US 3631555 A
A manually actuated, automatically operated pellet gun for propelling felt pellets through the tube of a heat exchanger in order to clean the interior of the tube. Pellets are magazine fed to the bore of the gun and means are provided for selectively propelling dry pellets through the tube or pellets saturated with a cleaning agent.
Description (OCR text may contain errors)
United States Patent Inventors Kenneth Hurst; R f r nces Cited Charles W. Linz, both of Chattanooga, UNITED STATES PATENTS Tenn 1,814,766 7/1931 Oberhuber 15/3.5 p 17,634 2,669,936 2/1954 Elkins et al. ..l5/l04.06 A ux Mar-9,1970 3,322,140 5/1967 Scott l5/l04.06 A patfitmed 19,72 3,531,813 10/1970 Hurst l5/l04.06 A Asslgnee Combustion Engineering, Inc.
Windsor, Conn. Pnmary ExammerEdward L. Roberts Attorneys-Carlton F. Bryant, Eldon H. Luther, Robert L. Olson, John F. Carney, Richard H. Berneike, Edward L.
TUBE-CLEANING PELLET GUN Kochey, Jr. and Lawrence P. Kessler 6 Claims, 1 Drawing Fig.
US. Cl SHOLSAZESA, ABSTRACT: A manually actuated automatically operaed Bosh 9/04 pellet gun for propelling felt pellets through the tube of a heat 15/3 5 exchanger in order to clean the interior of the tube. Pellets are magazine fed to the bore of the gun and means are provided for selectively propelling dry pellets through the tube or pellets saturated with a cleaning agent.
- gym/ my TUBE-CLEANING PELLET GUN BACKGROUND OF THE INVENTION In the manufacture of heat exchangers, especially those of the shell and tube type wherein the interior of the shell houses a plurality of tubes whose ends are mounted to a tube sheet that closes the end of the shell, it is necessary that one of the final stages of the fabrication process include that of cleaning the interior of the assembled tubes. This need arises from the fact that during the various steps of the fabrication process the deposition of dirt, metal chips and other sediment in the tubes is inescapable. Moreover, prior to completion of the assembly, it must be heat treated which results in the generation of metal oxides within the tubes. To remove these oxides, the tubes are subjected to acid pickling and thereafter it is necessary to clean the tubes to insure that no acid residue remains in the tubes upon completion of the pickling step since the presence of such acid would ultimately result in contamination of the fluid passed through the tubes during operation of the heat exchanger.
In the past, it has been the practice to clean the tubes of such heat exchangers by manually drawing a swab attached. to a wire or the like through the tube. This is both a laborious and time consuming procedure especially when it is considered that it is not uncommon for heat exchangers of this type to include thousands of tubes. The present invention, therefore, is directed to apparatus that is operative to expeditiously reduce the time, effort and expense required to clean the interior of tubes mounted in the tube sheets of heat exchangers.
SUMMARY OF THE INVENTION According to the present invention, therefore, there is provided apparatus operable to propel a cleaning pellet by means of compressed air or other motive fluid through the interior of the tubes assembled in the tube sheet of a heat exchanger or other similar equipment. The invention comprises a manually manipulatable body forming a barrel into which pellets formed of absorbent material, such as felt or the like, are fed individually from a magazine. The body is adapted to be held against the tube opening in a tube sheet to effect communication between the barrel and the interior of the tube. Manually actuated pneumatical operating means are provided for manipulating a loading plunger for loading a single pellet into the barrel from the pellet magazine. Further pneumatic operating means which are manually actuated are provided for propelling the pellet into and through the tube to be cleaned. In addition, pilot-operated means are provided to selectively saturate cleaning pellets with a regulated amount of cleaning agent prior to propelling it into the tube.
By means of the disclosed invention easily manipulatable means are provided for cleaning the interior of elongated tubes without need of manually running swabs back and forth through the tubes to be cleaned.
For a better understanding of the invention, its operating advantages and other objects obtained by its use, reference should be made to the accompanying single drawing and description which relate to a particular embodiment of the invention.
DESCRIPTION OF THE DRAWING The single FIGURE is a schematic representation of the pellet gun organization of the present invention.
= DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing there is shown a pellet gun assembly that is constructed and arranged according to the present invention and which is shown in operative relation to a tube 12 to be cleaned that is mounted in a tube sheet 14. By means of the invention pellets 16 that may be formed of felt or the like and which are of an initial diameter slightly greater than that of the interior of the tube 12 are caused to be propelled through the tube in order to wipe the tube clean of any residue or sediment that may remain therein after assembly of the tube to the tube sheet 14.
The assembly comprises a body 18, generally rectangular in section, and having an axial through bore 20, the latter being of enlarged diameter, as at 22, at its rear end. At its rear the bore 20 is closed by means of a threaded plug 24, itself having a through opening attaching a pneumatic motor consisting of cylinder 28 and piston 30. Ports 32 and 34 are provided on the body of the cylinder for admitting air to and releasing it from the cylinder on either side of the piston as hereinafter further explained.
A pellet-loading plunger 36 is operable in the bore 20 and comprises a reciprocatable rod having a leading end that is slidably received within the bore and an enlarged shoulder 38 that slides within the enlarged diameter portion 22 of the bore. The plunger 36 is operably attached to the piston 30 of the pnuematic motor by means of a cylinder rod 40 that threadedly attaches to the two members. The plunger 36 is operable in its retracted position to expose a lateral opening 42 through which is passed pellets 16 from a magazine 44 that is attached to the body 18 and which houses a plurality of cleaning pellets. At the forward end of its stroke the plunger 36 is operable to locate a pellet 16 just downstream of an inlet opening 46 that laterally penetrates the body and that is operable to inject propellant fluid on the rear side of the pellet for propelling it out of the pellet gun assembly and through the tube to be cleaned.
At its forward end the body is provided with an internal thread that serves to attach a threaded fitting 52 for connecting one end of a transfer tube 54. The transfer tube 54 is hollow to permit passage of a pellet l6 and connects at its other end to a hollow cylindrical length of tubing 56 that is adapted to be held by a workman to the end of the tube 12 to be cleaned. Connection is made between the transfer tube 54 and tubing 56 by appropriate threaded connectors 58. The leading end of tubing 56 connects a hollow nozzle 60 whose interior bore 62 is tapered to compress the pellet 16 to a diameter that is easily receivable within the tube 12. The hereindescribed pellet gun assembly 10 further includes various operating mechanism that is effective to load a pellet within the bore 20; other mechanism that is operative to propel the pellet through the selected tube; and still other mechanism that is operative to inject cleaning fluid onto a pellet prior to its admission to the tube whenever desired. Also included is a manually actuated pneumatic control system that is effective to operate these various operating mechanisms to achieve the results desired.
1 Going first to the mechanism employed to load a pellet 16 within the bore 20 there is provided a pilot operated control valve 66 having a compressed air inlet port 68, two fluid discharge ports 70, 72 and two exhaust ports 74 and 75. Inlet port 68 connects with a source of compressed air (not shown) by means of fluid line 76. As shown, line 76 in the disclosed arrangement connects with T-connector 78 which, in turn, attaches lines 80 and 82, the former containing air filter 84 and being that which connects with the compressed air source while the latter connects with an air pressure regulator 86 for reasons hereinafter more fully explained. The fluid discharge ports 70 and 72 are caused to connect with the respective air motor inlet ports 32 and 34 by means of fluid lines 88 and 90 while the exhaust ports 74 and 75 are operative for exhausting operating fluid from the respective sides of the air motor piston 30.
The control valve 66 as is well known in the art is a normally closed valve containing a valve stem (not shown) that is operated by means of the pneumatically actuated pilot 92 to selectively connect the source of compressed air with one or the other of the ports 32 or 34 to move the loading plunger 36 to its forward or retracted positions. The valve contains a spring return for operating the stem to its original position upon deactuation of the pilot 92. As shown, the pilot 92 is operated in response to low-pressure compressed air that flows through line 94 from trigger-operated three-way operating valve 96 that received motive fluid through line 98 from the pressure regulator 86. The operating valve 96, along with similar operating valves 116 and 142 as hereinafter described are mounted by appropriate mounting brackets 100 and 102 to the tubing 56 for easy access by the workman.
Means for firing a pellet 16 that has been loaded into the bore 20 comprise pilot operated control valve 104 that is equipped with inlet and outlet ports 106 and 108 together with an exhaust port 110. This valve, having its inlet port 106 connecting with a source of compressed gas (not shown) preferably of an inert type such as nitrogen, connects through outlet port 108 with inlet opening 46 on the body 18 by means of line 112. The valve is operated by pneumatically actuated pilot 114 from a normally closed position to one placing the source of compressed gas in communication with the inlet opening 46. This valve is also of the spring return type. The pilot 114 is operated by trigger-actuated three-way valve 116 that connects with line 98 through safety valve 118 by means of line 120. The discharge side of the valve 116 communicates with the pilot 114 by means of fluid line 122. An O-ring seal 123 is provided on the plunger 36 adjacent its leading end to prevent retrograde flow of propellant fluid through the bore 20.
Safety valve 118 is a trigger-operated three-way valve comprising an operating pin that is caused to extend into the enlarged portion 22 of the bore 20 and which is capable of being depressed by the enlarged shoulder 38 of the loading plunger 36 when the latter is in its forward position. The valve is normally closed and connects lines 98 and 120 when the pin is depressed. Thus, due to the presence of the valve 118, the problem of actuating control valve 104 with the plunger in its retracted position is prevented since it is only with the plunger in its forward position that operating fluid is permitted to communicate with the pilot 114. An additional safety valve 119 is operatively connected between the pilot 114 of the firing valve 104 and pilot 92 of loading valve 66. Its construction is such as to include an actuator 121 and an exhaust line each being operative when air is passed through line 122 to open the exhaust line in order to vent air that may be passed through line 94. By means of this arrangement operation of the air motor 28, 30 is prevented while the firing valve 104 is being operated.
The means employed to impart an acetone soak or the like to selected pellets !16 comprises a supply tank 126 containing acetone or other cleaning agent and a control valve 128 having a pneumatically actuated operating pilot 130. The tank 126 is connected to an inlet port 132 on the valve 128 by means of fluid line 134. The outlet port 136 of valve 128 is connected to the body 18 through fluid line 137, the latter being caused to communicate with the bore 20 by means of a lateral opening 138. it should be noted that the point of communication of the opening 138 with the bore 20 is approximately at the point of disposition of a loaded pellet 16 with the plunger 36 in its forward position.
Means for operating the cleaning fluid injection system include a fluid line 140 extending between the pressure regulator 86 and the tank 128 for pressurizing the latter. A manually operated trigger-actuated three-way valve 142 mounted by means of bracket 102 to the tube 56 connects with the pilot 130 of control valve 128 by means of fluid line 146. lnterposed in this line is a timing controller 148 of known construction that is operative to deactuate the pilot 144 after a selected period of time, and thus terminate flow of cleaning fluid through line 136. In the disclosed arrangement a period of approximately onehalf second is deemed sufiicient for adequately wetting a pellet 16. The valve 142 receives its operating fluid through line 150 which connects with line 120 as shown.
In order to lend operating flexibility to the disclosed apparatus it is contemplated to fixedly mount the body 18, fluid motor 28, 30, valves 66, 104 and 128, acetone tank 126 and their ancillary equipment to a mounting means (not shown) in a remote portion of the work area. The tubing 56 that mounts nozzle 60 will be adapted for manual manipulation by a workman and all fluid lines and the transfer tube 54 that connect between tubing 56 and the fixed members will be formed ofa flexible material.
The operation of the herein disclosed invention is as follows. Compressed air at line pressure (approximately p.s.i.) enters lines 76 and 82 through line 80 from a source. This air is directed through line 76 to the inlet port 68 of control valve 66 and thence from discharge port 70 through line to the rear side of piston 30 to move the latter, together with plunger 36, to their forward position. At the same time, compressed air enters the air pressure regulator 86 where its pressure is reduced to 60 p.s.i. and the reduced pressure air thence passed through lines 98, and to the upstream sides of operating valves 96 and 116 and acetone tank 126. Energizing the tank 126 causes acetone to be passed through line 134 to the inlet port 132 of control valve 128. With the loading plunger 36 disposed in its forward position the actuating pin on safety valve 118 is depressed to open the valve and allow air to pass to the upstream sides of operating valves 116 and 142.
Thereafter when the workman has the nozzle 60 aligned with the end of a tube 12 to be cleaned he first depresses the operating trigger of valve 96. This allows air to enter line 94 to the pilot 92 of valve 66 causing its stem to shift and thereby pass compressed air at line pressure from port 68 to port 70 while port 72 is caused to communicate with its associated exhaust port 75. The result is that piston 30 and loading plunger 36 are caused to move to their retracted position thereby placing opening 42 in open communication with the bore 20 by which a single pellet 16 will be caused to drop into the bore from magazine 44. It will be noted that with the plunger 36 retracted the pin on safety valve 118 is no longer depressed thereby deactuating both the firing valve 116 and acetone actuating valve 142. When the pellet 16 has been loaded the trigger on loading valve 96 is released and the stem of control valve 66 is spring returned to its original position thus causing the plunger 36 and the loaded pellet to be moved forward to the position shown in the drawing. At this point safety valve 118 is again opened and operating pressure is admitted to firing valve 116 and acetone valve 142.
In order to fire the loaded pellet 16 the workman depresses the trigger on valve 116 causing compressed air to pass through line 122 to the pilot 114 of control valve 104. Actuation of the pilot 114 causes the internal stem of the valve to be positioned so as to place port 106 in communication with port 108 thereby admitting propellant fluid, nitrogen in the disclosed arrangement to the rear side of the pellet 16 thereby propelling it through transfer tube 54, tubing 56 and nozzle 60 into and through the abutting tube 12. Due to the tapered bore 62 in nozzle 60 the pellet 16 will be somewhat compressed prior to entering the tube 12 such that its entry can be easily effected. Once within the tube the pellet, due to the nature of the material of which it is formed, felt in this case, will expand to substantially fill the diameter of the tube so that a wiping action can be effected. After firing has occurred the trigger on valve 116 is released and the system returns to its original position.
If it is desired to wet a loaded pellet 16 with cleaning agent prior to firing the workman will depress the trigger on the valve 142 to pass air from line through line 146 the controller 148 which, in turn, operates the pilot 130 of control valve 128. By this means the stem within the valve 128 is positioned to permit flow of acetone from port 132 to port 136 and thence through line 137 and opening 138 in the body 18 to the loaded pellet. Due to the construction of controller 148 a preselected amount of cleaning agent is capable of being passed through the valve 128 with the valve closing after a predetermined duration. The mechanism employed in this arrangement provides for the opening of valve 128 for a period of one-half second.
By means of the present invention there is provided a relatively simple yet effective mechanism for cleaning the interior of tubes assembled in a tube sheet. Moreover, the arrangement is such as to render, the operation flexible and available in areas where space is limited.
It will be understood that various changes in the details, materials, and arrangement of parts which have been hereindescribed and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.
What is claimed is:
l. Apparatus for propelling compressible cleaning pellets through a tube assembled in a tube sheet, or the like, comprismg:
a. an elongated body having an axial bore therethrough;
b. means forming a manually manipulatable nozzle for registry with the end of the tube to be cleaned;
c. an elongated, flexible tube connecting said nozzle with the discharge end of said bore;
d. means forming a first transversely extending opening in said body communicating with said bore for loading a pellet therein;
e. means forming a second transversely extending opening in said body communicating with the bore forwardly of said first opening for admitting propellant fluid to said bore;
. a plunger reciprocable in said bore from a position placing its leading end rearwardly of said first opening for loading a pellet into said bore and forwardly to place said loaded pellet forwardly of said second opening;
fluid motor means for reciprocating said plunger;
. means for supplying propellant fluid to said second opentrigger means for selectively actuating said fluid motor means and said propellant supply means; and
j. control means operative to render said propellant supply means actuable only when said plunger is in its forward position.
2. Apparatus as recited in claim 1 wherein said nozzle is in- 3. Apparatus as recited in claim 1 including a control system 5 for operating said apparatus comprising:
a. first pilot-operated control valve means operatively connected to said fluid motor to retract said plunger when actuated and to extend said plunger to its forward position when deactuated;
. means for actuating said first control valve means;
second pilot-operated control valve means operatively connected to said body for supplying propellant fluid to said second opening;
d. means for actuating said second control valve means; and
e. means operated by said plunger for rendering said control means operative to deactivate said second control valve actuating means when said plunger is in its retracted position.
4. Apparatus as recited in claim 3 including:
a. a source of fluid cleaning agent;
b. means forming a third transverse opening in said body disposed at the point of location of the loaded pellet with the plunger in its forward position;
c. a line connecting said fluid cleaning agent source with said third transverse opening; and
d. third pilot-operated control valve means disposed in said line and operative to supply selected amounts of cleaning agent from said source to said opening.
5. Apparatus as recited in claim 4 including control means operative to render said third pilot-operated control valve means inoperative when said plunger is in its retracted position.
6. Apparatus as recited in claim 1 including means forming a magazine containing a plurality of cleaning pellets, said magazine having an open lower end communicating with said first transversely extending ppe ning.