Pulsing Flow Coater

Q.  My company makes oil-filled transformers. Most of the tanks are corrugated for cooling, and a small number have cooling radiators attached. We found that we were not getting enough paint on the radiators and decided to flow coat them. We are now painting the tanks by spray painting and the transformer radiators by flow coating. After painting, we attach the radiators to the tanks.

Because such a small number of transformers have radiators, we couldn’t justify buying a flow coater, so we had our maintenance department build one using a diaphragm pump. The output nozzle allows enough paint to flow, but it is pulsating rather than constant. 

What can we do to get a constant flow? –G.P.

A.  What you really need is a hydraulic engineer, however, I believe there are two relatively inexpensive things your maintenance department can do. 

1. Replace the diaphragm pump with a rotary or centrifugal pump. You don’t want to run the pump too fast, because the high shear rate could change the rheology of the paint. 

2. Build an overhead tank having an outlet on the bottom. Suspend the tank from the plant ceiling. Pump the paint into the tank using your existing setup. Attach a hose to the tank-bottom outlet to supply paint to the flow coater nozzle.