MXPA00008566A

MXPA00008566A - Progressive cavity pump with meltable stator

Info

Publication number: MXPA00008566A
Application number: MXPA/A/2000/008566A
Authority: MX
Inventors: M Osborne Alfred
Original assignee: Dyno Nobel Inc
Priority date: 1999-11-03
Filing date: 2000-09-01
Publication date: 2001-12-04

Abstract

The invention comprises a progressive cavity pump for pumping a flowable explosive composition or other heat-sensitive material comprising an inlet and an outlet;a stator that is meltable at or above a selected maximum pump operation temperature;a rotor, and a drive shaft connecting the rotor to a power source;wherein the stator will melt above the selected temperature to prevent the generation of temperatures within the pump high enough to create a hazard. The invention also relates to a method of safely pumping a flowable explosive composition or other heat-sensitive material comprising the use of a progressive cavity pump having a stator that is meltable above a selected maximum pump operation temperature for the similar result.

Description

"PROGRESSIVE CAVITY PUMP WITH FUSE STATOR" The present invention relates to a novel pump for pumping a fluent explosive composition or other heat sensitive material, and more particularly to a progressive cavity pump for this purpose. The present invention also relates to a novel method for safely pumping a fluent explosive composition or other heat-sensitive material. A progressive cavity pump is well understood to imply a rotary positive displacement pump in which a helical rotor shaft is rotated within a stationary stator. The stator is composed of a resilient material and has a real longitudinal cavity defining a helical groove. When it is rotated inside the stator cavity, the rotor makes contact with the stator to form a series of cavities that move in an axial direction thus forcing the pumped medium progressively along the axis towards the pump outlet . In the present invention, a fusible stator is provided which will begin to melt at a predetermined elevated temperature, so that the pressure and frictional heating inside the pump will be reduced or released in order to prevent degradation or high temperature reactions.

- "Fe. i - F * - R-harmful or unsafe of the pumped explosive composition or other heat-sensitive material, Because the explosive compositions are sensitive to heat, pressure, friction and shock, the pumping of these Compositions must be carried out in a manner to eliminate the presence or creation of hazardous conditions caused by exceeding the safe limits for these variables. For example, in a progressive cavity pump, there is internal friction between the rotor and the stator, and this friction continuously generates heat during the pumping operation. The amount of heat generated is usually small enough so that it can simply be transferred to and dissipated within the composition being pumped, without heating the composition to an undesirable temperature. When there is little or no flow in the pump due to a closed or restricted outlet or lack of flow of the composition towards the inlet, however, friction or friction heat can accumulate in the rotor and stator itself, which after a time period, it can become hot enough and can transfer enough heat to the composition to cause it to ignite. Some approaches have been used or suggested to address this pumping problem of explosive composition. The safety work stop systems are used which electronically monitor the temperature and pressure parameters in various places in or near the pump, so that if these conditions exceed the determined maximum limits, the systems will automatically stop the operation of the bomb. Another approach has been to provide a connection between the drive shaft of the pump and the rotor that compresses a heat-sensitive release bond of a thermal-fuse metal alloy, the connection of the metal alloy being fused during the generation of heat inside. of the pump cavity in order to disconnect the mechanical linkage between the driving shaft and the rotor. Despite these previous approaches, there is a need for a reliable, simple, fail-safe and economical means to prevent overheating of a progressive cavity pump that is pumping explosive compositions or other heat-sensitive materials. The present invention meets this need by providing a fusible elastomeric stator, having a melting temperature at a predetermined level above the normal or desired operating temperature of the pump but lower than the thermal reaction temperature of the explosive composition or material sensitive to the heat that is being pumped. This stator melting causes the heat buildup to cease so that the temperature inside the pump decreases and becomes essentially constant at a temperature lower than the thermal reaction temperature of the explosive composition or other material. In this way, the temperature of the pump simply can not be increased above the unwanted thermal reaction temperature, because the fusible stator no longer provides any resistance and therefore no friction to the rotating rotor. The fusion occurs naturally and simply as the result of the increase in temperature in the pump, and thus does not depend on external controls or monitors. Another advantage of the fusible stator is that it can be easily and inexpensively retrofitted to existing pumps that are used to pump heat-sensitive materials. In this way, the present invention provides an important safety improvement to progressive cavity pumps that are used to pump explosive compositions and other heat sensitive materials. In summary, the invention comprises a progessive cavity pump for pumping a fluent explosive composition or other heat-sensitive material comprising an inlet and an outlet; a stator that is capable of melting at or above a selected maximum pump operating temperature; a rotor, and a driving arrow that connects the rotor with a power source; where the stator will melt above the selected temperature to prevent the generation of temperatures within the pump high enough to create a hazard. The invention also relates to a method for safely pumping a fluent explosive composition or other heat sensitive material comprising the use of a progressive cavity pump having a stator that is capable of melting above a pump operating temperature. maximum selected for the similar result. In the drawings, Figure 1 is a longitudinal cross-sectional view of a typical progressive cavity pump, and Figure 2 is a graphic illustration of the tests carried out on a progressive cavity pump of the present invention. Referring to Figure 1, which is shown in a longitudinal cross-sectional view of a typical progressive cavity pump, generally indicated at 1. The pump 1 has a driving shaft support box 2, a driving shaft 3 which connects with a power source (not shown), an inlet 4, an outlet 5, a stator 6 and a rotor 7. In the embodiment shown, the driving shaft 3 is flexible and rotates rotationally due to both the rotational force supplied by the power source as the eccentric shape of the rotor 7 in which the driving shaft 3 is connected, in the position 8. Preferably, the flexible driving shaft 3 is directly coupled with the driving shaft of a hydraulic motor power source (not shown). This eliminates the need for pump drive bearings that could be another potential source of heat if the bearings fail. In this way, the hydraulic motor bearings are used as the bearings of the pump 1, and since these bearings are continuously cooled by the flow of the hydraulic oil passing through the motor, the bearings do not become a source of heat potential. During operation, the rotation of the flexible arrow 3 in turn causes the rotor 7 to rotate, thereby forcing the pumped medium (which enters the inlet 4) through the cavities defined by the assembly of the rotor 7 and the stator 6 and then out of the outlet 5. For purposes of the present invention, the key and novel component of the pump 1 is the stator 6. The stator 6 is resilient and preferably comprises a thermal plastic elastomer, which preferably it is selected from the group consisting of urethanes, thermal plastic rubbers and thermal plastic polyolefins. A preferred urethane is a polyester-polyether blend obtainable from the Anderson Development Company, of Adrián, MI, as Andur 700-AP, and as described further in U.S. Patent Number 4,182,898. A preferred polyolefin is polyethylene. For pumping most of the explosive compositions, the operating temperature of the maximum pump for safety reasons is from about 140 ° C to about 150 ° C. Correspondingly, the stator has a melting temperature of about 140 ° C to about 150 ° C. If for any reason the operating temperature of the pump rises beyond this scale, the stator will start to melt and thus prevent the operating temperature from rising further. (In fact, the temperature will usually begin to decrease). If the thermal reaction temperature of the explosive composition or of the heat sensitive material being pumped is above this operating temperature of the pump or melting, then the explosive composition or material will not reach a temperature high enough to react thermally to create a safety risk. Preferably, the operating temperature of the selected maximum pump is at least 10 ° C above the crystallization or solidification temperature of the explosive composition being pumped, and most preferably at least 20 ° C higher. The following example further illustrates the present invention. A progressive cavity pump was intentionally operated in a manner for no-return return flight while an explosive water-in-oil emulsion composition is pumped. Initially, the pump was filled with hot emulsion explosive and was operated slowly with the outlet open. After a few minutes, the pump was caused to return without load, creating a pressure of more than 35.15 kilograms square centimeter and a temperature that reaches 140 ° C. At or about 140 ° C, the stator of the thermoplastic elastomer (urethane) (Andur 700-AP) began to melt, thereby releasing the pressure, and after 1 hour, the initial temperature of the pump had dropped from 140. ° C to 80 ° C and the pressure had decreased from more than 35.15 kilograms per centimeter to 2.81 kilograms per square centimeter. No burning or scorching occurred to the continuous oil (fuel) phase of the emulsion, and no decomposition occurred in the internal droplets of the oxidizing solution. This test is illustrated graphically in Figure 2. While this invention is illustrated and described with reference to modalities that have been proposed at present as the best way or modes to carry out this invention in actual practice, it will be understood that Various changes can be made by adapting the invention to the different embodiments without departing from the broader concepts of the invention disclosed herein and which are encompassed by the claims which will be given below.

Claims

CLAIMS:

1. A progressive cavity pump for pumping a fluent explosive composition or other heat sensitive material comprising: (a) an inlet and an outlet; (b) a stator that is capable of melting at or above an operating temperature of the selected maximum pump; (c) a rotor, and (d) a driving shaft that connects the rotor to a power source; where the stator will melt above the selected temperature to prevent the generation of temperatures inside the pump high enough to create a risk of explosion.

2. A progressive cavity pump according to claim 1, wherein the stator is a thermoplastic elastomer.

3. A progressive cavity pump according to claim 2, wherein the thermoplastic elastomer is selected from the group consisting of urethanes, thermoplastic rubbers and thermoplastic polyolefins. "^ ¿" "'

4. A progressive cavity pump according to claim 3, wherein the urethane is a polyester-polyether -.- and

5. A progressive cavity pump according to claim 3, wherein the thermoplastic polyolefin is polyethylene.

6. A progressive cavity pump according to claim 1, wherein the driving shaft is flexible and is directly coupled with a driving shaft of a hydraulic motor power source.

A progressive cavity pump for pumping an explosive composition according to claim 1, wherein the operating temperature of the selected maximum pump is from about 140 ° C to about 150 ° C.

8. A progressive cavity pump according to claim 7, wherein the stator is a thermoplastic elastomer having a melting temperature of about 140 ° C to about 150 ° C.

9. A progressive cavity pump according to claim 8, wherein the thermoplastic elastomer is selected from the group consisting of urethanes, thermoplastic rubbers and thermoplastic polyolefins.

10. A progressive cavity pump according to claim 8, wherein the urethane is a polyester-polyether mixture.

11. A progressive cavity pump according to claim 8, wherein the thermoplastic polyolefin is polyethylene.

12. A method for safely pumping a fluent explosive composition or other heat sensitive material comprising the use of a progressive cavity pump having a stator that is capable of melting above an operating temperature of the selected maximum pump of such that the stator will melt if the operating temperature of the pump exceeds the selected temperature to prevent the generation of temperatures inside the pump high enough to create a risk of explosion.

13. A method according to claim 12, wherein the stator is a thermoplastic elastomer.

A method according to claim 12, wherein the thermoplastic elastomer is selected from the group consisting of urethanes, thermoplastic rubbers and thermoplastic polyolefins.

15. A method according to claim 12, wherein the urethane is a polyester-polyether mixture.

16. A method according to claim 12, wherein the thermoplastic polyolefin is polyethylene.

17. A method according to claim 12, wherein the pump has a driving shaft that is flexible and that engages directly with a driving shaft of a hydraulic motor power source.

18. A method for pumping a fluent explosive composition according to claim 12, wherein the operating temperature of the selected maximum pump is from about 140 ° C to about 150 ° C.

A method for pumping a fluent explosive composition according to claim 18, wherein the stator is a thermoplastic elastomer having a melting temperature of about 140 ° C to about 150 ° C.

20. A method according to claim 18, wherein the thermoplastic elastomer is selected from the group consisting of urethanes, thermoplastic rubbers and thermoplastic polyolefins.

21. A method for safely pumping a fluent explosive composition according to claim 12, wherein the operating temperature of the selected maximum pump is at least 10 ° C above the crystallization or solidification temperature of the explosive composition.

22. A method according to claim 21, wherein the operating temperature of the selected maximum pump is at least 20 ° C above the crystallization or solidification temperature of the explosive composition.

23. A method for safely pumping a fluent heat sensitive material according to claim 21, wherein the operating temperature of the selected maximum pump is above the normal operating temperature for pumping this material. _- _¡_