Hello Experts,

What possible cause for hunting Level transmitter?

We replaced all components one by one and as well as new Transmitter, but still we are not Succeed to solve this issue.

 

No one here can see your installation. We only know what you tell us, which thus far, is practically nothing (your level sensor has a problem). You need to tell us a lot more if you want us to help.

Did any level sensor ever work properly in this installation?

Is this a newly installed level instrument?

What model E&H?

What technology (DP, radar, ultrasonic, capacitance, bubbler DP) does the E&H use?

How do you know what the level should be? Tape and weight? bypass sight indicator? something else?

What does 'hunting' mean? Please give several examples of what the level should have been and what was reported, which reflects 'hunting'.

How often does hunting occur? only at night? only when the 10,000HP motor next to starts up?
Once an hour?

What kind of vessel is this installed on?

What is the instrument measuring the level of? what kind of liquid, what kind of solid?

What temperature does the level sensor see on the process side? What temperature on the ambient side?

What pressure or atmosphere (chemical vapor? steam?) does the level instrument see on the process side?

Where is the level instrument installed on the vessel? Give a description of its location.

What changes the level? Where is the level in the process? Does a pump fill the vessel? valve drain? gravity fill?

 

Perhaps the level is going up and down. Or there are pressure changes (turbulance) that look the same as far as the transmitter is concerned. Since you don't mention exactly what type it's hard to know. But whatever the parameter it is actually measuring you need to see why that is changing since there is a good chance that the transmitter is working.

Regards
cww

 

One possible reason for a level loop being reported as "hunting" is a phenomenon called hydraulic resonance. If you set up a u-tube with liquid in it, you will notice that if the level is disturbed somehow it will oscillate back and forth at a steady rate. With an external standpipe connected to a vessel, you get the same sort of effect, ad if the level in the vessel is changing rapidly (because it's boiling, or you have an incoming stream falling on to the top, or it's being stirred) then the indicated level may appear to be cycling. It just so happens that for most installations the period of the cycle is between 2 and 10 seconds, which makes it very noticeable.

 

> Did any level sensor ever work properly in this installation?
yes since 5yrs

> Is this a newly installed level instrument?
No

>What model E&H?

> What technology (DP, radar, ultrasonic, capacitance, bubbler DP) does the E&H use?

> How do you know what the level should be? Tape and weight? bypass sight indicator? something else?

> What does 'hunting' mean? Please give several examples of what the level should have been and what was reported, which reflects 'hunting'.

> How often does hunting occur? only at night? only when the 10,000HP motor next to starts up?
> Once an hour?

> What kind of vessel is this installed on?

> What is the instrument measuring the level of? what kind of liquid, what kind of solid?

> What temperature does the level sensor see on the process side? What temperature on the ambient side?

> What pressure or atmosphere (chemical vapor? steam?) does the level instrument see on the process side?

> Where is the level instrument installed on the vessel? Give a description of its location.

> What changes the level? Where is the level in the process? Does a pump fill the vessel? valve drain? gravity fill?

For your reference as your questions

Yes since 5 yrs its working.

Model Levelflex M FMP40 Guided level-Radar E+H make.

There is no separate manual level indicators.
because this sensor using for crushed bath and alumina mixed materials. But while we dumping 50% at a time, the material will fill to other system.

while filling as well as dumping the silo suddenly its shooting up to 100% or more and tripping the system.

Ambient temp around 47 in summer.

Installed on top of the Silo.

material filled by air pressure around 400mbar

And unload by gravity with fluidisation.

Thanks

 

You can compare the parameters of newly installed E+H module with the replaced one.

There is a damping rate in modules for level measurement, by default they are set in milli-seconds. You can check all parameters and change accordingly.

Second you connect the mA source at the transmitter module with fix value (like 12 mA)up-to one or two hour, to ensure that the loop from transmitter to the control system (DCS or PLC) is healthy.

 

Most all modern level instruments can be configured to indicate a high or a low level (or sometimes a specific intermediate level) if the instrument's detection circuits fail to get any reading or if the reading is of very low confidence.

Is this unit configured for 'fail high' at 100%? I suspect it is.

If so, it leads to the question as to why the instrument is faulting during fill or dump conditions.

It isn't clear whether this 100% jump has always been there for 5 years and that's been tolerated or whether the jump-to-100% condition has just started.

If it just started, then it could be

- 5 years of service has affected the ability of the instrument to make a good reading (wear (I know rope probes are subject to wear), probe build-up, or ambient heat exposure (is there a sunshield?) has affected the transmitter's efficiency)

- a replacement unit is not configured or set up the same same as the original.

- something in the process changed. The change affects how the instrument makes its readings. Like the fill port moved to the 'other' side of the silo, right next to the wave probe?