CAREFULLY Consider ISOLATION Valves on HYDRAULIC Pump Intake Lines

摘要

At a recent hydraulic maintenance workshop, I was asked for my opinion on isolation valves on pump intake lines and whether a more expensive ball valve is mandatory as opposed to the generally cheaper butterfly type. At the root of this question is the negative effect of turbulence in the pump intake line. The argument for using a ball valve as an intake-line isolation valve is that when it's open, the full bore of the valve is available for oil flow. So if you have a 2-inch ball valve installed in a 2-inch intake line, when the valve is open, it's as if it isn't there at all (from the oil's point of view at least). On the other hand, a butterfly valve is not full bore. Even when fully open, the butterfly remains in the bore and presents a partial restriction, which is irregular in shape. This causes turbulence, which can result in dissolved air coming out of solution in the intake line. If this happens, these air bubbles will collapse when exposed to pressure at the pump outlet. In other words, a butterfly valve may cause gaseous cavitation.