Gas separation control in a centrifugal pump vacuum pump

A method of operating a centrifugal and vacuum pump combination in which the centrifugal pump has an impeller disposed on the same shaft as a rotor of the vacuum pump, and a gas outlet duct extends between the centrifugal pump and the vacuum pump, the vacuum pump including a suction opening having a predetermined cross sectional area and positioned in the gas outlet duct;

• the method comprising the steps of:
• (a) operating the pumps so that as the centrifugal pump pumps fluent material, gas is separated from the material, and the vacuum pump draws the gas from the centrifugal pump through the gas outlet duct;
• and
• (b) positively controlling the flow of the gas passing through the gas outlet duct between the centrifugal pump and the vacuum pump, by changing the cross sectional flow area of the vacuum pump suction opening.

A method of operating a centrifugal and vacuum pump combination in which the centrifugal pump has an impeller disposed on the same shaft as a rotor of the vacuum pump, and a gas outlet duct extends between the centrifugal pump and the vacuum pump, and wherein the fluent material pumped by the centrifugal pump is a slurry having a solids consistency;

• the method comprising the steps of:
• (a) operating the pumps so that as the centrifugal pump pumps fluent material, gas is separated from the material, and the vacuum pump draws the gas from the centrifugal pump through the gas outlet duct;
• and
• (b) automatically positively controlling the flow of the gas passing through the gas outlet duct between the centrifugal pump and the vacuum pump, in response to the solids consistency of the slurry pumped by the centrifugal pump.

A pump comprising:

• a volute casing and a pump body;
• a centrifugal pump impeller mounted for rotation by a shaft in said volute casing;
• a suction opening in said volute casing, and a substantially tangential outlet extending from said volute casing;
• said impeller including a back plate having a front side facing said suction opening and an opposite back side;
• at least one working blade connected to said first side of said back plate, and at least one back blade connected to said second side thereof;
• said pump body including a vacuum pump having a housing and containing a rotor with rotor blades, said rotor mounted on said shaft;
• said vacuum pump housing including a rear wall and a front wall, said front wall adjacent said volute casing and said rear wall spaced from said front wall and said volute casing, said front wall having a suction opening therein;
• said vacuum pump housing further comprising an eccentric inner wall surrounding said rotor, an auxiliary air channel, and an outlet leading from said vacuum pump housing to the exterior thereof;
• a back wall of said volute casing disposed between said impeller back plate and said vacuum pump housing front wall;
• a gas outlet duct extending through said back wall from said volute casing and said suction opening;
• and
• a control device disposed in said gas outlet duct for controlling the flow of gas through said outlet duct.