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: http://www.aquflowpumps.com/ <br />Phone: 949-757-1753 <br />E-mail: sales@aquflow.com