US3045893A - Compressor system - Google Patents

Description

July 24, 1962 F. S. YOUNG COMPRESSOR SYSTEM Filed March 12. 1959 I CoM/@HEMA I 1N:gg/23,1251(I BY m:

Zig/Vm United States Patent 3,045,893 COMPRESSOR SYSTEM Farrile S. Young, Houston, Tex., assgnor to Gulf Inteb state Company, Houston, Tex., a corporation of Dela- Ware Filed Mar. 12, 1959, Ser. No. 799,0'22 13 Claims. (Cl. 230-95) This invention relates to gas transmission lines, and more particularly to a compressor system for `a gas transmission line.

The present method of boosting pressure of gaseous fluids is by using reciprocating or centrifugal type compressors. These compressors are driven by electric motors, reciprocating engines, gas turbines, steam engines, etc. Their disadvantage is that with any large flow, a great quantity of horsepower and expense is required. Part of the expense is due to the necessity of handling all of the gas through the compressor with the resulting large pipings and valves at each compressor station.

Conventionally compressor stations are spaced approximately 90 miles apart. It is well known that by locating compressor stations at smaller spacings, such `as l5 miles apart, that approximately 20% less total horsepower is needed to maintain a given pressure boost in the line. It has not been practical with conventional compressor stations to utilize this horsepower saving, as the cost per horsepower of the small horsepower stations greatly exceeds that `of the larger horsepower installations at greater spacing. This is true primarily because the compressors, pipes, valves and fitting sizes are `determined by the flow being handled rather than by the horsepower requirements.

From the above it will be seen that there is needed a new approach to compressor stations in which only a fraction of the gas in the line need be handled by the pressure boosting equipment to permit the utilization of more closely spaced compressor stations. Accordingly, it is an object of this invention to provide compressor stations in which the Istation will handle only `a small percentage of the gas in the line, thus permitting the utilization of small diameter pipes, valves, fittings, etc.

The use of compressors to pressurize even a small percantage of the gas in a pipe line involves relatively high horsepower -apparatus of large size having many moving parts. It is therefore an object of this invention to provide the necessary energy in a gas sidestream for pressurizing the transmission line by heating the gas to a high temperature rather than pressurizing it to 'a high pressure. Inasmuch as the primary energy force is a heater which incorporates no moving parts and has extremely high effciency, considerable saving both in initial cost and maintenance of the compressor station is possible.

Conventional compressor stations require the constant attendance of operating and maintenance personnel. It is, therefore, another object of this invention to provide, in combination with apparatus for heating `a sidestream yfrom a transmission line and injecting the sidestream into the line to increase its pressure, a control system for automatically controlling operation of the compressor station and thus eliminating the necessity of constant Iattendance of operating personnel.

Other objects, features and `advantages of the invention will be apparent from the drawing, the specification and claims.

In the drawing wherein two forms of this invention are illustrated: n

FIGURE l is Ia schematic view of a compressor statlon constructed in accordance with this invention and manually controlled; and

constructed in accordance with this invention and pro- Ffice vided with automatic controls for maintaining a predetermined condition in the gas transmission line.

Referring to FIGURE l, a portion of a gas transmission line is shown `at 10. The line 10 is representative of the many lines conveying gaseous products long distances throughout this country, such as those conveying natural gas from the Southwest section of the country to other sections of the country. As is well known, these lines extend many hundreds of miles and it is necessary to recompress the gas Iat spaced intervals to maintain the desired line pressure.

A gas jet compressor indicated generally at 11 is provided in the pipe line and delivers gas which has been heated and slightly compressed in accordance with this invention to the line 10. The gas jet compressor may take any desired form, and is represented here schematically as including a venturi 12. into which the gas is delivered from jet 13. The temperature of the gas intro duced by the jet into the transmission line is reduced upon association with the gas in the line. The effect of this temperature reduction is to -suck gas from upstream and thereby increase the pressure in the line downstream of the jet.

Gas is fed to the gas jet compressor 11 through a conduit 14 which receives gas from the transmission line 10, preferably upstream from the gas jet compressor 11.

In order to provide the heat which is the primary energy force for compressing gas in the transmission line 10, a heater indicated generally at 15 is provided. For purposes of economy, it is preferred that the heater be fired by gas from the transmission line, but it will be understood that other forms of heater might be used. It will be apparent that the gas passing through the heater 1S in conduit 14 is heated but is not ignited and the chemical structure of the gas in the conduit 14 remains unchanged as it passes through said heater.

Where gas for the heater is taken from the transmission line, it may be drawn from the system at any desired point. For instance, in FIGURE l this gas is drawn through line 16 from conduit 14 adjacent the upstream end of conduit 14. A Valve 17 controls flow of the fuel to the burner '18 of heater 15. By varying the setting of valve 17, and B.t.u. output of heater 15 may be controlled to heat the gas passing through conduit 14 to the desired temperature.

For purposes of eciency and to avoid overheating of heater 15, means should be provided for insuring the passage of a predetermined volume of gas through the heater 15. For this purpose, a relatively small horsepower compressor 19 may be provided in line 14. The compressor should be sized to provide a ratio of pressures upstream and downstream of the compressor which will insure adequate flow through the heater |15.

It is preferred that means be provided for controlling the amount of gas passing through the conduit 14. For this purpose a valve 21 may be provided in the conduit and by properly setting valveY Z1 the ow through the conduit 14 may be controlled.

`In some instances it may be desirable to in part bypass heater 15. A bypass conduit 22 controlled by a valve 23 will permit such bypass. It is contemplated that in normal operation the valve 23 will remain closed and the setting of valves 17 and 2'1 and the output of compressor 19 will be regulated to provide the desired amount of heated gas without utilizing the bypass 2.2.

In operation approximately 10% of the gas passing through line 10 is desirably bypassed through conduit 14. The compressor may be of any desired type driven by any desired form of prime mover, and need only compress the gas suflicient to insure passing of the desired volume of gas through the heater. This compressor is relatively small as compared to compressors convention- 3 ally employed in compressor stations and need only develop a few hundred horsepower.

The slightly compressed gas passes through check valve 24 to the heater 15 where it is heated. The check valve 24 prevents reverse flow of gas in conduit 14 upon the occurrence of any 4malfunction of the system. The heater A15, being controlled by valve |17, heats the gas passing through the heater to the desired temperature and discharges it through line 1'4 to the gas jet compressor 1.1. The compressor in turn utilizes the heat of the gas as the primary energy source for compressing the gas in the main line 10.

Referring to FIGURE 2, there is shown a form of this invention in which the compressor system is automatically controlled. The line 10, conduit 14, compressor 19, jet compressor 11, and heater 1S are identical with those illustrated and described in FIGURE 1, and they operate in the same manner except that the system is automatically controlled.

The output of the heater is controlled in accordance with the pressure in the line downstream of the jet compressor 111. Such a control is indicated at and is sensitive to the pressure in line 10 through a pressuresensing device 26 and a connecting conduit 27. In accordance with the pressure conditions sensed by the instrument 26, the burner valve control 25 regulates the degree of opening of burner valve 28 through a control conduit It is also desirable to control heater output in response to the temperature of the gas leaving the heater. For this purpose a temperature-sensing device 31 may be associated with conduit 14 and signals from this device are received by the burner valve control 25 through conduit 32. Thus the burner valve control 25 is sensitive both to temperature in line 14 and pressure in line 10, and will control the heater output to maintain this temperature and pressure within desired ranges.

The compressor should desirably maintain a predetermined diierential thereacross to insure adequate ow of gas lthrough heater 15. For this purpose a differential controller 32 is sensitive to the pressure upstream and downstream of compressor 19 through lines 33 and 34 and controls the output of the compressor through a control conduit 35.

Desirably the volume of gas passed through conduit 14 is a percentage of the volume of gas passing through the line 10. To maintain this percentage within a predetermined range, a control device for controlling the relative volume of flow through line 14 should be provided. Such a control may be provided by a ditrential controller 36 receiving signals through lines 37 and 38 which sense the pressure conditions in lines 10` and 14 through the medium of orifice plates 39 and 40, respectively. In accordance with the differential in pressure at the orice plates 39 and 40, the differential controller adjusts the opening of valve 41 through control conduit 42 .to maintain the desired percentage of ilow in line 14.

It will be appreciated that the several controllers are inter-related in their operation, and, as certain conditions change, the action of one controller will influence the action of another controller. For instance, a decrease in line pressure upstream of the jet compressor would result in a reduced ow of gas through line 14, and this of course would result in increasing the temperature of gas leaving heater 15. When this occurs the temperaturesensing device 31 would signal the burner valve control to reduce the output of the heater 15.

It will be appreciated that all of the controls shown in FIGURE 2 are merely desirable and not necessary to automatic operation of the system. For instance, the burner valve control may be utilized alone and may be sensitive only to the pressure in line 10 as a primary means of controlling the system. To maintain a proper flow through the heater the compressor output should be maintained above -a predetermined minimum. It is not absolutely necessary to maintain the compressor output below a predetermined maximum, but in the absence of this type of control excessive compressor output will cause cycling of the outlet pressure controller. It is also apparent that the compressor may be controlled directly in the manner indicated in the drawing, or it may be indirectly controlled by the differential controller system for maintaining a predetermined percentage of ow of gas through line 14. This system might regulate the flow through line 14 by varying the speed of the compressor to maintain a predetermined percentage of ilow through line 14.

The various differential controllers and burner valve control may be operated by instrument air and may each be provided by controllers sold by the Foxborro Company and known as Type 40 Stabilog. As is well known to those skilled in the art, these controllers may accomplish the diierent functions hereinabove described by the manner in which they are connected in the system.

In using instrument air the valves 41 and 28 would preferably be two-way diaphragm-operated motor valves, of which many different forms are available and well lrnown to those skilled in the art.

It will be apparent from the foregoing that the amount of compressor horsepower required for a given length of main line is much less than in conventional compressor installations, and may be reduced to as low as approximately 10%, or less, than the horsepower normally required. As the main energy source is provided by a high-efficiency heater, low `fuel consumption is obtained, and as there are no moving parts in the main energy source, maintenance of the system is much less than conventional compressor systems. The cost of the system is much less than conventional systems, both due to the fact that the piping, ittings, Valves, etc. -may be of small size, and that the heater 1S is much less costly than conventional compressors of the size normally employed at compressor stations. In fact, the entire station has very few working parts, and therefore has very little maintenance. The `station can be left unattended and, because of the small size compressors employed, spare portable compressors can be used to replace compressors should any trouble occur. Additional savings result from the ability to eliminate all buildings normal to conventional compressor stations and to reduce spare parts inventory. Also equipment, such as large cranes required on conventional stations, Will be eliminated, as well as dwellings for conventional maintenance and operating crews.

A further -advantage of this invention is that a higher line pack is obtained by boosting the line pressure on frequent intervals. This assists the gas transmission companics in supplying iiuctuating ows from the line pack when necessary.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is:

1. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding lthe gas to the jet compressor, a compressor in the -branch conduit for maintaining positive ow through the conduit in one direction, and heater means for heating the gas in the branch conduit whereby 'the gas -fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure.

2. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, a compressor in the branch conduit for maintaining positive flow through the conduit in one direction, heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line tempervature and pressure, and means for controlling the B.t.u.

output of said heater means in response to the pressure in the transmission line downstream of the jet compressor.

3. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, a compressor in the branch conduit for maintaining positive flow through the conduit in one direction, heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure, and means controlling the B.t.u. output of said heater means in response Ito the pressure in the transmission line downstream of the jet compressor and in response to the temperature of the gas in said conduit downstream of the heater means.

4. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, a compressor in the branch conduit for maintaining posiltive ilow through the conduit in one direction, heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at greater temperature and pressure than the temperature and pressure, and means controlling said compressor in the branch conduit to maintain a predetermined minimum pressure differential thereacross.

5. Apparatus -for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, a compressor in the branch conduit for maintaining posiytive iiow through the conduit in one direction, heater means `for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure, and means controlling the B.t.u. output of said heater means in response to the pressure in the transmission line downstream of the jet compressor and means controlling said compressor in the branch conduit to maintain a predetermined minimum pressure differential thereacross.

6. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the iet compressor, a compressor in the branch conduit for maintaining positive flow through the conduit in one direction, heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure, and means including a valve controlling ilow through said branch conduit and maintaining a predetermined ratio of ow between the conduit and main line.

7. Apparatus -for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, a compressor in the branch conduit for maintaining positive flow through the conduit in one direction, heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure, means controlling the B.t.u. output of said heater means in response to the pressure in the transmission line dowstream of the jet compressor, and means including a valve controlling ilow through said branch conduit and maintaining a predetermined ratio of ow between the conduit and main line.

8. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, a compressor in the branch conduit for maintaining positive flow through the conduit in one direction, heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure, means controlling the B.t.u. output of said heater means in response to the pressure in the transmission line downstream of the jet compressor, means controlling said compressor in the branch conduit to maintain a predetermined minimum pressure diierential lt-hereacross, and means including a valve controlling ow through said branch conduit and maintaining a predetermined ratio of ow between the conduit and main line.

9. The apparatus of claim 8 in which the means controlling the compressor in the branch conduit maintains a predetermined maximum as Well as minimum pressure differential across said compressor.

10. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, means for causing a predetermined percentage of the gas in said transmission line to pass through said branch conduit, and heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure.

11. Apparatus for increasing pressure in a gas transmission line comprising, a gas transmission line, a jet compressor in the line, a branch conduit receiving gas from the line and feeding the gas to the jet compressor, means for causing a predetermined percentage of the gas in said transmission line to pass through said branch conduit, and heater means for heating the gas in the branch conduit whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than line temperature and pressure, and means controlling the B.t.u. output of said heater means in response to the pressure in the transmission line downstream of the jet compressor.

12. Apparatus for increasing pressure in a gas transmission line comprising, a branch conduit having an inlet and an outlet, a jet compressor connected to the outlet of said conduit, heater means for heating gas in said branch conduit upstream of said jet compressor, and a compressor in the branch conduit upstream of said jet compressor for maintaining positive flow through the conduit from its inlet to its outlet, whereby the gas fed to the jet compressor through said conduit is at a greater temperature and pressure than at the inlet of said conduit.

13. The apparatus of claim 12 in combination with means for controlling said compressor in response to the pressure diierential thereacross.

References Cited in the ile of this patent UNITED lSTATES PATENTS 1,737,894 Reynolds Dec. 3, 1929 1,948,907 Egli Feb. 27, 1934 2,170,587 Crocker et al Aug. 22, 1939 2,519,531 Worn Aug. 22, 1950 2,776,087 Walter a Jan. 1, 1957 FOREIGN PATENTS 310,331 Germany Ian. 14, 1919

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