Mill coolant system design
Pipes and Reservoirs. Simple coolant systems use a pump to generate coolant flow and pressure, plumbing to carry and dispense liquids to a point of application, and troughs to contain and return the coolant to a reservoir. A simple system like this requires specification of coolant flow to provide proper flushing and cooling of each production process, with the total flow requirement being equal to the sum of the individual requirements (see Figure 1). This calculation is important because the components used in coolant purification all are flow rate-specified. This number is used to develop pump specifications, reservoir capacity, plumbing diameter, containment/collection troughs, and any inline filtration.
Adding to the complexity, this flow rate ideally should be 25 to 30 PSI at the point of dispensing because pressure is lost within each plumbing component. The mill reservoir should be placed close to the mill and use larger-diameter pipe over shorter distances to provide the least change in coolant pressure from the pump to the mill.
A rule of thumb with plumbing is to maintain the largest required plumbing diameter as long as possible when carrying coolant to the mill because any reduction in diameter limits flow and pressure at the application point. Include butterfly or ball valves throughout the plumbing to allow for pressure limits at specific zones and the ability to shut off coolant during setup and observation of the mill in operation.
Troughs, splash guards, ID plugs, return flow impeders, foam pads, and air blowoffs all are used to collect coolant and related solids from the forming process and route them back to the reservoir. Systems should be designed with easy access for cleaning and uninhibited flow back to the reservoir. Fluid containment should be designed so that no "dead zones" exist within the return flow system.
Flood-type coolant tanks used in welded tube production can range in capacity from less than 100 gallons up to tens of thousands of gallons. Tank volume is based on flow, cooling requirements, and space constraints, with a starting point minimum of five times the flow capacity the pump.
If one central tank is used to feed multiple mills, then a smaller catch tank with its own pumping mechanism must be maintained at each mill. Tanks should be accessible for maintenance, viewing, and repair. A containment dike no less than two-thirds of the overall system capacity is recommended and may be required by law under many circumstances.
At the point of application, use 1/4-inch NPT connectors; this provides versatility in the nozzle/hose type at an economical price and acceptable pressure with minimal flow requirements. Also, include unions throughout the plumbing for quick disassembly and cleaning.
