US2613026A - Vacuum pump suction control - Google Patents

Description

Oct. 7, 1952 D. B. BANKS 2,613,026

VACUUM PUMP SUCTION CONTROL Filed Nov. 15, 1948 I4 L 29 Q I 24 '28 2o 2a 6 a 0 0 a 22 Recording Pressure fl/25 27 COIIffO/ltl' +l| +|l HI +l| Compressor km A *1] *ll +l| *ll INVENTOR. Daniel B. Ban/rs A Hame s Patented Oct. 7, 1952 Daniel B. Banks, Drexel Hill, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a. corporation of New Jersey Application November 13, 1948, Serial No. 59,808

Claims. 1

a This invention relates to compressors, and especially to regulating devices to be connected to compressors for exhausting systems requiring vacuum conditions for operation. An object of the invention is to disclose a method and apparatus for unloading a suction compressor during the starting-up operation. It has been found that the start-up.on systems requiring high vacuum or greatly reduced pressures, place an initial burden on the compressor far in excess of the power demands re-' quired later in the cycle to maintain these low pressures. Experience shows in the operation of a. vacuum pump or compressor on two, pounds absolute suction pressure and twenty pounds discharge pressure, the horsepower requirements when reducing suction pressure to nine pounds absolute are approximately 200% higher at this point than they are at the final reduction to two pounds absolute.

,In the preferred form of this invention the initial unloading of the compressor is attained by circulating the discharge of the compressor backto the suction or intake side until it is brought up to maximum speed and thoroughly warmed. The required reduced pressure is then built up within the compressor after which it is transmitted to the system without undue strain on the driving mechanism. This method and the apparatus used to obtain these results greatly reduces the initial power requirement.

It is, therefore, a further object of this invention todisclose a method of operation and the apparatus for combining the automatic control features used in operation at reduced pressures, with initial unloading required in the economical design and operation of systems presenting such overload problems.

The accompanying drawing illustrating one form which the invention may assume in practice, is a diagrammatic view of a compressor with the unloading and automatic operational control apparatus constructed in accordance with the invention. Referring more particularly to the drawing, a compressor I0 is shown in which a suction header II and a discharge header 12 are designed to coordinate the functions of the operating cylinproximity of the compressor, a manually controlled valve I1 is installed. Connected to the discharge header I2, here shown at the end opposite to the connection with the discharge or exhaust mains I6 but which may be connected at any convenient point to the discharge header I2, the by-pass I8 is shown. A valve I9, manually controlled, is inserted in the by-pass 18 at an easily accessible location. The by-pass I8 is conducted around the compressor to connect at a point 20 with the suction lines of the system. A manually controlled valve 2| is shown between the by-pass connection 20 and the systerm to permit disengaging the suction compressor, if desired. i

As shown, an automatically operated valve 22, which may be of the butterfly type, is inserted in the suction line l3 adjacent the compressor suction header II and the connection 20 of the by-pass IS. A diaphragm head 23 for the operation of the valve 22 is shown in the line 24 which, in the disclosed apparatus, is a conduit permitting the transmission of pressures from the recording pressure controller 25. This con- 1 troller is a commercially available instrument and is, therefore, not detailed in the d rawing. It includes gauges G and G for comparison of pressures. It is connected to the suction side of the compressor for suction operation as at the point 25 by conduit 21. In the conduit 28-24 connecting the pressure controller 25 with the pressure responsive valve 22, a 3-way, 4-port cook 29 is shown with operating lever L, together with the necessary piping arrangement to present a variety of pressure conditions to the valve The conduit 30 is a .by-pass to the instrument air source and taps the inlet, line 3| of the pressure controller. The conduit 32 is a vent to the atmosphere which permits complete exhaustion of any pressure existing on the valve for facility of operation.

The method of operation and the details of the functions of the apparatus will best be understood if it is remembered that although the auto: matic control is a necessary adjunct of the operational function of the suction compressor during the maintaining of low pressures on the system, it also plays a very necessary part in the unloading of the compressor during the starting up period. With this in mind, the details of the unloading incidental to start-up of the compres sor Will be described. Before starting the compressor, the 3-way, 4- port cook 29 is turned by lever L to connect the pressure controlled valve 22 with theconduit 30 mains I6.

so that it is subjected to the instrument air pressure source in line 3| which, for purposes of illustration, will be considered as pounds gauge pressure. Thus, the pressure of 15 pounds admitted to the valve will hold it open and connect the suction header II directly to the suction side of the system to be exhausted. The valve 2I in the suction line, between the system to be exhausted and the connection of bypass I8, is opened, thereby connectiong the system to the suction side of the compressor.

The valve I9 in the by-pass I 8 is opened whereby the by-pass I3 is connected to the suction lines I4 at the point 20 as previously noted. The valve I1, which is a manually operated device to connect and disconnect the discharge header I2 with the exhaust mains I6, is closed. By adjusting these valves as directed, a path of circulation is established through the compressor, thence through the by-pass to the suction side of the system, which is open to the circulation effeet, and then back through the compressor. The circulation from the discharge header I2 through the by-pass I8 to a point in the suction line 20 adjacent the suction header but outside the automatic control valve 22, as noted, greatly reduces the starting load on the compressor by cutting down the discharge load which, without the by-pass I8, would have to be overcome in the starting period.

The pressure controller 25 is now set to the desired reduced pressure at which the system is to operate. In our example, this will be considered as 2 pounds absolute, as previously stated. The engine which operates the compressor is now started and is heated and checked for proper operation. It is then speeded up to the maximum R. P. M. A suction circulation is now established in which the discharge of the compressor is returned to the system suction line adjacent the comperssor intake just outside the automatic control valve 22, and the discharge circulation is restricted to the by-pass return and not permitted to exhaust to the discharge mains.

After the compressor is warmed up and running properly the 3-way, l-port cook 29 is rotated to the valve 22 connection with the exhaust line 32 to remove the 15 pounds air pressure which held it open, and thence to the instrument control position through which direct control is established with the pressure controller 25. As soon as the 15 pounds air pressure is exhausted, the automatic control valve 22 closes rapidly and remains closed until opened by the pressure controller. 25 which has been set to operate at 2 pounds absolute. Valve 22 is located adjacent suction header II to reduce the volume between it and the suction side of the compressor I0 which affords quick and complete exhaustion in a few strokes of the compressor.

The valve 22 now under the automatic control of the pressure controller will remain closed until the desired 2 pounds absolute pressure, or less, is reached between it and the compressor intake I I. It will be evident that the compressor is now establishing the suction within itself as both the suction lines and the discharge lines of the system are closed. The manually operated valve I9 in the by-pass I8 and the valve I1 connecting the discharge header I2 to the exhaust lines I6 are respectively closed and opened concurrently. The compressor now discharges to the exhaust The pressure controller'25 directly connected to the suction side of the compressor is effectively brought into operation and the automatic valve 22 opens to the system to establish the desired reduced pressure without placin excessive demands on the compressor engine. The valve 22 now being controlled from the suction header II through the recording pressure controller 25 maintains the two pounds absolute pressure at the suction of the compressor regardless of the pressure applied at any time ,up-stream from valve 22. The maintenance of pressure relationship makes it impossible to overload the compressor.

I claim:

1. A fluid pressure reducing device in combination. with a reduced pressure system which includes a compressor having suction and discharge conduits, said suction conduit being connected to said system, said device comprising a valve in said suction conduit positioned between said system and said compressor, an automatically operating pressure controller meansfor actuating said valve, and a conduit connecting said controller means with said suction conduit at a point between said compressor and said valve so that said valve is actuated in accordance with the pressure in said suction conduit between said compressor and said valve.

2. A fluid pressure reducing device in combination with a reduced pressure system which includes a compressor having suction and discharge conduits, said suction conduit being connected to said system, said device comprising a valve in said suction conduit positioned between said system and said compressor, an automatically operating pressure controller means for actuating ,said valve, a conduitconnecting said controller means with said suction conduit at a point between said compressor and said valve so that said valve is actuated in accordance with the pressure in said suction conduit between said compressor and said valve, and additional valve means for operatively connecting said first-mentioned valve with said pressure controller.

3. A fluid pressure reducing device comprising in combination with a reduced pressure system which includes a compressor having suction and discharge conduits, said suction conduit being connected to said system, said device comprising a valve in said suction conduit positioned between said system and said compressor, an automati cally operating pressure controller means for actuating said valve, a conduitconnecting said controller means with said suction conduit at a point between said .compressor and said valve so that said valve is actuated in accordance with the pressure in said suction conduit between said compressor and said valve, and means to unload said compressor during the starting-up period preliminary to automatic control including a bypass connecting said discharge conduit and said suction conduit.

4. A fluid pressure reducing device comprising in combination with a reduced pressure system which includes a compressor having suction and discharge headers, a conduit connecting said system to the suction header, said device comprising an automatically operating pressure controller, conduit means connecting said pressure controller to said suction header for direct operation by the pressure within said suction header, a pressure operated valve actuated by said pressure controller positioned in said connecting conduit, valve means for operatively connected said pressure operative valve with said controller for automatic control during reduced pressure operation, and means to unload said compressor during the starting-up period preliminary to automatic control including a by-pass connecting the discharge header to said connecting conduit.

5. A fluid pressure reducing device comprising in combination with a reduced pressure system which includes a compressor having suction and discharge headers connected thereto, a conduit connecting said system to the suction header, said device comprising an automatically operating pressure controller, conduit means connecting said pressure controller to said suction header for direct operation by the pressure within said suctio header, a pressure operated valve actuated by said pressure controller positioned within said connecting conduit, valve means for operatively connecting the pressure operated valve and said controller for automatic control during reduced pressure operation, and means to unload said compressor during the starting-up period preliminary to automatic control including a bypass connecting the discharge header to said connecting conduit between the reduced pressure system and the pressure operated valve.

DANIEL B. BANKS.

REFERENCES CITED The following references are of record in the file of'this patent:

UNITED STATES PATENTS Number Name Date 933,731 Hennebohle Sept. 7, 1909 1,152,400 Dennedy Sept. 7, 1915 1,248,467 Eby Dec. 4, 1917 15 2,044,867 Woodard June 23, 1936 2,401,910 Condit -1 June 11, 1946 2,449,217 Graham Sept. 14, 1948 FOREIGN PATENTS 20 Number Country Date 16,268 Great Britain 1901

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