Abstract:
High pressure pumps for injecting cement mixtures are provided. Such pumps are configured so that the frequency and costs of servicing are greatly reduced.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and benefit of Italian Patent Application No. TO2011A001029 filed Nov. 8, 2011, the contents of which are incorporated by reference in their entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to high pressure pumps (or jet pump) for injecting cement mixtures. 
       BACKGROUND OF THE INVENTION 
       [0003]    The primary consolidating fluid used in such pumps is generally a binary fluid consisting of water and cement. This fluid is injected into a hole in the soil to be consolidated through a drilling rod string at the bottom of which there is fixed an injection head, called a “monitor”, which has at its outlet at least one very small diameter nozzle capable of increasing the injection pressure to very high values. It is also a common practice to inject ternary fluids consisting of plastic mixtures of water, cement and bentonite, which are used to make a soil impermeable instead of increasing its mechanical characteristics. Sometimes it is possible to use a pumping system for injecting only one of the fluids described above (e.g. water), in order to treat the soil, to bring about hydraulic disaggregation or for other purposes known in the field. There is also a known practice of combining with the primary fluids particular additives to vary some of their characteristics (setting time, plasticity, consistency, strength etc.). 
         [0004]    The range of pressures of such pumps runs from 50 to 1000 bars, while the flow rates vary from a few hundred liters per minute to more than 1000 liters per minute. The cement makes the mixture abrasive, with consequent wear problems for some components of the pump. 
         [0005]    For a better understanding of the state of the art and of the problems relating thereto, a description first will be given of a high pressure pump of a known type for injecting cement mixtures (primary fluid), making reference to  FIG. 3  in the attached drawings. 
         [0006]    The pump makes use of three single-action suction and force plungers such as the one indicated by reference number  11 . The plunger is sealingly supported and guided in its reciprocating motion by a sealing device  20 , which includes a cylindrical sleeve  21  locked by means of a clamping ring  22  coaxially inside a flanged supporting bush  23 . A closed circuit is formed in the sealing device for a second lubricating fluid (or secondary fluid), in particular lubricating oil, with two ducts, inlet  24  and outlet  25 , formed in the inner sleeve and in the bush, and an axially extended annular chamber  26  formed in the internal cylindrical cavity  27  of the sleeve, around the plunger. At the two opposite sides of the lubrication chamber  26  a respective annular oil sealing gasket  28 ,  29  is provided, fixed to the cylindrical sleeve  21  and acting against the plunger. At the end of the sleeve on the “wet” side facing towards the pumping chamber, there is fitted in the internal cylindrical cavity a sealing gasket  32  sealing against the primary fluid, particularly cement; at the opposite end, on the dry side near the clamping ring  22 , a scraper ring  33  is mounted. 
         [0007]    Currently, gaskets sealing against cement have an average life of about 200-300 hours, depending on the type of cement and the operating conditions: pressure, flow rate and SPM (number of strikes per minute). There is no device capable of indicating wear on the seals. Failure of the cement gasket to seal causes contamination of the secondary fluid lubricating the plungers. The presence of cement in the lubricating oil indicates that the gaskets are no longer sealing; in these conditions, however, it becomes necessary to replace not only the gaskets but the oil itself, and often overloading problems are created for the pump, the filter and the other components in the circuit. In these conditions the sleeve of the sealing device, too, is subject to premature wear due to an increase in friction with the plunger (no longer guided by the worn gasket) and to the presence of cement in the lubricating oil. The oil must normally be replaced every 500 hours, and thus it would be particularly useful to have gaskets capable of working for at least the same amount of time in order to reduce the frequency and cost of servicing. In fact servicing procedures to replace seals are very complex and require the dismantling of many components. Such servicing can take several hours; if performed simultaneously with replacing the oil, there would be an enormous simplification of the servicing process and costs would be drastically reduced. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides high pressure pump capable of achieving excellent results in terms of reliability and life of the wearing components, while optimizing servicing and reducing operating costs. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]      FIG. 1  provides a schematic partial cross-sectional view of an exemplary embodiment of a pump according to the present invention. 
           [0010]      FIG. 2  provides an enlarged view of a section of a sealing gasket for the pump of  FIG. 1 . 
           [0011]      FIG. 3  is a partial cross-sectional view of a pump of a known design. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIG. 1 , numeral  10  generally designates a reciprocating pump with suction and force plungers, capable of working at high pressures for injecting concrete mixtures in order to increase mechanical or moisture-proofing characteristics of soils. The pump  10  in this embodiment is a reciprocating pump with several cylinders side by side in line, in each of which there runs a respective single-action suction and force plunger  11 , only one of which is shown in the drawing. In particular, according to certain embodiments, the pump includes a system having three plungers, which define a so-called “Triplex pump”. The plunger  11  connected, by a connection system  12  (here represented as a collar joint, but as a variant it also may be made using a tie-rod or similar component) to a rod  13  driven by a crankshaft (not shown), by a respective connecting rod (not shown). The body  14  of the pump may be integral with a block  15  in which there are formed pumping chambers  16 , one for each plunger. The plunger may penetrate into the pumping chamber through an aperture  17 . By using a system of valves, the pumping chamber  16  reduces its volume as a result of the entry of the plunger  11  resulting in an increase in the pressure of the primary fluid contained therein. When the required pressure is reached, the valve (not represented) opens an outlet and the pressurized fluid is injected into the pumping line until it reaches the drilling machine. 
         [0013]    The pump described herein is not to be considered limited by the types of fluid with which it operates. In the remainder of the description and the annexed claims, the term “primary fluid” or “first fluid” refers to a fluid which is to be pressurized by the pump and injected into a soil. In many applications, the primary fluid will be a mixture containing cement (for example water and cement, or water, cement and bentonite). The expression “second fluid” or “secondary fluid” refers to a fluid which is used principally for lubricating the plungers (or the plunger) of the pump, according to procedures known per se. In certain embodiments, the second fluid includes lubricating oil. An important advantage of pumps according to certain embodiments of the present invention results from the presence of a third operating fluid, which is used to control the surfaces affected by the sliding of the plunger(s). This third cooling fluid can be, for example, water or an aqueous mixture or solution, suitable for the purposes set forth herein. 
         [0014]    The plunger  11  is sealingly supported and guided, in its reciprocating motion in a direction here described as “longitudinal”, by a sealing and guiding device designated overall by reference number  20 . The sealing device  20  includes a cylindrical sleeve  21  locked by clamping ring  22  arranged coaxially within a flanged supporting bush  23 . The bush  23  may be removably fastened to the body  14  of the pump. 
         [0015]    A closed circuit for forced lubrication, for a second fluid, such as oil, is formed in the sealing device  20 . The lubrication circuit may include two radial ducts formed in the inner sleeve and in the bush, specifically an oil inlet duct  24 , an oil outlet duct  25 , and an axially extended annular chamber  26  formed in the inner cylindrical cavity  27  of the sleeve, at the interface with the plunger. The inlet and outlet ducts for the secondary fluid may be inverted. On the two opposite sides of the lubrication chamber  26 , two respective annular oil sealing gaskets  28 ,  29  may be arranged, fixed to the cylindrical sleeve  21  and acting against the plunger  11 . The gasket  28  may be oriented with its principal sealing lip extending toward the “wet” side, while the sealing gasket  29  itself also may be oriented with its principal sealing lip towards the “wet” side. This orientation allows the seal from the lubrication chamber  26  not to be hermetic towards the “wet” side, thus allowing a slow and continuous controlled leakage of lubricating fluid which serves to moisten a sealing gasket  37 , described hereinafter, thus keeping it lubricated. Two further O-ring gaskets  30 ,  31  may be interposed between the sleeve  21  and the supporting bush  23 , with sealing functions against the secondary lubricating fluid. 
         [0016]    At the end of the sleeve  21 , on the “wet” side facing towards the pumping chamber for the primary fluid, there is fitted in the internal cylindrical cavity  27  a first sealing gasket  32  against the primary fluid (or “cement seal”); at the opposite end, on the dry side near the clamping ring  22 , there may be fitted a conventional scraper ring  33 . 
         [0017]    A cooling circuit with a third fluid, such as water (or other liquid) is formed in the sealing device  20 , with radial intake duct  34  and outlet duct  35  formed through the outer bush and the inner sleeve  21 , and an annular chamber  36  formed in the internal cylindrical cavity  27  of the sleeve around the plunger  11 . The intake and outlet ducts may be inverted with respect to what is shown, without altering the functionality of the system. 
         [0018]    The annular chamber  36  is sealed toward the “wet” side by the first sealing gasket  32  sealing against cement, while on the opposite side, facing towards the clamping ring  22 , the chamber  36  is sealed against the plunger  11  by a second guiding and sealing gasket  37  sealing against the primary fluid, particularly against cement mixtures. The second sealing gasket  37  may be axially interposed between the first sealing gasket  32  sealing against the first fluid and the annular chamber  26  of the lubrication circuit. As shown in the illustrated example, the second cement sealing gasket  37  is located adjacent to the oil sealing gasket  29 . The sealing gaskets  28 ,  29 ,  32 ,  37  and the scraper  33  may be seated in respective annular grooves formed in the internal cylindrical cavity  27  of sleeve  21 . 
         [0019]    The second sealing gasket  37 , in addition to sealing against the cooling water, also serves as a guide element for the plunger  11 , and therefore its shape and the material from which it is made are chosen appropriately to resist high specific pressures. In a variant (not shown), the second sealing gasket  37  also may incorporate the functions of the sealing gasket  29  which therefore could be omitted. In this case the sealing gasket  37  directly delimits the annular chamber  26  of the second lubrication fluid, and also would perform sealing functions against the secondary fluid on the “wet” side as well as sealing the primary fluid and guiding the plunger piston  11 . 
         [0020]    As it reciprocates, the plunger  11  can move between an axially retracted position (to the left in  FIG. 1 ) and an axially extended position (to the right) in which it enters deeper into the pumping chamber  16 . In every position taken by the plunger  11  along its stroke, at least a part of its cylindrical outer surface is always seated within the inner cylindrical cavity  27  and faces both of the annular chambers  26  and  36 . 
         [0021]    In the embodiment shown, enlarged in  FIG. 2 , the sealing gasket  37  has an annular body  38  from which protrude internally several annular reliefs, in this example three in number, suitable for sliding against the plunger  11 . A sealing lip  39 , of a generally truncated-conical shape, may project obliquely toward the wet axial side of the pump and radially towards the plunger. Two annular reliefs  40 ,  41 , axially spaced apart from one another, may project in radially internal directions, and each may terminate with a respective radially internal cylindrical surface suitable for guiding and stabilizing the plunger  11 . The sealing lip  39  may be located closer to the pumping chamber  16 , while the annular reliefs  40 ,  41  are farther from the pumping chamber. 
         [0022]    The compartments or cavities formed between the annular reliefs  40 ,  41  and between the relief  41  and the lip  39 , and open towards the plunger  11 , allow lubricating fluid coming from the leakage of sealing gasket  29  to be appropriated. This occurs because of the compartment identified between the two contiguous reliefs on which the specific pressure, necessary for guiding, is very high, unlike that which is generated in the cavities which is very low and which will favor the accumulation of lubricating fluid. The accumulation of lubricant helps to increase the life of the sealing gasket  37 . The alternation between full and empty also enables dispersal of the heat due to the friction between the internal cylindrical surface of the reliefs  40  and  41 , the lip  39  and the outer surface of the plunger  11 . In alternative embodiments (not shown), there may be only one of the two reliefs  40 ,  41 , or, in a further embodiment, there may be more than two reliefs. In the embodiment shown in  FIG. 2  in undeformed condition, the annular reliefs  40 ,  41  have an axial section of trapezoidal shape. The annular reliefs  40 ,  41  considerably reduce the radial loads and the friction on the first frontal sealing gasket  32 , which originally serves to seal against cement. The plain cylindrical side on reliefs  40  and  41 , rather than the normal apex which can be found on profiles with a triangular section, ensures that the plunger  11  is correctly guided. The cylindrical inner surface of reliefs  40 ,  41  may contain furrows or grooves suitable for allowing the passage of secondary fluid for lubricating at least one of the said reliefs and the sealing lip  39 . 
         [0023]    The second sealing gasket  37  also may function to provide a seal against cement. The third cooling fluid (water or other liquid) which circulates in the chamber  36  also serves to lubricate the second sealing gasket  37  and to further cool the plunger, by direct washing. This fluid therefore has two functions: the principal function of cooling the seals, the plunger and the sleeve, and the secondary function of lubricating sealing gaskets  32  and  37  which would not be reached by the secondary lubricating fluid. In fact the inner side, toward the “wet” part of sealing gasket  37  and the whole of sealing gasket  32 , would not be in contact with the secondary lubricating fluid. For this purpose, as a third fluid, it is possible to use liquids enriched with additives to improve this second function, or oil (in this case, to offset a disadvantage caused by the contamination of a valuable fluid, which provides a further extension of the life of the sealing components and the other parts in relative movement and subject to the presence of abrasive fluids (such as cement mixtures). Any contamination of the third fluid by the cement indicates wear on the first, outermost sealing gasket  32 . At the point when the first sealing gasket  32  deteriorates and loses its sealing function, it allows cement to pass which is diluted by the flow of water. In this case, however, unlike previously existing pumps, it is possible to determine that the water contains a second component, because the outlet allows the fluid to free-fall or fall into an open container, or to pass into a transparent tube close to the operator&#39;s station. While lubricating oil requires a closed and filtered circuit, the water can be directed and handled more freely because it does not represent an environmental pollutant. The second m sealing gasket  37 , in the event of damage to the first sealing gasket  32  (which is in direct contact with the cement zone and is therefore the most subject to deterioration), allows the pump to maintain its functionality because, as a secondary function, it acts as a cement seal. In this way the cement is prevented from ending up in the oil lubrication system, which allows it to be isolated and better protected. 
         [0024]    Furthermore, by inserting an overload sensor (not shown) in the washing line, downstream of the plunger, it is possible to detect the presence of cement in the cooling circuit, indicating that the first, outermost sealing gasket  32  is in a worn condition. This sensor will send a signal to a data processing unit (not shown), which, on processing the information, will display an alarm to the operator, on a control panel in a command area such as a warning light, an acoustic alarm or, if there is a monitor, a pop-up alarm with or without an audio signal. 
         [0025]    The overload sensor may be of a pressure type (any inclusion of cement mixture inside the duct for the third fluid will increase the pressure necessary for the contaminated fluid to circulate). 
         [0026]    Alternatively, optical sensors may be used, such as those which measure fluorescence in UV light. Such sensors are able to detect the presence of oil in water. They can therefore warn of a problem with the sealing of the system of lubrication with the secondary fluid. When the concentration of oil, coming from the leakage from sealing gasket  29 , in the third fluid is too high, a problem may be indicated with sealing gasket  29 . The combination of this sensor with the others described above can indicate either damage to sealing gasket  32  for the primary fluid and/or damage to sealing gasket  29  for the secondary fluid. 
         [0027]    Finally, it is possible to set up a suitable filter on the collection line for the third fluid, this filter, too, being provided with an overload sensor, which can provide a warning when the concentration of contaminant has reached a threshold level. 
         [0028]    It will be appreciated that a worn condition of the outer sealing gasket  32  is detectable from the presence of cement in the third cooling fluid (or liquid), and that the combination of the cooling circuit with the addition of the second sealing gasket  37  increases the life of the first outer sealing gasket  32 , as it is possible to circumscribe an isolated volume which can contain cooling fluid and lubricant. Since the second sealing gasket  37  still protects the seal, the operator can decide whether to proceed immediately with replacement or to defer it, without risking damage to the plunger  11 , the sleeve  21  or the lubrication circuit, or risking contaminating the lubricating oil. 
         [0029]    The invention thus results in lower maintenance costs, prolongation of life for the components (especially for the final sealing gasket sealing against cement, and for the sleeve of the sealing device), and extended and predictable maintenance intervals. A single maintenance intervention for changing the lubricating oil and the gaskets is possible. The state of wear of the sealing gaskets sealing against cement can be monitored. The gaskets no longer must be replaced only at scheduled and preventive maintenance intervals but can always be replaced promptly as soon as they are found to be in a worn condition. If necessary, if the final cement sealing gasket is moderately worn, it is possible to continue working without risking the sleeve or contaminating the oil, thanks to the second cement sealing gasket. Operators in the drilling field will appreciate that the second sealing gasket makes it possible to complete not only the execution of the jet column in progress, but for example to complete all the columns for the day or to reach a weekend or other scheduled break set aside for ordinary and for extraordinary maintenance on site. Thus it is possible to schedule maintenance activities without delaying planned production. Finally, it is possible to keep the life and the efficiency of the secondary fluid seal monitored. 
         [0030]    It should also be appreciated that the description above and the illustrated embodiments are exemplary of the present invention and should not to be taken in any way as a limitation of scope, applicability or arrangement of components of the invention. The drawings and description, however, will provide those skilled in the art with a convenient outline for the implementation of the invention, while it will remain understood that various changes may be made to the function and arrangement of the elements described in the exemplary embodiments, without departing from the scope of the invention. For example, the number of plungers may vary depending on particular needs, or the sealing gasket  32  also may have the same secondary function of guiding the piston and be conformed in the same manner as the sealing gasket  37 .