DE2949083A1 - PISTON PUMP WITH HIGH PRESSURE PUMP ELEMENT - Google Patents

Description

PATENTANWÄLTE Dlpl.-Ing. P. WIRTH Dr. V. SCH MIED-KOWARZIK

Dlpl.-ing. G. DANNENBERG Dr. P. WEINHOLD Dr. D. GUDEL Dfpl.-Ing. S. SCHUBERT

281134 GR ESCHENHEIMER STR.

TELEPHONE: (Oeil) _{e00Q FRANK} FURTAM MAIN

Gu / ki case: RC-1436-MO36

5th December 1979

DART INDUSTRIES INC.

8480 Beverly Boulevard

Los Angeles, California 90048

United States

Piston pump with high pressure pump element

030027/0643

description

The invention relates to a piston pump, the high-pressure pump element thereof has an assembly of a cylinder, a piston rod and a ring seal.

Piston pumps or plunger pumps are preferred because of their delivery characteristics with regard to the medium. However, they are not recommended at pressures above 1400 kg / cm ^{2 (20,000 psi).} Even at lower pressures, known piston pumps have flexible ring seals, the service life of which is very limited in the prior art. The seals age even faster at higher pumping speeds and / or when chemically active fluids are being pumped. At an operating pressure of significantly more than 1400 kg / cm, the steel components of the cylinder unit even experience fatigue fractures, which further reduces the service life of these known piston pumps.

Known piston pumps are therefore no longer used for pumping under high pressure and / or of corrosive fluids. although there is a need for it. As mentioned, this is due to the very short and economically unacceptable nature of the project Service life as well as the high maintenance costs of known constructions.

The invention is therefore based on the object of increasing the service life of the high-pressure pump element of such a piston pump to lengthen noticeably. The novel pump element should also have sufficient resistance to fatigue so that it can be used commercially at pressures which are felt to be in excess of 1400 kg / cm.

The invention is also based on the object of proposing a packing ring seal for such a pump element, which is effective even at very high pressures and is sufficiently resistant to wear and corrosion so that the sealing elements also have a high life

030027/0643

have duration, even if they are used to promote chemically active Fluids are used.

The new type of pump element should have a long service life even under difficult operating conditions. It should too can be used as a multiple piston pump, so that a constantly controlled volume of fluid at very high pressures can be pumped without fluctuations in delivery.

This problem is solved by the characterizing features of claim 1.

This creates a new type of piston pump whose high-pressure pump element protects against corrosion and fatigue is very resistant, even if it is used as a high pressure pump element is used. Furthermore, the novel assembly can be easily serviced.

To increase the fatigue resistance of the unit, what to extend the service life at the high pressure under consideration is very important, it is preferred if the housing, designed as a monoblock, is subjected to an autofrettage including the use of internal Pressures sufficient to cause partial flow or cold work of at least the inner layers of the metal to effect around the bores, which act as working pressure chambers in the housing.

In the simplest embodiment, the ring seal can be made from the combination according to c) of claim 1 be formed. The lifespan of this basic embodiment will be significantly increased if a cooling liquid is forced through the annular space between the housing and the pipe section is printed through, in accordance with e) of

030027/0643

- y-ΛΟ

Claim 1. The resultant improvement is particularly at higher pressures and / or pumping speeds essential. However, an annular seal such as that described in US Pat. No. 3,834,715 works most effectively. This embodiment is thus preferred and the disclosure of this patent specification is part of the disclosure of this invention. There is a pressurized sealing fluid used, which is distributed by means of a twisted ring within a series of packing rings, some of which zigzag or otherwise profiled, with a The concave profile points towards the twisted, middle ring.

In the novel piston pump, the design of the ring seal described works essentially with the cooling mentioned in the annular space between the housing and the pipe section to increase the lifetime together.

The invention is illustrated below using an exemplary embodiment explained in more detail, from which other important features result. The figure shows a longitudinal section through the new high pressure pump element of a new piston pump.

A piston rod 1 is shown in the figure in a position in which it is just before its front reversal point, which is shown in the figure as a dash-dotted line 2. The reverse point of reversal of the piston rod is through the line 2 'indicated The piston rod 1 consists of Tungsten carbide or some other hard, wear-resistant Material. The rear part of the piston rod 1 is free for connection to a suitable drive mechanism accessible and therefore has an annular collar which serves as a connecting piece 4.

030027/0643

29A9083

The working part of the piston rod 1 moves inside a heavy, cylindrical housing 5 made from a block. The main working pressure chambers of the housing are two uniform axial bores 6 and 7. The bore 6 in the front end of the housing 5 has a length which exceeds the stroke of the rod 1 and an inner diameter which is slightly larger than the diameter of the piston rod . In order to achieve a good sliding fit, the bores 6 and 7 are exactly concentric and coaxial with one another. They have highly polished surfaces with a roughness that does not, for example, exceed 40 χ 10 cm (16 microinches). It is preferred if the roughness of the bores is approximately 20 × 10 " ⁶ cm (8 microinches). The outer surface of the working part of the piston rod 1 is also highly smooth. That is, its smoothness is at least equal to the smoothness of the bores. The piston rod is preferably smoother, for example the roughness is less than 5 × 10 cm (2 microinches). The bore 7 has a much larger diameter than the bore 6, so that a space is formed for a ring seal 10, which acts as a pressure seal between the piston rod 1 and the housing 5 acts.

The ring seal 10 is shown in the preferred embodiment Embodiment shown being pressurized by a fluid. The ring seal closes a central, twisted ring 12 (cage ring) and additional sealing elements, which have feature c) of claim 1 go out. In addition to the multiple, resiliently flexible sealing rings of this feature c), due basically are required, the illustrated and preferred embodiment comprises a plurality of these rings including cooperating ring types 11, 13 and 14 on both sides of the middle ring 12. There will be thereby forming two separate sets of packing rings.

03 0 027 / 06A3

The front set comprises in the embodiment shown three rings 11 which are substantially V-shaped or zigzag-shaped in cross-section. The back sentence contains four such rings 11, which are also profiled V-shaped or zigzag, with their concave ends point towards the middle ring 12. In this preferred embodiment each set should have at least two such profiled rings 11, which between a middle Follower ring 13 and a follower ring 14 at the end are provided which have flat radial surfaces at the ends facing away from the profiled rings 11.

The packing rings 11, 13 and 14 are made of inert plastic, for example a fluorinated hydrocarbon polymer, for example from TEFLON, which is made of a finely divided solid filler material with a higher melting point is reinforced, which is characterized by better thermal conductivity and better thermal resistance, for example graphite, molybdenum disulfide, powdery Metals, glass fibers, carbon and the like. In addition, it is preferred if the follower rings 13 and 14 are made of TEFLON reinforced with copper powder, while the profiled rings 11 are made of graphite filled TEFLON are made so that a balanced combination of sliding properties, resilience and thermal stability given is.

Simple, block-shaped spacer rings 15 and 16 limit the Ring seal at the front ends. Similar to the middle ring 12, the spacer rings are made of metal or another hard, non-compliant material to support the compliant packing rings and are held in alignment with one another in their cooperating position. In addition, the spacer rings hold the entire

030027/0643

Sealing arrangement concentric including the piston rod. The rear spacer ring 16, which is also used in the basic Minimal construction is essential, also serves as free sliding contact against the last, resilient packing ring of the Seal, for example against the follower ring 14 in the exemplary embodiment shown. This will make the forward-facing axial pressure is transmitted uniformly so that any sagging that occurs in the sealing rings, based on a compression set, flow, or other dimensional changes in the resilient rings can occur.

The axial pressure is exerted through a bush 16 which into an internal thread 9 on the rear end of the housing 5 is screwed in. The dimensions are such that the radial end face 19 at the front of the bush 18 is attached the pole ring 14 applies, a good bit before this comes to rest on the internal thread 9.

The adjustable connection that is established by the bushing 18 that can be screwed in in the axial direction is also important. In the basic design of the seal, the bushing can therefore exert sufficient pressure on the ring seal be exercised, whereby the sealing effect of the ring seal is improved. Is used in an embodiment of the seal such that pressure is exerted on the seal by a fluid, the main back pressure by the pressurized fluid exercised, the result is an even better sealing effect Pressure essentially about getting a good fit between the adjacent ring elements so that these elements work properly together.

The middle ring 12 serves to adequately distribute the pressurized fluid through the interior of the pressure seal elements. For this purpose, the ring 12 has a fairly wide, flat,

030027/0643

undercut groove 22 on the central part of its circumference with a plurality of conduits 24, only two of which are shown extending from the groove on the outer periphery of the ring inwards to the circumference of the piston rod 1. Because the pressure fluid is supplied from the outside of the assembly must be, a radial bore 8 is provided through the housing 5, via which the fluid in this preferred embodiment is fed.

The housing 5 is concentrically surrounded by a pipe piece 30, the walls of which are considerably thinner than those of the housing 5. The pipe section, however, is thick enough to allow a structural Maintain rigidity under operating conditions. The inner diameter of the pipe section 30 is along its main central part essentially the same. The inner diameter exceeds the outer diameter of the housing 5 at its main central portion (i.e. along its full length with the exception of a short, widened head part 28) by a few mm. Through this a narrow annular space 32 is formed around the greatest length of the housing 5. The inside diameter of the pipe section 30, however, is reduced at lines 31 and 33, so that short sections are formed whose inner diameter is only is slightly larger than the outer diameter of the main body of the housing 5. This creates a sliding fit between them Share trained. At the front end, the pipe section 30 has a widened head part 34, the front part of which has an incision which is sufficient to insert the head part 28 of the housing 5 there.

The pipe piece 30 is so constructed that it can be brought into the working position shown in the drawing can by sliding it over the housing 5 from behind after two elastic O-rings 21 in slots 20 inserted on the outer circumference of the housing 5 adjacent to the sections with the smallest diameter of the tubular piece 30

030027/0643

whereby the necessary peripheral seals are formed at both ends of the annulus 32. Threaded holes and 36 lead to the annular space 32 and serve as an inlet opening or outlet opening for a KUhlfluid. The pipe piece 30 has also a larger bore 38, concentric to the smaller bore 8 through the housing 5, so that in the bore a fluid can be introduced from an external pressure source.

After the pipe section 30 has been pushed onto the housing 5 the construction is completed as follows:

(1) The pipe piece 30 is inserted into a cap 40 which the head part 34 completely surrounds. For this purpose, the cap 40 has a larger inner bore 42 to which it extends a shoulder connects to a smaller inner bore 44.

(2) The nose part of a connecting rod 50 with a fluid line 52 from a valve chamber, not shown, is inserted into a suitably dimensioned, end-face receptacle inserted in the housing 5, so that a tapered end face 54 on the nose part on a flat, radial Ring shoulder 3 is seated on the bottom of the receptacle 29.

(3) The seal between the connecting rod 50 and the housing 5 is sealed and the pipe piece 30 becomes at the same time thereby fastened by threaded bolts are used in threaded holes 45 in the cap 40, the extend through symmetrically arranged holes 55 in a flange 56, so that a tapered shoulder 58 is pressed on the connecting rod 50 towards the housing 5.

(4) via inlet 35 and outlet 36 now becomes a Cooling fluid supplied to the annular space 32.

030027 / 06A3

(5) To activate the ring seal, the supply of the pressurized fluid must be completed by a pressure-tight connection with the bore 8 in the housing 5 the opening 38 is made.

In the embodiment shown, this is achieved by that an auxiliary ring 60 in a sliding fit on the pipe piece 30 is pushed so that a radially extending threaded opening 61 concentric with the opening 38 and the Hole 8 is aligned. A cylindrical insert 66 with a widened front part 68 is somewhat narrower than that opening 38 and is inserted through the opening so that the The blunt end face 69 on the insert fits into a shallow depression 39 in the housing 5 at the outer end of the bore 8 settles. A gland nut 70 surrounds the insert concentrically, by means of an internal recess which exactly matches the contour of the shoulder 67 on the rear of the insert follows. The nut is then screwed into the threaded opening 62, until a good pressure seal between the end face 69 and the recess 39 is achieved. The low pressure seal between the pipe piece 30 and the insert piece 66 is achieved via an O-ring 65 in a circumferential groove 63 which is located in the part of the widened end part 66 which is surrounded by the wall of the pipe section 30.

U.S. Patent 3,834,750 discloses the rule of thumb for operating a pressure seal of the preferred embodiment that the pressure fluid should be supplied to the packing seal with a back pressure substantially equal to the pressure of the working fluid being pumped under pressure. Optimal efficiency is achieved when the counter pressure is + 10 % of the operating pressure of the pump elements. Occasionally, very good results are obtained when the differences are greater than 10 % , especially on the minus side. This depends heavily on the particular combination of variables, for example the pumping speed,

030027/0643

the number, type and construction of the packing rings, the operating pressure level etc.

In the following, important features in the manufacture of the housing are discussed in particular, with which its service life is increased significantly. It is known that the housing is subject to the pressure peaks during operation of the piston pump.

For this purpose, the housing consists of a monoblock cylinder and takes both the piston rod and the Ring seal, namely combined with a simple, ring-shaped envelope for forced cooling, whereby the heat generated inside the housing during operation is dissipated through the walls of the housing.

The materials from which the housing is made and how it is manufactured are also important. Those for the purposes mentioned Most suitable materials are iron alloys, which are very resistant to breaking, especially if the alloy is noticeable Contains chromium and some nickel. The concentration of chromium should contain at least about 10 wt .- # and nickel at least about 4 96% by weight. These additions result in excellent corrosion resistance, which also extends the service life. Independent of depending on the alloy used, it should be very pure and free from dirt and discrete foreign bodies, so that small discontinuities, which would serve as starting points for stress concentrations, can also be avoided. That Casing is said to be made from an alloy ingot by arc melting or electrical slag melting will. Steel alloys with about 11 to 19 wt. 96 chromium and about 3 to 9 wt. # nickel as the main additives are preferred.

030027/0643

Particularly good results are obtained from similar alloys which contain molybdenum in small additions and which have undergone precipitation hardening through a suitable heat treatment. Such an alloy contains about 13 % chromium, about 8 % nickel and about 2 % molybdenum together with 0.03 # carbon and other minor additions (wt .- #).

In order to manufacture the housing, it is important that the surfaces of the bores are well smoothed. Also is it is essential to avoid sharp edges inside the high pressure chambers. To increase resistance to fatigue the high pressure chambers of the housing are to be subjected to an autofrettage sufficient to cold flow or flow initiate the boundary layers of the metal in the vicinity of the holes, after which the inner surfaces of the holes should no longer be disturbed by machining, honing, polishing or the like. In the case of the drawn The embodiment is the diameter of the ring seal 10 much larger than that of the piston rod. The auto-freezing should be done in two stages because of the large size Difference in these diameters between the bores 6 and 7 take place, so that the flow in both bores is achieved.

In other words, during the manufacture of the housing 5 first of all, the bore 6 is created through the entire length of the housing. Then the bore is honed and polished, at least the front part of the bore. Finally, the aforementioned autofrettage is carried out. Afterward the larger hole 7 is created in the rear part of the housing, which is then honed and polished. Then the further mechanical machining operations are carried out, for example the radial bore 8 and the like appropriate. Then the car is lifted for the second time,

030027/0643

at a lower pressure that is required for the bore 7 sufficient.

The preferred application of the novel piston pump is the delivery of catalyst solutions to polymerization reactors which operate at very high pressures, for example at pressures above 1750 kg / cm (25,000 psi) up to about 3500 kg / cm (50,000 psi). In such chemical reactions, uniform delivery at a precisely controllable flow rate with minimal pressure fluctuations is very desirable. At lower pressures it appears that the combination of two of the structural units described, which are driven by a suitable, phase-shifted drive, is sufficient. However, at pressures in excess of 1750 kg / cm ² (25,000 psi), the compressibility of the fluids becomes essential, so a combination of three or more piston-cylinder units is preferred.

As an example, a combination of three cylinder arrangements of the same size may be mentioned, each of which as shown in the drawing shown, was built. The piston rod was 3/8 inch in diameter. The piston rods were via a common crankshaft with a stroke of 100 mm (4 inches) for each piston rod and with a phase shift of 60 ° between cylinders 1 and 2 and the Cylinders 2 and 3 driven. This piston pump was tested that a solution of organic peroxides in Hexane solvent was fed at a suction pressure of about 10.5 kg / cm (150 psi) and at a Released reactor pressure of about 2100 kg / cm (30,000 pel) was using a variable speed DC motor as the drive that connected to the crankshaft a reduction gear was connected, the rotational speed of the crankshaft from 10 to 200 revolutions per minute allowed. There were excellent awards associated with

030027/0643

- yf- 10-

unusually accurate dispensing flow rates. The fluctuations in sales pressures seldom exceeded three percent, in particular in the middle range of the rotational speed of the crankshaft from about AO to about 120 revolutions per minute. This area is particularly interesting in practice.

A direct current shunt motor is recommended to drive the new type of piston pump, its speed of rotation can be controlled via the armature voltage, while the field voltage remains constant. The turning speed Such a motor can be regulated very precisely through the use of electrical sensors and feedback circuits that are customary in the trade. Such a speed control is, for example, made by Reliance Electric Company under the name MAXPAK SOLID STATE DC V * S DRIVE.

During the operating time of the new type of piston pump, no signs of wear could be found. The cooling As already mentioned, the housing wall increases the service life of the pressure seal.

It is therefore important for the invention that a high-pressure pump element a piston pump is proposed, which is characterized by a long service life and ease of repair excels. The new type of component is characterized by its high resistance to fatigue and corrosion. The component is suitable for use as a pumping element in a piston pump or plunger pump for pressures that are even greater than 1400 kg / cm (20,000 psi). Such Piston pump can even pump chemically active fluids without significant leaks or delivery fluctuations or Pressure fluctuations and also without excessively high maintenance costs.

030027/0643

The described design of the housing for the working part of the piston rod is essential for this as a thick-walled monoblock cylinder, made of heavy-duty metal alloy, which is connected to the its outer jacket is cooled.

The aforementioned US Pat. No. 3,834,715 corresponds to DE-OS 2,321,250.

030027/0643

-U-

Blank page

Claims (20)

Patent claims or protection claims: 1. ) Piston pump, the high-pressure pump element of which has a structural unit consisting of a cylinder, a piston rod and a ring seal,
marked by a) an elongated, cylindrical piston rod (1) hard material with a high modulus of elasticity, the rear part of which is freely accessible and connecting means (4) for connecting the piston rod to a drive for its back and forth movement, b) a thick-walled housing (5) made of one piece made of a corrosion-resistant alloy of high breaking strength, which surrounds the working part of the piston rod (1) and which has a smooth-walled inner bore (6), which is slightly larger than the diameter of the piston rod and which is axially adjacent from one point the front end of which extends backwards by a length that is slightly greater than the stroke of the piston rod, and a similar, coaxial bore (7) with a directly adjacent to the rear end of this bore much larger diameter, c) an annular one inserted into the larger bore (7) Pressure seal (10), consisting of several flexible, rigid packing rings (11, 13) with good lubricating properties and a follower ring (14) made of hard, essentially non-compliant Material at the rear of the pressure seal, d) an adjustable connection (9, 18) at the rear end of the housing (5) via which pressure is applied to the follower ring (14) can be exercised, which in turn exerts pressure on the packing rings (11, 13), and through G30Q27 / 0643 ORIGINAL INSPECTiID β) a tubular piece (30) surrounding the housing (5) in a ring shape, the wall of which is thinner than that of the housing, wherein an annular space (32) is formed around most of the housing, the end face through Sealing rings (20) is sealed, with an inlet opening (35) and an outlet opening (36) in the pipe section for a coolant are attached. 2. Piston pump according to claim 1,
characterized in that the cylindrical piston rod (1) consists of tungsten carbide. 3. Piston pump according to claim 2,
characterized in that the outside of the piston rod (1) is honed so that a smooth surface with a roughness of less than 14 χ 10 cm (16 microinches) is achieved. 4. Piston pump according to claim 3,
characterized in that the roughness is no greater than about 5 x 10 "cm (2 microinches). 5. Piston pump according to one of claims 1 to 4, characterized in that that the connection for the piston rod (1) with the drive is a collar-shaped connecting element (4) includes, which in the shrink fit around the freely accessible, rear part of the piston rod is put on. 030027/0643 29A9083 6. Piston pump according to one of claims 1 to 5 »characterized in that that the alloy for the housing (3) is made of a highly fatigue-resistant iron alloy consists of at least about 10% by weight of 96 chromium and comprises at least about 4% by weight nickel. 7. Piston pump according to claim 6, characterized in that the alloy also «inen tangible amount of molybdenum and is hardened by precipitation hardening by means of a suitable heat treatment. 8. Piston pump according to one of claims 1 to 7, characterized in that that the alloy of the housing (5) by vacuum arc melting is preserved, whereby discrete foreign bodies are excreted. 9. Piston pump according to one of claims 1 to 8, characterized in that that the two bores (6,7) in the housing (5) have been treated by a high-pressure autofrettage, after all mechanical operations including honing the surfaces of the bores have been carried out. 10. Piston pump according to one of claims 1 to 9 *, characterized in that that the pressure seal (10) has a centrally arranged, has turned ring (12) which has a flat undercut groove (22) of substantial width in the middle part of its outer circumference, with connecting lines (24) the groove (22) with the inner Connect the circumference of the ring at several points and means are provided to pressurize a sealing fluid to feed the groove, and at least one of the 030027/0643 fixed packing rings (11, 13) in the pressure seal in in both directions from the central ring (12) has a substantially zigzag cross-section, all zigzag rings so that their concave ends are aligned with the middle ring (12). 11. Piston pump according to claim 10,
characterized in that the central ring (12) is made of metal and that the solid packing rings (11, 13) are made of a fluorocarbon polymer, nylon or other low coefficient of friction synthetic resin filled with a fine solid filler higher melting point is enhanced. 12. Piston pump according to claim 11,
characterized in that the fine, solid filler material consists of graphite, molybdenum disulfide, carbon, glass fibers and / or finely powdered metals. 13. Piston pump according to one of claims 1 to 12, characterized in that that the adjustable connection has a short end portion at the rear end of the housing (5), which is a Having an internal thread (9), and an annular bushing (18) with an external thread corresponding to the internal thread, so that the front end of the socket can touch the follower ring (14) after it has been pressed in firmly has been, but before the complete contact on the internal thread. 14. Piston pump according to one of claims 1 to 13, characterized in that that the pipe piece (30) has limited sections at both ends which have reduced inner diameters, 030027/0643 so that the pipe piece in a sliding fit on the housing (5) can be pushed on, with low-pressure seals being provided between the housing and the pipe section at the ends are made up of O-rings (21) mounted in circumferential grooves (20) in the housing or in the pipe section are and thereby form the sliding fit. 15. Piston pump according to one of claims 1 to 14, characterized in that that the annulus (32) has a depth of less than about 4.6 mm (1/4 inch). 16. Piston pump according to claim 15, characterized in that the annular space (32) has a depth of about 1.6 to 4.8 mm has (1/16 to 3/16 inch). 17. Piston pump according to one of claims 1 to 16, characterized in that that the inlet connection (35) at a small distance from the face of the rear end of the Ring seal (10) is located, and that the outlet opening (36) is at a small distance from the rear end of the front part of this ring seal is located. 18. Piston pump according to one of claims 1 to 17, characterized in that that several such pump elements are driven by a common crankshaft, which in turn is driven by an electric motor with adjustable rotational speed with a downstream gear. 19. Piston pump according to claim 18, characterized in that that the electric motor is a direct current shunt motor whose speed of rotation is about its armature voltage 03G027 / 06A3 - 6 is controlled. 20. Piston pump according to claim 19 »characterized in that that the speed of rotation of the DC motor over whose armature voltage is regulated within narrow limits. The patent attorney 03 0 027/0643