1.5 percent, depending on the exact configuration of piping and length of pipe run upstream of the meter."

http://www.flowcontrolnetwork.com/articles/flowmeter-piping-requirements

The author Livelli is in the biz, but doesn't cite the independent studies that claim that swirl error due to short upstream pipe maxes out at 1.5%.

(as an aside, note that the graphic illustration is in gross error. The horizontal meter has no upstream run and is too close to the upstream elbow. I suspect that the graphic is for a coriolis tube because of the statement "No (straight run required)" Why parentheses? Where is the editor?)

Anyhow, if a 1.5% error is too great, then you'll need some flow conditioning. You need to cut the pipe to install the mag tube anyhow.

Login to Reply Good Answer (Score 2)
Commentator
United States - Member - VT

Join Date: Jun 2014
Posts: 55
Good Answers: 4
#10
In reply to #7

Re: Electromagnetic Flow Meter Installation Issue

12/03/2014 8:54 AM

Most of our newer flow meters are ultrasonic (Panametrics), but we have a few Cadillac CMAG flow meters, chosen to accommodate the piping. Cadillac specifies a 1.5D piping limit, up and downstream. I don't have any experience with Siemens' mag meters to compare, but Cadillac has provided better customer service, an important consideration for me.

How do you commission/check/calibrate the accuracy of these things over time? If I knew I had only 1.5% error on the flow signal, I would be happy.

__________________
Teach your cat to write
Login to Reply
Associate

Join Date: Apr 2009
Location: Australia
Posts: 54
Good Answers: 5
#8

Re: Electromagnetic Flow Meter Installation Issue

12/02/2014 10:46 PM

There is one way to help straighten the flow for the flow meter and that is to install straight vanes upstream. The length of the vanes should be about 2-3D and you could use 3-4 vanes in a parallel configuration or a "star" configuration.

Of course, if there are likely to be items of debris in your flow, they would catch on the vanes, so you could not use this idea for sewage flow.

__________________
Frankston
Login to Reply
Guru

Join Date: Jun 2011
Location: Mossel Bay, SA
Posts: 777
Good Answers: 21
#9

Re: Electromagnetic Flow Meter Installation Issue

12/03/2014 2:08 AM

Modify the pipework.

Login to Reply
Member

Join Date: Aug 2014
Posts: 5
#11

Re: Electromagnetic Flow Meter Installation Issue

12/03/2014 4:53 PM

In line diffuser. Maybe ?

Login to Reply
Login to Reply 11 comments
Interested in this discussion?
You can "subscribe" to this discussion to be notified of new comments.
Click on the Subscribe menu at the top of the page.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

AminHasan (1); az mech (1); Crabtree (3); Frankston (1); Hilton (1); Iris (1); jack of all trades (1); jonaparker (1); Noudge79 (1)

Previous in Forum: SMC IP801   Next in Forum: Magnetic Flow

Advertisement