Three-screw pump of 3V type and electric pump units on its base are intended for pumping nonaggressive liquids without abrasive admixtures possessing lubricating power, with kinematic visсosity 0,1*10-4 up to 7,5*10-4 m2/s (from 1,9 up to 1000 E) and at a temperature of up to 353 К (80°С).
Lower limit of viscosity is restricted by lubricating power of the pumped liquid. When pumping liquids being analogous to diesel fuel, the outlet pressure is to be reduced up to 0,5 МPа (5,0 kgf/сm2). The upper limit of viscosity is restricted by rotational speed and driving power.
By agreement with the Manufacturing plant it is admitted to use pumps for pumping liquids with temperature of up to 373 К (100°С).
It is necessary to inquire about tolerable pump pressure at the Manufacturer in every specific case when liquids different from petroleum products (oils, diesel fuel) on their physical-mechanical properties are pumped.
Pump is related to items of general purpose (ION) aspect 1 (repairable ones) GOST 27.003-90. Climatic version U, in-service location category 3, and also, climatic version Т, in-service location category 2 as per GOST 15150-69.
Electric pump unit consists of three-screw pump and electric motor, which are mounted on common frame and connected by coupling, protected with housing.
As to the operating principle the three-screw pump – is a positive displacement machine.
Pump consists of the following main components: casing with covers, shell, one driving and two driven screws and end-face seal.
The shell is inserted inside the casing with three adjacent cylindrical bores, in which the driving screw and two driven screws are placed. The driven screws are intended for sealing the driving screw.
The screw thread profile is a special one ensuring their mutual conjugation, the thread is a double–start one, the driving screw is provided with counterclockwise thread, the thread of the driven screws is a clockwise one.
During rotation of screws a vacuum is created in the pump suction chamber, as a result the pumped liquid flows under the action of atmospheric pressure to the screw thread depressions mutually closed during rotation of the screws. The liquid volume closed in the screw thread moves in the shell rectilinearly without mixing and then it is forced into the discharge chamber.
The direction of the inlet and outlet of the liquids being pumped is indicated in the drawings by arrows.
Type of shaft sealing – end-face sealing (single or double).
|Flow, m³/h, least||50|
|Rotation speed, rpm||1000|
|Rotation speed, c˜¹||16|
|Pump inlet pressure, kgf/sm², max||2.5|
|Pump outlet pressure, kgf/sm², max||6.3|
|Type of current||AC|
|Allowable vacuum suction, m||5|
For example А1 3В 125/25-90/6,3B-1 U3, TU 26-06-1546-89, where: