GB1268245A - Pumping apparatus incorporating a centrifugal pump - Google Patents

Abstract

1,268,245. Centrifugal pumps. A. SERGENT. March 19, 1969 [March 22, 1968], No. 14533/69. Heading F1C. In a pumping apparatus comprising a centrifugal pump receiving liquid through a pipe 6 from a chamber 1 supplied with liquid through a pipe 2 from a tank (not shown), the pump impeller 12 is automatically moved axially along shaft 13 in a direction away from the pipe 6 to reduce the effectiveness of seal 16 and thereby the output of the pump, when there is a drop in the liquid level in the chamber 1. Thus drainage of the chamber 1 and consequent ingress of gas or vapour into the pump is avoided. The axial movement of the impeller occurs when a cavity 10, normally at pump discharge pressure, is communicated through a pipe 7 with the chamber 1 by automatic opening of a float-controlled valve 8 due to the drop in liquid level in the chamber 1. If the supply to the chamber should cease, the impeller moves axially as described and the consequent lowpressure developed by the pump is insufficient to maintain a spring-loaded valve 20 in its open position. Thus some liquid is retained and the pipe 6 is kept full. The chamber 1 has a float-controlled vent valve 4. The wall member 19 of a continuously-effective seal 17 may be of the same diameter as that of the impeller and arranged so that the impeller channels are partly or completely closed when the impeller moves axially from its normal operating position. The impeller may be of the open type. The flow through the inlet duct 2 may be accelerated by a screw-type impeller or by a nozzle connected to the pump discharge. Alternatively, a partition may be provided in the upper portion of the chamber 1 below the valve 4, the position having a non-return valve therein coupled to a float.