US2959131A - Pumps - Google Patents

Description

PUMPS Guy Taite Shoosmith, St. Mary Bourne, England, assignor to Plenty and Son Limited, Newbury, England Filed May 6, 1958, Ser. No. 733,417

Claims priority, application Great Britain May 13, 1957 3 Claims. (Cl. 103-44) This invention relates to pumps, and more speciically to diaphragm pumps.

In certain nuclear power plants, pure water is circulated through or near to the reactor. This water can become radio-active and stringent measures must be taken to prevent its leakage. The present invention is concerned with a pump for circulating the water which does not allow leakage from the circuit past the moving parts of the pump.

According to the invention, a diaphragm pump for pumping liquid comprises a metal diaphragm which is fastened round its edge without a break to its support, and which is designed to be exed during operation of the pump between two positions in both of which it remains convex so that reverse bending of the diaphragm is avoided.

In order that the invention may be thoroughly understood, a specic pump in accordance with it will now be described, by way of example, with reference to the accompanying drawing, in which:

Figure l is a diagrammatic part-sectional View of the pump; and

Figure 2 is an enlarged vertical section through part of the pump.

The pump shown in the drawing is designed to circulate pure water which is at a temperature of about 600 F. and at a pressure of about 2000 p.s.i., the water pressure being boosted by the pump to about 3000 p.s.i. It cornprises a cylinder block having three cylinders 12 in which are arranged sliding pistons or rams 14. The upper parts of the cylinders lead into shallow liquidtight chambers 16 containing pure water which serves as hydraulic iluid, the chambers 16 each having an upper portion comprising a dish-shaped metal diaphragm 18. Driving means including a motor 20 and a shaft 22 are provided for reciprocating the rams 14 in the cylinders 12 so that the diaphragms 18 can be ilexed in synchronism with the rams by the pressure of the water in the chambers 16.

The exing of the diaphragms 18 provides a pumping action which is transmitted to pure water on the sides of the diaphragms remote from the cylinders 12 and forces the water round a circulatory system (not shown in the drawing). The pumping action of the diaphragms is made eiective by providing pumping chambers 24 immediately above the diaphragms 18 through which the circulating water is passed. As shown in Figure 2, each of these chambers 24 has a valve-controlled inlet 26 and a valve-controlled outlet 28 in the same way as a normal piston pump, the inlet valve 30 being spring-loaded so that it opens automatically on the suction stroke, and the outlet valve 32 being spring-loaded so that it opens automatically on the delivery stroke.

The operation of the pump is as follows.

As each ram 14 is moved upwards within its cylinder 12, the hydraulic fluid in the chambers 16 leading from the cylinders 12 (which chambers are referred to hereinafter as the primary chambers) is placed under pressure States Patent and flexes the diaphragm 18 upwards. The movement of the diaphragm 18 places the water in the associated pumping chamber 24 under pressure, and some of the water is forced out through the outlet 28 against the action of the spring associated With the valve 32. The return movement of the ram 14 causes the diaphragm 18 to return to its normal position (the position shown in Figure 2), and this has the effect of closing the outlet valve 32 in the pumping chamber 24 and drawing water by suction from the circuit into the pumping chamber through the inlet 26. The inlet valve 30 closes when the ram 14 reaches the lowermost position of its stroke, and the cycle described above is then repeated as the ram 14 moves upwards again.

In the particular pump described herein, the three rams 14 have a diameter of 1% inches and are made of stainless steel or other metal which does not corrode when in contact with water. The driving means 20 and 22 for reciprocating the rams 14 are designed so that the rams have a stroke of 11/2 inches and a rate of reciprocation per minute in the region of 1140. The rams are arranged for movement in labyrinth glands 34, and any leakage of water from the primary chambers 16 past these glands is compensated for by make-up water supplied to the primary chambers 16 from a separate feed pump (not shown) through an hydraulic accumulator operating at 2000 p.s.i. and a non-return valve (also not shown). A leak detection device 36, 3S is provided so that, in the event of a diaphragm fracture, the pump is automatically taken out of the circuit and stopped through the operation of control means 40 shown in Figure 1. The device 36, 38 can comprise, for example, a radiation counter.

The diaphragms 18 are welded round their edges without a break to thin lips 42 machined in the cylinder head. This is very important having regard to the fact that the circulating water will probably become radio-active at some stage of its passage round the system. The diaphragms are preferably made of high carbon content heat-treated steel and are of convex shape, the diaphragms being so disposed in relation to the rams 14 that their convexity is increased during the compression stroke of the rams. Thus, the diaphragms work between two degrees of convexity, reverse bending with its consequent risk of fracture being avoided. Each diaphragm 18 has a pair of radial expansion rings 44 pressed in it, and is of about 8 inches diameter.

The central portions of the diaphragms 18 have a working stroke of about 0.22 inch between steel grids 46 and 48 arranged one on either side of each diaphragm. These steel grids limit the movement of the diaphragm and serve also to clamp its outer portions 50 between them so as to reduce bending stresses. Annular grooves 52 are provided in one or both of the grids 46 and 48 to accommodate the rings 44 on the diaphragms. Preferably, the steel grids take the form of thick plate portions having straight holes bored through them which lie parallel to the longitudinal axes of the rams 18.

A pump of the design described above meets the severe requirements of nuclear power plants where the possibility of leakage must be reduced to a minimum, and where uid circuits must remain isolated from one another. The leakage of water from the circulatory system past the moving parts of the pump can only happen if one of the diaphragms 18 is fractured, and this can be avoided by determining in advance the minimum working life of the diaphragms. If such a leakage does occur however, the pure water in the circuit Will not be harmfully contaminated because the hydraulic liquid used in the primary chambers 16 is also pure Water.

I claim:

1. A diaphragm pump for pumping liquid comprising 3 agenerally-cylindrical pumping chamber arranged with the longitudinal axis thereof extending in a substantially vertical direction, an annular diaphragm support forming part of the lower portion of the cylindrical wall of said chamber, a circular dish-shaped metal diaphragm extending across the entire area of the circular aperture defined by said annular support and fastened in a liquid-tight manner to said support round the entire edge of said diaphragm, a rigid metal grid opposing the upper side face of said diaphragm and in close contact with a peripheral portion of said diaphragm, a second rigid metal grid opposing the lower side face of said diaphragm and in close contact with a peripheral portion of said diaphragm, a plurality of vertically-extending apertures in each of said grids, a depression of substantially concave cross-section in one of said grids, said depression opposing said one side face of said diaphragm, a raised surface of substantially convex cross-section in said other grid, said raised surface opposing said other side face of said diaphragm, said concave depression and said convex raised surface in said grids being of diierent curvatures whereby a Working space for said diaphragm is formed between said grids, -at least one radial expansion ring pressed in said diaphragm, a corresponding annular groove in said concave depression of said one grid adapted to receive saidexpansion ring when said diaphragm is exed towards said one grid, a corresponding annular ridge -in said convex raised surface of said other grid, adapted to enter said expansion ring when said diaphragm is flexed towards said other grid, a primary chamber containing hydraulic liquid bounded at the upper *portion thereof by said diaphragm, a reciprocatory piston arranged to act directly on said hydraulic iluid in said chamber whereby said hydraulic uid transmits movement of said piston to said diaphragm, said hydraulicv fluid being the same in composition as uid handled by said pumping chamber, and power means operatively connected to said piston whereby to cause reciprocation of said piston. Y

2. A diaphragm pump as claimed in claim 1 wherein said hydraulic fluid is pure water.

3. A diaphragm pump as claimed in claim 1 wherein said diaphragm is made of high carbon content steel and is welded to said support.

References Cited in the le of this patent UNITED STATES PATENTS 116,669 Blake July 4, 1871 356,997 Gil Feb. 1, 1887 2,117,863 Szekely May 17, 1938 l2,145,937 Lockwood Feb. 7, 1939 2,239,481 Christensen Apr. 22, 1941 2,362,822 Houser et al Nov. 14, 1944 2,662,478 Surre Dec. 15, 1953 2,691,943 Wilson Oct. 19, 1954

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