Installation of DP Transmitter at Suction Filter of Air Compressor

K

Thread Starter

karanbansal

We having an package IR air compressor with an DPT (honeywell ST3000) installed at suction. Both the tapping have been taken from same pipe (opposite sides) after suction filter and normally it shows 2-3 mmwc where as range is 800mmwc. If I open HP tapping to atmosphere, it shows 200-300 mmwc.

Could any one pls help? what is correction installation procedure to install a DPT at air compressor suction filter with UPSTREAM as atmosphere and DOWNSTREAM as suction pipe?
 
The impulse tubing/piping is backwards with respect to the ports on the transmitter.

The upstream side of the filter connects to the high side of the transmitter.
The downstream side of the filter connects to the low side of the transmitter.

When the plumbing is backwards, the differential pressure is negative because the high side pressure is lower than the low side pressure. The reason you 'see' 2-3mm wc is due to a slight positive offset between the 4.0mA output and whatever analog input the loop is connected to. If the output was exactly calibrated to the input, you'd see either zero or a negative value.

When you open the high side tap on the pipe to atmosphere, the low side on the transmitter sees zero and the transmitter high side sees 200-300mmwc pressure, and the output is positive.

Move the impulse lines to the other port on the transmitter (swap them).
 
R
> If I open HP tapping to atmosphere, it shows 200-300 mmwc.

The impulse lines should slope up towards the transmitter so any moisture will run back into the main line.

The HP connection is before the filter, the LP connection between filter and compressor.

The 200mm reading you are seeing would be consistent with a pressure of -200 mm before the filter and -400mm after the filter. You can easily check this with a simple manometer made from clear plastic hose or even a hose dipped into a bottle of water it should suck up the hose by 200 and 400 mm.
 
K
> The HP connection is before the filter, the LP connection between filter and compressor.

Both HP and LP connections are after suction filter, that is confusing me. How it will show DP if both HP and LP connections are taken after suction filter?
 
R
The connections are on either side of the filter, it's on the suction not the discharge.

>> The HP connection is before the filter, the LP connection between filter and compressor.

> Both HP and LP connections are after suction filter, that is confusing me.
> How it will show DP if both HP and LP connections are taken after suction filter?
 
> How it will show DP if both HP and LP connections are taken after suction filter?

It's doing what it's been installed to do - showing you the DP between the tapping points, 2-3mmwc, which sounds about right, depending on far apart the taps are. Unfortunately, that's a useless measurement; it's not the DP measurement you need.

You need a measurement of the DP across the filter to show you how the filter is getting clogged over time.

So you need to create a new tapped point upstream of the filter and move the high side impulse line to the new tap.
 
K
> So you need to create a new tapped point upstream of the
filter and
> move the high side impulse line to the new tap.

On upstream there is atmosphere.
 
R
I think you misunderstood, by "other Side" I think he meant the other side of filter Upstream and Downstream.

I think the upstream is at a negative pressure caused by the intake structure i.e. less than atmosphere. Because when he opens the HP impulse line the pressure changes.

>> So you need to create a new tapped point upstream of the filter and
>> move the high side impulse line to the new tap.

>On upstream there is atmosphere.
 
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