Mag Meter
Mag Meter
(OP)
I spoke with Siemens today about their Magmeters they want us to use on our equipment.
He stated flat out that they care not at all about flow runs or pipe and fittings before or after their flow meter.
The 2" model I looked at was flanged on either side, about 10" long.
This seems about right to me because this is a mass meter, but is that agreed upon by peers or the engineering community?
He stated flat out that they care not at all about flow runs or pipe and fittings before or after their flow meter.
The 2" model I looked at was flanged on either side, about 10" long.
This seems about right to me because this is a mass meter, but is that agreed upon by peers or the engineering community?
PUMPDESIGNER





RE: Mag Meter
(Often, for a given flow, you will find that it is more economical or even necessary to use a flowmeter one size smaller than the process pipe size, depending on the flow velocity through the meter).
Within this 5D / 3D distance, no bends, fittings, etc. are allowed.
Further, the angle for reducers / expanders in the vicinity of the flowmeter has to be maximum 4 degree.
I think, it would be prudent for you to follow the above guideline - since your line size is only 2", this might not pose any problems.
RE: Mag Meter
We will be using 2" - 6" most of the time, so that pipe run is important, and we always put that flow run in. But this guy claims it is not necessary for the Siemens magmeter. He was a factory guy, not some local rep.
It is tempting to consider what they say because those flow runs are hard to get, would release us from that design parameter, lower cost too.
Here is one thought, if turbulence reduces accuracy in a predictable way and not too much reduction in accuracy, we could work with that, "suitable for purpose". We are not involved in custody transfer, or sales per volume, we just want a general idea of flow rate with accuracy of 3% and high repeatability and reliability. The Magmeters are attractive because they have no moving parts, and potentially could work in tougher piping situations with less up and downstream requirements.
PUMPDESIGNER
RE: Mag Meter
RE: Mag Meter
Magnetic flow meters are only suited for the conductive fluids.
John
RE: Mag Meter
RE: Mag Meter
Last point in your first post,
is not clear to me.
Regards,
RE: Mag Meter
RE: Mag Meter
I think quark would have gotten to me also on this.
Thank you guys, I am weak on flow meters so I have some study to do on the subject.
PUMPDESIGNER
RE: Mag Meter
bmsg - We are dealing primarily with groundwater on this application, but sometimes we do potable water. Do such fluids easily accomplish 20 microsiemens by your experience?
Can I put a 110 line into the water and tell with my tongue?
PUMPDESIGNER
RE: Mag Meter
But there are true massflow meters(for ex. corriolis, thermal etc.) that don't require density compensation. Straight length requirement is insignificant in this case.
There is no problem with conductivity if the water is potable(you will have problems with purified water and better quality waters apart from other pure liquids). As a thumb rule you can calculate conductivity as TDS x 0.6.
I once again caution you to check for full pipe flow as the volumetric flow calculations consider full pipe diameters. BMSG's suggestion about the expander and reducers should not be overlooked.
Good luck,
RE: Mag Meter
Our water temp is 60-90 F., very little density variation there.
We never have less than full pipe, high pressure systems only (High pressure meaning 60-120 psi), always full pipe.
So quark, if our pipes are always full, water temperature is always 60-90, is a magmeter's accuracy much affected by fluid flow conditions as affected by upstream/downstream conditions?
PUMPDESIGNER
RE: Mag Meter
Generally magmeters can be selected upto 8m/s velocity, to reduce first cost, if the permanent pressure drop is insignificant. The expander and reducers may create a chance for formation of vena contracta. Except that everything is perfect for a magmeter to be in your application.
If a 2" magmeter has a length of 10" and if the sensor is at the midlength then you already have 2.5D straight length on either side. Seems to be ok.
Regards,
RE: Mag Meter
I had an application of using 2 mag meters, I was limited in space so the configuation was, 10" mag meter, 12" diaphram operated control globe valve, 12" tee (run-run), 24" of 12" pipe, second 10" mag meter, On each side of each mag meter was a 12" x 10" reducer, we were not looking for high accuracy in the second mag meter, just to find out about how much water was flow in or out of the tee, The first mag meter was within the accurancy of a turbine meter 2 miles up stream, so it was OK, the second mag meter read up to 10% low or high (depending upon the position of the control valve) when it was known there was no change in flow due to the tee. When the valve was closed and flow from the tee (bull) to the second mag meter accuracy was better.
Results: 5D is vital when a globe valve is upstream, anything downstream 1d maybe
As for conductivity, a means of grounding the meter to the water is required, you can use ground rings installed in the flanges or a corporation on the downstream side, lack of a good ground will give fluctating readings at steady flow.
A Mag meter works by inducing a magnetic field and measuring the deformation of the field by the fluid moving through the pipe, so small eddies should cancel out hence the reducers had no effect except to increase velocity for higher accurancies.
Hydrae
RE: Mag Meter
Thank you, Tribal Knowledge good stuff, send you fire water if you want some.
PUMPDESIGNER