US3640585A

US3640585A - Maintenance of slurry explosive pumping assembly for successive loadings

Info

Publication number: US3640585A
Application number: US844114A
Authority: US
Inventors: John F Hamilton; Donald J Pederson
Original assignee: Hercules LLC
Current assignee: Ireco Inc
Priority date: 1969-07-23
Filing date: 1969-07-23
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08

Abstract

The invention provides method, and system, for automatically removing residual slurry explosive from a delivery conduit, or hose, of a slurry explosive pumping-loading assembly, after each loading, to maintain the assembly operable during a series of successive loadings. Thus, after the loading, residual slurry explosive is evacuated from the delivery hose while the hose remains extended into the emplacement zone and into the resulting mass of emplaced explosive therein, by introducing a gas (generally air) into the hose for displacement of the residual slurry into the emplaced slurry mass, and automatically terminating introduction of said gas into the hose in response to addition of a predetermined amount of the gas sufficient for the displacement. The system includes means for introduction of the displacement gas into the hose, and means for maintaining the gas in displacement flow; and means for terminating the gas introduction in response to addition of the predetermined displacing amount. In preferred practice, and as specifically illustrated, the invention terminates the gas flow in response to expiration of a predetermined time required for the displacement. The invention, by automatic termination of the displacement gas flow, eliminates human error inherent in manual operation to prevent concomitant, and often violent, flow of excess displacement gas into the emplaced slurry and to thereby eliminate resulting impairment of the emplaced explosive properties encountered in manual operation heretofore.

Description

United States Patent Hamilton et al.

[ Feb. 8, 1972 MAINTENANCE OF SLURRY EXPLOSIVE PUMPING ASSEMBLY FOR SUCCESSIVE LOADINGS John F. Hamilton, Wilmington, DeL; Donald J. Pederson, St. Louis, Minn.

Assignee: Hercules Incorporated, Wilmington, Del.

Filed: July 23, 1969 Appl.No.: 844,114

Inventors:

US. CL ..302/17, 302/66 FieldoiSearch ..302/l7, 55, 53,66

[56] References Cited UNITED STATES PATENTS 2,576,543 11/1951 Smith ..302/17 2,660,034 11/1953 Kemper ..302/l7 Primary Examiner-Andres H. Nielsen AttorneyS. Grant Stewart [57] ABSTRACT The invention provides method, and system, for automatically removing residual slurry explosive from a delivery conduit, or

FROM MIXING STATION AIR i IOO PSI hose, of a slurry explosive pumping-loading assembly, after each loading, to maintain the assembly operable during a series of successive loadings.

The system includes means for introduction of the displacement gas into the hose, and means for maintaining the gas in displacement flow; and means for terminating the gas introduction in response to addition of the predetermined displacing amount.

In preferred practice, and as specifically illustrated, the invention terminates the gas flow in response to expiration of a predetermined time required for the displacement.

The invention, by automatic termination of the displacement gas flow, eliminates human error inherent in manual operation to prevent concomitant, and often violent, flow of excess displacement gas into the emplaced slurry and to thereby eliminate resulting impairment of the emplaced explosive properties encountered in manual operation heretofore.

11 Claims, 2 Drawing Figures SOLENOID lz3l l7 PAIENIQUFEB 8 I972 M4 mm x23 9 mus-C. 4

vm mm JOHN F. HAMILTON DONALD J. PEDERSON INVENTORS ATTORNEY MAINTENANCE OF SLURRY EXPLOSIVE PUMPING ASSEMBLY FOR SUCCESSIVE LOADINGS This invention relates to method, and system, for maintaining operability of a slurry explosive pumping assembly during a series of successive loadings. In one aspect this invention relates to method, and system, for the evacuation of a pumpable explosive from a delivery conduit containing same as residual explosive after a quantity of such explosive has been pumped through the conduit into an emplacement zone. In another aspect the invention relates to method and system above described wherein the pumpable explosive is an inorganic oxidizer salt explosive of the aqueous slurry type containing active ingredients for in situ cross-linking, or cross-linking and aeration, after final emplacement of the explosive, and the evacuation is accomplished without impairment of either of those in situ reactions. In still another aspect, the invention relates to method, and system, in which the above-described oxidizer salt-type explosive is of the nitrocarbonitrate type, and the delivery conduit extends from a truck-mounted slurry supply station into an adjacent borehole as the emplacement zone. Other aspects of the invention will be apparent in light of the accompanying disclosure and the appended claims.

Pumpable slurry explosives have been utilized extensively in recent years. These explosives are generally of the aqueous inorganic oxidizer salt type and are of three classes, viz 1 those containing a sensitizer which is itself a high explosive such as TNT, PETN or the like, or a fast-burning material such as smokeless powder, (2) those referred to in the art as nitrocarbonitrates (NCNs) which are devoid of any ingredient which, per se, is a self-explosive, and which are insensitive to detonating action of a No. 8 blasting cap when packed for shipment, and (3) those containing no ingredient which, per se, is a selfexplosive but which nevertheless are sensitive to detonating action of a NO. 8 blasting cap.

Aqueous inorganic oxidizer salt explosives of the aqueous slurry type, above described, contain an inorganic oxidizer salt, water, a sensitizer, and generally, a thickener in at least an amount to hold all ingredients in suspension. In accordance with recent practice, these slurry-type compositions contain gas bubbles incorporated by direct injection, or by in situ generation, for regulation of density, and hence sensitivity; and in numerous instances the thicker is a gel formed by in situ cross-linking of a suitable gelation agent. The in situ crosslinking, and aeration reactions often proceed under similar pH conditions and hence, when they are utilized concurrently, they are readily selected so that the pH of the slurry explosive after final emplacement for shooting is suitable or, alternatively, the required pH can be maintained by the addition of a suitable acidic or basic material to the formulation.

Exemplary of inorganic oxidizer salt explosives of the aqueous slurry type are those disclosed in U.S. Pat. No. 3,235,425, in which the sensitizer is smokeless powder, and in U.S. Pat. No. 2,930,685, in which the sensitizer is TNT, or is a particulate metal such as aluminum. ln numerous other patents are disclosed various formulations of inorganic oxidizer salt aqueous slurry-type explosives, exemplary of which are U.S. Pat. Nos. 3,356,545, 3,333,998, 3,235,424 and others. U.S. Pat Nos. 3,288,658, 3,288,661, 3,390,028, 3,390,030, 3,390,031 and 3,390,032 describe various aeration systems for aqueous slurry-type explosives above described, for incorporation of gas bubbles into the formulation for the regulation of slurry density and sensitivity, and U.S. Pat. Nos. 3,318,470 and 3,401,067, and numerous others, illustrate guar gum as a thickener together with a cross-linking agent therefor at an acid pH. Various other cross-linked thickeners, particularly of the polyacrylamide type, are well known in the art and are cross-linked under such conditions as, for example are disclosed in U.S. Pat. Nos. 3,097,120, 3,321,344 and 3,341,383.

Generally, inorganic oxidizer salt explosives of the aqueous slurry type contain, on a weight basis,.from about 825 percent water, 40-75 percent inorganic oxidizer salt component, 3-30 weight percent of a suitable sensitizer, and a thickener generally in the amount of from about 0.2 to percent,

together with well-known, and optionally selected, supplemental ingredients generally including those for effecting cross-linking and/or aeration, as described above.

Although various procedures have been utilized in the past for mixing and packaging such aqueous slurry-type explosives, frequent practice has involved mixing the ingredients at a central mixing station and bulk transporting the resulting mixture to the shooting site; or, alternatively, mixing the ingredients in a truck-mounted mixing system at the shooting site; and, in either event, directly pumping the resulting bulk slurry mixture into a borehole through a hose-type delivery conduit extending into the borehole so as to convey the slurry into the resulting mass of emplaced slurry, as it is formed, to thereby minimize turbulence within, and hence facilitate stability of, the emplaced explosive mass. When a cross-linking agent for the thickeneris to be utilized it is generally added to the formulation with a pH regulation agent at, or near, the time that the final slurry is to be pumped into the delivery hose, in order to limit the available time for cross-linking to assure pumpability of the slurry for emplacement prior to the final setup" or gelation. Similarly when aeration is to be carried out, the aeration agent is added just prior to pumping the slurry into the delivery hose to minimize the amount of aeration taking place before gelation.

At the end of the loading cycle, i.e., after pumping the slurry into the borehole, and when the slurry contains a cross-linking agent for the thickener, or gelation agent, it is important that the residual explosive in the delivery hose be promptly evacuated in order that gelation does not proceed to the extent of causing the residual slurry to set up and become unpumpable to thus take the hose out of operation; and it is equally important that the hose be promptly removed from the emplaced slurry in order that it be not entrapped in the set or gelled mass that subsequently forms. When an in situ aeration agent is also present in the residual explosive, prompt evacuation is of still further importance inasmuch as upon standing and undergoing aeration, the residual slurry undergoes aeration to grow" to thus cause bridging, or plugging, in the hose, with accompanying impairment of the residual explosive flow.

Although the delivery hose can be promptly removed from the borehole and the residual slurry drained therefrom, such is disadvantageous particularly due to the weight of the residual explosive in the hose and the unwieldy maneuvering that is necessary in handling it. A still more serious disadvantage is that resulting from the degree of cross-linking, and any in situ aeration that takes place in the residual slurry during the time that the hose is being removed from the borehole to decrease its pourability and seriously impair, or even preclude, its removal by routine pumping or draining from the hose.

It has, therefore, been general practice, following termination of the loading cycle, to displace the residual slurry by force of air under pressure, directly from the delivery hose, while still in operating position, into the mass of emplaced slurry. The air displacement procedure has heretofore been conducted manually, so that control of valves in the air lines, time, pressure, and the like, have been subject to the skill of the operator for applying only the required amount of air. Obviously, if too little air is added the hose is not completely evacuated and cross-linking, and any in situ aeration, proceeds in the residual slurry to make it unpumpable and hence require removal of the hose from service. The major problem however has been the lack of control of airflow by the operator so as to consistently limit the amount of air passed into the hose. Accordingly, in numerous instances, manual operation has been such as to permit an excess of air to violently pass from the emptied hose into the mass of emplaced slurry in the borehole with churning" or bubbling upwardly through the slurried mass with upset of both chemical ,nd physical balance of the slurry to seriously impair its operability. For example, turbulent airflow from the emptied hose into the emplaced slurry mass obviously causes mixing of emplaced slurry with borehole water when present, to cause undue water dilution of the explosive and to disrupt the pH conditions generally preset in the slurry for gelation and/or aeration. A resulting increase in pH disturbs the set pH of the formulation to substantially "kill" or unduly impair the rate of either or both of the aeration and cross-linking actions that are in progress in the emplaced mass, the result being a premature termination of the cross-link reaction and/or the aeration, and hence a serious impairment of both physical and chemical characteristics of the finally emplaced slurry.

Further, the accompanying additional aeration of the emplaced slurry explosive inherently results in density lowering of the formulation to the extent that in water-containing boreholes, the density is lowered to a value below the density of water, and portions of the emplaced slurry rise, or float, toward the surface of the borehole with accompanying disintegration and impaired operability. Even when the borehole is dry and the explosive does not contain a cross-linking system, the rush of excess air from the delivery hose into the emplaced mass, with accompanying undue agitation can, by entrainment, carry portions of the mass from the borehole with resulting impairment of the loading operation; and, when a cross-linking system is present in the explosive, the accompanying undue agitation in the dry hole often develops gaps or air pockets in the emplaced mass to thus impair the integrity of the mass, and particularly so when the cross-linking reaction proceeds at a high rate to further support the gaps, or air pockets, in the rapidly gelling mass, such as when a boratetype cross-linking system is present.

This invention is concerned with method and system for evacuating a pumpable explosive from a delivery conduit containing same as residual explosive after flow of such explosive through the conduit directly into an emplacement zone and into a mass of resulting emplaced explosive therein, while avoiding the above-described disadvantages incurred heretofore in such practice.

in accordance with the invention, a method is provided for evacuation of a pumpable slurry-type explosive from a delivery conduit, containing same as residual explosive after flow of a quantity of such explosive through said conduit for emplacement, when the conduit extends into the emplacement zone and terminates in a resulting emplaced explosive mass therein, said method comprising introducing a gas into said conduit at an upstream end thereof, and then passing said gas downstream in said conduit against said residual explosive under force of sufficient pressure to displace said explosive from said conduit into said emplaced mass; and automatically terminating introduction of said gas into said conduit in response to introduction of a predetermined amount thereof sufficient for displacement of all of said residual explosive from said conduit into said emplaced mass.

In preferred practice, the delivery conduit is a flexible hose member extending into a borehole from a truck-mounted assembly at the shooting site. The truck-mounted assembly can be either a system for mixing all or some of the ingredients at the shooting site, or for transporting finished explosive to the site from a central mixing plant. Various truck-mounted assemblies for handling slurry explosives are well known.

By way of example, the delivery hose in preferred practice involving truck mounted assemblies above described, is often of a length in the order of from 50 to 150 feet and has a diameter in the order of from l 4 to 2 inches and may contain from 4 to 12 gallons of slurry explosive, generally having a total weight of from about 50 to 150 pounds. Of course, dependent upon the particular system, the hose dimensions and hence volume and weight of residual explosive may be outside the above exemplary ranges.

In practice of a now preferred embodiment of the invention, air, as the displacement gas, is introduced into the delivery conduit for a period of time required for delivery of the abovedescribed predetermined amount of air, and in response to expiration of that time period, the introduction of air into the delivery conduit is automatically terminated.

in one form of preferred practice, the time period is that necessary for introduction of a sufficient amount of displacement air into the delivery conduit to displace all of the residual explosive from the delivery conduit into the emplaced mass, i.e., the time period starting with the initial introduction of displacement air into the delivery conduit and terminating immediately upon completion of the displacement to thus empty, or evacuate, the delivery conduit of its entire residual explosive content. In that practice a portion of the emplacement air in the emptied conduit enters the emplaced explosive mass. This embodiment is more often utilized in those instances in which the displacement air is introduced into the delivery conduit at a sufficiently low pressure that the portion of exit flowing displacement air from the emptied delivery conduit into the emplaced slurry mass does not in any way impair the integrity of the emplaced mass, e.g., such as that which would tend to cause undue disintegration of that mass. Generally, in this practice, the displacement air is introduced into the delivery conduit at a pressure not exceeding about 50 to p.s.i., dependent on the particular system.

In another form of preferred practice, the displacement air is introduced into the delivery conduit during a time period less than that required for air displacement of all residual explosive from the conduit,and, in response to expiration of that time, introduction of the displacement air into the conduit is automatically terminated. However, at the time the introduction of air into the delivery conduit is terminated, there is a sufficient volume of displacement air accumulated in the delivery conduit, under the existing pressure conditions therein, for expansion toward the conduit exit end to provide the necessary pressure force for completion of the displacement; and, when desired, by the time the entire residual explosive mass is displaced, the difference between the displacement air pressure at the conduit exit, and the head of adjacent emplaced explosive mass, is substantially zero, so that there is substantially no flow of displacement air from the emptied conduit into the emplaced mass.

It will be appreciated that when initially introducing displacement air into the delivery conduit, there is a significant pressure drop across the body of residual slurry but that the pressure drop decreases as the displacement proceeds, so that under any given set of pressure conditions the rate of travel of residual explosive from the conduit increases as introduction of displaced air continues; and that the rate of displacement of residual explosive is also a function of the particular residual explosive material, dimensions of the delivery conduit, physical characteristics of the conduit inner wall, and the like. Hence, or any given system, the requisite time period for introduction of air into the delivery conduit, at the expiration of which the air introduction is terminated, whether the period be prior to, or at time of completion of the displacement, is of necessity determined by pretrial, or calibration.

in carrying out the calibration, a first of a plurality of boreholes, or other contemplated emplacement zones, is loaded from the delivery conduit by extending the conduit into the borehole, at the bottom thereof, for termination within the emplaced mass of explosive as formed, and then pumping the explosive through the conduit into the borehole up to the desired level. Without moving the conduit from its operating position, i.e., at the end of the pumping cycle, displacement air is introduced under a selected constant pressure into the upstream end of the conduit for the displacement and for an estimated preset period, whether the preset period is to expire before, or at the time the entire residual slurry is displaced. By visual observation it can be detennined whether, under the estimated time condition an excess of displaced air was introduced into the conduit as indicated by bubbling of air upwardly through the emplaced mass, or whether the flow of explosive from the delivery conduit was incomplete, as indicated by observation of the final air pressure within the delivery hose. By repeating the trail and adjusting the time for introduction of air into the delivery conduit, a second evaluation of the estimated time period is accomplished and is generally sufficient for determination of the requisite time period. However in some instances a third trial is required and in all events the time period is predetermined as basis for subsequent evacuation of residual slurry for each of the various loadings contemplated, and involving that system.

By way of example, the period of time for introduction of air at a constant pressure of 50 psi. into a delivery conduit of l -inch diameter by 100 feet in length, for the evacuation of an NCN-type aqueous slurry having a specific gravity of about 1.40 into a mass of emplaced explosive of -inch diameter when the exit end of the conduit is about 6 feet below the top surface of the emplaced mass, is in order of about 4 seconds under which conditions the predetermined time is substantially that during which all of the residual explosive is displaced into the adjacent emplaced mass. On the other hand if the displacement air is introduced into the conduit at a higher pressure, say at 100-150 p.s.i., the predetermined time is that during which only a portion of the residual explosive is displaced so that the resulting volume of accumulated air is sufficient for expansion to provide the necessary force of pressure for completing the displacement, but substantially insufficient for flow of remaining displacement air from the conduit exit into the emplaced mass.

One form of this embodiment involves utilization of a timer associated with auxiliary mechanical equipment, which, upon actuation by the operator, prompts a valve to be opened for introduction of the displacement gas into the delivery conduit, and which, upon expiration of the predetermined time, prompts closing of the valve to thus terminate the flow of the air into the conduit. In this manner, actuation of the timer, by the operator, concurrently moves the airflow valve into open position, and upon expiration of the predetermined time the valve is automatically moved into closing position to accurately, and reliably, control the airflow for dependable evacuation of the residual explosive and thus eliminate all control errors heretofore inherent in manual operation.

In another embodiment, a a suitable displacement gas is introduced into the delivery conduit from storage in a constant volume vessel at an initial pressure just sufficient to provide the necessary force for displacement of the residual explosive from the conduit. In that practice, pressure of the air introduced into the delivery conduit is necessarily correlated with the volume of both the conduit and the vessel so as to flow under its own pressure, and in sufficient volume, to displace all of the residual explosive from the conduit; but under insufficient pressure volume conditions for flow of any appreciable amount of displacement gas from the emptied conduit into the adjacent emplaced mass. Accordingly, pressure in the delivery conduit at the time of completion of displacement is about equal to the head of mass of emplaced slurry adjacent the conduit exit end so that substantially no gas passes from the conduit into the emplaced explosive after evacuation of the residual explosive therefrom. In this embodiment, the flow of displacement gas thus introduced into the delivery conduit is automatically terminated, i.e., independently of manual operation, by exhaust of the preset supply of gas in the constant pressure vessel.

In still another embodiment, displacement gas is introduced into the delivery conduit under suitable pressure for evacuation of the residual explosive therefrom, and a suitable sensing means is disposed at the downstream end of the delivery con duit to constantly detect exit flow of residual explosive therefrom and to detect the sudden change in exit fluid flow rate attributable to the relatively high, and sudden, rate of gas travel from the exit conduit that occurs at the time the conduit is emptied. In response to initial detection of the sudden velocity increase, introduction of the gas into the conduit is automatically terminated to thereby preclude passage of more than a fraction of the displacing gas into the adjacent mass of emplaced slurry. In the practice of this embodiment the amount of displacing gas flowing into the emplaced slurry mass is insufficient to cause any degree of agitation leading to impairment of integrity of the emplaced explosive mass.

Further in accordance with the invention a system is provided for evacuation of a pumpable explosive from a delivery conduit, present as residual explosive after a quantity of such explosive has been pumped through said conduit for emplacement, when the conduit is extended into the emplacement zone and into a resulting mass of emplaced explosive therein, which comprises means for introduction for a gas into an upstream end of said conduit, and for then passing same downstream against said residual explosive therein under force of sufficient pressure to displace said explosive from said conduit into said emplaced mass; and means for terminating introduction of said gas into said conduit in response to introduction of a predetermined amount of same sufficient or displacement of all of said residual explosive from said conduit into said emplaced mass.

The invention is further illustrated with reference to the drawings which are diagrammatic and of which FIG. 1 shows an embodiment of method, and system, of the invention, utilizing a four-way valve-type pneumatic actuator assembly, and FIG. 1A shows a variance of method and system of FIG. I in which the pneumatic actuator assembly is a spring-returntype actuator with a three-way valve.

Referring to FIG. 1, a pumpable nitrocarbonitrate (NCN type aqueous slurry inorganic oxidizer salt explosive 10, with suitable thickener-cross-linker, and aeration agent, ingredients, is pumped from a mixing station (not shown) through a suitable valve system 9, at a pH, generally on the acid side, suitable for the contemplated cross-linking and aeration reactions into, and through, delivery hose l2 and into borehole l3. Often, an inorganic nitrite aeration system is utilized in the NCN explosive with or without, sulfamate and/or sulfamic acid accelerator as described herein above with reference to prior art practice, at a pH in the range of about 3.0 to 5; and guar gum-potassium pyroantimonate cross-linking system is utilized in conjunction therewith under the same pH conditions.

Delivery hose 12 extends into borehole 13 so as to dispose the downstream end 12' thereof sufliciently close to the bottom 13 of the borehole to enable slurry 10 to be discharged from conduit 12 directly into the mass of emplaced slurry as it is formed in borehole 13. Thus as slurry 10 is delivered from conduit 12 through downstream conduit end 12 it accumulates in borehole 13 to gradually rise to form a resulting columnar mass 14 of emplaced slurry for shooting. Column I4 of slurry 10 is formed by initial delivery of slurry into the bottom end 13' of borehole 13, and by gradual rise due to accumulation of the delivered slurry, to the predetermined top level 14. The quantity of slurry l0 pumped through conduit 10 and to emplacement in borehole l2 varies, dependent upon the particular shooting requirements, being often in the range of from say 50 to 1,500 pounds.

Except for the sulfamate, which is often added during the initial mixing step, the guar gum-potassium pyroantimonate gelation system and the odium nitrite-ammonium sulfamate and/or sulfamic acid aeration system, are last added to the formulation, generally just prior to pumping of slurry 10 into delivery hose 12, so as to reduce to a minimum the available time for gelation and aeration to take place in delivery hose 12 to preclude impairment of pumpability of slurry 10 while in conduit 12, and to minimize aeration until after emplacement. The pH of slurry l0, utilizing the above thickener and aeration systems, is advantageously regulated by the addition of fumaric acid to the formulation, generally along with addition of the gelation and aeration systems.

The rate of pumping slurry 10 into borehole 13 is necessarily correlated with residence time of the slurry in the delivery hose so as to limit the cross-linking and aeration reactions in the slurry sufficiently that the thickening and aeration that does occur in conduit 12 does not seriously limit pumpability of the slurry 10 through the hose 12.

After the loading cycle, i.e., after the desired amount of slurry has been emplaced in borehole 12 to form a resulting mass of emplaced slurry (slurry column I4), the delivery hose 12 remains substantially filled with slurry 10 which at the end of the loading cycle constitutes remaining, or residual, slurry 10 which must be removed from delivery hose 12 before sufficient crosslinking and aeration takes place to cause residual slurry 10 to become unpumpable, and hence necessitate taking delivery hose 12 out of service.

Prompt evacuation of residual slurry 10' from conduit 12 is therefore required, and it is necessary from a time standpoint that the evacuation be accomplished while the delivery hose remains in operating position, i.e., as it still extends into the borehole and into the resulting mass of emplaced slurry 10 therein. Thus residual explosive 10, to be evacuated, is moved from the conduit 12 into the resulting adjacent mass of emplaced explosive 10, at a point adjacent the exit end 12' of conduit 12.

Evacuation of residual explosive 10' from conduit 12 is accomplished in practice of this embodiment by method and system involving gas displacement of the residual slurry from the delivery conduit directly into the mass of emplaced explosive 14, by a stream of air introduced into an upstream end portion of the delivery hose. As illustrated, the displacement air is introduced into conduit 12 via line 17; and, immediately in response to introduction of a completely displacing amount of the air into the delivery conduit, the introduction of air through conduit 17 into conduit 12 is automatically terminated by diagrammatically illustrated airflow regulation system 16.

Airflow control system 16 comprises a pneumatic valve assembly 19, solenoid 31, timer 32, line 18 for delivery of air from a pressurized air source, not shown, to pneumatic valve assembly 19 and to a conventional air pressure reduction valve 21 and a conventional ball-type valve 38 operated by the pneumatic valve assembly to admit air under pressure from reduction valve 21 into the delivery conduit 12 via line 17.

As diagrammatically shown, pneumatic valve assembly 19 includes piston 22 adapted to be moved longitudinally in elongated casing, or bore, 23, in response to an increase or decrease in air pressure in casing end section a together with corresponding pressure decrease or increase respectively in casing end section b. Thus with air introduced into section a via line 24 and exhausted from section b via line 26, piston 22 is moved toward casing end 27, and when air is introduced under pressure into section b via line 26 and exhausted from section a via line 24, piston 22 is moved toward casing end 28.

Air under pressure from line 18 is introduced via four-way valve 29 which is a part of pneumatic valve assembly 19, into either section a or b, with exhaust respectively from the section b or section a. Four-way valve 29 is operated by solenoid 31 by any suitable communication means, which in turn is moved into and out of operating position in response to actuation by timer 32. Timer 32 is in turn operated by electric current in powerline 34 to the timer motor, actuated by switch 33, generally a momentary contact switch.

A suitable mechanical link mechanism 36 is operatively connected with piston 22 and with ball valve 38 so as to move valve 38 into opening or closing position in response to longitudinal travel of piston 22 in casing 23. Mechanical linkage 36 is connected outside the casing 23 with shaft 37 extending substantially coaxially in the casing 23 and connecting with piston 22. Valve 38 in line 17 connects on the intake side with the discharge side of reduction valve 21 so as to deliver air under reduced pressure, from valve 21 via line 17 into an upstream end 12" of delivery hose 12. Thus valve 38 is moved into open and closed position in response to longitudinal travel of piston 22.

In the operation of pneumatic valve assembly 19, passageway 2-3 of four-way valve 29 connecting

lines

18 and 24, and passageway 14 thereof, connecting

lines

26 and 25, conduct flow of air into casing end a from line 18 and exhaust of air from casing end b to the atmosphere via line 25. Fourway valve 29 can be moved by solenoid 31, to place passageway 1-4 in connecting relationship with

lines

18 and 26 and passageway 2-3 in connecting relationship with

lines

24 and 25, to move air into section b under pressure with exhaust from section a. Thus, solenoid valve upon actuation by timer 32 moves valve 29 into position for admitting air under pressure into section a and for exhaust of air from section b hence causing piston 22 to move longitudinally toward casing end 27 and cause linking mechanism 36 to move valve 38 into open position for admitting airflow under pressure into conduit 12 as above described. Timer 32 is actuated by manual operation of switch 33 in powerline 34 leading electric current to the timer motor and in turn during the preset time period maintains solenoid 31 in the position shown for prompting valve 38 in open position. At the end of the predetermined time period, timer 32 terminates actuation of solenoid 31 which moves into normal position by any suitable means such as spring-biasing means to responsively move valve 29 into position for reversal of airflow into and from casing 23 and to prompt valve 38 to be moved into a closed position. Timer 32 is reset, generally automatically, so as to be in readiness for repeating the cycle when required after another borehole loadmg.

In accordance with one embodiment of method of the invention, after slurry 10 is pumped from the mixing station directly through delivery hose 12 into borehole 13 to form a resulting emplaced mass 14, the pumping step is terminated and residual explosive 10' is promptly evacuated from conduit 12 before the extent of gelation and aeration in conduit 12 is sufficient to cause residual slurry 10' to become unpumpable.

Prompt evacuation of slurry 10 from conduit 12 is initiated by manually operating power switch 33 to actuate timer 32. Timer 32 is preset to move solenoid 31 into position for a predetermined time to operate valve 29 to admit air from line 18 into section a and in turn actuate mechanical linkage 36 to move valve 28 into open position (as shown) to conduct air at predetermined reduced pressure from valve 21 through line 17 and check valve 11 into upstream end 12" of conduit 12. Under these conditions air at predetermined pressure for a predetermined time is moved into delivery conduit 12 at the upstream end, and is directed against slurry 10 under force of pressure sufficient to displace slurry 10 downstream in conduit 12 and out of conduit 12 at the downstream end 12 into the adjacent and already emplaced explosive mass 10.

The time necessary for air, under pressure from reduced pressure valve 21, to displace the entire amount of the particular residual slurry 10 in conduit 12 is determined by precalibration as described above, so that at the end of the predetermined time period timer 32 prompts mechanically responsive termination of airflow from line 12 into hose 12.

Referring to FIG. 1A, showing another form of pneumatic actuator assembly for utilization in practice of invention, pneumatic assembly 19 includes solenoid-operated three-way valve 29, elongated casing 23', and piston 22' in casing 23' longitudinally movable therein in response to a change in air pressure in casing end section a and biasing action of elongated spring member 20; spring 20 coaxially extending in opposite casing end section b intermediate piston 22' and casing end 27 so as to bias piston 22 away from casing end member 27'.

Thus, upon energizing solenoid 31 (FIG. 1) passageway 1-2 of valve 29' is opened to connect line 18 (FIG. 1) with casing end section a to thereby direct air under pressure from line 18 into section a and move piston 22' toward casing end 27' against biasing action of spring 20. In that manner, shaft 37', connecting with piston 22 and extending coaxially from casing 23' through end member 28' in operative communication with mechanical linkage 36 (FIG. 1) actuates linkage 36 to open valve 38 (FIG. 1) as described with reference to FIG. 1. At the end of the time cycle, solenoid valve 31 is actuated to cause passageway 2-3 of valve 29 to open for exhaust of air from casing end section a, via line 25', and permit piston 22' in response to biasing action of spring 20 to move toward end 28' and hence to axially move shaft 37' away from end 27' to in turn actuate linkage 36 to close valve 38.

It is to be understood that any suitable arrangement of airflow control equipment can be utilized in practice of the invention, it being required only that the gas, for displacement of slurry is introduced into the delivery hose or conduit under conditions for displacement of the residual slurry into the already emplaced mass, and that the flow of displacement gas into the delivery conduit be automatically terminated in response to introduction of a displacing amount of gas into conduit 12.

Now preferred airflow control systems diagrammatically illustrated with reference to FIGS. 1 and 1A of the drawings are available commercially the system in each instance being a single unit solenoid 31, valve 29 (or 29) and piston casing assembly 22-23 (or 22'23) mechanical linkage 36 and valve 38, all packaged as a single unit.

As will be evident to those skilled in the art, various modifications can be made or followed in light of the foregoing disclosure and discussion without departing from the spirit or scope of the disclosure or from the scope of the claims.

What we claim and desire to protect by Letters Patents is:

1, In a method for the emplacement of an aqueous slurrytype inorganic oxidizer salt explosive, containing a crosslinkable thickener and an in situ cross-linking agent therefor or said thickener and cross-linking agent together with an aeration agent for in situ generation of gas bubbles throughout said mass of slurry, by pumping same into a borehole through a conduit extending into said borehole so as to dispose the terminating end of said conduit within a mass of resulting emplaced explosive, wherein said explosive pumped through said conduit contains insufficient of said thickener and cross-linking agent or said thickener and cross-linking agent together with said aeration agent, to cause said explosive to become unpumpable through said conduit to said displacement but sufficient to cause said explosive to soon become unpumpable through said conduit if retained therein as residual explosive after termination of said pumping to said displacement, and said residual explosive, while still pumpable, is evacuated from said conduit by gas displacement, the improvement comprising, upon terminating said pumping to said emplacement, introducing a gas into said conduit at an upstream end the eof, and then passing said gas downstream in said conduit against said residual explosive under force of sufficient pressure to displace said explosive from said conduit into said emplaced mass; and automatically terminating introduction of said gas into said conduit in response to introduction of an amount thereof sufficient, but not substantially greater than that required, for displacement of all of said residual explosive from said conduit into said emplaced mass.

2. In a method of claim 1, continuously measuring time concurrently, and beginning, with said introduction of gas into said conduit; and terminating said introduction of gas into said conduit in response to expiration of a predetermined cumulative period of said time, just sufficient for all of said explosive to be evacuated from said conduit by action of said force.

3. A method of claim 2 wherein said slurry explosive is of the nitrocarbonitrate type and contains a gelation agent as said thickener, and said emplacement zone is a water-containing borehole.

4. A method of claim 3 wherein said slurry explosive contains said gelation agent and cross-linking agent therefor together with said aeration agent.

5. A method of claim 4 wherein guar gum is said gelation agent and potassium pyroantimonate is said cross-linking agent, and said emplaced slurry mass is maintained at a pH on the acid side.

6. A method of claim 5 whereinsaid slurry explosive contains, as said aeration agent, a nitrite selected from the group consisting of sodium nitrite, potassium nitrite, calcium nitrite, barium nitrite and silver nitrite, and said emplaced mass is maintained at a pH of from about 3.0 to 5.0.

7. A method of claim 6 wherein said aeration agent contains, as an accelerator for said aeration, at least one of the group consisting of sulfamic acid, ammonium sulfamate, potassium sulfamate and sodium sulfamate.

8. A method of claim 7 wherein said nitrite is sodium nitrite. 9. In a system for the emplacement of an aqueous slurrytype inorganic oxidizer salt explosive, containing a crosslinkable thickener and an in situ cross-linking agent therefor or said thickener. and cross-linking agent together with an aeration agent for in situ generation of gas bubbles throughout said mass of slurry, by pumping same into a borehole through a conduit extending into said borehole so as to dispose the terminating end of said conduit within a mass of resulting emplaced explosive, wherein said explosive pumped through said conduit contains insufficient of said thickener and cross-linking agent or said thickener and cross-linking agent together with said aeration agent, to cause said explosive to become unpumpable through said conduit to said displacement but sufficient to cause said explosive to soon become unpumpable through said conduit if retained therein as residual explosive after termination of said pumping to said displacement, said residual explosive, while still pumpable, is evacuated from said conduit by gas displacement, the improvement which comprises means for introduction of a gas into an upstream end of said conduit, and for then passing same downstream against said residual explosive therein under force of sufficient pressure to displace said explosive from said conduit into said emplaced mass; and means for terminating introduction of said gas into said conduit in response to introduction of an amount of same sufficient, but not substantially greater than that required, for displacement of all of said residual explosive from said conduit into said emplaced mass.

10. In a system of claim 9, means for continuously measuring time concurrently, and beginning, with introduction of said gas into said conduit; and means for terminating said introduction of gas into said conduit in response to measurement of a predetermined cumulative time period for said introduction of an amount of said gas sufficient for displacement of all of said residual explosive from said conduit into said means of emplaced explosive.

11. In a system of claim 10, gas delivery means; a normally closed valve connecting at an intake side thereof with the discharge end of said gas delivery means and at a discharge side thereof with said conduit; means for moving said valve into open position in response to initiation of said measurement of time; and means for moving said valve into closed position in response to measurement of said cumulative time period.

UNITED STATES PATENT FICE QE'EIHCATE EH10 Patent No. U.S.P. 3, 640 585 Dated February 8, 1972 Inventor(s) John F. Hamilton and Donald J. Pederson (Case 1) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 2, Line 72 of "cal, nd" should be "cal, and" Col. 4, Line 47 of p. p.-;

"or" should be "for" Col. 5, Line 35 of p.p.;

"a" (second occurrence) should be deleted Col. 8, Line 46 of p.p.;

"line 12" should be "line 17" Signed and sealed this 20th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents *zggg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. U.S.P. 3, 640,585 Dated February 8, 1972 Inventor(s) John F. Hamilton and Donald J. Pederson (Case 1) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 2, Line 72 of "cal, nd" should be "cal, and" Col. 4, Line 47 of p. p.;

"or" should be "for" Col. 5, Line 35 of p.p.;

"a" (second occurrence) should be deleted Col. 8, Line 46 of p.p.;

"line 12" should be Signed and sealed this 20th day of June 1972.

"line 17" (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

1. In a method for the emplacement of an aqueous slurry-type inorganic oxidizer salt explosive, containing a cross-linkable thickener and an in situ cross-linking agent therefor or said thickener and cross-linking agent together with an aeration agent for in situ generation of gas bubbles throughout said mass of slurry, by pumping same into a borehole through a conduit extending into said borehole so as to dispose the terminating end of said conduit within a mass of resulting emplaced explosive, wherein said explosive pumped through said conduit contains insufficient of said thickener and cross-linking agent or said thickener and cross-linking agent together with said aeration agent, to cause said explosive to become unpumpable through said conduit to said displacement but sufficient to cause said explosive to soon become unpumpable through said conduit if retained therein as residual explosive after termination of said pumping to said displacement, and said residual explosive, while still pumpable, is evacuated from said conduit by gas displacement, the improvement comprising, upon terminating said pumping to said emplacement, introducing a gas into said conduit at an upstream end thereof, and then passing said gas downstream in said conduit against said residual explosive under force of sufficient pressure to displace said explosive from said conduit into said emplaced mass; and automatically terminating introduction of said gas into said conduit in response to introduction of an amount thereof sufficient, but not substantially greater than that required, for displacement of all of said residual explosive from said conduit into said emplaced mass.

6. A method of claim 5 wherein said slurry explosive contains, as said aeration agent, a nitrite selected from the group consisting of sodium nitrite, potassium nitrite, calcium nitrite, barium nitrite and silver nitrite, and said emplaced mass is maintained at a pH of from about 3.0 to 5.0.

8. A method of claim 7 wherein said nitrite is sodium nitrite.

9. In a system for the emplacement of an aqueous slurry-type inorganic oxidizer salt explosive, containing a cross-linkable thickener and an in situ cross-linking agent therefor or said thickener and cross-linking agent together with an aeration agent for in situ generation of gas bubbles throughout said mass of slurry, by pumping same into a borehole through a conduit extending into said borehole so as to dispose the terminating end of said conduit within a mass of resulting emplaced explosive, wherein said explosive pumped through said conduit contains insufficient of said thickener and cross-linking agent or said thickener and cross-linking agent together with said aeration agent; to cause said explosive to become unpumpable through said conduit to said displacement but sufficient to cause said explosive to soon become unpumpable through said conduit if retained therein as residual explosive after termination of said pumping to said displacement, said residual explosive, while still pumpable, is evacuated from said conduit by gas displacement, the improvement which comprises means for introduction of a gas into an upstream end of said conduit, and for then passing same downstream against said residual explosive therein under force of sufficient pressure to displace said explosive from said conduit into said emplaced mass; and means for terminating introduction of said gas into said conduit in response to introduction of an amount of same sufficient, but not substantially greater than that required, for displacement of all of said residual explosive from said conduit into said emplaced mass.

10. In a system of claim 9, means for continuously measuring time concurrently, and beginning, with introduction of said gas into said conduit; and means for terminating said introduction of gas into said conduit in response to measurement of a predetermined cumulative time period for said introduction of an amount of said gas sufficient for displacement of all of said residual explosive from said conduit into said mass of emplaced explosive.