Abstract: A high pressure centrifugal slurry pump in which the impellers and their associated diffusers are formed of hard chrome iron. A liquid-tight high pressure containment shell surrounds the impellers and diffusers and is radially spaced from them. The resulting space between the array of impellers and diffusers and the containment shell is in fluid communication with the interiors of the impellers and diffusers, preferably through a channel located between the last diffuser of the pump and the end wall at the high pressure end of the pumping chamber.

Abstract: A method and apparatus for controlling the discharge time of a fluid activated diaphragm pump. The control system regulates the discharge time, by measuring the discharge time and comparing the measured time with a predetermined desired discharge time. The control system includes, inter alia, a programmable logic controller, an upper and lower proximity switch, a target, a rod to hold the target, a pilot controlled pressure regulator, a set of digitally controlled solenoids which control a pilot valve, a solenoid, and a pressure switch. The rod is secured to the diaphragm of the diaphragm pump, and the proximity switches respond to the movement of the rod to detect the movement, or stroke, of the diaphragm. The pressure supplied to the diaphragm pump is automatically, and continuously, adjusted to maintain a desired discharge time.