In a hydraulic diaphragm metering pump, pressurized oil is sent through a hole into the spool valve chamber. Pressurized hydraulic oil that is displaced is sent to the back of the diaphragm. The adjuster knob can be turned from 0-100 depending on capacity control needs. This video further demonstrates the working principle of the control spool valve and capacity control. br br CONTACT AQUFLOW: br Website: br Phone: 949-757-1753 br E-mail: sales@aquflow.