US20170227002A1

US20170227002A1 - Cryogenic pump and inlet header

Info

Publication number: US20170227002A1
Application number: US15/427,903
Authority: US
Inventors: Ben MIKULSKI; Floyd GUEST; Donald R. LUFT
Original assignee: AHMS INC.; Trican Well Service Ltd
Current assignee: AHMS INC.; Trican Well Service Ltd
Priority date: 2016-02-08
Filing date: 2017-02-08
Publication date: 2017-08-10
Also published as: CA2957321A1; WO2017136934A1

Abstract

A header and a pump end for a cryogenic pump are provided for efficient liquid pumping operation. The header directs supplied liquid into a sump and gas into a freeboard. The liquid in the header can be distributed along the header and decanted over a weir to the sump, the liquid being drawn from the sump and up through the vessel to the pump end. Gas in the freeboard is collected for venting or return to the liquid source. Pump head plunger stroke can be lengthened and operated at slower stroke rates using a large cross-sectional area intake and discharge valves. Plunger seals, supported as a seal pack in a sleeve, are field installable over the plunger. A plunger to drive shim arrangement permits filed adjustment of the stroke.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/292,792. filed Feb. 8, 2016, and to U.S. Provisional Patent Application No. 62/427,005, filed Nov. 28, 2016, the entirety of both of which are incorporated herein by reference.

FIELD

In embodiments, a liquid inlet and pump head for a cryogenic pumper are provided, the header having a sump, a return conduit for unused liquid to a liquid source, and a freeboard for gas removal, the pump head having long stroke, low speed plunger and low back pressure valve assembly.

BACKGROUND

In many industries, including the oil and gas industry, liquefied gases are vaporized to a gaseous form for a variety of high volumetric operations including use of vaporized nitrogen liquid for delivery to subterranean destinations for downhole stimulation. Nitrogen gas is one type of inert gas that can be used to reduce the hydrostatic pressure exerted by stimulation fluids. This minimizes the amount of fluid pumped into formation and enables rapid clean-up in low pressure reservoirs. Further, as a non-reactive gas, nitrogen can be used in a variety of ways to support pipelines and industrial facilities, including: displacement, inerting otherwise potentially flammable spaces, helium leak testing, pneumatic testing, purging, freeze plugs, accelerated cooling, blanketing, catalyst handling support, hot stripping and heating.
Liquid nitrogen is supplied in liquid form, in a cryogenic state. Stimulation often occurs at high pressures in the order of 10,000 to 15,000 psi. The nitrogen is pressurized to the high pressures using specialized cryogenic pumping equipment. For the rates and pressure, multiple positive displacement pumps are used, arranged in parallel.
Liquid nitrogen, at very low temperatures is provided to a header at the inlet of the gang of pump heads at a pumper. The liquid enters each pump head suction at a cold end, and is displaced from a displacement chamber by a pressure stroke of reciprocating plunger of the pump head to discharge through a pump outlet at high pressure. The plunger returns and draws more liquid into the displacement chamber to repeat the cycle. The associated drop in suction pressure upon drawing fluid into the displacement chamber can alter the liquid properties and degrade pump performance, even to the point of eventual damage to the pumping components. Further recirculation of un-used liquid during a pumping cycle is returned to the source. The circulation and warming of the recirculating liquid can result in the entrainment of air with the liquid nitrogen.
Some of the symptoms of pump distress include cavitation, fluid knock or hammer, suction end vibration, reduced plunger life and catastrophic failures in the power end including plunger connecting rods, crankshafts and related fasteners and seals. Pump distress and failures are exacerbated by high stroke rates.
While the industry has been focused on net positive suction head (NPSH) of the liquid delivered to the suction, poor quality of a liquefied gas delivered to the pump head is a further factor exacerbating poor pump behaviour and failure.
Other areas of frustration for the field operator, pump heads can suffer short mean times between failures (MTBF) and repairs are typically performed in a shop environment, requiring frequent transport of each failed pump head or pump offsite.
There is a desire for reduced incidences of pump repair, extended MTBF, a field repair capabilities when a failure does occur.

SUMMARY

Herein, Applicant provides a manifold or header to the suction of one or more cryogenic liquid pump heads. The manifold provides suction stabilization, and thermal maintenance of the cold end of a cryogenic pump. For simplicity, the apparatus and methodology is described in the context of providing liquefied nitrogen for the oil and gas industry although the apparatus and processes described herein are equally applicable to the pumping of other liquids handled in both cryogenic liquid and vaporized gaseous forms.
Further, in instances of entrained gas, the manifold can also aid in gas desaturation of the liquid nitrogen provided to the nitrogen pumper. Applicant has determined that the liquid circulated between the source of liquid gas and the cryogenic pump heads can entrain gas such as air or evolve N2 gas. N2 gas evolution is exacerbated by warming of the conveyed cryogenic liquids. Handling of the liquid, including transfer through piping and vessels can result in the incorporation of gas during transport or evolution of gas within the liquid, resulting in a gassy liquid. Gassy liquids, and the release of gas therefrom under pressure reduction, including pump suction conditions and flow irregularities, increase the handling difficulty and risk of damage for the form of positive-displacement or other pumps used in this area.
Herein, for convenience, the gassy liquids are referred to as gas-saturated liquid regardless of the extent of saturation. The extent of gas removal, using embodiments described herein, is referred to qualitatively as moving from a saturated to a desaturated state even through the liquid may not be fully saturated, nor gas free respectively.
In one aspect, a manifold or intake header is provided having a vessel comprising liquid storage belly portion in a lower portion of the vessel, and a gas freeboard at a top of the vessel. Provision of a gas freeboard with a liquid sump in the belly portion aids gas separation from the liquid destined for the pump suction. A recirculation line removes excess liquid such as from a mid-vessel liquid port or from an optional launder after an overflow weir.
The belly portion includes a sump from which a substantially gas-free liquid is collected or stored and then drawn from for delivery to the pump inlet. The freeboard portion is a gas cap above the liquid sump for collection and subsequent removal of any gas released from the liquid stored for pump intake. The removed gas can be vented or recirculated to the cryogenic liquid supply.
In one embodiment, the liquid supplied to the header is separated into liquid pooled in the belly portion and any gas released from the liquid collects in the freeboard. Gas is removed from the freeboard leaving a desaturated liquid in a sump of the belly portion. Desaturated liquid intended for the pump suction, is drawn from deep within the liquid sump. In an embodiment, the liquid is delivered along the vessel through a distributor, the distributor releasing supplied liquid upwardly into the header for encouraging gas release to the gas freeboard, and said release further occurring within the level of the belly portion to minimize gas portion re-entrainment with the incoming liquid.
In an embodiment, the liquid supplied to the vessel is decanted or overflows a tray weir and collects in a sump portion of the belly portion. The desaturated liquid overflows the weir, intended for the pump suction, and is drawn the liquid sump.
In an embodiment, liquid removal by each pump suction is through a conduit extending downward through the vessel, through the freeboard and into the liquid stored in the belly portion, to access the sump. The sump provides a consistent liquid storage for control of the NPSH and supply of substantially gas-free liquid under the normal pumping conditions. The liquid removal conduit, immersed in the cold liquid, maintains the low temperature delivery of liquid to the pump head.
As noted by Applicant, the described intake manifold or header provides a constant, desaturated liquid flow to the cold ends of the pump heads. The intake header separates and eliminates flow of gas-saturated liquid to the pump heads and the operational problems associated therewith. Further, the sump and liquid suction design, including routing through the interior of the header itself, aids in maintaining cold temperatures of the suction conduit and conveyed liquid to the heads. Any unused, oversupply of desaturated liquid is recirculated back to the liquid source tank.
All cryogenic plunger pumps benefit from desaturation of entrained air or other gas from the liquid through the design of the intake manifold.
Broadly, an intake header for a high pressure displacement pump head comprises a horizontal vessel having a liquid storage belly portion, a gas freeboard and a mid-vessel liquid input. One or more suctions extend from the belly portion to a suction of its respective pump head. In embodiments, the conduit forming each suction extends upwardly from the sump, internal to the vessel, and exits through an upper wall of the vessel for connection to its respective pump head cold end. Gas exit ports are formed along the upper wall of the vessel and collected in a gas header.
In one embodiment, a tray divides the belly portion into an upper liquid receiving portion and a desaturated liquid sump therebelow. The tray extends from one end of the vessel for receipt of gas-saturated liquid, distribution horizontally along the header vessel, for separation of gas and for liquid. The gas reports to a freeboard and liquid decants from the tray for delivery of desaturated liquid to the sump.
In another aspect, Applicant has determined that pump head cold end performance is improved sufficiently to permit longer stroke operation with reduced incorporated gas-related problems resulting in maintenance of comparable volumetric liquid pumping performance at lower pump stroke rates. Lower stroke rates results in lower stress on pump components and longer MTBF.
In another aspect, valve design further improves cold end performance. The implementation of a large cross-sectional liquid inlet area results in a low pressure drop and minimizes gas-release, cavitation and other reduced pressure liquid effects. Such valve design also results in pump head configuration having longer stroke operation for comparable volumetric performance at lower pump stroke rates.
In another aspect seal arrangements result in reliable pump plunger sealing and ease of field installation and replacement, as a retrofit or as a provided sealing arrangements
In combination, both a desaturated liquid supply header and improved valve components, embodiments of both of which are provided herein, result in a reliable, long lasting cryogenic pump head.
Further, in other aspects, embodiments of the pump head design enable field installation and repair including plunger stroke adjustment on assembly and plunger seal repair onsite.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram of a manifold or intake header according to one embodiment;

FIG. 2A is a perspective drawing of an embodiment of the intake header to the heads of a Quintuplex pump;

FIG. 2B is a perspective drawing of the embodiment of FIG. 2A with the outer wall of the vessel and the collection header rendered transparent;

FIG. 3A is a perspective schematic view of a header illustrating the liquid supply to the header belly portion, a gas freeboard, liquid flow from the sump to each pump head, and liquid recirculation;

FIG. 4A is an end cross-sectional view according to FIG. 3A;

FIG. 3B is a perspective transverse cross-sectional view of a header illustrating a liquid supply distributor and suction conduit extending from the sump to one of the pump heads;

FIG. 4B is an end cross-sectional view according to FIG. 3B;

FIG. 3C is a perspective transverse cross-sectional view of the header of FIG. 2B, illustrating a section through a suction conduit of one of the five pump heads;

FIG. 4C is an end cross-sectional view according to FIG. 3C;

FIG. 5 is a side view of the intake header of FIG. 2B, with the internals shown in hidden lines;

FIG. 6 is an end view of the intake header of FIG. 5 with the internals shown in hidden lines;

FIGS. 7A-7C illustrate various individual components of the intake header;

FIG. 8A shows a partial cross-sectional side view of a triplex pump according to the prior art;

FIG. 8B is a perspective view of a side cross-section of a pump head illustrating the pump cylinder and pump plunger valve, seals and pony rod connection. The pump inlet is shown as usual on the bottom of the pump cylinder;

FIGS. 9A and 9B are perspective views of the pump head of FIG. 8B, with the pump cylinder (FIG. 9A) illustrated separately from the internal components (FIG. 9B);

FIG. 10A is a side cross-sectional view of the pump head of FIG. 8B with a first embodiment of the field installable plunger seals;

FIG. 10B is a side cross-sectional view of the pump head of FIG. 8B with an alternate embodiment of the field installable plunger seals and with the pony rod coupling shown removed, the clamp 132 shown installed in solid lines and apart in dotted lines;

FIG. 10C is a close-up side cross-sectional view of the packing sleeve and seals of FIG. 10A;

FIG. 10D is a close-up side cross-sectional view of the packing sleeve and seal of FIG. 10B;

FIGS. 11A and 11B illustrate the valve in operation, more particularly illustrating the beginning of the liquid intake stoke (FIG. 11A), and the liquid discharge stroke (FIG. 11B);

FIG. 12 is an exploded view of the valve illustrating the flow passages, seals and springs;

FIG. 13 is a transverse cross-section of the cylinder and plunger to illustrate the splined internal cylinder sleeve;

FIG. 14 is a transverse cross-section of the cylinder and plunger to illustrate the cross-flow ports at the end of the internal cylinder sleeve;

FIGS. 15A and 15B are perspective ends view of the drive end of the pump head and illustrating the plunger end and plunger clamp apart (FIG. 15A) and assembled (FIG. 15B); and

FIGS. 16A and 16B are side cross-sectional views of the drive end of the pump head and illustrating the plunger and pony rod interface with shims added to adjust the plunger's piston head closer to the valve (FIG. 16A) and shims removed to adjust the plunger's piston head further from the valve (FIG. 16B), the shims permitting field adjustment of the pump head and drive.

DESCRIPTION

With reference to FIG. 1 a schematic illustrates an embodiment of an intake header coupled between one or more high pressure cryogenic pump heads and a source of cryogenic liquid. Herein, the treatment and handling of the cryogenic liquid is described in the context of providing liquefied nitrogen for pressurization and then vaporization in the field of fracking and hydraulic lift operations. Thus, while the description refers to Nitrogen (N2), in liquid and gaseous forms, the apparatus and processes described herein are equally applicable to other liquids capable of handling in both liquid and gaseous forms.
A charge pump 10, such as a centrifugal pump, delivers a liquid supply LS from a liquid source, such as a N2 tank 12 to an embodiment of the pump header 20. Gas G separates from the liquid LS and is directed back to the source or tank 12. Liquid LP is delivered to the cold end of each pump head 22 and pressurized liquid LV is directed to a vaporizer 24 for producing high pressure gas to the process.
In a first embodiment, a header 20 for one or more cryogenic pump heads 22 is provided.
With reference to FIGS. 2A and 2B, 5 and 6 the header 20 comprises vessel 30 having a liquid intake 32 for receiving liquid nitrogen from the source, such as cryogenic tank 12. The vessel 30 is cylindrical and is oriented generally horizontally. In an embodiment, the intake 32 is coupled to a distributor 34 (FIG. 2B) extending generally horizontally along vessel 30 for delivery of liquid along the length of the vessel 20.
The intake 32 is located at about the axis of the vessel 30 with discharge of the supplied liquid upwardly thereto. In embodiments, the intake 32 is located in the liquid stored in the vessel.
Liquid intended for the pumper, is drawn from a sump 38 of a belly portion 40 of the vessel 30. A freeboard portion 44 above the liquid in the belly portion 40 receives any gas released from the liquid or otherwise accompanying the liquid into the vessel. Liquid collects in the belly portion, the level of which can be controlled including by intake-discharge control, or pressure control of the gas collected in the freeboard.
A plurality of pump suctions 36,36,36 . . . are spaced along the length of the vessel 30. To minimize disruption to the liquid supply to the pump, each pump head has its own pump suction 36 between the pump's cold end and the sump 38. A portion of the pump suction 36 is also physically located in the vessel, from a suction inlet 42 located in the sump 38, passing upwardly through the cold liquid stored in the belly portion, and passing upwardly through a freeboard portion 44 above the liquid for exit from the vessel. The suction inlet 38 is immersed in the liquid in the vessel and remains cold, to minimize thermal disruption to the liquid directed to its respective pump head.
The horizontal distributor 34 delivers the liquid supply LS along the length of the vessel 30, such as through discharge of the liquid through a plurality of discharge a holes 47. The holes 47, such as circular or slots, can be located along an upper wall of the distributor 34 for aiding in gas/liquid separation; gas separating upwardly to the freeboard, and de-saturated liquid downwardly to the sump 38.
The length of the vessel and distributor 34 is dependent upon the number of pump heads 22 for the pump, the spacing between pumps heads 22 dictating the spacing of pump suctions 36 and the length of the header vessel necessary to accommodate the number of pump suctions 36. A vessel suitable for a Quintuplex pump (5 pump heads) is shown, a shorter vessel could be employed for a single pump and common triplex pumps (3 pump heads) as appropriate.
As shown in FIGS. 3A and 4A, the vessel separates liquid and gas, the gas G reporting to the freeboard portion 44 and liquid L reporting to the belly portion 40. The liquid supply LS is provided to the midpoint of the vessel. G gas separates from the liquid L and liquid LP for the pump heads 22 is drawn from the sump 38. Gas GV, for venting or return to the liquid supply 12 is withdrawn from the freeboard portion 44. Liquid L is typically provided in excess of the amount of liquid LP used by the pump heads and therefore a recirculation liquid LR is return to the liquid supply 12.
As shown in FIGS. 3B and 4B, a portion of the vessel 30 incorporating two horizontally spaced pump suctions 36,36 is shown. The distributor 34 is shown extending along the axis of the vessel 30. Liquid supply LS from the source 12, is discharged to the vessel interior, such as through holes 47. A liquid interface or level LL is formed.
A port 46 for recirculation of excess liquid LR is provided at a distal end of the horizontal distributor 34. At a top of the vessel 30, a chamber 48 is provided for the collection of gas G. One or more gas outlets 50 are provided for the controlled removal of collected gas. Equilibrium between gas arriving with the liquid supply LS, and gas removed from the vessel, can be controlled, including through a sized orifice, or needle valve, or large capacity valve fit with a bleed orifice. A large capacity valve at gas outlet 50, when opened, permits a large capacity, cold liquid, recirculation for startup, and when closed permits a small bleed flow of gas therethrough to maintain a liquid gas interface in the vessel. While the provision of freeboard 44 provides a chamber for collection of separated gas G, separation can be further aided by low pressure drop release of gas from the distributor, such as through generously sized holes 47, and by releasing the liquid supply beneath the interface or liquid level LL.
As shown in FIGS. 3C and 4C, in this additional embodiment, the length of the vessel 30 can also fit with a generally transverse extending baffle for forming an upper liquid storage thereabove, a still sump 38 below and liquid communication therebetween. One form of baffle can be an internal tray 60. Saturated or partially saturated liquid supply LS containing some gases, spills from the distributor 34 into the tray 60. At least some gas G separates from the liquid LS and rises to the upper, liquid-free volume of the freeboard 44.
The liquid LS, which can still be partially saturated, flows into the upper liquid receiving portion of the tray 60 and collects until steady-state operations in which the liquid level LL reaches a tray level TL, all the while being provided with an opportunity to release gas, after which the liquid spills over a weir portion 62 of the tray and into the lower desaturated liquid sump 38 in the lower volume of the belly portion 40.
Gas G in the freeboard 44 is collected in the chamber 48 along an upper wall of the vessel 30 for return to the source tank. As stated, the gas outlet 50 can be controlled to meter the gas exiting the vessel, controlling the liquid level LL. Other known liquid level controllers can be employed.
As above, the de-saturated liquid LP intended for the pumper, is drawn from the sump 38. To minimize disruption to the liquid supply to each pump head 22, each pump head has its own suction 36. Each suction 36 is a conduit also physically located in the vessel, having liquid inlet 42 immersed in the liquid of the sump 38, the conduit of the suction passing through the freeboard 44 and through the upper wall of the vessel 30 for connection to the cold end of the pump head 22. The suction 36 and a large portion of the conduit forming the suction, in this embodiment being greater than half the length, is immersed in the liquid of the sump and remains cold, minimizing thermal disruption to the liquid directed to its respective pump head.
The tray 60 is shaped, in cross-section as a letter “J”-shape or eaves-trough shape, having a raised tip or spillover weir 62 at a lower end. The generally vertical portion 64 of the upper stem of the “J”-shape separates the gas/liquid separation volume of the freeboard from the conduit of the pump suction 36 rising from the sump 38 to exit the vessel 30. One or more portals 66 in the upper wall of the vessel permit gas therein to be collected in the discharge header or chamber 48.

EXAMPLE

A vessel about 3.5 feet long and 8 inches in diameter can process 150 USgpm for supplying a triplex pump (three (3) pump heads 22 and corresponding suctions 36) and 300 USgpm for a quintuplex pump (five (5) pump heads 22 and corresponding suctions 36). The saturated liquid enters via a 2 inch (Sch 40) pipe as a distributor 34 with a plurality of exit holes 47 formed along the wall along the top, in this embodiment twenty-eight (28) holes are shown, each about 0.375 inches in diameter. Gas exits through openings 66 along the top of the 8 inch vessel. For integrity, the openings are spaced apart with vessel structure therebetween, formed as several (three) 1.75″ wide slots, each 10 inches long, aligned end to end. Each suction 36 is 1.25″ (Sch 40) is a pipe with a 90 elbow as an inlet 42. The gas chamber 48 can be a 2″ (Sch 40) pipe cut longitudinally along its axis for forming a half-pipe to sealably cover the openings 66.
Pump Head
The cryogenic pump 22 contemplated herein is a plunger-type pump having a reciprocating plunger. One pump of a prior art triplex pump is shown in FIG. 8A, the figure drawn from issued U.S. Pat. No. 8,543,245 B2 issued 2013-09-24 to Halliburton. As shown a conventional arrangement is a pump head 90 having a plunger 91 that alternately draws liquid through a one way intake valve 92 into a pump chamber 94 and then pushes the liquid out of the chamber through a one way discharge valve 95. The chamber 94, plunger 91, valves 92,95 and seals 96 for the plunger are part of the pump head 90, otherwise known as a cold end. The plunger 91 is driven in a reciprocating manner by a crankshaft 97 and drive arrangement 98.
In the case of the cold end, conventional problems with volumetric pumping capacity and reliability are usually related to the inflow and outflow of liquid nitrogen on the return stroke of the plunger. Flow restrictions, resulting in high dP across both intake and discharge, can result in one or more of flashing of gas from the liquid and cavitation, resulting in damage to the components. Conventionally, pump stroke is limited to minimize such phenomenon and lessen damage associated therewith. A limitation on plunger stroke and pumping stroke rate limits pump capacity.
Herein, the axial length of the stroke of the plunger has been significantly increased without degradation of the fluid handling performance. Indeed fluid handling is improved. Applicant has directed the improvement in design to mechanical reliability and ease maintenance rather than increasing pump output. Industry output rates are maintained while reducing the stress on the pump components.
In an embodiment, Applicant has adapted having about three times the stroke length which results in three times the volume of fluid per stoke. Accordingly, given a design flow rate, one can pump the same flow rate as the prior pumps at one third (⅓) the stroke speed.
The reduced stroke speed of the reciprocation of the plunger results in multiple improvements in mechanical component life. The conventional pump comprises a drive including a motor and a gear box, a crank, a piston or pony rod and a piston plunger, the plunger reciprocating in the pump head. Seals are located between the moving plunger and a cylinder head and also within one-way or check valves to regulate liquid intake to the cylinder chamber.
Reduction of the speed of the plunger results in reduced wear on seals and the check valve. Heat generated by the reciprocating plunger and seal friction is reduced. Forces are reduced on the piston rod connections, the gear box and the motor.
Herein, additional improvements include an improved liquid inlet and discharge head, and improved seals. The seals are both simpler and shorter. The plunger and cylinder are longer and better supported for co-axial alignment.
Further, various improvements are possible to aid in field maintenance including ease of installation and seal and head repair. During installation, the head needs to be aligned with the plunger to minimize seal misalignment and wear resulting therefrom. Further, the connection between the piston and the pony rod needs to be carefully set to avoid bottoming out the end of the piston and the head whilst ensuring maximal pump performance.
Further, after some time, seals will wear and require repair. Here prior art seals need to be repaired in a shop setting, herein a seal cartridge or sleeve is provided that can be replaced in the field.
In more detail and with reference to FIG. 8B, pump head 100 supports a cylinder such as a cylinder sleeve 102 supported in a pump housing 104 and having a pump plunger 106. The plunger 106 is slidable within the sleeve 102 for alternately increasing and decreasing the pump chamber 108 within. The plunger 106 is has a piston end 110 that reciprocates in the cylinder sleeve 102. The cylinder head 112 is a cylindrical body arranged axially opposing the piston end 110. The piston end 110 is reciprocated away from a cylinder head 112 to create a suction in the chamber 108 so as to draw new liquid into the chamber 108 through an intake valve 116. The piston end 110 is reciprocated towards the cylinder head 112 to compress liquid in the chamber 108 against a cylinder head 112 and discharge liquid through a discharge valve 114.
The piston end 110 is fit with a rider ring 120 and seals 122 for sealing the plunger's piston end 110 to the cylinder sleeve 102. The plunger 106 is cylindrical, and is sealable in a tubular surround, the piston end 110 sealable in a cylindrical cylinder sleeve 102 and the balance of the plunger sealable in a cylindrical bore of the pump housing 104. Annular seals 124 are fit about the plunger 106 at a tail or connection end 126 opposing the piston end 110.
The plunger 106 is removably connected at the connection end 126 to a pony rod (not shown) that is driven back and forth along a plunger axis by a connection rod and crank arrangement. The pump housing 104 is secured to a skid or other structure, securing the housing 104 at a flange 128. The flange 128 is secured to a fixed frame which is dimensionally set or also fixed dimensionally for locational stability relative to the connecting rod and crank arrangement.
As shown, the pump housing has an inlet 117 for the receipt of cryogenic liquid FP. The inlet 117 is shown as usual and conventional, located on the bottom of the pump housing 104. Liquid can be provided by a header, such as that used in conventional ganged cryogenic pumps, or a header as set forth in FIGS. 1 through 7C.
From the valve end, the internal components comprise a valve assembly 130 comprising the intake valve 116 and the discharge valve 114. The intake valve 116 receives liquid through the liquid inlet 117 and the discharge valve 114 discharges liquid through discharge outlet 115. The cylinder housing 104 supports the cylinder sleeve 102 within which the piston end 110 reciprocates. The piston end 110 is the leading end of the plunger 106 adjacent the cylinder head. The tail end 126 of the plunger 106 extends sealingly through the seal packing 124 for coupling to a pony rod end (not shown) by a rod end clamp 132.
Note that while other drawings may be oriented with the liquid inlet 117 as oriented upwards, this is merely an artifact of the computer generated drawings.
FIGS. 9A and 9B illustrate the cylinder housing 104 in isolation and internal components for housing therein respectively. From a discharge end of the cylinder housing 104, an installation bore 105 is provided for axially receiving the cylinder sleeve 102 and valves 114,116. From the tail end 126, the housing 104 comprises a packing bore 107 for receiving a seal assembly including the seal packing 124.
FIG. 10A is a side cross-sectional view of the internals according to FIG. 9B and having a first embodiment of a field installable seal assembly including the plunger seals 124. The seals 124 are housed in a packing sleeve 140. The packing sleeve has a plunger bore for receiving the plunger 106 therethrough. When the pony rod-to-plunger clamp 132 is removed, a packing nut 142 can be removed and the entire packing seal sleeve 140 and contained seals 124 can be removed for replacement.
The packing sleeve 140 has a first proximal shoulder or inboard lip 150 at an inboard end and a distal shoulder 144 at an outboard end. The inboard lip 150 axially supports the seal pack 124 firstly as a stop for enabling axial retention of the seal pack 124 therein and as a pull structure enabling removal of the seal pack 124 as a complete set of otherwise individual seals, the sleeve 140 and seals 124 removable over the tail end 126 of the plunger 106. The proximal lip 150 of the packing sleeve 140 is sealed, such as at an O-ring 146, for sealing the sleeve 140 to the pump housing 104. The opposing or outboard end of the sleeve 140 is open for axially receiving the seals 124.
FIG. 10B is a side cross-sectional view of the field installable plunger seals and according to a second embodiment having a reduced number of seal components and hence being a less expensive seal. The seal sleeve 140 and packing 124 can be of the same length as that of FIG. 10A, such as for ease of retrofitting a seal of the first embodiment with a seal of the second embodiment. Alternatively, as shown, the seal sleeve 140 and packing 124 can be axially shorter, such as by incorporating a fewer number of hat or lip seals. A shorter seal can resulting in a shorter pump housing when engineered in combination.
With reference to FIG. 10C, in greater detail, and illustrated from left to right, the inboard lip 150 of the sleeve 140 is shoulder 150 having opposing shoulder faces, one inboard face against the pump housing 104 and the other outboard face against the seal pack 124.
The seal pack 124 of FIGS. 10A and 10B comprises a first seal adjacent the inboard end, a stack of lip seals adjacent the outboard end, and a spacer therebetween. The entire seal pack is axially retained to the sleeve 140 and the sleeve is retained to the housing 104. The first seal, is axially compressible by the balance of the seal pack 124 to actuate a radial energizing profile such as a wedge to drive the seal against the plunger 106.
The first seal can comprise a first ring seal carrier 152 at the proximal end adjacent the outboard face of the inboard lip 150. The ring seal carrier 152 supports a rod seal 158 that is axially compressible to actuate a radial energizing profile to drive the rod seal 158 into sealing engagement with the plunger 106. The carrier 152 forms an annular space to the plunger 106 for supporting a ring seal compressor 156 axially slidable therein and a spring 157, such as a Belleville washer, for energizing the structure of the compressor 156 relative to a carrier shoulder 150b. The carrier shoulder 150b is sealably supported at the sleeve's inboard shoulder 150. Compressor 156 has a ramp or wedge corresponding to a matching wedge on the rod seal 158 for driving the rod seal 158 radially inwardly and sealably against the plunger 106.
Next is a lantern ring 160 spacing the rod seal 158 from a series of hat seals assemblies 162,162 . . .
Six hat seal assemblies are shown, each seal assembly 162 comprising an annular seal spacer 164 having a generally square or slightly trapezoidal cross section, and a hat seal 166 itself having a generally “L” shape supported over the seal spacer/spacer 164.
All of the ring carrier 152, lantern ring 160 and hat seal assemblies 162 are supported in the plunger bore forming a packer sleeve annulus. Axial extraction of the packer seal sleeve 140, and support by the sleeve shoulder inboard lip 150, pulls all of the seal components from the cylinder housing 104.
The packer seal sleeve 140 is releasably retained to the cylinder housing 104 using a packer nut 170. The nut 170 has a narrow annular shoulder 172 that engages a hat ring O-ring seal 176 that engages the packing seals 124. The seals are compressed axially, for increasing the radial sealing capability. The axially engaged seals press on the seal sleeve shoulder, retaining the assembly to the cylinder housing 104. The nut can include a rider ring 179 for axial alignment with the plunger 106.
FIG. 10D is a close-up side cross-sectional view of the alternate packing sleeve and seal of FIG. 10B. The sleeve and seal are shown removed from the plunger. Again, from left to right, the sleeve and seal comprise from the sleeve shoulder 150: a rider ring 180 instead of a ring seal carrier and seals, an extended length lantern ring 182 and a diminished number of hat or lip seal assemblies 162. The lantern ring 182 can be as long as needed to space the seal assemblies 162 from the rider ring 180 and, in some embodiments, to match the previous length of the first seal assembly for retrofit applications, or shortened so as the entire sleeve and seal assembly can be shortened.
FIGS. 11A and 11B illustrate the intake and discharge valves 116,114 in operation. FIG. 12 illustrates the valve assembly 130 in exploded view illustrating various flow passages, seals and springs.
In greater detail, the valve assembly 130 is supported in the cylinder housing 104 at the piston end 110 of the plunger 106. The cylinder sleeve 102 is first installed axially into the installation bore 105, and then the valve assembly 130, forming the liquid pumping end of the pump head 100. From the piston end 110 (right side, moving left), the cylinder sleeve 102 has a valve end 190 which axially supports and seal the cylinder head 112 thereto. The valve end 190 has a stepped bore for forming an annular sealing shoulder 191 for sealably and supportably receiving the cylinder head 112, between the liquid inlet and the chamber 108. The valve end's stepped bore further forms a smaller diameter within the sealing shoulder 191 for forming the pump chamber 108. The chamber 108, of variable axial extent, is formed between the piston end 110 of the plunger 106 and the cylinder head 112.
The intake valve 116 is operable against and works in combination with a piston face of the cylinder head 112.
The body of the cylinder head 112 has a plurality of intake ports therein, arranged about the annular periphery of the cylinder head to access a radial periphery of the chamber, the intake ports being alternately opened and blocked by a ring-plate of the intake valve 116. The plurality of intake ports are arranged and spaced circumferentially about an annular valve seat on the face of the cylinder head. The valve seat of the cylinder head 112 is fit with a plurality of circumferentially-spaced inlet passages forming the intake ports 192 to the chamber 108. The intake ports 192 are located between the fluid inlet and the chamber 108 for fluid communication therealong. The intake valve 116 comprises a ring-plate 194 biased against, and to close, valve seat having the inlet ports 192 therein. The ring-plate is an annular ring having a bore through which the piston end 100 can reciprocate. The complementary annular faces of the cylinder head 112 at the ports 192 and the ring-plate 194 seal when engaged.
Radially within the annular valve seat, the face of the cylinder head 112 is concave or dished, having a truncated, right conical recessed portion therein and a face of the piston end 110 can also have a complementary convex truncated, right conical protruding portion. The dished and protruding portions are complementary to minimize the chamber volume on the discharge stroke.
A coil spring 196 is fit operably between a shoulder the stepped bore of the cylinder sleeve piston end 190 and the ring-plate 194. The ring-plate is operable axially between open and closed positions. The ring-plate 194 is movable axially against the biasing of the spring 196 to move away from and open the ports 192 as the piston end reciprocates away from an intake valve seat the cylinder head 112. The ring-plate 194 is movable axially with the biasing of the spring 196 to move towards the cylinder head 112 to close the ports 192 as the piston end reciprocates towards from the cylinder head 112. The interface of the intake valve seat of the cylinder head 112 and ring-plate is a sealing interface, shown as a finished and complementary metal-to-metal surface.
The stepped shoulder of the cylinder sleeve can include an annular and axially extending recess as an axial stop and to retain the coil spring 196 about its periphery.
An annular inlet port 199 about the outer circumference of the body of the cylinder head fluidly communicates with the inlet ports 192. The annular inlet port aligns axially with the liquid inlet 117 in the cylinder housing 104 and distributes liquid received from the header about the annular inlet port for access to the intake ports 192.
The intake ports 192 are distributed and spaced circumferentially about the intake valve 116 and provide significant cross-sectional area for minimal restriction to the incoming flow from the liquid inlet 117. Minimal pressure drop minimizes gas evolution. Liquid provided to the annulus inlet port is distributed thereabout to each port.
The cylinder head 112 also supports the discharge valve 114 retained in the installation bore 105 in the cylinder housing 104. The discharge valve 114 is a one way valve having a valve plunger 200 biased by spring 202 closed against an annular valve seat 204 in the downstream side of the cylinder head 112. In this embodiment the plunger 200 is arranged along the axis of the valve assembly. The plunger has a valve face and a shaft 201 supporting the valve plunger 200 for axial movement between open and closed positions. An annular discharge passage 203 is formed axially through the cylinder head 112 and about the plunger 200 and is in fluid communication with the discharge port 115 through a discharge cover 206.
The discharge cover 206 is an annular plate having a plurality of circumferentially spaced discharge passages 208 formed therein, also comprises a boss 209 and a bushing 211, located along the axis, for slidably supporting the plunger's shaft 201. The discharge cover 206 receives liquid flowing from the annular discharge passage 203 of the discharge valve 114 and discharges same to the discharge outlet 115. A discharge valve retainer 210, having a discharge bore forming the outlet 115 therein, concludes the functional valve components. The discharge valve retainer 210 retains the discharge cover 206 against the cylinder head 112.
Downstream from the discharge valve retainer 210, a retaining ring nut 212, with wrench ports 214 arranged circumferentially thereabout, threadably engages the cylinder housing 104 to retain the valve components 114,116 and a distal end 220 of the cylinder sleeve 102 axially against a main shoulder 222 of the cylinder housing 104 (FIGS. 9A,9B). The retaining nut 212 engages a wear ring 216 sized to the installation bore, extending all along the installation bore 105 to the main shoulder 222.
Fit to the installation bore 105 are the wear ring 216 and the discharge valve retainer 210, with an O-ring 230 sandwiched therebetween. The discharge valve retainer 210 engages the ported discharge cover 206, having a copper ring seal 232 sandwiched therebetween. The ported discharge cover 21—supports the boss 209 and coil spring 202 for guiding and biasing the discharge valve plunger 200 upstream against valve seat 204. The ported discharge cover 206 engages the cylinder head 112, having a copper ring seal 234 sandwiched therebetween.
An outside diameter of the cylinder head 112 engages the cylinder sleeve 190 and drives the sleeve against the housing's main shoulder. Annularly within the cylinder head end of the cylinder sleeve is an annular suction valve chamber. The suction valve, having an annular ring valve, is biased downstream to seal the inlet passages. The spring is sandwiched between the annular ring valve and annular chamber wall at the cylinder sleeve.
As shown in FIG. 11A, on the liquid intake stroke, the piston end 110 moves away from the cylinder head 112 and a low pressure results in the pump chamber 108. The annular ring-plate 194 pulls away from the circumferentially spaced inlet passages, against the spring bias. The one way discharge valve is securely retained in the closed position by the large differential pressure between the discharge and the pump chamber. Thus liquid flows from about the annular inlet port 198, through the inlet ports 192, physically displacing the annular ring-plate 194 axially to fill the piston chamber 108.
As shown in FIG. 11B, on the liquid discharge stroke, the piston end 110 is craven towards the cylinder head 112 for generate a high pressure in the pump chamber 108. The annular ring-plate 194 is biased closed against the cylinder head 112 to avoid any backflow and pressure differential ensures it stays closed against the circumferentially spaced inlet ports 192. The plunger 200 of the one way discharge valve 114 is forced open, off of valve seat 204, against the small biasing of the coil spring 202 and liquid flows around the valve plunger 200 and out the discharge ports 208 of the discharge cover. The liquid flows through the bore of the discharge valve retainer 210 and out the pump outlet 115.
The cylinder sleeve 102 is provided with cooling circulation. FIG. 13 is a transverse cross-section of the cylinder housing 104 and plunger 106 to illustrate an externally-splined internal cylinder sleeve 102. The cylinder sleeve 102 firstly provides a piston barrel or complementary cylindrical surface 240 for receiving the piston end 110. The piston end 110 is sealably and slidable thereon. Secondly, the cylinder sleeve has an external surface 242, upon which is formed one or more axially-extending splines 244 forming passages 246 therebetween. The sleeve 102 is fluid cooled by the flow of liquid through the passages 246 and therealong.
As shown in FIGS. 8B, 9B, 13 and 14 a first annular cooling passage 248 is located circumferentially about the cylinder sleeve 102 and about the piston end adjacent the cylinder head 112. The axial passages 246 are fluidly connected to the annular cooling passage 248 end and extend axially back toward shoulder 222. As also shown in FIG. 8B, a circulation port 250 is provided at the shoulder 222, for fluid communication with a second annular cooling passage 252 and axial passages 246. The circulation port 250 fluidly connected at the distal end of the cylinder sleeve 102. The second annular cooling passage 252 is fit with radial cross ports 254 through the sleeve 102 and in fluid communication with a backside chamber 256 of the piston end 110. FIG. 14 illustrates the cross-flow ports 254 at the distal end of the internal cylinder sleeve 102.
FIG. 15A and 15B are perspective ends view of the drive end of the pump head 100 and illustrating the tail or connection end 126 of the plunger 106 and plunger clamp 132. In FIG. 15A, the clamp 132 is illustrate split apart for disconnecting the plunger 106 from the pony rod 260 (See FIG. 16A), and in FIG. 15B is shown assembled for connecting the components drivably together.
Turning to FIGS. 16A and 16B, cross-sectional views of the plunger 106 and pony rod 260 connection of FIG. 15A illustrate field adjustment of the plunger's axial position, to adjust the top dead center (TDC) to the plunger's piston end 110 closer and further from the cylinder head 112. The stroke and axial position of the pony rod 260 is set by the motor, gear box, crank and connecting rod position on a pumper. Once installed in the field, the TDC can be adjusted.
In FIG. 16A, one or more ring shims 261 are added to the end of the pony rod 260 to space the plunger's tail end 126 a distance h further from the pony rod 260, in turn locating in the piston end 110 closer to the cylinder head 112. Ring shims 261 can be removed to draw the plunger closer to the pony rod 260, in turn spacing the piston end 110 a clearance c further from the cylinder head 112.
The tail end and the pony rod are fit with beveled ends 262,264 respectively, the bevelled ends being complementary with internal annular beveled surfaces 272,274 of the clamp 132. The end of the pony rod is fit with an insert 280 having the bevelled end 264 formed thereon. The insert 280 has a shaft portion 282 and a larger upset end 284 bearing the beveled end 264. The ring shims 261 are located about the shaft portion 282 and axially between the upset end 284 and the pony rod. The insert 280 is secured to the pony rod 260 with a cap screw 288 or other suitable fastener.
A face 300 of the insert 280 of the pony rod 206 engages a 302 face the tail end 126 of the plunger 106. Thus, the relative axial position of the piston end 110 and pony rod 206 are set. Removing one or more ring shims 261 causes the plunger 106 to be secured by the clamp 132 closer to the drive end, with the piston end 110 further from the cylinder head 112. Thus, onsite maintenance and adjustments can be performed by adding and removal of shims to adjust the plunger's piston end 110 closer and further from the cylinder had and valve assembly 130.

Claims

1. An intake header for a cryogenic pump having one or more pump heads comprising:

a generally horizontally extending vessel having a liquid sump and a gas freeboard;

a liquid intake to the vessel and connected to a source of cryogenic liquid;

a gas outlet connected to the freeboard for venting gas ; and

one or more conduits, each conduit forming a suction corresponding to the one or more pump heads, each suction extending from the sump to a respective pump head for delivery of liquid in the sump to the pump head.

2. The header of claim 1 wherein two or more of the one or more suctions are spaced horizontally along the vessel for corresponding to the one or more pump heads

3. The header of claim 1 wherein each suction extends upwardly from the sump, through the liquid in the sump, through the gas in the freeboard and through an upper wall of the vessel for connection to the pump head.

4. The header of claim 1 further comprising a gas header along the upper wall of the vessel and in fluid communication with the freeboard for collecting gas therefrom.

5. The header of claim 1 wherein the vessel is cylindrical and having a horizontal axis, the liquid inlet being located at one end of the vessel at about the axis thereof.

6. The header of claim 1 further comprising a generally horizontally extending baffle in the sump.

7. The header of claim 6 wherein the baffle is a tray dividing the sump into an upper liquid-receiving portion above and a lower desaturated liquid portion therebelow, the tray having a weir for spilling liquid from the upper portion to the lower portion.

8. The header of claim 1 further comprising a distributor extending along the vessel for receiving liquid from the intake and having a plurality of openings for distributing the liquid along the horizontal extent of the vessel.

9. The header of claim 1 further comprising

a generally horizontally extending tray dividing the sump into an upper liquid-receiving portion above and a lower desaturated liquid portion therebelow, the tray having a weir for spilling liquid from the upper portion to the lower portion;

a distributor extending along the vessel for receiving liquid from the intake and having a plurality of openings for distributing the liquid along the horizontal extent of the vessel, the distributor extending along the tray in the upper portion, the opening being located within the liquid in the upper portion.

10. A pump head for a cryogenic pump having a cylinder, a cylinder head, and a plunger axially slidable in the cylinder for forming a chamber of variable axial extent between the cylinder head and the plunger, comprising:

a liquid inlet to the chamber;

a discharge outlet through the cylinder head and having a discharge valve; and

an intake valve comprising

a plurality of inlet passages spaced circumferentially-spaced about the cylinder head and situate between the liquid inlet and a periphery of the chamber, and

a ring-plate movable axially relative to the cylinder head between an open position away from the cylinder head for receiving liquid through the inlet passages to the chamber and a closed position engaged sealingly against the cylinder head to close the inlet passages.

11. The pump head of claim 10 wherein the cylinder head further comprises a cylindrical body having an annular valve seat formed thereabout for sealingly engaging the ring-plate in the closed position, the inlet passages formed about the valve seat.

12. The pump head of claim 10 wherein the cylinder head further comprises an annular inlet port about an outer circumference of the cylinder head, the annular inlet port in fluid communication with the liquid intake for distributing liquid about the cylinder head to the inlet passages.

13. The pump head of claim 10 further comprising a spring for biasing the ring-plate to the closed position.

14. The pump head of claim 10 wherein the cylinder head has a generally concave face, the plunger having a complementary protruding convex piston end face.

15. The pump head of claim 10 wherein the pump's cylinder comprises a cylindrical sleeve supported within a pump housing, the cylindrical sleeve and cylinder head retained axially within the pump housing.

16. The pump head of claim 15 wherein the pump housing has the liquid inlet formed therethrough, the annular Inlet port of the cylinder head being axially aligned with the fluid intake for receiving liquid from the liquid inlet.

17. The pump head of claim 10 wherein the pump's cylinder comprises a cylindrical sleeve supported within a pump housing, the cylindrical sleeve and cylinder head retained axially within the pump housing, further comprising a valve assembly, the valve assembly comprising the intake and discharge valves.

18. The pump head of claim 17 wherein the valve assembly is supported in the pump housing, aligned axially with the plunger, comprising:

the cylinder head, having a cylindrical body co-axially aligned with the plunger and having an annular valve seat formed thereabout,

the ring-plate located in the chamber between the plunger and the cylinder head and movable axially towards the annular valve seat in the closed position for blocking the inlet passages and directing liquid to the discharge valve and axially away for the intake of fluid into the chamber,

the discharge valve comprising a plunger arranged within the discharge outlet through the cylinder head and forming an annular passage thereabout, the plunger supported in the discharge outlet and slidable between open and closed positions; and

a retaining nut to axially retain the valve assembly within the pump housing.

19. The pump head of claim 17 wherein the valve assembly further comprises:

a discharge cover between the retaining nut and the cylinder head, the discharge cover comprising an annular plate having a plurality of circumferentially spaced discharge passages formed therein and in fluid communication with the annular passage of the discharge valve.

20. The pump head of claim 19 wherein the discharge cover further comprises a boss for slidably supporting the plunger in the discharge outlet.

21. The pump head of claim 10 wherein the plunger has a piston end operable in the chamber and a tail end adapted for connection to a drive, the tail end, the plunger supported for reciprocation in a pump housing further comprising:

a cylindrical sleeve supported within the pump housing for forming the cylinder and having the piston end slidable therein; and

a seal assembly supported within the pump housing, the plunger's tail end sealably slidable therein.

22. The pump head of claim 21 wherein the plunger has a piston end operable in the chamber and a tail end adapted for connection to a drive, the tail end, the plunger supported for reciprocation in a pump housing further comprising:

a cylindrical sleeve retained axially within the pump housing for forming the cylinder and having the piston end slidable therein; and

a seal assembly retained axially within the pump housing, the plunger's tail end sealably slidable therein.

23. The pump head of claim 22 wherein the seal assembly comprises:

a seal pack for slidably sealing the tail end of the plunger;

a sleeve replaceably retained axially within the pump housing, the sleeve having a first lip for supporting the seal pack for axial removal from the pump housing; and

a packing nut for axially retaining the sleeve and retained seal pack within the pump housing.

24. The pump head of claim 10 wherein a tail end of the plunger is releaseably connected to a drive, further comprising one or more ring shims between the tail end of the plunger and the drive for adjusting a spacing of the plunger from the cylinder head.

25. A sealing assembly for cryogenic pump, the pump having a cylinder and a cylinder head supported in a pump housing, and a plunger axially slidable in the cylinder for forming a chamber of variable axial extent between the cylinder head and a piston end of the plunger, the sealing assembly between a tail end of the plunger and the pump housing, the sealing assembly comprising:

a sleeve replaceably retained axially within the pump housing and having a plunger bore therethrough for receiving the tail end of the plunger, the sleeve having a inboard lip and an open outboard end, the sleeve being axially removable from the pump housing;

an annular seal pack fit through the outboard end into the plunger bore and supported axially at the inboard lip, the seal pack sealing between the seal pack and the sleeve and between the seal pack and the plunger; and

a packing nut for axially releasably retaining the seal pack to the sleeve and the outboard end of the sleeve to the pump housing.

26. The sealing assembly of claim 25 wherein the seal pack comprises:

a first rod seal adjacent the inboard lip;

a stack of lip seals;

a spacer between the first rod seal and stack of lip seals.

27. The sealing assembly of claim 26 wherein the first rod seal comprises a ring seal carrier supporting a compressor and a rod seal, the compressor and rod seal having complementary wedges for driving the rod seal radially inwardly and sealably against the plunger.

28. A cryogenic pump comprising the pump head of claim 10 and the header of claim 1.