US3742822A

US3742822A - Close clearance viscous fluid seal system

Info

Publication number: US3742822A
Application number: US00168613A
Authority: US
Inventors: W Talbert
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1971-08-03
Filing date: 1971-08-03
Publication date: 1973-07-03
Anticipated expiration: 1990-07-03

Abstract

A close clearance viscous fluid seal system has been developed for use in high pressure reciprocating pumps. This system does away with the conventional high pressure packings used in such pumps and relies on a viscous fluid to form the seal between the plunger and the pump body. A floating piston seal is employed to separate the pumped fluid from the viscous fluid and impose the pumped fluid pressure to the viscous fluid sealant.

Description

United States Patent Talbert July 3, 1973 [541 CLOSE CLEARANCE v scous F I E L 2,430,723 11 1947 Lupper 417 497 SYSTEM 3,270,674 9/1966 Allen 92/865 2,795,195 6 1957 Amblard 61 al 417 437 Inventor: Wayne Mason Talbert, Houston. 2,330,781 9/1943 Lanymyar et al 92/86.5

Tex. [73] Assignee: Union Carbide Corporation, New Primary Examiner-William L. Freeh York, N.Y. Attorney-Paul A. Rose et al.

[22] Filed: Aug. 3, 1971 211 Appl. No.: 168,613 [57] ABSTRACT A close clearance viscous fluid seal system has been developed for use in high pressure reciprocating pumps.

52 E 5 92/86 92/1 56 1 This system does away with the conventional h1gh pres- [58] Field 92/168 sure packings used in such pumps and relies on a vis- 92786 5 cous fluid to form the seal between the plunger and the pump body. A floating piston seal is employed to sepa- [56] References Cited rate the pumped fluid from the viscous fluid and im- UNITED STAT AT N pose the pumped fluid pressure to the viscous fluid ES P E TS sealant.

3,019,739 2/1962 Prosser 92/168 2,612,116 9/1952 Lowther 92/865 5 Claims, 4 Drawing Figures I23 HIGH PRESSURE PUMPED FLUID IO! RECEIVER 121 a 3 I24 IIO rel T IZOI I07 I05 IO lll 2 I22 l06b 1066 I W '25 i k 4 I 1 H 7) |O4 I02 --l26 x LOW PRESSURE 119 1 11s 127. PUMPED FLUID SOURCE l H5 PAIENIEBJuLs I ma SiEHIOFZ H'GH PRESSURE PUMPED FLUID RECEIVER LOW PRESSURE PUMPED FLUID SOURCE HIGH PRESSURE PUMPED FLUID RECEIVER 420 v v 403 (4m rel? /4|9 492 I 42? J 404 I H I:

43l I I INVENTOR Wayne M. Toiberf ATTORNEY PATENIEDJUL3 191s 3,742,822

SHEU 2 [If 2 0 /lllll llllllllllllllllllb" INVENTOR Wayne M. Tulbort ATTORNEY 1- CLOSE CLEARANCE VISCOUS FLUID SEAL SYSTEM The present invention relates to an improvement in apparatus for producing high pressures in pumped fluids and more particularly to a close clearance viscous fluid seal system used in such apparatus.

Many of todays commercial processes require the use of extremely high pressures for the introduction of materials into reaction equipment that is being operated at extremely high pressures. Such pressures require specially designed equipment that will withstand the pressure and also require the use of pumps that have the capacity of functioning for prolonged periods of time at the high pressures. It is known that in many instances the pressure will exceed 40,000 psig.

Positive displacement type pumps in which a reciprocating plunger is used to compress the pumped fluid and raise it to the desired pressure are commonly used in high pressure processes. One of the major problems encountered in this equipment is the deterioration and failure of the packing materials and plungers used in the pumps. The reciprocating action of the plunger rapidly deteriorates the packing materials surrounding the plunger, necessitating the shutting down of the equipment. This requires the replacement of the packing material with consequent loss in operating time. To date most of the reciprocating pumps in use rely on solid packing materials to maintain a seal. Though these packing materials are not completely satisfactory they are practically the sole known means used in the industry, and much effort in time and money has been expended in attempts to improve the known materials and to find better lower cost substitutes. The reciprocating motion of the plungers has a wearing effect on them and in many applications solid tungsten carbide plungers must be used to obtain reasonable packing and plunger life. These plungers are very expensive and present a hazard due to the brittle type fracture failure that is characteristic of this material. Several instances have been reported in which ,solid tungsten carbide plungers have failed and shattered fragments thereof together with a flammable fluid or gas were released into an operating area.

According to the instant invention the use of conventional packing materials in high pressure positive displacement pumps can be obviated. This is accomplished by the use of pumping apparatus having a close clearance viscous fluid seal in the annular space between the reciprocating plunger and the barrel of the pump in which the plunger is located. Throughout this annular close clearance seal zone there is maintained a flowing viscous fluid which has approximately the same pressure imposed on its high pressure side as the pressure of the pumped fluid. The viscous sealant fluid acts as a seal and it is introduced into the annular close clearance seal zone by sealant fluid circulating means that are readily constructed from available equipment with known technology. The upstream pressure of the viscous fluid in the annular close clearance seal zone is maintained by means of said sealant fluid. circulating means and by means of a floating piston seal which separates the pumped fluid chamber from the viscoussealant fluid and imposes the pressure of the pumped fluid on the sealant fluid.

In the present invention, as the plunger compresses the pumped fluid, the pumped fluid in turn applies an seal moves in the opposite direction of the movement of the plunger during the compression stroke and exerts pressure on the viscous sealant fluid located on the.

sealant fluid side of the floating piston chamber forcing viscous sealant fluid into the annular close clearance zone between the plunger and the main body of the pump. During the return stroke of the plunger, when low pressure pumped fluid is drawn into the pumped fluid chamber, the floating piston seal reverses direction and the viscous sealant fluid circulating means replaces any viscous fluid which passed out of the system during the cycle. In one version, where the viscous sealant fluid is introduced via a bore in the plunger (see FIG. 3), the viscous sealant fluid is replenished during a short period of the suction stroke, and sealant fluid passes through the annular closeclearance zone during the pumping cycle. Inthe operation of this invention, viscous fluid sealant physically separated from the pumped fluid chamber is always present between the plunger and the main body of the pump. It is possible to maintain this viscous sealant fluid in the annular close clearance zone even at relatively high pressures because of the close clearance between the plunger and the main body of the pump and the viscosity of the lubricant itself.

The seal is so designed and a viscous sealant selected so that classic laminar flow conditions will always exist in the annular close clearance zone. With laminar flow conditions, the flow rate of sealant through the annular clearance zone is directly proportional to pressure differential, varies as the square of the clearance in the annulus, is inversely proportional to the sealant viscosity and the length of the annulus. The speed and direction of the plunger also affects the flow rate in accordance with basic text book laminar flow theory. An acceptable flow rate of sealant through the annulus for a given pump and a given set of operating conditions can be obtained by selecting proper values for the above variables.

Pressure and temperature both significantly change the viscosities of most fluids. As an example the viscosity of a typical parafflnic oil with a given viscosity at atmospheric pressure and F. will have a viscosity 500 times greater at 40,000 psig and 100 F., 4 times greater at 40,000 psig and 210 F., and 0.08 times at 40,000 psig and 425 F. Silicone fluids have significantly different properties. As an example, the viscosity of a typical silicone oil with a given viscosity at atmospheric pressure and 100? F. will have a viscosity 1,900

times greater at 40,000 psig and 100 F., 10 times greater at 40,000 psig and 210 F., and 0.64 times at 40,000 psig and 425 F.

Heat is generated in the annulus as viscous fluid is sheared by differential pressure and the motion of the plunger. A typical temperature rise for a silicone sealant passing from 38,000 psi to atmospheric pressure through an annulus is 350 F., provided no heat is removed during the throttling. A controlled rate of sealant leakage through the. annulus can be obtained by controlling sealant viscosity. This is achieved by knowledgable selection of sealant fluid, initial viscosity of the fluid, and the amount of heat removed as it passes through theannulus. The approximate leakage rate fora 2"/;- inches diameter plunger during the com pression stroke, moving at 1 foot per second, is 1.8

cubic inches per second when the plunger is positioned concentrically in the annulus, the annulus radial clearance is 0.008 inch, the length of the annulus is nine inches, the differencial pressure across the annulus is 38,000 psig, the average viscosity of the sealant in the annulus is 5,000 centipoises. Clearance at operating conditions is greater than initial clearance due to the expansion of the cylinder and contraction of the plunger caused by the very high operating pressures. This effect must be calculated so that a seal can be assembled to an initial clearance that will give the desired clearance at operating pressure.

The present invention finds particular application in the known high pressure process for the polymerization of ethylene both in the compression pumps used to compress the ethylene to the desired pressure and in the injection pumps used to introduce catalysts and other reactants into the reaction process.

Accordingly, the present invention comprehends a system for pumping fluids at high pressures wherein reciprocating plungers of positive displacement pumps, intensifiers or injection pumps are sealed against leakage along their axial length and annularly by means of an annular close clearance seal and a floating piston seal which forces the viscous sealant fluid to flow through the close clearance annulus. This eliminates the need for conventional packing materials and their periodic replacement.

With the foregoing in mind and other features which shall hereinafter more fully appear, the present invention will be described in greater particularity with reference to the appended drawings.

FIG. 1 is a schematic diagram of the mechanical portion of a high pressure process system containing the close clearance viscous fluid seal according to the pres ent invention.

FIG. 2 is a schematic diagram of another modification of the mechanical portion of a high pressure process system containing the close clearance viscous fluid seal showing only the main body, plunger and seal sections of the pump.

FIG. 3 is a schematic diagram of a modification of the mechanical portion of a high pressure intensifier or injection pump system containing the close clearance viscous fluid seal, showing only the main body, plunger and seal sections of the pump.

FIG. 4 is a schematic diagram of a modification in which the free floating piston seal is located extraneous of the high pressure process system containing the close clearance viscous fluid seal.

Referring to FIG. 1 of the drawings there is shown a positive displacement pump, designated generally as 101, comprising a main body 102 and a pumped fluid chamber 103. A plunger 104 is arranged in the pumped fluid chamber 103. Not shown are the mounting means for the positive displacement pump 101, the motive means for activating the plunger 104, viscous fluid res ervoir means and cylinder cooling facilities. The plunger 104 moves reciprocally in the pumped fluid chamber 103 during operation of the pump. An annular pressure zone 105 connects the pumped fluid chamber 103 to annular seal chamber 106a and l05b which contains therein an annular floating piston seal 107 having thereon an outside and inside scraper-seal 108 and 109 (both made of conventional packing material) thus dividing the seal chamber. into two sections, 106a connecting through annular pressure zone 105 to pumped fluid chamber 103 and l06b connecting through a close clearance annular seal zone to viscous fluid chamber 111, which is sealed by an annular seal 112 made of conventional packing material. Viscous fluid chamber 111 connects via pressure fluid conduit 113 to viscous fluid reservoir 114. Constant pressure viscous fluid pump 115 operates with a discharge pressure slightly higher than the minimum pressure that occurs during the suction stroke in fluid chamber 103, it pumps the viscous fluid through pressure fluid conduit 116 into the viscous fluid side of seal chamber l06b through passage 117 bored through the main body 102 of the positive displacement pump 1011. Located on pressure fluid conduit 116 are suitable viscous fluid check valves 1 18 and pressure regulator 119. At a point distant from passage 117 a vent passage 120 attached at its exterior end to a suitable pressure valve 121. activatable in the event of an emergency can be included; this, however, is not a necessary part of the apparatus.

In an embodiment shown in FIG. 1, the compression stroke of the pump 101 involves a movement of the plunger 104 from leftto right. During the compression stroke plunger 104 will displace pumped fluid from pumped fluid chamber 103 through the discharge valve 122 into the high pressure pumped fluid receiver 123 through high pressure pumped fluid conduit 124. During this compression stroke inlet suction valve 125 is closed preventing the pumped fluid from escaping via low pressure pumped fluid conduit 126 into low pressure pumped fluid source 127. At the same time the pressure produced on the pumped fluid by the compression stroke exerts a pressure on floating piston seal 107 causing it to move from right to left; this movement imposes a pressure on the viscous fluid in seal chamber 106b forcing some of it into close clearance annular seal zone 110. The amount of this leakage is low because of the laminar flow conditions established by the fluid viscosity and the close clearance in the annulus. The amount of viscous fluid or pumped fluid flowing past scraper-

seals

108 and 109 is minimal since there is essentially no differential pressure across the scraper seals to force flow. The return stroke involves a movement of the plunger 104 from right to left. During this return stroke discharge valve 122 is closed, inlet suction valve 125 opens permitting pumped fluid to fill pumped fluid chamber 103 from low pressure pumped fluid source 127 via low pressure pumped fluid conduit 126. At the same time floating piston seal107 is forced from left to right until it mechanic-ally rests against the end of floating piston seal chamber by viscous fluid that is pumped into oil seal chamber 106b by the constant pressure viscous fluid pump 115 via pressure fluid con-- duit 116 and passage 117 to replace the viscous fluid that may have leaked out through annular seal zone 110 during the compression stroke. In this manner pumped fluid is transferred from a low pressure source to a high pressure zone using pumping means that donot have the conventional packing materials in annular close clearance seal zone 110. The annular close clearance surface and the plunger are not subject to excessive wear since they are separated by a continuous strata of viscous fluid having lubricating properties.

Referring to FIG. 2 of the drawings, there is shown the barrel portion of a reciprocating compressor pump designated generally as 201, comprising a main body 202, a pumped fluid chamber 203 and a plunger 204 arranged in the pumped fluid chamber 203. Not shown are the mounting means for the reciprocating compressor pump 201, the motive means for activating the plunger 204, cylinder cooling facilities, the pumped fluid portion of the equipment designated by numerals 122 to 127 inclusive of FIG. 1 and the viscous fluid circulating means designated by

numerals

113, 114, 115, 1 16, 118 and 119 of FIG. 1. The plunger 204 moves reciprocally in the pumped fluid chamber 203 during operation of the pump. The main body 202 is preferably of several pieces that are assembled together. A pressure pumped fluid passage 205 connects via an annular pressure zone 205a to the pumped fluid chamber 203 and to annular seal chamber 206a and 206b which contains therein an annular floating piston seal 207 having thereon a scraper-seal 208 and 209 (made of conventional packing material) thus dividing the seal chamber into two sections with 206a connecting through annular pressure zone 205a through pressure pumped fluid passage 205 to pumped

fluid chamber

203, and 206b connecting to the viscous fluid circulating means of the close clearance seal 214. The external viscous fluid circulating means are not shown except for the viscous fluid inlet point 210 and the viscous fluid exit point 21 1 both of which connect to circulating means similar to those described in FIG. 1. The viscous fluid is pumped in through viscous fluid inlet point 210, passes check valve 212, continues through viscous fluid conduit 213 bored through a section'of main body 202 and into the viscous fluid side of seal chamber 206b which connects to a close clearance annular seal zone 214 to annular viscous fluid receiving chamber 215 which connects to viscous fluid exit point 211 via viscous fluid passage 216 bored through a section of main body 202. Conventional low pressure packing 217 is used to confine the viscous fluid. A plunger scraping seal ring 218 prevents excessive amounts of viscous fluid from entering pumped fluid chamber 203 and in operation the end of plunger 204 does not pass to the left of plunger scraping seal ring 218.

In an embodiment as shown in FIG. 2, the compression stroke of the reciprocating compressor pump 201 involves a movement of the plunger 204 from left to right. During the compression stroke plunger 204 will displace pumped fluid from the pumped fluid chamber 203 into the high pressure fluid receiver (not shown). At the same time the pressure produced on the pumped fluid by the compression stroke exerts a pressure on the floating piston seal 207; this pressure is imposed on the viscous fluid in seal chamber 206b forcing some of the viscous fluid to flow in close clearance annular seal zone 214. The amount of this leakage is low for the reasons discussed in relation to FIG. 1. The return stroke involves a movement of the plunger 204 from right to left. During this return stroke pumped fluid fills pumped fluid chamber 203 from a low pressure pumped fluid source (not shown). At the same time floating piston seal 207 moves from left to right until it is in its full position to the right. Viscous fluid is pumped into seal chamber 206b via'viscous fluid conduit 213 by viscous fluid circulating means (not shown) to replace viscous fluid that passes through annulanseal zone 214 into annular viscous fluid receiving chamber 215 and out through viscous fluid receiving chamber 215 and out through viscous fluid passage 216 during the compression stroke. In this manner pumped fluid is transferred from a low pressure source to a high pressure zone using pumping means that do not have the conventional packing materials in annular close clearance seal zone 214 without excessive wear or significant sealant contamination of the pumped fluid, as discussed in relation to FIG. 1.

Referring to FIG. 3 of the drawings, there is shown the barrel portion of a reciprocating pump,.designated generally as 301, comprising a main body 302, a pumped fluid chamber 303 and a plunger 304 arranged in the pumped fluid chamber 303. Not shown are the mounting means for the reciprocating pump 301, the motive means for activating the plunger 304, the cylinder cooling facilities, the pumped fluid portion of the equipment designated by numerals 122 to 127 inclusive of FIG. 1 and the viscous fluid circulating means designated by

numerals

113, 114, 115, 116, 118 and 119 of FIG. 1. The plunger 304 moves reciprocally in the pumped fluid chamber 303 during operation of the pump. An annular pressure zone 305 connects pumped fluid chamber 303 to annular seal chamber 306a and 306b which contains therein an annular floating piston seal 307 having thereon an outside scraper-seal 308 and an inside scraper-seal 309 (both made of conventional packing material) thus dividing the seal chamber into two sections, 306a connecting via annular pressure zone 305 to pumped fluid chamber 303, and 306b connecting to the viscous fluid close clearance seal system. The external viscous fluid circulating means are not shown except for the viscous fluid inlet point'310 and the viscous fluid exit point 311 both of which connect to viscous fluid circulating means similar to those described in FIG. 1. These points can be located on throttling bushing 312 which can have a static annular packing seal 313 to prevent viscous fluid leakage from seal chamber 306b along main body 302 and low pressure packing seal 314 to prevent viscous fluid leakage from plunger 304. Fitted into the face end of plunger 304 is check valve 315 at the end of viscous fluid passage 316 bored through the lengthwise direction of plunger 304. Viscous fluid passage 316 is connected at the check valve 315 end to annular seal chamber 306b via viscous fluid conduit 317 and at the other end to annular viscous fluid chamber 318 via viscous fluid conduit 319. Viscous

fluid conduits

317 and 319 are borings through plunger 304 that intersect viscous fluid passage 316.

In an embidiment as shown in FIG. 3, the compression stroke of reciprocating injection pump 301 in- 1 the high pressure pumped fluid receiver (not shown);

At the same time the pressure produced on the pumped fluid by the compression stroke exerts a pressure on annular floating piston seal 307 causing it to impose a pressure on the viscous fluid in sea] chamber 306b forcing viscous fluid to flow in annular close clearance seal zone 320. During the compression stroke check valve 315 is closed preventing viscous fluid from leaving seal chamber 306b via viscous fluid conduit 317 and into viscous fluid passage 316; the only path for the viscous fluid to follow'is into annular close clearance seal zone 320. The small amount of viscous fluid that flows through annular close clearance seal zone 320 enters annular viscous fluid chamber 318 and by the external viscousfluid circulating means is recycled; the amount is small for the reasons discussed in relation to FIG. 1. The return stroke of plunger 304 involves a movement from right to left. During the latter portion of this return stroke pumped fluid fills pumped fluid chamber 303 from a low pressure pumped fluid source (not shown). During the initial portion of the return stroke annular floating piston seal 307 moves from right to left until viscous fluid conduit 319 contacts the viscous fluid chamber 318. When this occurs check valve 315 opens because the pressure in the viscous fluid circulating means system is greater than the pressure of the suction pressure of the pumped fluid and viscous fluid is pumped in to fill seal chamber 306b by external viscous fluid circulating means (not shown) via viscous fluid inlet point 310 passing through viscous fluid conduit 319, viscous fluid passage 316 and viscous fluid conduit 317 into seal chamber 30Gb. This forces the free floating piston seal 307 to its extreme right position. In this manner pumped fluid is transferred from a low pressure source to a high pressure zone using pumping means that do not have the conventional packing materials in annular close clearance seal zone 320 without excessive wear, or significant sealant contamination of the pumped fluid as discussed in relation to FIG. 1. An advantage of the arrangement shown in FIG. 3 is that viscous fluid passages are not required to be drilled in the main body 302 section of the high pressure reciprocating pump, but rather the viscous fluid sealant enters via the plunger 304. This arrangement eliminates stress raisers in the main body 302 of the high pressure pump which would lessen its fatigue resistance and reduce its service life. Stress raisers in the plunger 304 do not shorten its life since it is always in compression and stress raisers are of little significance to the life of a component that is always in compression.

Referring to FIG. 4 of the drawings, there is shown a reciprocating compression pump, designated generally as 401, comprising a main body 402 and a pumped fluid chamber 403. A plunger 404 is arranged in the pumped fluid chamber 403. Not shown are the mounting means for the reciprocal compression pump 4011, the motive means for activating plunger 404, the cylinder cooling facilities and the viscous fluid circulating means. Plunger 404 moves reciprocally in pumped fluid chamber 403 during operation of the pump. A pressure fluid conduit 405 connects pumped fluid chamber 403 to floating piston seal chamber 406 which contains therein a floating piston seal or diaphragm 407 having thereon a scraper-seal 408 (made of conventional packing material) that divides the floating piston means into two sections, seal chamber 406a connecting to pumped fluid chamber 403 through pressure fluid conduit 405 and bore 409 and seal chamber 406b con necting to viscous fluid circulating means hereinafter described. Bore 409 can enter pumped fluid chamber 403 at any point through main body 402 and is not limited to the position shown. Viscous fluid is pumped into seal chamber 406b by constant pressure pump 410 from viscous fluid reservoir 411. The viscous fluid sealant travels through pressure conduit 412, check valve 413 and pressure conduit 414; essentially constant pressure is maintained by means of pressure regulator 415. The same pump 410 is used to pump viscous fluid into annular close clearance seal zone 416 via pressure conduit 412, check valve 413, pressure conduit 417 and bore 418. Annular oil seal and scraper rings 419 prevent mixing of the viscous fluid and the pumped fluid. At a point distant from bore 418, one can, if desired and as shown, have a vent bore 420 attached at its exterior end to a suitable pressure valve 421 activatable in the event of an emergency. This feature is optional and not a necessity. Viscous fluid chamber 422 connects annular close clearance seal zone 416 to viscous fluid reservoir 411 via pressure conduit 423. Conventional packing material is used in annular seal 424. In an embodiment shown in FIG. 4, the compression stroke of pump 401 involves a movement of plunger 404 from left to right. During the compression stroke plunger 404 will displace pumped fluid from pumped fluid chamber 403 through discharge valve 425 into high pressure pumped fluid receiver 426 through high pressure pumped fluid conduit 427. During this compression stroke inlet suction valve 428 is closed preventing pumped fluid from escaping via low pressure pumped conduit 429 into low pressure pumped fluid source 430. At the same time the pressure on the pumped fluid by the compression stroke exerts a pressure on floating piston seal 407, this imposes a pressure on the viscous fluid in seal chamber 406b, closing check valve 413and pressuring viscous fluid via pressure conduit 417 and bore 418 into annular chamber 431 and through annular close clearance seal zone 416. The amount of viscous fluid passing through annular close clearance seal zone 416 is low for the reasons discussed in relation to FIG. 1. The return stroke involves a movement of plunger 404 from right to left. During this return stroke discharge valve 425 is closed, inlet suction valve 428 opens permitting pumped fluid to fill pumped fluid chamber 403 from low pressure pumped fluid source 430 via low pressure pumped fluid conduit 429. At the same time floating piston seal 407 moves from left to right until it is restrained by the end of floating piston seal chamber 406 due to the viscous fluid sealant pumped into viscous fluid seal chamber 4061) by constant pressure pump 410 via

pressure conduits

412 and 414 and through check valve 413 to replace the viscous fluid that has passed through annular close clearance zone 416 during the compression stroke of the pumping operation. In this manner pumped fluid is transferred from a low pressure source to a high pressure zone using pumping means that do not have the conventional packing materials in annular close clearance seal zone 416 without excessive wear or significant sealant contamination of the pumped fluid as discussed in relation to FIG. 1.

From the foregoing description it will be recognized by those familiar with the art that the apparatus accord ing to this invention comprehends a high pressure fluid activating system or pumping system comprising a reciprocating pump having a plunger arranged interior of the pump and adapted to move reciprocally therein in a continual series of compression and return strokes to compress and transfer pumped fluid from pumped fluid chamber to the high pressure pumped fluid receiver or reactor, a close clearance viscous fluid seal zone situated annularly to the plunger and the pump body and separated from the pumped fluid chamber by a floating piston seal, and viscous fluid circulating means. During each compression cycle, pumped fluid at high pressure is expelled from the pumped fluid chamber into the high pressure pump fluid receiver. Simultaneously, the pressure of the pumped fluid exerts a pressure on a floating piston seal that separates the pumped fluid chamber from the viscous fluid sealant side of the seal chamber in which the floating piston seal is situated and from the close clearance viscous fluid seal zone. The pressure exerted on the free floating piston is transmitted to the viscous fluid sealant forcing viscous fluid from the viscous fluid seal chamber into the annular close clearance seal zone and forcing the floating piston seal in a direction opposite to the direction of the plunger. The pressure of the viscous fluid sealant is essentially equivalent to the pressure of the pumped fluid. During the return stroke low pressure pumped fluid is drawn into the pumped fluid chamber and simultaneously the floating piston seal or diaphragm again moves in a direction opposite to the direction of movement of the plunger during a period that is all or just a portion of this stroke. During the compression and return strokes, the viscous fluid circulating means are in continuous operation to maintain an adequate supply of viscous fluid in the high pressure fluid activating system, particularly in the viscous fluid seal chamber and the annular close clearance seal zone. During the return stroke, accompanied by the movement of the floating piston seal, the viscous fluid circulating means pumps viscous fluid sealant into the viscous fluid sealant seal chamber to replace that viscous fluid that was forced through the annular close clearance seal zone during the compression stroke and return stroke. By this manner of operation high pressure can be achieved in a system that does not employ the conventional solid packing materials normally used as sealants around the plunger of a reciprocating pump. The pressure of the system can vary from slightly above atmospheric pressure to a pressure of about 40,000 psig or higher.

The clearance between the plunger and the pump body will vary depending upon the size, alignment capability, the specific viscous fluid sealant selected, and the operating pressure, temperature and speed of the pump. This clearance is sufficient to permit free movement of the plunger in the pump but it is not of such a size as to permit the viscous fluid sealant to flow through in uncontrolled amounts. In view of the teachings disclosed herein, one skilled in the art of constructing high pressure pumps and determining viscous flow rates can readily determine the clearance required for a particular size pump. Among the main reasons that the dimensions of the annular close clearance viscous fluid seal zone cannot be set forth with particularity is that the dimensions will vary not only for the reasons previously stated but also with the size of the pump, and the pumping capacity of the reciprocating compressor pump. Thus, this invention can be used in pumps that vary in size from small labo'ratory units in which capacity is measured in grams per hour to large commercial units in which capacity is measured in tons. The pressure at which the unit is operated will also vary from slightly above atmospheric to 40,000 psig, or higher.

The apparatus and system described in this specification can be used, for example, in the high pressure polymerization of ethylene. In such processes ethylene is compressed to reaction pressures of from 10,000 psig to 40,000 psig by huge reciprocal compressor pumps and pumped into the polymerization reactors. Often these processes employ additionally, high pressure reciprocating injection pumps used to introduce catalysts and other modifiers to the reaction. The concept disclosed here can be used in both types of these high pressure pumps. The pumps of the instant invention are, of course, used in conjunction with the necessary support equipment in which the reaction is carried out.

What is claimed is:

l. A pumped fluid actuating system comprising, in combination, a reciprocating positive displacement pump having pressure viscous fluid circulating means, pumped fluid chamber, low pressure pumped fluid source means and a high pressure pumped fluid receiver means; a plunger arranged interior of said reciprocating positive displacement pump and adapted to move reciprocally therein in a continual series of compression strokes and return strokes to effect discharge of pumped fluid at a high pressure from said pumped fluid chamber during each of the compression strokes and intake of pumped fluid into said pumped fluid chamber during each of the return strokes; an annular close clearance viscous fluid sealant seal zone annularly surrounding at least a portion of said plunger at an area discrete from the pumped fluid chamber; floating piston seal means separating said pumped fluid chamber from said annular close clearance viscous fluid sealant zo ne contacting said pumped fluid chamber on one side thereof and responsive to changes in pressure in said pumped fluid chamber and contacting said annular close clearance viscous fluid sealant seal zone situated between the plunger and the pump body on the other side thereof to impose the pumped fluid pressure on the viscous fluid sealant; said pressure viscous fluid circulating means connected to said annular close clearance viscous fluid sealant seal zone to effect substantially constant delivery of viscous fluid sealant thereto; control means operatively connected to said pressure viscous fluid circulating means to effect delivery of viscous fluid sealant into and out of the annular close clearance seal zone.

2. A pumped fluid actuating system as claimed in claim 1, wherein the floating piston seal means is in contact with and between the main body and plunger of said reciprocating positive displacement pump, and wherein the viscous fluid sealant passage means and check valve means are located in the plunger.

3. A pumped fluid actuating system as claimed in claim 1, wherein the floating piston seal means and viscous fluid sealant check valve are located in the main body of said reciprocating positive displacement pump.

4. A pumped fluid actuating system as claimed in claim 1, wherein the floating piston seal means is in contact with and between the main body and plunger of said reciprocating positive displacement pump and the viscous fluid check valve means is located externally thereto.

5. A pumped fluid actuating system as claimed in claim 1, wherein the floating piston seal means and the viscous fluid check valve means are located externally of said reciprocating positive displacement pump.

Claims

1. A pumped fluid actuating system comprising, in combination, a reciprocating positive displacement pump having pressure viscous fluid circulating means, pumped fluid chamber, low pressure pumped fluid source means and a high pressure pumped fluid receiver means; a plunger arranged interior of said reciprocating positive displacement pump and adapted to move reciprocally therein in a continual series of compression strokes and return strokes to effect discharge of pumped fluid at a high pressure from said pumped fluid chamber during each of the compression strokes and intake of pumped fluid into said pumped fluid chamber during each of the return strokes; an annular close clearance viscous fluid sealant seal zone annularly surrounding at least a portion of said plunger at an area discrete from the pumped fluid chamber; floating piston seal means separating said pumped fluid chamber from said annular close clearance viscous fluid sealant zone contacting said pumped fluid chamber on one side thereof and responsive to changes in pressure in said pumped fluid chamber and contacting said annular close clearance viscous fluid sealant seal zone situated between the plunger and the pump body on the other side thereof to impose the pumped fluid pressure on the viscous fluid sealant; said pressure viscous fluid circulating means connected to said annular close clearance viscous fluid sealant seal zone to effect substantially constant delivery of viscous fluid sealant thereto; control means operatively connected to said pressure viscous fluid circulating means to effect delivery of viscous fluid sealant into and out of the annular close clearance seal zone.