Pressure Gauge

Hi gkkumar,

Need more information.

How long have the gauges been reading zero?

Has a change to the system recently been made?

Did you just recently get assigned/been made aware of this problem?

What is the pressure range on the gauges?

You said: One thing I have noticed was after removing pressure gauge meter the air is sucking in to the pipe through the meter inlet valve.

If you are sucking air through an open port at the inlet, your inlet pressure would be a partial vacuum, which begs the question, "Where is the pump located?"

It should be discharging directly into the inlet of the heat exchanger.

If the suction of the pump is connected to the outlet of the heat exchanger, you will not get any (positive psig) pressure readings.

Check your physical setup and get back to us.

Mike

One more possibility for this situation may be that water outlet from exchanger is discharing to open drain or a tank with high velocity. The low pressure head in supply piping may fully convert in to velocity head and when pressure gauge tapping is opened, it may suck air.

Thanks for the interest taken.We have 2 heat exchangers and water is circulated form an Over head tank approximately 20 meter hight(there is no pump).It was a single line from (3 inch pipe) OHT and separates in to two immediately before heat exchanger and outlet is also comes in two lines and joined into a single pipe of same size and going to a distance of 25 meter into a tank.At this stage all the pressure meters were working OK. Recently we have given a separate line for each heat exchangers ,means inlet and outlet have separate 3" pipe .After that in one line ,the pressure meters (we have meters in both inlet and outlet)showing value but the second line both inlet and outlet meters showing zero. range is 0-30 psi.

I have removed one meter on which shows reading ,water is coming out of the valve where in the other which shows zero air is sucking in to the pipe . I have also released the air through air release valve.this make me lot of confusion why in the same systems behaves differently

Put a compound range range pressure gauge that shows vacuum and pressure on either side of zero so you can see how much vacuum the system is pulling.

Usually the pressure drop across heat exchanger in the water line will be low.

If it is drained in open or any low pressure lines the pressure will be next to atmosphere in outlet point.

If the supply line pipe crossection is lesser then flow area (which almost invariably it will be), then the Δp across cooler will be low and hence the inlet pressure will be almost ambient (plus the Δp→0)

Assuming your pressure gauge is not in a position to measure this low pressure it may well show zero.

What is the least count of the gauge(s) and the calibration status?

After the pressure gauge is removed, the sucking in of air is totally normal (Bernoulli) and that shows the flow is rapid enough (and that further shows that the pressure head at the inlet is less than atmosphere)

In heat exchangers usually (in our equipments) the pressure at inlet is supposed to signify the choking and the control is through the temperatures (the oil temperatures and the water inlet/outlet temperature). The differences show the effectiveness as well as health of the exchanger.

Check if the valve placed for isolate thegauge is open.Maybe a jocker change the position of the drive.