Pressure Switch or Flow Meter?

Neither will help you, "to avoid the cooling water supply failure".

They will just tell you when it's about to fail.

I'd be more concerned about flow than pressure.

Right - pressure is meaningless - there are possibilities of having pressure with no flow.

I have to agree with you redfred, and if the cooling water is a critical process, the temperature probe should also include 2 or 3 stage warnings, stage 1= a heads-up to a potential problem, stage 2= a critical warning and stage 3= equipment shut-down. Those are the scenarios I've had to deal with in the past dealing with critical cooling water.

Pressure gage tells you, that the pressure vessel is not broken. Flow indicator tells you, that you MAY have cooling. Temperature gage tells you, that the process is within control. Three different things. All are needed, and understanding, what happens when this that or something else goes wrong. You need to work that out ahead of the time, before things go wrong.

A pressure indicator tells you there is pressure - why it says nothing about - pressure but no flow is a distinct possibility.

A flow indicator tells you that cooling is there unless there is a situation of multiple failures.

A combination of flow indicator and temperature indicator tells you what is happening. If at all critical the data would be transmitted and alarmed.

A flow sensor and a bypass second cooling water supply line that automatically cuts in when the primary supply fails may help. Ther eshould also be an alarm annun ciator to take remedial action. The flow sensor should be in the primary line before the bypass.

All nice comments. I want to add a bit.

A control valve can be installed at the out going water pipe of the system, it shall be a TIC (Temperature Indication Control) globe valve. It should take feed from the system temperature you want to control for its operation. If temperature is going up, it shall open more to allow more water to flow for more cooling and vise versa.

It may so happen that temperature is not controlled even when valve is full open, then it should give alarm to act or cut-off temperature generating substance automatically.

Put VFD on the Pump that is supplying water to the device being cooled instead of a valve controling flow, this way you save energy and money in the operation. Base the VFD Speed reference signal on temp via transducer.

Redfred = GA, Right on the Money!

You state "Temperature control unit" so I assume that the control philosophy is fully covered, and you are already forewarned of possible cooling problems via temperature increase..

You should use a flow meter with a remote signal/ feedback for your application, where the reasons would be:

1. Heat is dissipated by the cooling water rate-of-flow, not the water pressure.

2. Line pressure may remain static, or decay only marginally for a substantial drop in flow, depending on your design. There is also a delay in reaction time (dead band) for the switch to operate for a drop in pressure.

3. A flow meter can be readily assimilated into the existing Temperature control loop, and it's feedback can be configured to alarm for any given flow rate within it's range. Multiple alarms are possible, not only for catastophic failure.

hi

you can put a level switch in main vessel of cooling tower set up to min. level that can keep a temperature in safe degree and when it goes down >alarm > shut down

ali

Just an extra level of security in the monitoring process. If you have the capability with the mechanical system; have the alarms go through the WebControl system so the alarms get sent to pagers or smart-phones that the service personnel carry.

It doesn't do any good to have alarm or safety monitoring if things head south when no one is around to see or hear.

As has been stated in earlier Posts it is good to have some redundancy checking different facets of the cooling system. The greater the risk if failure should occur, the more monitoring there needs to be.