Industrial Plumbing Problem

[MasterPlumbersKeymaster]

I am looking for a solution to a problem I have encountered at the factory that I work in. We have a 3/4″ supply line that feeds a hotwater tank going to water wash that has a continuous feed to the rinse section. My supply line also branches off before the hot water tank with a 1/2″ line to a heat exchanger on a large air compressor. The water leaves the exchanger via a 1/2″ line to the sewer. I only have access to the 3/4″ supply line and putting in a larger line is not possible.

I would like to reclaim this cooling water, as it is still clean, and divert it back to my hot water tank. One of the problems is that the compressor will shut off if the flow through it drops below 2 gpm (it wants to see at around 6 gpm to be happy) and if there is to much demand at the wash it does drop down enough to trip it now. My thought is that I can put a circulation pump in a loop with the heat exchanger and feed the water back to the 3/4″ supply before the hot water tank, thus saving some heating energy along with the water. The circulation pump would have to pressurize the water enough to overcome the supply water pressure and I would guess that I need to put a flow check valve on the supply line before the compressor loop, one in the loop between it’s return to the 3/4″ supply line and a (waste gate or pressure relief of some kind), and one between the supply and return lines of the loop itself on the 3/4″ line to keep every thing going the right direction.

My next problem is that if the wash is shut down I will have no demand for the returned water from the heat exchanger thus no flow and the compressor will shut down. I need some kind of system in this loop so that I have an uninterupted flow through my heat exchanger to either my hotwater tank/wash, if there is a demand, or the sewer, without venting my fresh water supply out with it.

My questions are:

1) is this possible?

if so:

1) What kind of valve will I need to put after my heat exchanger to act as a waste gate so that I will have flow to the sewer if my wash is shut down.

2) What kind of circulation pump will I need.

3) I am open to any other suggestions.

Thank You,
Ken C.

[wpcParticipant]

Your air compressor does it have a flow switch or temperature cutout on the circuit, also I assume this is a two stage compressor with an intercooler. You could possibly install a check valve with a five pound pressure drop before the tee to the hot water tank, this would give the circuit to the heat exchanger circuit first priority on the flow if the pressure drop through the heat exchanger is less than five pounds. You could install a pilot operated check valve in the outlet of the heat exhanger after the tee that is returning water to the water heater. What this could do is open the water flowing through the heat exchanger to the waste. To do this install a line to the line to water heater after the check valve to the pilot connecton of check valve. When the water pressure increases in supply to water heater it will open the pilot operated check letting water flow to the sewer. THE 5# check to water heater would divert water to heat exchanger, the pilot check in outlet of heat exchanger would allow flow through the heat ex. when wash unit is not used. This is a thought on the subject. Check with qualified person on this, pressures may have to be set up differently. This can be done if set up properly

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