Cutting wheel pump
Cutting wheel pumps are mainly used for the disposal of domestic wastewater, mostly in pressure drainage . These submersible motor pumps are mainly installed in small sewage pump shafts made of concrete or polyethylene (PE), which collect the sewage. The pump located in the collecting chamber then discharges the wastewater into the pressure pipe.
construction
They are submerged electric centrifugal pumps mostly made of gray cast iron. It is driven by three-phase motors with an output of around 1–10 kW. In front of the pump hydraulics at the end of the motor shaft there is a rotating, hardened cutting device, which shreds the conveyed material, because in domestic wastewater there are not only faeces but also fibrous components (hair, toilet paper, also hygiene articles). The hydraulics of the centrifugal pump work with a vortex or vortex impeller and pressurize the water at a speed of around 2900 rpm. The molded pressure port of the pump is usually designed as a flange with a coupling device with a nominal width of DN 32, DN 40 or DN 50. Due to the metallic materials used for the motor and housing, a cutting wheel pump with a 2.6 kW motor weighs around 40 kg.
Pumps in sewer shafts are equipped with a special self-sealing coupling device so that no assembly work is required in the sewer shaft for maintenance and repairs. The pump can be pulled out of the shaft with a suitable manual lifting device; A guide device in the shaft, the sliding tube, ensures safe and precise reconnection.
function
As a result of the rotation of the motor shaft, the sewage homogenized by the cutting unit is sucked through the suction opening (s) into the vortex or vortex impeller hydraulics of the pump, where it is pressurized. Because the wastewater is crushed, there is no need for a large free passage in the hydraulics, which is why large delivery heights can also be achieved. The pumps are switched on and off by an electrical control with a level transmitter system connected in the shaft.
Application limits
Cutting wheel pumps are used to transport domestic wastewater in small pressure pipes. It is not advisable to discharge surface water into collecting shafts with pumps of this type, as mineral additions (sand, soil) that have been washed in lead to increased wear of the cutting device and thus to impairment of the sewage disposal.
safety
Since sewage wells are connected through the pressure lines to the public channel, and in the shaft by fermentation gases such as hydrogen sulfide (H 2 S) and methane (CH 4 ) is the risk of formation of an explosive atmosphere are cutting system that operate in this environment, explosion protected performed . The regulations on design and mode of operation are described in the ATEX EC product guidelines.