US3389834A - Chambered pump piston with vent passage - Google Patents

Description

K. L. COLLINS CHAMBERED PUMP PISTON WITH VENT PASSAGE 2 Sheets-Sheet l INVENTOR. KEN/V L. C'flL/Nfi June 25, 1968 Filed Jan. 6, 1967 June 25, 1968 K. L. COLLINS 3,389,834

CHAMBERED PUMP PISTON WITH VENT PASSAGE Filed Jan. 5, 1967 2 Sheets-Sheet 2 INVENTOR. KENNETH L. COLL/IVS United States Patent "ice 3,389,834 CHAMEERED PUMP PISTGN WITH VENT PASSAGE Kenneth L. Collins, Odessa, Tex., assignor to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Fiied Jan. 5, 1967, Ser. No. 607,474 1 Claim. (Cl. 222-133) ABSTRACT OF THE DISCLOSURE Apparatus for injecting solid particles into a conduit containing fluids at high pressure. A piston housing exends from below a hopper for the solid particles into the conduit. A chambered piston having a central portion of reduced diameter between end portions sealingly engaging the walls of the piston housing is adapted to move from a position below the hopper into the conduit. Guide rails extend into the conduit to support the piston as it moves into the conduit.

This invention relates to an improved apparatus for injecting particles into a high pressure fluid stream. More particularly this invention relates to an improved method of transporting particles from a zone of low pressure into a zone of elevated pressure.

During various manufacturing, processing, refining, oil well drilling or oil well work-over operations, it is necessary to inject particles into an area of elevated pressure. Heretofore the principle apparatus utilized to perform this particle injection function has been a reciprocating plunger-type pump. Although plunger-type pumps will function to inject particles into a high pressure fluid stream, their efficiency is seriously decreased and the amount of maintenance increased, owing to the fact that these pumps are constructed to move fluids and not particles.

Reciprocating plunger-type pumps are generally constructed with an intake valve and a discharge valve positioned in front of a reciprocating plunger. The opening and closing sequence of the valves is controlled to open the intake valve and close the discharge valve when the plunger is moving to a retracted position. As the plunger moves to a retracted position, a partial vacuum will be created which will aid in loading the chamber ahead of the pump plunger. When the plunger reaches the limit of its retracted stroke and begins to move forward to an extended position, the intake valve closes and the discharge valve opens the pump chamber in communication with the zone of high pressure.

The operation efficiency of the intake and discharge pump valves is seriously reduced when solid particles suspended in fluid is passed through the high pressure pump. Owing to the hardness and concentration of the particles in the injected fluid, complete closure of a valve is often prevented by the entrapment of particles between the valves and the valve seats. In instances where the injected particles hardness is low, considerable crushing will take place which will degrade the particles from a substantial homogeneous size distribution to a mixture containing a large amount of fines.

This degradation of particle size is often detrimental, especially where particle size control is an essential element of the operation. The presence of fines in the pumped mixture also functions to shorten the operating life of the plunger packing which prevents fluids from flowing in the annulus between the cylinder wall and the plunger. When the plunger packing is destroyed the operation of the pump must be stopped and the packing replaced.

Further pump damage may be caused where the injected particles have highly abrasive properties. Abrasive 3,389,834 Patented June 25, 1968 fines entering the annulus between the cylinder wall and the plun er will not only destroy the pump packing but will often abrade and score the cylinder to the extent a fluid seal cannot be maintained and the cylinder must be replaced. The abrasive characteristics of injected particles will also erode the inlet valve, and particularly the discharge valve, to an extent pumping operation must be stopped and the valves replaced.

In an effort to alleviate these problems, operators generally reduce the speed of reciprocation while particles are being passed through the pump. A reduction in the speed decreases the severity of abrasion but such speed reduction seriously decreases the pumps output efflciency.

Another heretofore employed method of injecting particles into a high pressure stream is to install a series of particle hoppers downstream of the high pressure pumps and deliver particles from the hoppers, through transfer cases, and to the high pressure stream. In such an arrangement by-pass valving must be installed to isolate a particle hopper for filling. Owing to the high pressure on the particles in the hopper, uniform delivery of the particles into the high pressure stream is also difiicult to achieve.

My invention will materially increase the efficiency, decrease the maintenance, and simplify the operation of injecting particles into a zone of high pressure. My invention resides in a material injector having a piston housing in communication with a high pressure fluid stream and a particle hopper containing particles to be injected. A piston, slidably mounted within the piston housing, has a first end separated from a second end of the piston by a portion of the piston having a smaller cross sectional area of the first or the second end thereby forming a piston chamber. Sealing means are mounted on the outer periphery of the first and second end of the piston to prevent the flow of fluid through the annulus formed between the piston body and the inner Wall of the piston housing. A particle hopper is connected to and in communication with the inner chamber of the piston housing. A piston rod passes through the piston housing and is connected to the inner end of the piston. A power source operates through the piston rod to reciprocate the piston, and hence the piston chamber, to deliver particles from the hopper into the high pressure fluid stream.

In the drawings:

FIGURE 1 is a diagrammatic elevation view partially in vertical cross section of a preferred embodiment of the mixing tank and particle injection apparatus of this invention.

FIGURE 2 is a horizontal cross section, taken along line 11-11 of FIGURE 1, of the mixing tank and particle injection apparatus of this invention.

FIGURES 3 and 4 are horizontal cross sectional views taken along lines IlI-III and IV-IV of FIGURE 2, of the mixing tank and the particle injection apparatus of this invention during various stages of operation.

FIGURE 5 is a horizontal cross sectional view taken along line VV of FIGURE 2 showing a conduit and the apparatus of this invention during another stage of operation.

Referring to FIGURE 1, a mixing tank 2 having an inlet 4- and an outlet, best illustrated as number 5 of FIGURE 2, is installed in a high pressure fluid stream line (not shown) and is attached to a piston housing 6 of this invention. A particle hopper 8 is attached to a regulating valve 7 mounted on the piston housing 6 and in communication with the inner chamber of said piston housing 6, to provide a container for particles which will gravitationally feed into the inner chamber of said housing. A piston rod 10 connected to a power source (not shown) passes through a packing gland 12 into the piston housing 6 and is attached on its inner end to a slidably mounted chambered piston, as shown in FIGURE 2. A fluid relief valve 14 is attached to the bottom of the piston housing 6 at a lateral position between the mixing tank 2 and the particle hopper 8 to release the fluid trapped in the piston chamber 29 during its travel toward the retracted position.

Referring to FIGURE 2, the chambered piston is constructed of two piston bodies: a short front piston body 15', which enters the high pressure fluid stream, and a longer back piston body 18 which reciprocates within the piston housing 6 and seals the particle hopper 8 as the chambered piston slides forward into the high pressure stream.

These two piston bodies 18, 19 are connected by a piston support member 21 which has a cross sectional area less than the cross sectional areas of the piston bodies 18, 19, thereby forming a piston chamber 20 between the piston bodies 18, 19. These two piston bodies 18, 19 connected by piston support member 21 are collectively referred to in this application as a chambered piston.

Aithough the chambered piston may be manufactured from a single piece of stock by removing metal to form the chamber, it is preferred that the chambered piston be constructed of two separate bodies which are detachable. By so constructing the chambered piston, the forward piston body, which enters the high pressure fluid stream and is most likely to be damaged, may be replaced without replacing the entire chambered piston.

In regard to the sealing elements 24 which are mounted on the periphery of both the first and second piston body, it is essential that suflicient sealing elements 24 are installed on each piston body 18, 19 to prevent the passage of fluid between each piston body and the inside wall of the piston housing during reciprocation of the chambered piston.

Referring to FIGURE 3, the sealing elements 24 on the outer periphery of the front piston body 19 are sealing the passage of fluid from the high pressure stream into the particle hopper 8. In the pisto ns extended position, referring to FIGURE 4, the sealing elements 24 on the outer periphery of the back piston body 18 are sealing the passage of fluid from the high pressure stream into communication with the particle hopper 8 and the fluid relief valve 14. Referring to FIGURE 5, wherein the piston is located at an intermediate stage, the sealing elements 24 of the front piston body 19 are sealing the high pressure fluid stream from communicating with the fluid relief valve 14.

By so sealing the chambered piston, particles within the hopper will not be subjected to the high pressure of the fluid stream. Particle break up is thereby significantly reduced by eliminating pressure feed of particles, as heretofore employed. Because the particles in the bottom of the material hopper are not held in a static position by large pressures, the closing action of the extending piston will seldom shear or entrap and crush individual particles. As the piston closes the hopper opening, individual particles will generally move either back into the hopper or into the chamber of the piston thereby avoiding crushing of a considerable number of the particles. Avoiding a large amount of particle crushing gives the operator greater control of particle size concentration in the fluid stream and decreases the amount of piston and packing damage caused by fines.

FIGURES '3, 4 and 5 diagrammatically indicate respectively the fill position, injection position, and the fluid release position of the piston 18 of this invention.

Referring to FIGURE 3, the chambered piston is p0- sitioned in the retracted position wherein the chambered piston has traveled to its rearward limit thereby positioning the piston chamber 20 directly beneath the outlet of the par icle hopper 8. Particles contained in the particle hopper gravitationally feed into and fill the piston cham ber 20. The fluid relief valve 14 is closed by the piston body 19 and sealed by the sealing elements 24 mounted on the piston body 19 thereby preventing the high pressure fluid stream from communicating with the particle hopper 8.

Referring to FIGURE 4, the chambered piston is in its extended position wherein the chambered piston has traveled to its forward limit thereby positioning the piston chamber 20 within the high pressure fluid stream flowing through the mixing tank 2. The fluid stream washes the entrapped particles from the chamber 20 and carries them downstream through the outlet, best illustrated in FIGURE 2. The piston body 18, with sealing elements 24 mounted thereon, is located within the piston housing 6 and seals the particle hopper 8 and the fluid relief valve 14 from the high pressure fluid stream.

Referring to FIGURE 5, the chambered piston has moved toward its retracted position to a position wherein the piston chamber 20 is adjacent the fluid relief valve 14. The high pressure fluid trapped within the piston chamber 20 actuates the fluid relief valve 14 and allows the entrapped fluid to be discharged from the piston chamber 20. After the piston chamber 20 is empty it is in a condition to be refilled with particles from the particle hopper 8.

In order to substantially void the chamber when the high pressure fluid is liquid, it is preferred that the valve be laterally positioned on the piston housing between the hopper and the mixing tank or conduit and at a lateral distance between the valve and the hopper less than the lateral distance spanned by the chamber of the piston. By so positioning the fluid relief valve, the valve opens upon first communication with the chamber and reduces the pressure within the chamber to atmosphere pressure. At the instant the chamber of the piston spans both the hopper opening and the valve opening, air enters the chamber from the hopper and allows substantially all the liquid to drain from the chamber before the fluid relief valve is closed by the compression spring contained therein. The empty chamber of the valve subsequently continues to travel to a retracted position wherein the hopper inlet will be fully open into the material hopper and a new filling cycle will begin.

Under conditions which dictate the need for more than one injector to accomplish the desired particle concentration per volume of fluid, the operator may install any desired number of injectors. It is preferred however that where more than one injector is utilized, the injectors should be installed in sets, as shown in FIGURE 2, with two injectors 16 in each set.

The timing and synchronization of operation of each piston in a single set should be 180 opposed to each other. By timing the pistons to reciprocate 180 from each other in a single set, considerable power advantage is realized. The high pressure fluid applies a force to drive the first piston to a retracted position while the second piston of the set is operating against the force. Where the power source operates through a bell crank, common to both piston-s of a set, the forces counteract each other and the power source merely operates to overcome friction resistance. The operation timing from set to set will be governed by the type of power source and whether the operator desires continuous or intermittent power source loading.

It is preferred in this invention that a mixing tank be installed in the high pressure fluid conduit in such a manner that fluid entering the mixing tank will sweep longitudinally through the tank at a 90 angle to the reciprocating direction of the piston. Constructing the mixing tank in this manner enables the fluid stream to more readily remove particles from the piston chamber. Particles suspended in the fluid stream also have less chance to settle out and remain within the mixing tank when the particles do not change flow directions before they are discharged from the mixing tank and are moved into the high pressure conduit.

In certain facilities, space limitations may make it impossible to install a large diameter mixing tank in the high pressure conduit. In such instances the injectors of this invention may be directly installed on the conduit, as shown in FIGURE 5, without using a mixing tank.

Piston guide rails 22, as best shown in FIGURE 2, preferably extend from the piston housing into the fluid stream. The rails will function to stabilize the travel of the piston and facilitate re-entry of the forward portion of the piston into the piston housing.

The type of particles or materials injected 'by the apparatus of this invention is restricted only to materials which will gravitationally feed from the material hopper into the piston chamber. Common examples of such materials are sand, gravel, coal, glass beads, wood pulp, clay minerals and pellets.

My invention will thereby function to transport materials from a location of lower pressure into a fluid stream of high pressure without subjecting the material hopper to high pressure and with pump and particle damage decreased over methods heretofore employed.

Therefore I claim:

1. Apparatus for injecting particles from a particle hopper into a high pressure fluid stream without subjecting the particle hopper to high pressure fluid comprising:

a mixing tank traversed by the high pressure fluid stream;

a piston housing having an inner chamber connected to and in communication with the mixing tank;

a particle hopper connected to and in communication with the piston housing and positioned at a higher elevation than the piston housing;

piston guide rails attached to the piston housing and extending into the mixing tank;

a piston, slidably mounted Within the piston housing, having a first end and a second end with a chamber formed between said first and second piston ends;

sealing means mounted on the outer periphery of the first end of the piston to prevent the flow of fluid between the inner wall of the piston housing and the first end of the piston;

sealing means mounted on the outer periphery of the second end of the piston to prevent the flow of fluid between the inner wall of the piston housing and the second end of the piston;

a fluid relief valve connected to and in communication with the piston housing, positioned at a lower elevation than the piston housing and located between the mixing tank and the particle hopper at a distance from the particle hopper less than the length of the chamber between the first and second ends of the piston;

a piston rod passing through the piston housing connected to the second end of the piston and adapted to reciprocate the piston from a first position wherein the piston chamber is beneath the particle hopper and particles may gravitationally move from the particle hopper into the piston chamber, to a second posit-ion wherein the piston chamber is substantially within the mixing tank and particles held in the piston cham ber may be washed from the piston chamber and to a third position wherein the piston chamber is in communication with the fluid relief valve and fluid may discharge from the piston chamber through the fluid relief valve and to a fourth position wherein the piston chamber is in communication with the fluid relief valve and the particle hopper and air may flow from the particle hopper, through the piston chamber and through the fluid relief valve.

References Cited UNITED STATES PATENTS SAMUEL F. COLEMAN, Primary Examiner.

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