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Anonymous Poster

Foxboro Vortex Flow Meter

10/27/2010 1:11 PM

I had to work on a boiler today, the feedwater line going to the drum. For me to get any reading on the Foxboro flow meter, I have to have my control valve 37% open.

Meaning my flowmeter is not reading lower flows. When the boiler is running, the flowmeter will pick up a signal of 70 000 lb/h then go to zero, then read again, then go to zero again. Forcing the valve to open , close , open , close.

Anyone see this problem before with vortex flow meters? I know they're usually not good in lower flows, but it wont read anything below 50 000lb/h.

A contractor installed it 6 months ago, it worked good the 1st month, then this started to happen.

Anyone?
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Ducdude
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Join Date: Oct 2009
Posts: 60
#1

Re: Foxboro Vortex Flow Meter

10/28/2010 9:21 AM

If the sensor worked when installed and now it does not then something changed....

Very often with new installs we will see a lot of sensor adjustments taking place "dialing the sensor in" This often results in a change in the sensors gain or low flow cut off that will have the exact results you are seeing.

To remedy this try increasing the gain or reducing low flow cut off or check the devices span and make sure it matches up with your desired measurement range.

If the sensor is set up exactly the same as when it was installed, when it worked as desired, then there are a few things that could cause what you are seeing..

If there is material in the flow stream blocking the bluff body or affecting the formation of vortices then you will have this.

If the sensors inlet is not properly lined up with the process pipe you will also see this..

Cheers,
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PWSlack
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#2

Re: Foxboro Vortex Flow Meter

10/28/2010 1:03 PM

Yep. It sounds like the low flow cut off is incorrectly set-up. Get the manual out and have a good read of it.

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