US3174677A - Variable clearance bottle for gas compressors and gas leakage sealing means therefor - Google Patents

Description

March 23, 1965 F. H. RAMSTAD 3,174,677

VARIABLE CLEARANCE BOTTLE FOR GAS COMPRESSORS AND GAS LEAKAGE SEALING MEANS THEREFOR Filed March so, 1962 40 FIG. 2

F. H. RAMSTAD A TTOP/VEVS Fl 7 K INVENTOR.

| I I l United States Patent 3,174,677 VARIABLE ELEARANCE BOTTLE FOR GAS CGM- PRESSGRS AND GAS LEAKAGE SEALING MEANS THEREFOR Francis H. Ramstad, Berger, Ten, assignor to Phillips Petroleum Qompany, a corporation of Delaware Filed Mar. 30, 1962., Ser. No. 183,23 3 Claims. (Ql. 23l21) This invention relates to reciprocating compressors. In one aspect it relates to bottle-type clearance apparatus for such compressors.

The natural gas and gasoline industries use large numbers of reciprocating or piston compressors. The cornpressors are used, among other purposes, for compressing hydrocarbon gases prior to extraction of condensible or gasoline boiling range hydrocarbons, for pumping gas in gas gathering pipe lines, in transmission pipe lines and for many other and varied purposes.

Power units for operating many gas compressors are frequently selected to operate at or very near capacity for maximum operating efficiency and for savings in capital investment. And further, these power units are selected to operate at capacity for compressing gas from an available known intake pressure to a desired outlet pressure. For example, a compressor installation may be designed for compressing gas from a field, from which a small amout of gas may be available for compression at a relatively low pressure. After the field is fully developed or the gas-oil ratio increases, the pressure of the gas frequently starts to increase. This increase in field pressure often effects an increase in pressure in the suction manifold of the compressor system. Such a pressure rise means that the compressor cylinders will receive an increased quantity of gas on each suction stroke. Since the compressors are discharging against a constant pressure, the compression of this increased quantity of gas will increase the horsepower demand on the power unit which was originally operating at its full rated power out-put. This increased power demand will then overload the power unit. Another compressor installation may be designed for compressing a gas from a field which is in its flush period of production. During this flush period the gas pressure available in the suction manifold of the compressor installation is relatively high. However, it is known that this gas pressure will decline and that the field will subsequently produce at lower pressures and over a long period of time.

In either type of production, compressor cylinders are usually selected so that the power units will be fully loaded when the compressors are operating at the expected lower suction pressure. The compressor cylinders so selected will overload the power units during the higher pressure production period because of the higher inlet pressure. Thus it is necessary to adjust the volumetric etficiency of the compressor cylinders so as to load fully, but not overload, the power units during these higher pressure production periods.

Several methods have heretofore been available for solving such an engine-overload problem; 1st, installation of a larger power engine; 2nd replacement of the com pressor unit with one having a small r cylinder; 3rd, replacement of the original compressor cylinder and piston with a smaller cylinder and piston which procedure may sometimes be followed since many compressors are adapted for such alteration; and 4th, installation of external clearance pockets, a clearance pocket being defined as an attached gas receiving space in direct communication with the compressor cylinder such that there is an increase in residual gas volume at the end of compression stroke. The first two of these methods involves con- "ice siderable investment, while the third involves less, yet appreciable expense. The last method requires the least expenditure but its range of application is somewhat limited.

The installation of external clearance pockets on the side of a compressor near the head end is possible only when connections or passageways were provided by the manufacturer in the original castings. Frequently a compressor cylinder head has suitable connections and if not they may be provided later in many instances. However, the installation of external clearance pockets on the head end only is an undersirable means of decreasing the volumetric efficiency of a double acting compressor cylinder. When it becomes necessary to reduce the volumetric efficiency of such a cylinder by installation of external pockets on the head end only of the cylinder, approximately twice as much clearance must be installed on the head end when no connection is available on the rod or crank end of a double acting cylinder. When more than one pocket is installed on a compressor cylinder the clearance is regulated stepwise that is, by opening one pocket, two pockets or more. Likewise, removal of clearance is stepwise.

The third method mentioned above for solving such an engine overload problem, that is, changing to a smaller cylinder, may involve changing cylinders on compressors having, for example, a 17 inch diameter cylinder and piston to a 16, 15 or even 14 inch cylinder and piston. Thus a supply of cylinders and pistons would nedd to be available. Warehouse stock of this type runs into considerable expense.

I have found that the disadvantages in the stepwise use of conventional external clearance pockets are overcome by using the adjustable clearance bottle of this invention.

An object of this invention is to provide an inexpensive apparatus for adjusting the volumetric efiiciency of gas compressors. Another object of this invention is to provide an inexpensive apparatus for adjusting the volumetric etficiency of gas compressors to keep the compression load within the rated horsepower of the power cylinders driving the compressors. Still another object of the invention is to provide apparatus for regulating the volumetric efficiency of gas compressors gradually so that any desired degree of adjustment is obtained. Still another object of this invention is to provide an inexpensive apparatus for the gradual adjustment of the volumetric efficiencies of gas compressors without need for shutting down the compressors to make the adjustment. Yet another object of this invention is to provide means for the gradual adjustment of the volumetric eificiency of gas compressors, with the apparatus therefor being exterior of the compressor and of such size and construction that only a single piece of equipment is required. Many other objects and advantages of my invention will be apparent to those skilled in the art from a careful study of the following disclosure and attached drawing which respectively describes and illustrates a preferred embodiment of my invention.

In the drawing, FIGURE 1 illustrates, in diagrammatic form, a longitudinal View, partly in section, of a clearance bottle of this invention.

FIGURE 2 is a longitudinal view, in section, of apparatus parts of FIGURE 1.

FIGURES 3, 4, 5 and 6 are views of auxiliary ap paratus required for installing the clearance bottle on a compressor. FIGURES '7 and 8 show the bottle as in stalled.

In FIGURE 1 of the drawing, reference numeral ll. identifies a cylinder of the clearance bottle. To one end of this cylinder 11 is attached a swage 12, one end of which conforms with the diameter of cylinder H. and is attached thereto by weld 13. The other end of the swage is of such size as to be suited for attachment to the compressor cylinder. The other end of the cylinder 11 is closed by a cap 14. This cap is constructed of a half coupling 15"having one end closed by' a steel plate 16 attached thereto by weld 19. Handles 17 'are attached to the plate 16 by Welds 18 as illustrated. Between the steel plate 16 of the cap and the end of the cylinder 11 is provided a gasket 41. This gasket is ordinarily an asbestos gasket.

For the adjustment of the clearance volume there is provided a movable piston 23 provided with rings 29. An axial opening thru piston 23 provides a passageway for a fully threaded piston rod 27. A nut 24 is welded at 28 to rod 27 nearits end within cylinder 11 and a locknut fixes piston 23 firmly against fixed nut 24. This lock-nut is prevented from becoming unthreaded by a cotter key 26. This cotter key is inserted through an opening in nut 25 and through an opening in the piston rod 27. However, if desired nut 25 can be a castle type nut.

On the side of the cap plate 16 facing the piston is positioned a threaded nut 20 held rigidly in place by weld 22. This weld 22 as well as weld 28 may or may not be 'a gas tight weld.

On the upper surface of the cap plate 16 is provided a threaded nut assembly 21. This threaded nut and an important auxiliary piece of apparatus are illustrated in detail in FIGURE '2.

In FIGURE 2, the nut assembly 21 is shown as being composed of a threaded nut 30 having its lower end beveled as illustrated. The bevel surface 33 is so positioned that the bevel surface faces the threaded piston rod 27 when installed threadably inside this nut. While this nut 3% can be either a hexagon or a square nut the bevel surface 33 terminates at its downward edge substantially as a circular edge 39. The conventional threads in nut 39 are identified by reference numeral 32.

In the lowermost portion of FIGURE 2 is illustrated a'thermoplastic washer 31 the uppermost portion of which is also frusto-conical in shape to conform to surface 33.

This bevel or frusto-conical surface of the washer 31 is identified by reference numeral 36. The lower portion of washer 31 is actually a short cylindrical section 35. Thisrcylindrical section of the washer 31 extends outward beyond the edge 39 of nut 30. This outward extension is provided so that upon threading the nut 30 tightly toward the surface or element to be sealed the nut compresses the washer 31 in sealing relation. The washer 31 is provided with threads 34 of the same pitch and type as threads 32 of nut 3th A handle 37 is inserted through an opening 38 in the upper end of the threaded piston rod 27.

The small threaded end 12a, of swage 12 of the bottle can be threaded directly into the cylinder head or can, if desired, be attached thereto by a flange 40 which in turn is bolted to the exterior of the cylinder head.

Since compressors ordinarily vibrate somewhat means are herein provided for maintaining the clearance bottle assembly rigidly attached to the compressor.

The means for holding tightly this clearance bottle 16 inits proper'installed position includes a clamp or brace band 42. This band comprises semi-circular clamp sections 43 provided with ears 44 welded to the clarnp sections 43 by welds 48. Each of these ears is drilled for an opening 45 for accommodation of a bolt. The ends of the semi-circular clamp sections 46 are bent in the directions illustrated and provided with bolt holes for accommodation of bolts 47 as illustrated. FIGURE 3 is a top view looking downward or a bottom view looking upward on the clamp assembly while FIGURE 4 is an elevational view thereof. V

In order to hold the bottle actually in position the clamp assembly is positioned around the cylinder 11 of the bottle at a point fairly close to the cap end thereof.

' immaterial.

Braces 49 are provided as illustrated in FIGURES 5 and 6.

FIGURES 7 and 8 illustrate the clearance bottle of this invention as installed on the low pressure stage cylinder of a two stage compressor. In these figuresthe 10w stage compression cylinder 50 is provided with an opening matching the opening in swage 12. The small diameter end 12:: of the bottle is threaded into flange 453 which in turn is bolted to the cylinder head 50a. These diagrammatic illustrations of the compressor include piston 52, piston rod 53, source of motive power 54, valve 56, exhaust passageway 57, and passageway communicating the interior of the clearance bottle 6t) with the interior of the cylinder. This compressor rests on a foundation 51 positioned on ground level 58. Reference numeral 59 identifies the high pressure stage cylinder of the two stage compressor. I

in an actual installation of this adjustable clearance bottle of this invention the bottle cylinder 11 was 16 inches in length and was actually a piece of '6 inch schedule 40 seamless pipe. This pipe had an ID. of 6.1 inches. The swage 12 was a 6 inch x 2 inch extra heavy swage, butt welded at 13 as mentioned hereinbefore to one end of the pipe cylinder 11. The end of pipe 11 opposite the swage was threaded to accommodate the half coupling 15 of the cap. The piston 23 was 2 inches in length and was provided with two cast iron piston rings. The threaded piston rod 27 was a 1 inch diameter cold rolled steel rod. This rod was threaded with Va inch V threads. The rod was threaded throughout its entire length as illustrated in FIGURE 1. The nuts 29, 21, 24 and 25 were also threaded with Vs inch V threads to fit the exterior threads of the piston rod 27. Based on an ID. of 6.1 inches and a 14 inch (16 inch cylinder minus 2 inch piston length) piston stroke there is a volume of approximately 408.8 cubic inches for clearance adjustment purposes.

The clearance bottle of this invention was installed on a Toy low stage cylinder of a 2 stage compressor and provided proper and eiiective clearance adjustment. The low stage compressor cylinder of this compressor had a 15 /2 inch diameter cylinder and the high pressure stage had a 10 /2 inch cylinder with piston strokes of 7 inches. After use for some time on this compressor the clearance bottle was removed therefrom and permanently installed on one cylinder of an lngersoll-Rand compressor. This latter compressor comprised one low pressure cylinder and one high pressure cylinder. The low pressure cylinder was 18 inches in diameter and the high pressure cylinder 11 inches in diameter, both with a stroke of 5 inches.

The thermoplastic washer 31 was made or" Teflon thermoplastic material. This washer when constructed of the shape and form illustrated in FIGURE 2 fit tightly into the frusto-conical space and against the surface 33 illustrated in this figuure. The washer was also threaded with inch V threads to conform to the threads on rod 2'7. Upon tightening somewhat nut 3% the Teflon washer sealed tightly against the threaded piston rod 27, against the beveled or irusto-conical surface 33 of nut 30 and against the upper surface of the cap plate 16 of the bottle. Thus when the compressor was compressing an inflammable gas, such as natural gas, there was not-any leakage of the gas through the seal just described.

Whether there is a slight leakage at the piston rings is In other words, it is immaterial what the pressure is in the space within cylinder 11 between piston 23 and cap 14. The main point is to provide additional space in free communication with the space between piston 23 and the cylinder head for clearance purposes. Also, another very important point is that leakage of inflammable gas not be permitted around the threaded piston rod 27 where it passes through the cap 16 and seal assembly 21. I

The strap metal of which the brace band 42 was constructed was inch thick and 1 /2 inches wide. The

bolt holes through the cars 44 and ears 46 are of such size to accommodate bolts suitable for the intended purpose. The brace arms 49 were made of about ,4 inch strap steel of 1 /2 inches in width. One end of each brace 49 was attach d to the brace bands while the other ends were attached to the compressor at suitable points on the cylinder head.

The slant distance or slant length of the beveled surface 33 was approximately /8 of an inch while the vertical distance or length of the vertical section of the Teflon washer was approximately /s inch. The maximum thickness of the wall of this Teflon washer was about the same as the thickness of the wall of nut All that is necessary for making a clearance adjustment when using the clearance bottle of this invention is to loosen the nut assembly 21 and manually rotate the threaded piston rod 27 by use of the handle 37 and when the proper adjustment has been made then again tighten the nut assembly 21. Thus, it is seen that the clearance adjustment can be easily made without closing down the compressor.

While I have described in detail a clearance bottle positioned on the head end of a low stage cylinder of a 2 stage compressor, a clearance bottle is in some instances also employed on the crank end of the cylinder. By use of clearance adjustment on both ends of a cylinder the power requirements on each stroke of the piston will be equal.

Also, clearance bottles such as described herein can be used on the head end or on both ends of a 2nd stage or high pressure cylinder of a 2 stage compressor. Clearanace bottles employed on high pressure cylinders ordinarily are not as large as the bottles employed on low pressure cylinders. However, the ratios of the effective volumes of the bottles to the piston displacements are the same with respect to the low pressure and high pressure cylinders.

Whie I have disclosed use of a Teflon thermoplastic washer 3?. as the sealing washer, other suitable thermoplastic material or other suitable washer material can be used. I employed the Teflon material because it was inexpensive, available and quite suitable.

While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto.

I claim:

1. A variable clearance bottle for a reciprocating compressor having a compression chamber comprising in combination:

(1) a cylinder of smooth bore having a longitudinal axis and means at one end for attaching said cylinder to said compression chamber of said compressor;

(2) a closure member sealed directly to the opposite end of said cylinder having an axial opening therethru for a piston rod;

(3) a piston rod coaxial with said cylinder extending loosely thru said opening and being threaded from its inner end toward its outer end a distance substantially the length of said cylinder;

(4) a piston 0n the inner end of said rod firmly fixed thereon by threaded elements on each side of the piston and sildably engaging said bore; and

(5) threaded holding means threaded to said rod on each side of said closure member and in engagement therewith for releasably and adjustably holding said rod in a selected fixed position, said holding means including sealing means for sealing the joint between said rod and said closure member.

2. The variable clearance bottle of claim 1 wherein the attaching means of (1) comprises a tapered member providing an opening at the end remote from said cylinder of reduced bore having external threads and including an attaching plate threaded onto said member, said plate having bolt holes radially outside of said member for attaching to said compressor.

3. The variable clearance bottle of claim 1 wherein the holding means of (5) comprises:

(1) a first not on said rod welded to the piston side or" said closure member;

(2) the sealing means of (5) comprising a circumfcrentially continuous plastic deformable washer on said rod contiguous to the opposite side of said closure member having a short cylindrical section next to said closure member and a frusto conical section facing away from said closure member; and

(3) the threaded means of (5) comprising a nut having a matching frusto-conical section sealably engaging the trusto-conical section of said washer so as to bias and deform said washer against said clos ure member and said rod to form a seal between said rod and said closure member.

References Cited in the tile of this patent UNITED STATES PATENTS 851,262 Tatum Apr. 23, 1907 950,710 Williams Mar. 1, 1910 1,142,464 Sparks June 8, 1915 1,372,525 McCabe Mar. 22, 1921 1,779,896 Winter Oct. 28, 1930 1,856,460 Blank May 3, 1932 2,008,809 Wyld July 2-3, 1935 2,047,167 Heller July 7, 1936 2,384,953 Miller Sept. 18, 1945 2,481,762 Lewis Sept. 13, 1949 2,566,816 Work Sept. 4, 1951 2,752,177 Stevenson June 26, 1956 2,760,667 Moeller Aug. 28, 1956 2,770,477 Rankin Nov. -13, 1956 3,045,892 White July 24, 1962 FOREIGN PATENTS 496,244 France July 28, 1919 188,541 Germany Sept. 26, 1907 441,684 Germany Mar. 10, 1927 426,921 Italy Nov. 8, 1947 257,956 Switzerland Apr. 6, 1949

Claims (1)

1. A VARIABLE CLEARANCE BOTTLE FOR A RECIPROCATING COMPRESSOR HAVING A COMPRESSION CHAMBER COMPRISING IN COMBINATION: (1) A CYLINDER OF SMOOTH BORE HAVING A LONGITUDINAL AXIS AND MEANS AT ONE END FOR ATTACHING SAID CYLINDER TO SAID COMPRESSION CHAMBER OF SAID COMPRESSOR; (2) A CLOSURE MEMBER SEALED DIRECTLY TO THE OPPOSITE END OF SAID CYLINDER HAVING AN AXIAL OPENING THERETHRU FOR A PISTON ROD; (3) A PISTON ROD COAXIAL WITH SAID CYLINDER EXTENDING LOOSELY THRU SAID OPENING AND BEING THREADED FROM ITS INNER END TOWARD ITS OUTER END A DISTANCE SUBSTANTIALLY THE LENGTH OF SAID CYLINDER; (4) A PISTON ON THE INNER END OF SAID ROD FIRMLY FIXED THEREON BY THREADED ELEMENTS ON EACH SIDE OF THE PISTON AND SILDABLY ENGAGING SAID BORE; AND (5) THREADED HOLDING MEANS THREADED TO SAID ROD ON

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