Definition: Plant: meaning a facilities / operation where manufacturing is occurring. Cooling: 1) free of heat 2) capable of lowering temperature. System: an assemblage or combination of things or parts forming a complex or unitary whole: a cooling system. Pump: a mechanical means for forcing or causing to flow / move upon a fluid. Tank: a large receptacle, container, or structure for holding a liquid or gas.

A pump tank or more accurately a pump tank system is the go between of the cooling system. The components of a pump tank are a split tank, pumps, controls and various safety systems / monitoring systems combined with a piping.

In a simple way the tank is between the plant piping and the tower or chiller systems. It receives the plant process fluid, both from the cooling unit (tower or chiller) into the cold side of the tank, and receives the returned process fluid to the hot side of the tank. It pumps from the cold side to the plant, and pumps from the hot side to the approximate cooling unit. It is the reservoir for the fluids, and the balance in the system.

The pump tank on the cooling side allows the tower or chiller to run continuously, under the same load. They are only working with pump tank. Please note that if one were to use what is called chill plates, than this may take the place of the pump tank in some systems on the (cooling side) though a reservoir would be incorporated within the system to maintain fluid levels and volumes for operations. A pump tank would be used on the plant side so as not to restrict the flow to the plant.

By allowing both sides of the tank to run independently than there is not a hold up, pressure buildup, or restriction to flow on either side (load fluctuations) within the systems.

The tank:

The tank is split within itself so as to have baffle that is down the center to create in most cases two equal half's within the tank. This baffle does not seal both sides as there is a gap at the bottom to allow equalization of fluid to both sides and the baffle is short of the top so as to allow spill over if necessary.

Pumping out of the tank occurs at the bottom of the tank, and these are built in most cases with two ports per side of tank. One port is the primary and the second is a backup. Filling of the tanks from the process or the cooling equipment is via a simple pipe into the top of the tank. Covers are typical for tanks; this keeps contaminants out the system.

Pumps:

It is most common to have a pump tank set up with 3 pumps, but dependent of plant size and volume more may be required. But in a simple explanation of 3 pumps, #1 is for the process side supplying the plant, #2 is for the cooling side supplying the cooling method of choice, and #3 is the backup. The #3 pump is plumbed in such a way with valves and piping so that it can be used either on supplying the plant or supplying the cooling method. This pump is a safety, allowing operation if one of the other pumps fails and allows maintenance on the existing pumps and motors while not having to shut down the entire plant.

Pump volume and pressures along with pipe size need to be correct for the system.

Instrumentation:

Pressure gauges and or test ports to snap in gauges should be fitted to the output side of the pumps. This than yields what pressure is being supplied. Since the discharge is free flow and 0 as it exits into our tank the use of gauges here is debatable. If for example they do not free flow but are restricted in flow to the cooling mechanics than a gauge should be installed.

Temperature gauges can be mounted to the tank, both cold and hot sides along with the possibility and addition on the return pipe and supply pipe. These alone give a great indication of what is going on temperature wise. (Remember that standard units for cooling are based on a 10 degree delta)

Monitoring/ recording of both pressures and temperatures should be done as reference and maintenance function, this can be done with forms, entered into programs or if possible electronically by some of the new instrumentation out there. The other missed data is what was the temperature and humidity in the plant this day. What than has to be done is to use this data, does someone notice that when temperature outside air temperature goes up plant supply side goes up too? Does anyone notice that pressures are increasing and decreasing on supply and return lines, is there a buildup.

These systems are designed for the system to be used by numerous manufactures with all the engineering that has to accompany them. This does include but not limited to; volume of tanks, size of pumps, size of piping, and filtrations.

SL Silvey

PT 21082012.01

www.silveysplasticconsulting.com

360-882-3183