1. Field of the Invention
The present invention relates to fluid pump assemblies and, more particularly, to modular pump assemblies having a fluid pump A fluid activated motor for driving the fluid pump, and a precision adjustment unit for finely adjusting an output pressure.
2. Description of Related Art
Various fluid pump assemblies have been developed to pump fluid into a test vessel to test the integrity of a vessel by raising and sustaining the pressure therein to a proof pressure for a prescribed period of time. The fluid pump assembly developed has a piston assembly reciprocally mounted within a cylinder which is supplied with compressed air to pump fluid into the vessel being tested. The air is provided until the vessel reaches a predetermined pressure. However, existing fluid pump assemblies may not be sufficiently precise to accommodate stringent testing standards for pressure vessels, such as for example, the recent narrowing of a pressure range in which fire extinguishers are tested.
Accordingly, there is a need for an improved fluid driven pump which can bring a vessel within a narrow pressure range and maintain the pressure vessel within the pressure range for a prescribed time period.
The present invention provides a pressure testing apparatus and method for pressure testing a vessel. According to the present invention, the apparatus includes a pump and a precision adjustment unit connected at an outlet side of the pump. The precision adjustment unit includes a chamber and a piston assembly movably disposed in the chamber to vary the fluid volume of the chamber. Additionally, the precision adjustment unit can be connected to an intermediate position of a conduit which is connected to the outlet side of the pump. The piston assembly is comprised of an adjuster piston, an adjustment bar having a proximal end operably attached to the adjuster piston and a handle operably attached to the distal end of the adjustment bar. The adjuster piston can be moved by rotating the handle.
According to a first embodiment of the present invention, the apparatus includes an air-driven pump, a fluid pump and a precision adjustment unit. The air-driven pump is similar to the pump disclosed in U.S. Pat. No. 5,626,467 which is herein incorporated by reference. The air-driven pump includes an air motor, a motor cylinder within the air motor, a motor piston within the motor cylinder, and an air control system. The air control system supplies air from an air inlet to the motor cylinder alternately on each side of the motor piston while venting the motor cylinder on an opposite side of the motor piston to an air outlet to reciprocate the motor piston in the motor cylinder. The fluid pump is operably connected to the air motor and includes a pump cylinder and a pump piston within the pump cylinder. The pump piston is connected to the motor piston for reciprocable movement of the pump piston with the motor piston. The precision adjustment unit is connected at the fluid pump. The precision adjustment unit includes a chamber and a piston assembly to vary the fluid volume of the chamber.
According to an aspect of the present invention, the precision adjustment unit is connected at an outlet side of the fluid pump. The connection can be directly to the fluid pump, or indirectly through a conduit.
According to another aspect of the present invention, the precision adjustment unit includes a piston assembly movably disposed within the chamber. The piston assembly is further comprised of an adjustment bar having a handle so that the adjuster piston can be moved by rotating the handle. Further, the pressure test apparatus can include a manual air valve so that the air motor is supplied air only when the manual air valve is activated.
According to another embodiment of the present invention, the pressure testing apparatus includes an air-driven pump, a fluid pump and precision adjustment unit. The air-driven pump includes an air motor, a motor cylinder within the air motor, a motor piston within the motor cylinder, a shaft connected at its proximal end to the motor piston with the distal end of the shaft extending externally beyond the motor cylinder, and an air control system. The air control system supplies air from an air inlet to the motor cylinder alternately on each side of the motor piston while venting the motor cylinder on an opposite side of the motor piston to an air outlet to reciprocate the motor piston and the shaft in the motor cylinder. The fluid pump is operably connected to the air motor and includes a pump cylinder and a pump piston within the pump cylinder. The pump piston is connected to the motor piston for reciprocable movement of the pump piston with the motor piston. The precision adjustment unit is connected to the air motor and includes an adjustment bar having a first end removably connectable to the distal end of the shaft and a second end connected to a handle to allow manual adjustment of the position of the adjustment bar. Movement of the adjustment bar can impart movement to the shaft.
According to another aspect of the invention, the pressure testing apparatus further includes a bleeder valve to manually release air from the distal side of the cylinder, thereby producing a greater range of adjusting the pressure in the vessel. Still further, the pressure testing apparatus can be provided with an air valve connected to the air motor such that the air motor is supplied air only when the air valve is activated.
According to the method of the present invention, a precision adjustment unit is connected at a pump. A vessel is connected at an outlet side of the pump. The pump is operated until a predetermined pressure is reached within the vessel. Then the precision adjustment unit is operated until a proof pressure is reached within the vessel. The precision adjustment unit is periodically operated as necessary to maintain the vessel within the proof pressure range for a prescribed period of time. Additionally, the precision adjustment unit can be adjusted manually by turning a handle. Further, the precision adjustment unit can be connected at the outlet side of the pump. Still further, the precision adjustment unit can be integrally connected to the pump.
According to an aspect of the method, an air-driven pump having an air motor and a fluid pump, and a precision adjustment unit are provided. The precision adjustment unit is connected at the air-driven pump. A vessel is connected at an outlet of the fluid pump. Fluid is provided to an inlet of the fluid pump and air is provided to an air inlet of the air motor. When air is provided to the air motor, a piston within the air motor reciprocates until a predetermined pressure is reached within the vessel. Thereafter, the precision adjustment unit is adjusted until a proof pressure within the vessel is reached within a proof pressure range. The pressure within the vessel is maintained within the proof pressure range for a desired period of time by adjusting the precision adjustment unit as necessary.
According to another aspect of the method, a manual air valve is connected to the air inlet and provides air to reciprocate the motor piston until the predetermined pressure is reached within the vessel.
According to a further aspect of the method, the precision adjustment unit is connected at the outlet side of the fluid pump.
An alternative aspect of the method provides the precision adjustment unit integrally connected to the air motor. A valve can be connected to the air motor to release air from the distal side of the cylinder within the air motor. Operating the valve causes the motor piston to retract to allow sufficient piston travel so that proof pressure can be reached and maintained.