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Join Date: Sep 2016
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Krohne Magnetic Flowmeter

09/21/2016 6:16 PM

Hi,

I need help. We are using Krohne IFC100 Signal Converter for Magnetic Flowmeter in company.

The Range is 0 to 1000m3/hr. when the pump is in off condition the flow is hunting from -66 to 236m3.

when we make pump ON the value is same hunting.

at off condition i make zero calibration of transmitter. but also after that again flow reading shows hunting. After Calibration also the value is not getting zero and it start reading from -60 to 270m3

i am not able to understand about what the problem exactly. so Please anyone help how can i solve this problem.

i check manual as per manual i follow all step by step procedure after that also the same problem occurs.

Main Problem is Flow shows Continous Hunting when the is in OFF Condition and as well as ON Condition.

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#1

Re: Krohne Magnetic Flowmeter

09/21/2016 6:50 PM

Krohne will know. Your meter is probably toast.

Quit wasting time and call them.

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#2

Re: Krohne Magnetic Flowmeter

09/21/2016 7:26 PM

1) Vertical down flow

Mounting a mag tube vertically with downwards flow will produce erratic flow readings, correctable only by mounting the tube in different location with upwards flow or in a horizontal pipe in a low spot where air/gas will not collect.

2) remote mount cabling

These symptoms sound like when the transmitter is mounted remotely from the magnetic flowmeter tube in the pipe and the raw flow signal from the tube to the converter/transmitter is noisy.

If the transmitter/converter is mounted remotely, and the installation did not use the manufacturer's low-noise cable then that is the first thing to fix. To my knowledge, all magmeters can use 'alternative' low noise shielded twisted pair cable, but the cable has to meet the published spec by the flowmeter manufacturer. I can't tell you how many times I've seen remote mounted mag meters wired with THHN, or equivalent, with noise and shifting zero problems.

2) Missing grounding/earthing rings

The body of the sensor must have the same electrical potential as the liquid
being measured. Some magmeters need ground/earth rings between the mag tube and the pipe. You need to refer to the magmeter tube's installation guide for manufacturer's advice on whether ground/earth rings are needed AND how to wire them correctly.

3) It isn't noise, it's real

Sometimes the flow 'noise' is real. Expecting zero flow when a pump turns off might seem reasonable, but depending on what the piping is, there can be all sorts of flow, forward or reverse, once the pump turns off.

4) Magnetic slurry

A magnetic slurry will be noisy because of the magnetism of the slurry particles.

5) Electrical current in the fluid not generated by the magmeter

On rare occasions, electrical currents through fluid will affect the readings. Systems with cathodic protection corrosion protection can be subject to noise induced from the corrosion protection system.

I'm sure the manufacturer's manual has a troubleshooting guide.

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#6
In reply to #2

Re: Krohne Magnetic Flowmeter

09/22/2016 4:49 PM

The only thing I could think of to possibly add to this would be something like close coupling of a high decibel acoustic noise into the pipe. Is that possible? Plausible? Busted?

We have a mag meter (Signet) that runs from 0-1 m3 on a 3" pipe that supplies media filters upstream of our RO system at work. The probe is mounted on a vertical run (that stays solid (no air)), and it does not show fluctuations in flow or direction of flow when systems are offline. I am sure you are installed on a much larger pipe, so any differential heating (one side of pipe in the sun, other in the shade) will set up thermal currents. 264,172 US Gallons per minute might take a pipe of 50" radius?

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#7
In reply to #2

Re: Krohne Magnetic Flowmeter

09/24/2016 5:10 PM

The only thing I haven't seen mentioned how air bubbles in the mag tube will give you very erratic readings, with flow and no flow conditions.

I've seen air bubbles develop over time in piping with a high spot ahead of the flow meter, dissolved air collects in an elbow, until the fluid velocity increases enough to send a stream of air down the pipe. So a delayed reaction after pump start.

Also the meter can be set up to read reverse flow, or to ignore reverse flow, is it possible that there is flow with the pump off?

With very low conductivity fluids (polished condensate), your magnetic field may not be strong enough to generate the minimum voltage required by your sensor. Your Krohne spec guide will be able to help you there.

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#3

Re: Krohne Magnetic Flowmeter

09/22/2016 3:34 AM

It is really difficult to diagnose this sort of problem remotely. You need to be on the phone to the equipment manufacturer directly. I agree with #1 above.

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#4

Re: Krohne Magnetic Flowmeter

09/22/2016 5:50 AM

You say nothing about what is in the pipe, its temperature, or its pressure. You say nothing about the line size, the orientation of the meter and the number of diameters of straight pipe upstream and downstream. And, you say nothing about the telephone calls you need to have made with the equipment manufacturer, and the outcome.

And you still want help?

Marvellous.

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#5

Re: Krohne Magnetic Flowmeter

09/22/2016 6:17 AM

Whe we see that type of signal on a magflow meter that has been working properly, the cause usually relates to connection issues.

Corroded connections, flooded meter pits, broken connections and so on.

Experienced electrical maintenance staff required.

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#8

Re: Krohne Magnetic Flowmeter

09/26/2016 4:17 AM

Is it a new installation, or has it worked properly in the past?

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