On a new system it is not uncommon to get a call that a pump isn’t putting out adequate pressure. When we investigate we often find the culprit is high levels on entrained air. Pumps will deliver significantly less pressure when even 1-2% air is in the fluid, one reason why there are a lot of fluid defoamers on the market.
For one washer job our pump was sized at an operating point of 65 PSI. After a day or two of running the new washer, the pressure would drop from 65 to 48 PSI. We were called to plant to investigate. When we opened tank top lid, we saw lots of foam. So we asked the system to be shut down long enough for the fluid to settle and defoamer to be added. The pump would turn on and produce 65 PSI only to drop again after a day or two. And we would return to the plant to investigate again, because we can never be entirely certain what’s happening. The final solution required finding an effective defoamer for the abrasive “lapping compound” type fluid, coupled with the slow and small accumulation of tramp oils that enter the system on the parts to be washed. Tramp oils naturally act as a defoamer. With the washer now in operation for many months, the pump holds steady at 65 PSI.