Filter Press Feed Pumps    Operation & Construction     Hydraulic Operation & Control Secondhand Willett hydraulic flow control ram pumps     Filter Press Feed Pumps CONSTUCTION MATERIALS For most applications the pump is constructed from fabricated mild steel with a stainless steel main ram and polyurethane gland packing, ball valves and seats. However for applications where temperature or abrasion may be an issue the pump can be constructed with more suitable materials to withstand the duty. Hydraulic Power Pack The hydraulic unit comprises an hydraulic oil tank beneath which sits an electric motor driving through a bell housing and coupling to a variable speed, pressure compensated hydraulic oil pump. The hydraulic oil tank features internal baffles to encourage circulation and specific movement within the hydraulic oil, which prevents the hydraulic oil from passing straight between the suction and discharge ports in the tank. The tank is sealed except for a breather but has removable panels for access to clean the inside of the tank. A separate, sealed access point is available for topping up the tank. A visual level gauge is provided on the side of the oil tank. A hydraulic pressure gauge and isolator is provided with the hydraulic control valve stack to enable the hydraulic pressures to be set correctly. The hydraulic valve stack features a pressure relief valve and an open centre spool valve, which enables the electric motor to start under no load conditions. A drain plug is provided for draining the hydraulic oil tank during an oil change. A suction strainer is provided to protect the hydraulic oil pump against debris. Full flow oil filtration is provided which features a visual condition indicator. The hydraulic control valves are operated by solenoids positioned on the oil block located on the top of the tank. These control the position of the spool and hence the direction of the main ram. The solenoids are controlled by the proximity switches mounted through the fame at the side of the main ram. This identifies the position of the crosshead and initiates a signal to be sent to reverse the flow of hydraulic oil to the hydraulic cylinder. The length of stroke can be adjusted by the position of the proximity switches in the locating slots. Further fine adjustment can be made using the choke controls beneath the solenoid valve