JPS6226628Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a check valve for a pump installed on the pump discharge side and equipped with a recirculation valve.

In a centrifugal pump or an axial flow pump, the discharge flow rate may become small due to changes in the operating conditions of the discharge side equipment (boiler, chemical equipment, etc.). In such a case, if the pump continues to operate as it is, the fluid temperature will rise, eventually causing damage to the pump itself. To prevent fluid temperature increases, a minimum discharge flow is required to cool the pump, typically recirculating fluid from the discharge side to the suction side at a flow rate of 10-20% of the pump capacity. However, if the fluid is constantly recirculated, the power loss during steady operation is large, so if the fluid is recirculated only when the flow rate is low, power can be saved.

For the above purpose, a recirculation valve is installed on the pump discharge side, and when the flow rate is low, the recirculation valve opens automatically to recirculate the fluid from the pump discharge side to the suction side at the flow rate necessary for cooling. This is commonly done. There are two methods to automatically operate the recirculation valve: one is to operate it using auxiliary power based on signals such as flow rate and pump drive current, and the other is to operate it in conjunction with the valve body of a lift check valve installed on the discharge side. There is a method that operates mechanically. This idea belongs to the latter method.

FIG. 1 shows a pump lift check valve including a conventional recirculation valve. As shown in the drawings, the valve body 2 of the lift check valve 1 consists of a lower body 3 and an upper body 4, and the lower body 3 has a cylindrical branch 5 extending laterally.

Guide shafts 8 and 9 protrude from the lower and upper ends of the valve body 7, respectively.
0 and 11 so as to be slidable. During steady operation of the pump, the valve body 7 is pushed up by the fluid force of the fluid flowing in from below, and the lift check valve 1
is in an open state. In such a state, when the operating condition of the pump discharge side changes and the discharge flow rate decreases, the flow force acting on the valve body 7 decreases. When the flow force becomes smaller than the weight of the valve body 7, the valve body 7 descends. When the discharge amount is close to 0, the valve seat 7' of the valve body 7 comes into contact with the valve seat 12 provided on the lower main body 3, and the lift check valve 1 is closed.

The recirculation valve 15 is installed so as to close the opening of the branch section 5, and a short pipe 13 (connected to the fluid recirculation circuit) is connected to the outlet side. The recirculation valve 15 is composed of a piston valve 16 and a pilot valve 23.

The piston valve 16 has a generally cylindrical recirculation valve body 1
A piston chamber 18 provided concentrically with the branch part 5 at 7.
and a piston 19 slidably inserted into the piston chamber 18. An O-ring is attached to the outer periphery of the piston 19 to keep the piston chamber 18 airtight.
20 is attached. Further, a valve seat 21 is provided at the tip of the piston 19 (the right end in the drawing), which contacts the valve seat 14 provided at the rear end of the short pipe 13. Note that the main body 17 has a piston chamber 1.
A valve chamber 22 is provided following the valve chamber 8, and this valve chamber 22 and the inside of the branch portion 5 of the check valve 1 are communicated through a flow path 22' provided in the main body 17.

The pilot valve 23 includes a pilot valve chamber 24 provided near the rear end (left end in the drawing) of the recirculation valve main body 17. The main body 17 has a branch part 5
and the pilot valve chamber 24.
5 is provided, and the pilot valve body 2 is installed here.
6 is slidably inserted. Further, the pilot valve chamber 24 communicates with the piston chamber 18 through a bypass hole 27 and with the short pipe 13 through a discharge hole 28. A valve seat 29 is provided at the portion where the discharge hole 28 communicates with the pilot valve chamber 24, and the pilot valve body 26 contacts this valve seat 29 to close the pilot valve 23.

A lever 30 is attached to the rear end of the recirculation valve body 17 by a pin 30' so as to be freely tiltable. The tip of the lever 30 is the pilot valve body 26
is engaged with an adjustment screw 26' screwed into the upper part of the holder. The rear end of the lever 30 fits into an elongated hole 6 provided in the lower part of the check valve body 7.

In the conventional pump check valve configured as described above, when the pump is in steady operation, the check valve body 7 rises due to the fluid force, so that the left end of the lever 30 moves toward the valve body. It is pushed up by the lower surface 6' of the elongated hole 7. At this time, lever 3
Since the right end of 0 is lowered, the pilot valve body 2
6 is pushed down by fluid pressure and closes the discharge hole 28. Further, fluid flows into the pilot valve chamber 24 through a small gap between the peripheral wall of the shaft hole 25 and the pilot valve body 26. This inflowing fluid further flows into the piston chamber 18 through the bypass hole 27. Then, due to the pressure difference between the fluids in the piston chamber 18 and the valve chamber 22, the piston 19 is moved to the short pipe 1.
3, the recirculation valve 15 is closed. Therefore, all fluid from the pump flows out of the check valve 1.

When the discharge amount of the pump decreases and the flow force of the fluid decreases, the check valve body 7 descends, and when it reaches a certain position, the lever 30 pushes up the pilot valve body 26 and the discharge hole 28 opens. Since the cross-sectional area of the discharge hole 28 is larger than the cross-sectional area of the gap between the circumferential wall of the shaft hole 25 and the pilot valve body 26, fluid flows out from the pilot valve chamber 24 and the pressure inside the valve chamber 22 decreases. . Therefore, the pressure in the piston chamber 18 also decreases, the piston 19 moves away from the valve seat 14, and the recirculation valve 15 opens. A portion of the fluid from the pump therefore flows through the recirculation valve 15 to the recirculation circuit.

The conventional pump check valve constructed as described above has the following drawbacks.

(1) The recirculation valve opens fully at an unnecessary time, causing power loss to the pump.

A recirculation valve provided in a conventional pump check valve operates on and off as shown by curve a in FIG. Therefore, the recirculation valve is always fully open during the period from when the check valve opens to a certain degree until it fully closes.
This causes fluid from the pump to flow unnecessarily into the recirculation circuit for a relatively long period of time between the opening of the recirculation valve and the full closure of the check valve.
This results in a loss of power. A shaded area A shown in FIG. 2 indicates an amount corresponding to power loss.

(2) Fluid impacts the piping and pump when the recirculation valve opens and closes.

As described above, since conventional recirculation valves operate on and off, water hammer is likely to occur when the valve is fully closed or fully open, and fluid impacts the piping and pump.

This idea was made to improve the above-mentioned drawbacks of conventional check valves for pumps. It is an object of the present invention to provide a check valve for a pump with a recirculation valve that does not cause fluid shock.

In the pump check valve of this invention, one end of the recirculation valve is closed with a bottom plate having an outflow hole communicating with the recirculation circuit, and a communication hole is provided to communicate the inside of the branch part of the check valve box and the outflow hole. It has a cylindrical body. A cover having a shaft hole in the center is attached to the other end of the main body. Further, a recirculation valve body is slidably fitted into the main body and has a cup shape and has a discharge pipe at the bottom that communicates with the outflow hole. This valve body opens and closes the outflow hole. The opening of the discharge pipe provided in the recirculation valve body is opened and closed by a rod-shaped pilot valve body that passes through the shaft hole of the cover and is movable along the main cylinder axis. An adjustment piece is screwed into the part of the pilot valve body that protrudes from the cover. One end of a lever connected to the check valve body is engaged with this screw piece.

In the pump check valve constructed as described above, the recirculation valve opens gradually in response to the opening of the pilot valve, and does not open completely instantaneously as in conventional valves. Therefore, it is possible to avoid unnecessary flow of the fluid from the pump into the recirculation circuit, and it is also possible to prevent impact on the piping and the pump due to the warmer hammer.

Examples of this invention will be described below.

FIG. 3 is a longitudinal sectional view showing the pump check valve of this invention. Since the check valve itself is the same as the conventional one, the same parts are given the same reference numerals as those shown in FIG. 1, and a description of the check valve itself will be omitted.

The recirculation valve 31 mainly includes a main body 32 and a cover 3.
8, a recirculation valve body 42 and a pilot valve 49.

The main body 32 has a cylindrical shape with one end closed with a bottom plate 33, and has a valve chamber 34 inside. An outflow hole 35 is provided in the center of the bottom plate 33 to communicate the valve chamber 34 and the short pipe 17, that is, the recirculation circuit. An annular wall portion 36 surrounding the valve chamber 34 is provided with a communication hole 37 extending parallel to the cylinder axis. One end of the communication hole 37 opens to the branch portion 5 of the valve box 2, and the other end opens to the valve chamber 34.

The cover 38 covers the main body 3 so as to close the valve chamber 34.
It is detachably attached to the other end of 2. A shaft hole 39 is provided in the center of the cover 38, and a through hole 40 is provided near the periphery so as not to block the communication hole 37 of the main body 32.

The recirculation valve body 42 is cup-shaped and is slidably inserted into the valve chamber 34 . This valve body 4
2 is provided with a discharge pipe 43 that protrudes from the center of the bottom and whose tip opens into the short pipe 17.
A sealing O-ring 44 is fitted on the outer periphery of 2. Further, the base of the portion of the valve body 42 that protrudes outside the bottom serves as a valve seat 45, and the outflow hole 35
The outlet hole 3 is seated on the valve seat 47 provided on the inlet side of the outlet hole 3.
5 is now closed.

The pilot valve 49 has a rod-shaped pilot valve body 5.
0, and this valve body 49 freely passes through the shaft hole 39 of the cover 38. The tip of the valve body 49 is a valve seat 51, which is provided at the opening of the discharge pipe 43 of the recirculation valve body 42.
3 to close the discharge pipe 43. Further, a thread 55 is cut at the other end of the pilot valve body 50, into which an adjustment piece 56 is screwed. The pilot valve body 50 is provided with a vane foot guide 58 whose guide surface is the inner peripheral surface of the recirculation valve body 42.

A lever support fitting 60 is fixed to the cover 38, and a bell crank-shaped lever 64 is rotatably attached thereto by a pin 62. The tip of the lever 64 extends to near the center of the flow path of the check valve 1 and is inserted into an elongated hole 66 provided in the lower part of the check valve body 7. The rear end of the lever 64 has a fork shape and engages with the adjustment piece 56.

The entire recirculation valve 31 is inserted into the branch part 5 of the check valve box 2, and attached to the check valve body so that the flange part 75 of the recirculation valve body 32 is sandwiched between the branch part flange 73 and the short pipe flange 74. It will be done. Therefore, by removing the short pipe 17 from the branch portion 5, the recirculation valve 31 can be easily taken out from the check valve body.

Next, the operation of the pump check valve configured as described above, particularly the recirculation valve, will be explained.

During normal operation of the pump, the check valve body 7 is pushed up as shown by the chain line by the flow force of the fluid. At this time, the tip of the lever 64 comes into contact with the lower surface 70 of the elongated hole 66 of the valve body 7 and is pushed up, and the rear end is separated from the adjustment piece 56 of the pilot valve 49. Therefore, the pilot valve disc 5
0 is pressed against a valve seat 53 provided on the recirculation valve body 42 by fluid pressure to close the discharge pipe 43.
As a result, the recirculation valve body 42 is also pressed against the valve seat 47 provided on the bottom plate 33 by the fluid pressure, and the outflow hole 3
5 is closed and no fluid flows into the recirculation circuit.

When the pump operates abnormally and the discharge flow rate decreases, the check valve body 7 descends due to its own weight. Valve body 7
As the lever 64 descends, the upper surface 71 of the elongated hole 66 of the valve body comes into contact with the tip of the lever 64, and the lever 64 is further tilted counterclockwise. As a result, the rear end of the lever 64 engages with the adjustment piece 56 to move the pilot valve body 50 to the left and open the discharge pipe 43. When the discharge pipe is opened, the fluid within the recirculation valve body 42 flows out through the discharge pipe 43 to the short pipe 17 side. At this time, the discharge pipe 43
Since the amount flowing out from the recirculation valve body 42 is much larger than the amount flowing into the recirculation valve body 42 from the portion of the shaft hole 39 through which the pilot valve body 50 passes, the pressure within the recirculation valve body 42 decreases. Therefore, the recirculation valve body 4
2 is pushed to the left by the pressure difference between the inside and outside, and the outflow hole 3
Open 5.

In this way, the check valve body 7 descends, and the recirculation valve 3
Assume that in the process of opening the pilot valve 49, the pilot valve body 50 is moved slightly to the left by the lever 64, and the pilot valve 49 is slightly opened. At this time, since the pressure within the recirculation valve body 42 decreases as described above, the recirculation valve body 42 also moves to the left. Lever 6
The length from the pin 62 of No. 4 to the point where it touches the adjustment piece 56 is the length from the pin 62 to the elongated hole upper surface 71 of the check valve body 7.
Since it is quite small compared to the length to the point where it touches,
Compared to the movement of the check valve body 7, the pilot valve body 50
movement is quite small. Therefore, the recirculation valve body 42 moves to catch up with the pilot valve body 50. As a result, the pilot valve 49 opens less or closes, and the recirculation valve body 4
The pressure inside the valve body 2 increases, the pressures acting on the inside and outside of the valve body 42 reach equilibrium, and the movement of the valve body 42 stops.

When the pilot valve 49 opens further due to the lowering of the check valve body 7, the equilibrium between the pressures acting on the inside and outside of the recirculation valve body 42 is broken. The recirculation valve body 42 is then moved to the left until a new pressure equilibrium is reached;
The fluid passage area in the outflow hole 35 increases.

In this way, the recirculation valve 31 opens in response to the lowering of the check valve body 7. Also, based on the same principle of operation, the recirculation valve 31 closes in response to the rise of the check valve body 7.

As described above, in the pump check valve of this invention, the movement of the pilot valve body 50 is proportional to the movement of the check valve body 7. Therefore, the increase or decrease in the fluid passage area of the outflow hole 35 caused by the movement of the recirculation valve body 42 also changes in proportion to this. That is, the recirculation flow is controlled proportionally to changes in pump flow rate. Further, in the curve b in FIG. 2 showing the characteristics of the recirculation valve 31, the slope of the curve b is the point where the pin 62 of the lever 64 contacts the adjustment piece 56 and the upper surface 71 of the elongated hole of the check valve body 7. It can be adjusted by changing the ratio of the lengths to the points.

Note that the timing of operation of the recirculation valve, that is, the timing of starting or stopping fluid recirculation, is determined by adjusting the position of the adjustment piece 56. For stable pump operation, it is desirable that the recirculation flow rate reaches its maximum flow rate a little earlier than the fully closed position of the check valve body 7. To this end, the stroke of the pilot valve body 50 may be made slightly larger than the stroke of the recirculation valve body 42. Curve b in FIG. 2 shows that the recirculation flow rate has already reached its maximum value before the check valve is fully closed.

A coil spring may be provided between the vane foot guide 58 and the cover 38 to assist in the closing operation of the pilot valve 49. In addition, the check valve body 7
By appropriately selecting the length of the elongated hole 66 provided in the lower part of the pilot valve 49, the pilot valve 49 can be made to start operating when the check valve body 7 reaches a predetermined position. The stroke section l shown in FIG. 2 corresponds to such a dead zone.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional pump check valve, Figure 2 is a characteristic diagram of recirculation flow rate of the conventional and present pump check valves, and Figure 3 is the pump check valve of the present invention. It is a longitudinal cross-sectional view showing an example. 1... Check valve, 2... Valve box, 5... Branch, 7
... Check valve valve body, 15, 31 ... Recirculation valve, 33
... Bottom plate, 35 ... Outflow hole, 37 ... Communication hole, 3
8...Cover, 39...Shaft hole, 42...Recirculation valve body, 43...Discharge pipe, 49...Pilot valve,
50...Pilot valve disc, 56...Adjustment piece.

Claims (1)

[Scope of utility model registration request] It has a cylindrical branch part 5 that protrudes from the side of the valve body 2 and communicates with the recirculation circuit, and a check valve body 7 is installed in the branch part.
In a lift check valve fitted with a recirculation valve 31 actuated by a lever 64 engaged with the recirculation valve 31, said recirculation valve 31 is closed at one end by a bottom plate 33 having an outflow hole 35 communicating with the recirculation circuit; A cylindrical main body 36 having a communication hole 37 that communicates the branch part and the outflow hole, a cover 38 attached to the other end of the main body and having an axial hole 39 in the center, and a cup-shaped body 36 having a bottom part connected to the outflow hole. It has a communicating discharge pipe 43 and is slidably fitted into the main body along the main body cylinder axis,
A recirculation valve body 42 that opens and closes the outflow hole, and a recirculation valve body 42 that passes through the shaft hole of the cover and is movable along the axis of the main body cylinder, and opens and closes the opening of a discharge pipe provided in the recirculation valve body. A check valve for a pump comprising a rod-shaped pilot valve body 50 and an adjustment piece 56 that is screwed into a portion of the pilot valve body that projects from the cover and engages with one end of the lever.