Liner retainer assembly

Details Liner retainer assembly Liner retainer assembly

1998-09-03

2001-04-03

Look, Edward K. (Department: 3745)

Expansible chamber devices

With assembly or disassembly facilitating means

C092S171100

Reexamination Certificate

active

06209445

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an assembly for quickly securing and releasing a component to a pump housing and more particularly to a retainer assembly for releasably mounting a piston liner within a hydraulic cylinder on the module of a pump.
2. Description of the Prior Art
Heavy duty large horsepower pumps are used to pump fluids or slurries with entrained solids. In the oil industry, for example, slush or mud pumps are used to pump viscous fluids, such as drilling muds, cement, or other well fluids. Although mud pumps may be either centrifugal or reciprocating type pumps, typically mud pumps are reciprocating pumps using one or more pistons and hydraulic cylinders with liners to generate the high pressures required to pump these viscous fluids in and out of the well.
Mud pumps include a fluid end and a power end. In the fluid end of one type of a triplex mud pump, for example, there are three sets of suction modules and discharge modules in fluid communication. A suction manifold is connected to the fluid inlets of the suction modules for receiving fluids and passing those fluids to each of the suction modules. A discharge manifold is connected to the fluid outlets of the discharge modules for discharging the pumped fluids. Each module encloses a set of flow passages with check valves for controlling the direction of flow of the fluids. A check valve is disposed at the suction module fluid inlet to only allow fluids to enter the suction module inlet end of the module and another check valve is disposed at the discharge module fluid outlet to only allow fluids to exit the the discharge module for flow into the discharge manifold.
Each discharge module includes a liner retainer flange attached to the discharge module. The liner retainer flange attaches to a replaceable liner within which a pump piston reciprocates. The piston is a generally cylindrical steel member having a polymer, such as polyurethane, bonded to its outer diameter for sealingly engaging the inner cylindrical wall of the liner to ensure a fluid tight seal required for drawing the low pressure fluids through the suction manifold and module flow passages. The seal integrity must be maintained to withstand the high discharge pressure on the discharge stroke. The power end contains the gears that reciprocate the pump piston within the liner for pumping the fluid through the module passages in the fluid end and thence out the discharge valve.
In operation, on the suction stroke, the pump piston draws fluids through the suction manifold and suction valve as the piston strokes within the liner. On the discharge stroke, the check valve in the discharge module opens simultaneously as the suction valve closes preventing suction back flow into the suction module. Fluid in the liner is compressed and pressure is built up until the pressure overcomes well bore pressure so as to pump the mud into the well. The piston then reverses for another suction stroke whereby the check valve in the suction module opens and the discharge valve closes simultaneously, the piston now making a suction stroke.
As the piston reciprocates within the liner, friction wears the liner. Further, the fluid passing through the fluid end includes particulates and other solids which wear away and destroy the liner and piston. When the liner and piston degrade, the fluid seal is lost and the pump becomes much less efficient. Also, the reciprocation of the piston in the liner causes pulsations that over time cause the liner to become loose within the containment of the liner retainer flange thus resulting in a degradation of the seal at the face of the liner and the seal at the face of the liner wear plate. Therefore, it is important to be able to replace the liner as a part of routine maintenance (or when emergencies occur from seal failure while drilling) to ensure that the pump operates efficiently and can control well pressure. It is also important to have a means for fastening the liner to the liner retainer flange so as to ensure that the liner remains firmly secured despite extended reciprocation of the piston assembly within the liner.
Typically each liner retainer flange, and the cradle of the pump power end are all secured to the fluid end module by studs and threaded connections. Because of the environment in which the mud pump operates and the corrosive nature of the fluids being pumped, the studs and threaded connections, such as nuts, become corroded and are difficult to unthread for the replacement of the liner. Often, the threaded connections have been over tightened, making it even more difficult to unthread. Where the liner is retained by an end cap, a steel bar is inserted into a guide hole in the side of the end cap and then the cap is unscrewed using a significant amount of torque. This end cap is very heavy as it must have sufficient strength to keep the liner from moving, even with pressures up to 7500 psi. Where a nut or end cap resists unscrewing, a sledge hammer is used to hammer on a socket wrench or a special hammer wrench is used to loosen the nut or cap. Such activity is obviously dangerous. In some regions of the world local laws prohibit the use of sledge hammers for personnel safety reasons or to avoid the risk of an explosion due to sparks.
Prior art liner retention systems include spring mechanisms around each stud with an end flange for securing the liner against a fluid end module. Hydraulic pressure is applied to the spring mechanism of each stud by a small hydraulic pump to remove the clamping force of the spring mechanism. The release of the clamping force allows the removal of the clamping flange of the liner retention system. Individually actuated spring loaded studs cause an uneven pressure to be applied to the clamping flange. Further, the clamping force is limited because of the limited space available to hold numerous springs.
The present invention overcomes the deficiencies of the prior art.
SUMMARY OF THE INVENTION
The liner retainer assembly of the present invention includes a liner retainer flange that is mounted on the discharge module of the fluid end of a pump. A pressure actuated hydraulic clamping piston with related actuated, conical dished washers and necessary static and sliding seals is disposed within the retainer flange . The hydraulic pressure actuated clamping piston is configured to receive and hold the liner. The hydraulic clamping piston and an end cap maintain the liner in contact with the module during actuation. The hydraulic clamping cylinder includes a counterbore which is divided by the hydraulic piston into a fluid cavity and a spring cavity. The spring cavity houses a plurality of springs which bias the hydraulic piston, end cap, and liner towards the module, thus providing a strong clamping securing force when the hydraulic pressure is released. The fluid cavity communicates with a supply of hydraulic fluid for biasing the hydraulic piston away from the module to activate the springs. By pressurizing the fluid cavity, the springs are compressed so as to disengage the liner retaining end cap from the liner and allow the unthreading of the liner end cap to then remove the liner.
The liner retainer assembly permits preloading or prestressing of the liner against the module of the fluid end of the pump so that the liner will not loosen upon the reciprocation of the pump piston within the liner. Further, the liner may be easily secured and unsecured from the module without the necessity of a sledge hammer or other methods for applying excessive amounts of torque to a securing fitting. The assembly of the present invention permits the easy and quick replacement of the liner as necessary.
Other objects and advantages of the invention will appear from the following description.


REFERENCES:
patent: 2650868 (1953-09-01), Waldron
patent: 2717186 (1955-09-01), Campbell
patent: 2732809 (1956-01-01), Mattingly et al.
patent: 2981575 (1961-04-01), Leman
patent: 3008429 (1961-11-01), Stahl et al.
patent: 3037460 (1962-06-01), Guest et al.
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