CA1064409A - Lubrication system for reciprocating plunger compressors - Google Patents

Abstract

IMPROVED LUBRICATION SYSTEM FOR
RECIPROCATING, PLUNGER COMPRESSORS

ABSTRACT OF THE DISCLOSURE

An improved lubrication system is pro-vided for the cylinder of a reciprocatory plunger rod compressor, having a stationary annular seal assembly around said plunger rod.
The key feature of this system resides in the incorporation of check valves in lubricant supply passages located internally within the seal assembly surrounding the plunger rod.
Preferably, said check valves are located within suitable recesses bored into the rear face of an interior packing cup element of said seal assembly. The use of such internal lubricant check valves protects the lubricator quills, fittings, and other components of the lubrication system against fatigue failures and lengthens the continuous on-line operating life of the entire lubrication system.

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Description

'' 106~409 BAC~I~GRO[~NI) 01' Tl~l, INVr.NTIOl~l , ¦I This invention rela-tes to improvements in lubricated compressor cylinders of the reciprocating plunger type. More ¦ particularly, it is directed to an improved lubrication system S l,l for such compressor cyllnders involving modified packing cup ele- ¦
ments especially adapted for use in the annular seal assemblies thereof.
Rcciprocating compressors have been dcvcloped extensi-vely in order to provide various commercial operations, e.g. poly-o I! ethylene manufacturing, ~itll ~eed streams at the elevated pres-ll sures required, e.g. around 1000 atmospheres and above. In order i~ to achieve co~mercially practical performance, much effort has been applied towards minimizing two basic enginecring problems ,I which are virtually inherent in reciprocal hyper-compression, l! namcly (1) fatigue failures in components subject to cyclic pres-I¦ sure fluctuations and (2) maintenance difficulties with high pres-~I sure seals, particularly around the periphcry of the reciprocating plunger rod.
l¦ In order to provide adequate and serviceable sealing ~! around the periphery of the plunyer; it has been common practice to employ an axial series of close-fitting annular packing cups with inner peripheral recesses therein in whi~h are carried speci ally shaped and fitted seal rings. The assembled series of pac-¦¦ king cups is rigidly mounted to provide a cylindrical bore sur-1I rounding the plunger rod with the .seal rings bcaring against the periphery thereof. In order to reduce frictional effects and ,, wear, a lubricating liquid is normally fed to the ~eriphery of Il said plunger at one or more locations, e.g. as shown in U.S.
¦ Patent 3,490,774 to ~lenry ct al.
ll ~lany differcnt appl^oaclles have beell appl ed in dealing ~I with the aforementioned fatigue problems, includ~ng the use of !I' ~ ' - -- ~
f . ','. ': . _ . . , . -10ti4409 ¦l autofrettage treatments, shrink fit constructions and similar ¦~ methods of insuring that critical parts are maintained in compres-¦¦ sion throughout the working cycle. For example, Figure 1 of the I above mentioned U.S. 3,490,774 depicts a seal assembly~w~ich most of the packing cups (i.e. 40-46) are of the familiar compound construction comprising an inner (a~ ring onto which an outer (b) ring is shrink-fitted.
An alternative approach which has ~ound commercial utility in this field is to subject the outer periphery of the ¦ seal assembly to the actual working fluid of the compressor at substantially full discharge pressure as disclosed in U.S. Patent 3,128,941 to Waibel. As depicted in Fig. 4 of said patent, this ¦ so-called "pressure-wrapped" seal assembly design permits the use ¦¦ of simpler, unitary packing cups which are automatically main-¦ tained largely under compressive stress by the working fluid during the actual operation of the compressor.
Through the adoption of such special measures, the sus-¦ ceptibility of the packing cups in reciprocating compressors to I ¦ suffer fatigue failures has been greatly alleviated in recent ¦ years. However, difficulty is still being experienced in trans-lating these gains in packing cup fatigue resistance into extended - on-line uninterrupted compressor service because of fatigue fai-lures occuring in certain associated components of the compressor which necessitate shut downs for repairs. Notable among the aux-iliary components showing greatest vulnerability in this respect are the bottom end spacer at the crank end of the compressor cyl-inder and the lubricant feed quills, check valves and other ele-ments of the lubricating system.
The primary object of the present invention is to improv~ .
the reliability and service life of the lubrication system for a ¦reciprocating compressor. A closely allied object is to integrate ¦the lubricating system into the annular seal assembly of a reci-

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1~6~409 `-procating plunyer compressor to form a more durable and efficient overall machine, thus providing e~tended on-line service life for the entire compressor.
Still other objects and related advantages of the pre-sent invention will become apparent from the following detailed description thereof.

In accordance with the present teachings, there is provided an improvement in a lubricated reciprocatory plunger rod compressor cylinder which has an annular seal assembly laterally surrounding the plunger rod and which includes a plurality of rigid closely abutting continuous annular seal elements, the inner peripheries of which lie immediately ad~acent the outer periphery of the plunger rod and at least one of the annular sealer elements contain a board, completely confined lubricant supply passageway running internally through the solid body of the same. The improvement provided comprises a check valve which is located directly in the passageway of the seal element thereby preventing the trans-mission of full cyclic compressor cylinder pressure fluctuations into the lubricant supply upstream of the seal element.

DETAILED l)ESCRIPTION

The above objects have been achieved and the average continuous operating period between shutdowns for a high pressure reciprocating compressor has been greatly e~tended in accordance with the present invention by incorporating internal check valves in one or more of the packing cups therein having passageways therethrough for the transmission of lubrlcating fluid.

A full understanding of the present invention and the detailed construction involved in concrete embodiments thereof can be readily obtained from the following ~escription and accom-panying drawings wherein:

1~64409 Fig. 1 is a longitudinal sectional view through a por-tion of the main housing of a reciprocating compressor cylinder showing the working portion of the plunger unsectioned, and most remaining parts in section, such as the "pressure-wrapped" seal assembly surrounding the plunger and the lubrication system in-corporated therein in accordance with the present invention;
Fig. lA is an enlargement of the portion of Fig. 1 gen-erally enclosed within circle "A" on Fig. 1 and including the principa] packing cup which incorporates the key feature of the present inventi~n;
Fig. 2 is a full longitudin~l sectional view of the same packing cup on approximately half the scale of Pig. lA.

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~ 1064409 ¦ Fig. 3 is an end view of the "crank-end" of the packing i cup of Fig. 2; and Fig. 4 is a longitudinal, partly sectional and somewhat ¦diayrammatical view of another compressor cylinder wherein the packing cups are of the compound design and the lubrication sys-tem encompasses three separate lubricant delivery points instead of two as in Fig. 1.
In Fig. 1, there is depicted a portion of the main hou-si.ng 10 of a reciprocating compressor cylinder equipped internally with a plunger rod 12, the head end of which is shown both in the position 14 representing the end of a discharge stroke, as well as a~t the end of a suction stroke (by dotted lines) 14'. The plunger rod 12 is, of course, driven in conventional manner by means of an external crank mechanism (not shown) connected to its rear end (cutaway in Fig. 1). The compression chamber in which said plun-ger rod 12 acts is formed by an axially aligned series of annular elements, i.e. head end sleeve member 16, bottom end spacer 18 and ¦ mounted therebetween the annular seal assembly 20 (which in turn l comprises a series of packing cups carrying appropriate seal rings at their inner periphery). In the embodiment depicted in Fig. 1, the annular seal assembly 20 is composed of six separate packing cups 21, 22, 23, 24, 25 and 26 in closely abutting parallel se-quence~ Packing cup 22 is fitted at its inner periphery with wear ring 29, while the other packing cups 21, 23, 24, 25 and 26 are provided with peripheral recesses 32 in their back faces in which are mounted seal rings 34 which in compression bear against the ¦ outer periphery of plunger rod 12 and front faces of adjacent cups ¦ in order to prevent leakage of compressed fluid around same.
¦ The working fluid enters the compression chamber throug~
1 intake passage 36 by means of a conventional high pressure valve ¦l (not shown). During the compression stroke, said valve closes ¦~ forcing the compressed fluid to exit through annular space 38 ___ 11 _~ ~

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~644~9 whic~l connects by internal passageways (not shown) with peripheral passageways 40 around the outside of head end sleeve member 16.
~¦ This, in turn, supplies full working fluid pressure to the space ¦¦ 41 surrounding annular seal assembly ~0 as the compressed fluid ! is being delivered through discharge port 42. The compressor valve and manifold assembly 37 is held in place at the front end of the compressor by means of a cylinder head (not shown) which is attached with appropriate seals to the cylinder housing 10 at I the front end (cut away in Fig. 1). A static seal assembly 30 is provided around the outer periphery of bottom end spacer 18.
Lubricating ~luid supply is provided through bo~tom end spacer 18 yia internal passageways 44 and 44' which communicate with similar internal passageways through packing cups within seal assembly 20 to deliver lubricant to points 46 and 46' at the outer periphery lS of plunger rod 12. The lubricating system includes conventional elements such as a high pressure pump (not shown) feeding in direc _ tion 47 to high pressure fitting 48 attached to the outside of ¦ main cylinder housing 10 and thence through a lubricator quill 50 into bottom end spacer 18. It may also include external check j valve 49 immediately upstream of fitting 48 but definitely includ s at least one check valve located internally within seal assembly 20, for example, ball check valves 52 and 52' in packing cup 25.
The detailed construction of this key feature of the present invention can best be explained by considering the larger scale drawings oF Figs. lA, 2 and 3. Thus, in Fig. lA, passage-ways 44 and 44' will be seen to communicate directly with internal passages 45 and 45' respectively through packing cup 26. The face of packing cup 25 which is immediately adjacent to cup 26 contains enlarged recessed bores 51 and 51' which are in concèntric axial ¦ alignment with passages 45 and 45' respectively. Within these recessed bores are located -the conventional parts of a ball check ' ~

1~64409 l valve, namely the movable closure ball 53, the compressibly biasing : , spring 55 and the spring guide retainer 54. Leading from the bot-tom of bores 51 and 51' are suitable internal passages 5~ and 56' respectively in cup 25. Passage 56 leads to point 46 while passage 56' leads to communicating passage 58 through cup 24.
¦ The relative location of bores 51 and 51' can be better seen from Figs. 2 and 3, the latter of which also shows the loca-¦ 'cion of holes 59 which are adapted to receive alignment roll pins I or bolts, which may be used in assembling the various parts inclu-ding the seal assembly of the compressor.
; It will be obvious that certain optional variations of the above described embodiment are encompassed within the present invention. For example, based upon factors such as plunger rod size, service conditions and materials of construction employed ; lS only one lubricant delivery point might be employed, in which case only one internal check valve would be necessary within the seal assembly. Also, when two or more internal check valves are em-ployed, more than one packing cup can be modified with suitable bores therefor. For example, instead of equipping cup 25 in the above described embodiment with both bores 51 and 51', one of thes~
could have been located in packin~ cup 24. It should also be ap-parent that a lubricant delivery system e~uipped with an internal check valve located in one of the packing cups of the seal assembl in accordance with this invention can be operated with or without external check valves such as valve 49, in the lubricant feed sys-I , tem, although in the interest of economy such valves could be eli-minated as unnecessary. Likewise, poppet or other types of check valves can be used in place of the ball-type valves shown.
Turning now to Fig. 4, many of the basic elements of ~ 30 ~ this compressor cylinder and the reference numerals used thereon ; ! will be seen to correspond closely with Fig. 1. ~lowever, the seal ~ .
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~ i 106~409 ~assem~ly 20 of Fig. ~ compriscs eight compound packiny cups con-sis-ting of inner rings 21a, 22a, 23a, 4a, 25a, 26a, 27a, and 28a ¦Iwith shrunk fit outcr rings 21b, 22b, 23b, 24b, 25b, 26b, 27b and - l¦28b respectively. The compressor valve block 37 is mounted by l¦ means of cylinder head 11 and spacer ring 13 but the actual valves ,Iwhich supply working fluid ~hrough intake passagc 36 and withdraw ame throu~h discharge passage 38 are not shown. Also, three lu-bricant delivery points 46, 46' and 46" are provided at the peri-l,phery of plunger rod 12, supplied via passageways 56, 56' and 56"
,lrespcctively from internal chcck valves 52, 52' and 52'' located in packing cup elemcnt 28a. 'rhe additional lubricant quills and lubricant feed passages leading to check valves 52' and 52'' are llnot visiblc in Fig. 4 but are of course equivalent to 50 and 44 1l as shown. ~lso, as previously indicated thc use of ~xtcrnal check valves such as valve 49 in thc lubricant feed supply system is ¦optional in connection with the present invention.
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i, Il Thc lubricating system cornponents of a hypercoMpressor ¦lincorporating the design shown in Fig. 1 hereof havc exhibited no ¦I tendency toward fatigue failures in test involving substantially ¦Icontinuous operation for periods of 9 to 18 months at pressures of over 1000 atmospheres. In contrast thcreto, under the same ~conditions of scrvice, thc same compressor, cxcept that conven-tional packing cups lackiny any intcrnal check valve were used ,¦throughout the annular seal assembly 20, had to be shut down for service on an average frcquency of about once per month because of ;fati~ue failures in either bottom end spacer 18, lubricating quillc 50 or various parts of external check valves 49.

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' - ~ 1064409 Furthermore, the lubrication system as shown in Fig. 1 .
_. has operated more reliably and efficiently as shown by reduced wear of plunger rod 12 and seal rings 34 and increased life of the entire annular seal assembly 20.
Having disclosed completely our invention together with several specific embodiments thereof, it is to be understood that . ~ all modifications and variations thereof which are obvious to ! l those skilled in the art are to be included within the spirit of cope of ~he i~ tio~ as defired by ehe appende- cl-ims.

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Claims (6)

WHAT IS CLAIMED IS:

1. In a lubricated reciprocatory plunger rod compressor cylinder having laterally surrounding said plunger road an annular seal assembly which includes a plurality of rigid closely abutting continuous annular seal elements the inner peripheries of which lie immediately adjacent the outer periphery of said plunger rod and at least one of which annular seal elements a bored, completely confined lubricant-supply passageway running internally through the solid body of same, the improvement which comprises a check valve located directly in said passageway of said seal element, thereby preventing the transmission of full cyclic compressor cylinder pressure fluctuations into the lubricant supply upstream of said seal element.

2. The improvement of claim 1 wherein said check valve is located in a portion of said passageway which is longitudinally relative to the plunger rod.

3. The improvement of claim 2 in which said seal assembly comprises a plurality of closely abutting annular packing cups and said check valve is located in an enlarged bore in the rear face of one of said packing cups communicating with said longi-tudinal portion of said passageway.

4. The improvement of claim 3 in which said check valve comprises spring biased movable ball or poppet closure element.

5. The improvement of claim 3 in which said seal assembly comprises at least three annular packing cups.

6. The improvement of claim 5 in which said seal assembly comprises more than three annular packing cups and the packing cup in which said check valve is located is one nearer the crank end of the compressor.