US1953827A - Controlling means for feed pumps - Google Patents

Description

April 3, 1934. H. HILLIER CONTROLLING MEANS FOR FEED PUMPS Filed Oct. 11, 1952 2 Sheets-Sheet 1 Jizz/enbr:

P 1934- H. HILLIER 1,953,827

CONTROLLING MEANS FOR FEED PUMPS Filed Oct. 11, 1932 2 Sheets-Sheet 2 I JAM J1 Patented Apr. 3, 1934 CONTROLLING MEANS FOR FEED PUMPS Harold Hillier, Cathcart, Glasgow, Scotland, as-

signor to G. & J. Weir, Limited, Glasgow, Scotland, a corporation of Great Britain Application October 11, 1932, Serial No. 637,342 In Great Britain December 5, 1931 4 Claims. (Cl. 103-11) In steam power installations the practice is often adopted of installing two boiler feed pumps, newhich may be called the normal pumpto be employed normally for feeding the boiler,

5 while the other-which may be called an emergency pump-is employed only in case of failure of the normal pump. (It is understood there may be a plurality of normal pumps or a plurality of emergency pumps or a plurality of normal pumps and a plurality of emergency pumps; for convenience in this specification a single pump of each class will be referred to, but it is to be understood. that the invention covers the use of a single pump or a plurality of pumps of each class aforesaid.)

The amount of water in boilers in modern steam power installations, especially where high pressures are employed, is often small in relation to the steaming rate, and it is necessary to put the emergency pump into action very quickly if and when the normal pump fails, or the water level may fall to such an extent as to cause serious damage to the boiler.

By failure of the normal pump is meant, not

only breakdown, but failure to supply at a sufficiently high pressure or in sufficient amount.

The present invention provides a device (for employment in a steam power installation) operative to put the emergency pump into action automatically whenever the pressure in the feed main-that is, on the discharge side of the normal pump-falls below what is desired, due to failure (as above defined) of the normal pump.

Broadly considered, the device according to the invention comprises a pressure-responsive member for controlling the supplyof actuating medium to a pump, said member being subject to the discharge pressure of said pump and to the oppositely directed discharge pressure of another pump, and being biased in opposition to the discharge pressure of said other pump and opera tive on emergency to act on a valve, switch or the like to bring the first mentioned pump into operation and maintain it in operation.

The pressure-responsive member may be constituted, for example, by a piston movable in a cylinder, or a diaphragm, one face of which is subject to the discharge pressure of the normal feed pump and the opposite face of which is subject to the discharge pressure of the emergency pump, and a spring or the equivalent acting on said pressure-responsive member against the pressure of the normal feed pump, effective to cause said pressure-responsive member to act, directly or by means of a relay, on a valve, switch, or the like, to put the first mentioned pump into operation and maintain it in operation.

Thus, when the pressure of discharge from the normal feed pump is not below a certain amount, this pressure is sufficient to overcome the spring and maintain the valve in closed position or the switch in open position; but, when the pressure falls below a predetermined minimum, the spring acts to move the pressure-responsive member and so operate the valve or switch or the like, and through its agency to put the emergency pump into action, e. g., by supplying actuating medium to its driving motor.

Immediately the emergency pump commences to function, the pressure generated by this pump is communicated to the pressure-responsive member and assists. the spring to act on the valve, switch or the like, thereby increasing the supply of motive fluid to (or otherwise assisting) "the emergency pump until this pump develops sufiicient'pressure to open a non-return valve provided on its discharge branch and discharge water into the feed main.

As long as the emergency pump is in action its discharge pressure holds the pressure-responsive member in the position it has attained withthe valve in full open position or the switch in closed position.

When the emergency pump is put out of actionsay, by hand-the pressure on one face of the pressure-responsivemember falls to zero, and the member, being moved by the discharge from the normal pump acting against the force of the spring only, acts to close the valve or to open the switch.

It is a feature of the invention that, immediately the emergency pump commences to run, its pressure of delivery assists the spring to complete the opening movement of the valve, or eifect the equivalent action on the switch or the like. This effect is important, because the emergency pump can be arranged to be put into operation when the pressure of discharge from the normal feed pump falls to that corresponding to the limit of its capacity, when, although the normal pump is discharging at a pressure still substantially above the working pressure of the boiler and continues to discharge into the boiler at its maximum capacity, it has failed, or there is risk of failure, to supply feed water in sufiicient amount.

It is also an important feature of the invention that, when the emergency pump is put into operation, its pressure of delivery, acting in conjunction with the force of the spring, maintains the valve in full open position or theswitch in closed position, thus maintaining the emergency pump in operation irrespective of the subsequent rise in the feed main pressure due to the emergency pump being put into action. In-' termittent action of the emergencypump is thus prevented.

It will be-appreciated that, when the emergency pump is stopped by hand, and the discharge of the normal pump is in excess of the predetermined minimum, the pressure-responsive member will cause the valve to return automatically to the closed position or the switch to return to open position in which the emergency pump may be put into action. when occasion arises.

In the accompanying drawings Fig. 1 is a diagrammatic view showing an arrangement of a centrifugal feed pump driven by a steam turbine the steam supply to which is controlled by a device in accordance with the invention, the said device being shown in detail in vertical section.

Fig. 2 is a diagrammatic view showing an arrangement of a centrifugal feed pump driven by an electric motor the current supply to which is controlled by a device in accordance with the invention, the said device being shown in detail in vertical section.

Referring to Fig. 1, a device in accordance with the invention is arranged in the steam supply pipe 1 to a turbine 2 which drives a feed pump 3 and comprises an automatic valve 4 balanced in respect of the steam pressure, with the exception of a small diameter valve spindle 5 which is secured to the valve 4 and passes through a gland 6 in the cover '7 of the valve body 8. The valve spindle 5 passes through a screw-threaded sleeve 9 which is screwed into a lower spring cap 10, and which is provided with a collar resting on the bottom of a spring cage 11 securely attached to the top of the valve body 3, said sleeve 9 being rotatable for the purpose of raising or lowering the spring cap 19 and adjusting the stress of the spring 12.

The valve spindle 5 projects upwardly through an upper spring cap 13 and is provided at its upper end with a collar which rests inside the upper spring cap 13 so that any extension of the spring 12 lifts the valve spindle 5 and opens the balanced valve 4. Downward movement of the upper spring cap 13 is efiected against the action of the spring 12. The upward movement of the upper spring cap 13 is limited by an extension of a chamber 14 which is arranged to form a stop.

An intermediate spindle 15 rests on the valve spindle 5 and passes through a sleeve 16 into the chamber 14 which accommodates a piston 17 coaxial with the valve spindle 5. The piston 17 makes contact with the upper end of the intermediate spindle 15 so that downward movement of the piston 17 depresses the intermediate spindle 15, upper spring cap 13 and valve spindle 5 and closes the valve 4, while upward movement of the piston 1'7 enables the spring to open the valve 4.

The piston 17 works in a cylinder 17' the lower end of which is open to the chamber 14 and whose upper end is closed by the cover 18.

The discharge branch of the feed pump 3 is provided with a non-return valve 19, a pipe 20 being led from the outlet side of the non-return valve 19 to the cover 18, so that the pressure in the feed main 21 is always exercised on the top of the piston 17. A pipe 22 connects the inlet side of the non-return valve 19 to the chamber 14 so that the discharge pressure of the emergency feed pump 3 is exercised on the bottom or" the piston 1'7.

The emergency feed pump 3 is not in operation normally; normally, therefore, the pressure set up in the feed main 21 by the normal feed pump (not shown) maintains the non-return valve 19 in closed position. The pressure on the pump side of the non-return valve 19 corresponds to the suction pressure of the feed pumps so that this pressure is normally exercised on the underside of the piston 17.

The pressure on the top or" the piston 17 is the feed main pressure, and, so long as this pressure is in excess of a predetermined pressure, the piston 17 maintains the valve 4 in closed position against the action of the spring 12, the stress of which is adjusted as necessary by rotation of the sleeve 9.

Immediately the feed main pressure falls below the predetermined pressure, the force exercised by the spring 12 causes the valve 4 to open, allowing steam to pass to the turbine 2, which is immediately put into operation, and, as the pump 3 rotates, the rising pressure at the discharge branch of the pump 3 is communicated by way of the connecting pipe 22 to the underside of the piston 17, and assists the spring 12 to open the valve 4 further, thereby increasing the quantity of steam passing to the turbine 2 until the pump 3 develops sufiicient pressure to discharge water into the feed main 21.

The discharge pressure at the branch of the emergency feed pump 3 is now in excess of the pressure in the feed main 21 and therefore holds the piston 1'7 in the top position, thus permitting the spring 12 to maintain the valve 4 in the full open position so long as the feed pump 3 is in operation. The pressure in the feed main 21 can therefore be maintained in excess of the predetermined pressure by the emergency feed pump 3 without causing the valve 4 to close. .he emergency feed pump is thereby maintained in operation irrespective of the subsequent rise in the feed main pressure due to the emergency pump being put into operation, and intermittent operation of the emergency pump is thereby prevented.

It will be appreciated that, when the emergency feed pump is stopped by hand, and the discharge of the normal pump is in excess of the predetermined minimum, the piston 17 will cause the valve 4 to return automatically to the closed position in which it will be ready to put the emergency pump into operation when occasion arises.

An isolating valve 23 may be arranged in the connecting pipe 20 between the feed main 21v and the piston 17 so that the pressure supply from the feed main 21 may be cut off, to enable the spring 12 to open the valve 4. A valve 24 enables the water above the piston 17 to be released to atmosphere, so that the emergency feed pump 3 can be started up, if desired, when the normal feed pump is in operation and maintaining a pressure in the feed main in excess of the predetermined pressure.

Referring to Fig. 2, a device in accordance with the invention is arranged to control the supply of electric current to a motor 25 which drives the emergency feed pump 3. The spindle 5 is connected to the pivoted arm 26 of a rheostat 2'2, so that movement of the spindle 5, efiected by the extension of the spring 12, causes the arm 26 to move and cut out sections of the rheostat resistance 28 progressively, thereby controlling the supply of electric current to the motor 25 until the motor gradually reaches its full speed.

Normally, the emergency feed pump 3 is stationary and the several parts of the device are in the relative positions shown in Fig. 2.

Immediately the feed main pressure falls below the predetermined pressure, the force exercised by the spring 12 causes the spindle 5 to move the arm 26 and allow current to flow to the motor 25 which is immediately put into operation, and, as

the pump 3 rotates, the rising pressure at the discharge branch of the pump 3 is communicated by way of the connecting pipe 22 to the underside of the piston 1'7, and assists the spring 12 to continue the movement of the arm 26, so that the speed of the motor is increased until the pump 3 develops suflicient pressure to discharge water into the feed main 21. The discharge pressure at the branch of the emergency feed pump 3 is now in excess of the pressure in the feed main 21 and therefore holds the piston 17 in the top position, thus permitting the spring 12 to maintain the rheostat 27 in the full open position so long as the feed pump 3 is in operation.

What I claim is:

1. A device for controlling the supply of actuating medium to the driving member of a boiler feed water pump adapted to discharge into a boiler feed water delivery line, comprising a movable substantially balanced cut-off member in the line of supply of actuating medium, a spring urging said cut-off member towards a position permitting full supply of actuating medium to said driving member, a non-return check valve interposed between said pump and the boiler feed water delivery line, and a pressure-responsive member disconnected from said cut-off member and having opposed faces of equal area, one face subject to the boiler feed water delivery line pressure normally acting on said pressure-responsive member to overcome said spring and hold said cut-off member in the position of no supply of actuating medium to said driving member, and the other face in communication with a point located on the discharge side of said pump and in front of said check valve, and subject to the discharge pressure of said pump acting to move said pressure-responsive member away from said cut-off member, to permit said spring to move said cut-off member to the position of full supply of actuating medium, whereby on a fall in the boiler feed water delivery line pressure to a predetermined pressure actuating medium is permitted to pass to said driving member and said pump is put in operation and subsequently maintained in operation.

2. A device for controlling the supply of actuating medium to the driving member of a boiler feed water pump adapted to discharge into a boiler feed water delivery line, comprising a substantially balanced cut-off valve in the line of supply of actuating medium, said valve having a stem, a spring urging said valve towards full open position, a non-return check valve interposed between said pump and the boiler feed water delivery line, a chamber isolated from said cut-off valve and valve stem, a pressure-responsive member movable in said chamber, said pressure-responsive member being disconnected from said cut-off valve and valve stem, and a loose interponent between said pressure responsive member and said valve stem, said pressure-responsive member having opposed faces of equal area, one face subject to the boiler feed water delivery line pressure normally acting on said pressure-responsive member and through said interponent to depress said stem and hold said cut-off valve closed in opposition to said spring, and the other face in communication with a point located on the discharge side of said pump and in front of said check valve, and subject to the discharge pressure of said pump acting to move said pressure-responsive member away from said stem, and thus to permit said spring to move said cut-off valve to full open position, whereby on a fall in the boiler feed water delivery line pressure to a predetermined pressure actuating medium is permitted to pass to said driving member and said pump is put in operation and subsequently maintained in operation.

3. A device for controlling the supply of actuating medium to the driving member of a boiler feed water pump adapted to discharge into a boiler feed water delivery line, comprising a substantially balanced cut-off valve in the line of supply of actuating medium, said valve having a stem, a spring urging said valve towards full open position, a non-return check valve interposed between said pump and the boiler feed water delivery line, a pressure-responsive member disconnected from said cut-off valve and valve stem, and a loose interponent between said pressure-responsive member and said valve stem, said pressure-responsive member having opposed faces of equal area, one face subject to the boiler feed water delivery line pressure normally acting on said pressure-responsive member in opposition to said spring and through said interponent to depress said stem and hold said cut-off valve closed, and the other face in communication with a point located on the discharge side of said pump and in front of said check valve and, subject to the discharge pressure of said pump acting to move said pressure-responsive member away from said stem and thus to permit said spring to move said cutofi valve to full open position, whereby on a fall in the boiler feed water delivery line pressure to a predetermined pressure actuating medium is permitted to pass to said driving member, and said pump is put in operation and subsequently maintained in operation.

4. A device for controlling the supply of actuating medium to the driving member of a boiler feed water pump adapted to discharge into a boiler feed water delivery line, comprising a substantiallly balanced cut-off valve in the line of supply of actuating medium, said valve having a stem, said stem having a collar, a rotatable sleeve traversed by said stem, a spring urging said valve towards full open position, a lower spring cap in screw-threaded engagement with said sleeve, an upper spring cap affording a support for said collar, a non-return check valve interposed between said pump and the boiler feed water delivery line, a pressure-responsive member disconnected from said cut-off valve and valve stem, and a loose interponent between said pressureresponsive member and said valve stem, said pressure-responsive member having opposed faces of equal area, one face subject to the boiler feed water delivery line pressure normally acting on said pressure-responsive member in opposition to said spring to depress said stem and hold said outoff valve closed, and the other face in communication with a point located on the discharge side of said pump and in front of said check valve, and subject to the discharge pressure of said pump acting to move said pressure-responsive member away from said stem, and thus to permit said spring to move said cut-off valve to full open position, whereby on a fall in the boiler feed water delivery line pressure to a predetermined pressure actuating medium is permitted to pass to said driving member, and said pump is put in operation and subsequently maintained in operation.

HAROLD I-LILLIER.

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