US3561645A

US3561645A - Viscous material spraying device

Info

Publication number: US3561645A
Application number: US720931A
Authority: US
Inventors: Roger H Hopkins
Original assignee: ROGER HOPKINS CO
Current assignee: ROGER HOPKINS CO
Priority date: 1968-04-12
Filing date: 1968-04-12
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09

Abstract

An apparatus and method for spraying coal tar and other thixotropic viscous materials comprising a first vibrating container having therein a feed screw and having pumping means for removing materials from the first container to an adjacent heating container for heating the viscous materials. A second high-pressure pumping means are connected to the heating container to remove the lower viscosity material therefrom which is then pumped through conduit means for spraying. A heating conduit circuit is arranged so that when not in use a limited amount of viscous material may be heated and prepared for spraying without having to heat the entire bulk of raw material.

Description

United States Patent 72 Inventor Roger R. Hopkins 3,407,972 10/1968 Cymbalisty.... zz'z/ibx Pasadena, Calif. 1,862,752 6/1932 Jones et a1. 222/238 [2]] Appl. No. 720,931 3,049,302 8/1962 Simmons, .lr.. 239/75 [22] Filed Apr. 12, 1968 3,226,030 12/1965 Rossi 239/135 [45] Patented Feb. 9, 1971 3,235,231 2/1966 Dietze et a1 259/7 [73] Asslgnee g Hopkniisfcompany Primary Examiner-Robert B. Reeves asa Assistant ExaminerNorman L. Stack,Jr. a corporanon of Cahfomla AttrneySpensley, Horn, and Lubitz [54] VISCOUS MATERIAL SPRAYING DEVICE 10 Claims 6Draw' F mg gs ABSTRACT: An apparatus and method for spraying coal tar [52] U.S.Cl.. 222/146 and other thixotropic viscous materials comprising a first [51] f B67d /62 vibrating container having therein a feed screw and having Fleld ofSearch means for removing materials from the fir t con- 196, 216, 238, 236, 318, 321, 320, 333, 8 miner to an adjacent heating container for heating the viscous 198/64, 62; 239/135, 133, 71, 75; 259/l 7, 9; materials. A second high-pressure pumping means are con- 222/146 146, 146mg 239; lgs/(lnqulfed); nected to the heating container to remove the lower viscosity 3O2/(Inqu1red) material therefrom which is then pumped through conduit [56] References Cited means for spraying. A heating conduit circuit 18 arranged so that when not In use a limited amount of viscous material may UNITED STATES PATENTS be heated and prepared for spraying without having to heat 3,106,344 10/1963 Baird, Jr. et a1 222/146X the entire bulk of raw material.

5 v v 56 COMM/NEE 54 55 65 P $521 la Wale/17g? g @639 EMF 2 f f 4 I! so .i /;7 Ii I wa izl i 22a 50 52 5 6 05 3565 i ii a u P -:::::f:i l w 21d 67 I- \1 $50 2 6 FI/MP E% 5 Joesw VISCOUS MATERIAL SPRAYING DEVICE BACKGROUND OF THE INVENTION I. Field of the Invention This invention relates to an apparatus and method for spraying highly viscous materials and more particularly to a vibrating and heating device for lowering the viscosity of thixotropic materials such as coal tar derivatives so that they may be sprayed.

2. Description of the Prior Art Heretofore the means employed for spraying high viscosity coal tars or other materials were generally high-temperature heating devices which lowered the viscosity of the coal tar or coal tar derivatives by heating the material to about 450-60 F. At these temperatures coal tar material has a viscosity low enough that it can then be sprayed. However, there are many problems with such a high-temperature spraying device. One such problem is that at these elevated temperatures of over 450 F. many noxious fumes are given off by the coal tar with hazardous consequences to the health of the spraying apparatus operator. Another difficulty arising from the hightemperature method is that as it is sprayed, the hot material to be sprayed has a tendency to spatter. When such a drop of hot material contacts the skin of an operator, serious burns and injury can occur. The high-temperature method cannot be used when additives are in the viscous material such, for example, as diluents in some small percentage or solvents. The high temperatures required to lower the material viscosity either decompose or evaporate off the additives and solvents. Also, spraying above the boiling point of additives results in spongy and porous coatings which are defective in quality.

Accordingly, it is a primary object of the present invention to provide a viscous material spraying device with which the material is sprayed at temperatures below about 270F.

It is another object of the present spraying device to make it possible to spray coal tars containing therein small amounts of solvents.

It is yet another object of the present coal tar spraying device to provide an apparatus for lowering the viscosity of the thixotropic coal tar by first vibrating it and then heating it whereby it can then be sprayed.

SUMMARY OF THE INVENTION In one of its broadest aspects, the invention comprises a container having a discharge port, means connected to the container for urging material out of the container through the discharge port and means connected to the container for vibrating the material within the container. There are heating means connected to the container for heating material discharged from the container and conduit means located adjacent the heating means for spraying the heated material.

The advantages of the invented apparatus and method for spraying highly viscous thixotropic materials are that materials of over 1,000,000 centipoise viscosity can be vibrated, then transferred to a heating box and heated to about 270 F. and sprayed. This low-temperature spraying capability prevents formation of noxious coal tar fumes and also prevents the dangers of spattering of 450-600 coal tar which can be very hazardous to the apparatus operators. A further advantage of the invented apparatus and method is that coal tar materials containing a small amount of additives such as amino acids or solvents can be sprayed whereas in the prior art methods the high temperatures required for spraying caused additives and solvents to be evaporated off. Thus, with a very low percentage of solvents and amino acids still retained in the coal tar it is possible to spray steel pipelines without the use of any priming materials on the steel since the solvent and amino acid aids in the wetting of the steel pipe by the coal tar. Still another advantage of the present invention is that the cold thixotropic material is vibrated when first emptied out of its drum into the vibrating container in such a manner that it does not adhere to the walls of the vibrating container. The viscosity of the thixotropic material is lowered by the vibration so that the material can be pumped to a heat box for further lowering the viscosity. Yet another advantage of the present invention is the ability to circulate and heat in the apparatus a small amount of heated material to be sprayed while the spraying device is not in'operation. Therefore, a heated supply of material is kept on hand at all times to start operations immediately. Prior art devices circulate the hot material to be sprayed (at a temperature of 425450 F.) that is not in use back into the original container of material. This, of course, is far less thermodynamically efficient than the present invention. The prior art methods require heating of a metal spraying hose to prevent hardening of the tar; this is unnecessary in the present spraying device since a small amount of material is kept circulating even when the spray guns are not operating, this material containing sufficient solvent to prevent harden- The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof will be better understood from the following description considered in connection with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a simplified flow sheet in diagrammatic form of the invented spraying apparatus.

FIG. 2 is a simplified side elevation partially sectioned of the vibrating chamber and feed screw.

FIG. 3 is a simplified view in the direction 3-3 of FIG. 2.

FIG. 4 is an elevation partially sectioned in the direction of 4-4 of FIG. 1.

FIG. 5 is an elevation partially sectioned in the direction of 5-5 of FIG. 1.

FIG. 6 is a side elevation partially sectioned of an alternate embodiment of the invention having an eccentric feed screw.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention can be used for spraying any high viscosity materials, however it is particularly useful for, and is hereinafter described in connection with the spraying or coating of thixotropic high viscosity coal tar materials.

Referring now to FIG. I, a viscous material container I0 having an opening 12 in the upper side thereof into which is introduced viscous materials can be made of steel or other metals which are chemically resistant to the viscous material that is to be placed into the container. The container is mounted on rubber shocks 16 or on other shock-absorbing means such as springs. The function of these mounts is to absorb vibrations emanating from container 10. In the presently preferred embodiment of the invention, container 10 is adapted to receive thixotropic high viscosity coal tar. The container can conveniently be about 60 inches long, 48 inches wide and 48 inches deep. Drums of thixotropic coal tar or other viscous material can be lodged in opening 12 of the container and when vibration is commenced, container I0 vibrates sufficiently to communicate vibration to the drums to aid the flow of the highly viscous material from the drums into container 10.

Referring to FIG. 1, proximate the bottom I] of the container is a feed screw 30. The feed screw 30 can conveniently be an augerlike tool which when it rotates in a counterclockwise direction helps to force the highly viscous material in the indicated direction by means of blades 31 towards a discharge opening 22. Discharge opening 22 can be located between the feed screw 30 and the bottom II of the container. The rotation of the feed screw also serves the important func tion of mixing and lowering the viscosity of the thixotropic coal tar in which it is rotating and also of decavitating the charge. in the presently preferred embodiment of the invention, the feed screw is made of 6-inch diameter steel pipe having steel or other metallic continuous strips spirally wound around the pipe circumference and welded to the pipe to form blades 3i. The blades can be approximately 6 inches apart. it is, of course, within the scope of the invention to use other rotating augerlike tools. in one preferred embodiment of the invention the feed screw 30, FIG. 6, is constructed so that it rotates eccentrically and causes vibration. This may be ac complished by mounting an offcenter weight 32 on feed screw 30 which causes the feed screw to rotate eccentrically and thus to vibrate. in this embodiment of the invention, weight 32 comprises a metallic rod which is inserted along the inside of pipe 30 adjacent one side thereof. In the presently preferred embodiment of the invention, an off-balance metallic shaft 39 (FIG. 1) is mounted in container if) such that it can rotate in dependently of feed screw 30 and at various speeds so that container 10 is caused to vibrate.

The feed screw as shown in FIGS. 2 and 6 is connected by shafts to bearing mounts 21 mounted by brackets 21a onto the container. One end of the shafts 20 is connected to a drive shaft 18' which in turn can be connected to a conventional variable speed motor. In one preferred embodiment of the invention the feed screw 30 is rotated at a speed calculated to provide the maximum amount of vibration due to the eccentric revolutions of the screw. The vibrations cause the thixotropic coal tar or other viscous material to become thoroughly mixed with any solvent or any diluents added thereto and also to be decavitated. This thorough mixing and decavitation (i.e., the driving out of all entrapped air) causes the coal tar to become less viscous until it has achieved a sufficiently low viscosity to be urged out of the container by the combined force of threads 31 of auger 30 and suction of pump 50. During this vibration of container 10, additional thixotropic coal tar can be loaded into the container by placing drums along opening 12 in the container. it has been found that when the feed screw 30 turns in the range of approximately 150 r.p.m., the viscosity of the thixotropic coal tar originally 1,000,000 centipoise or higher is reduced to a viscosity at which it is sprayable by the vibration of container it) alone. The revolutions per minute of the feed screw can be varied to compensate for the material viscosity and climatic temperature condition. The revolutions of shaft 39 can be varied to increase or to decrease the vibrations of container 10.

it is also within the scope of the invention to vibrate container 10 and to agitate the material therein by independent vibrating means externally connected to said container. This could be accomplished by mounting container 10 on vibrating spring means or by attaching an unbalanced fly wheel.

Referring again to H6. 1, discharge line 22a is connected to a pump 01, designated 50. Pump 50 is a positive displacement pump of a Well known type and is designed to produce 1,000 p.s.i. pressure to the material moving through the conduit 22a. Thus, feed screw forces the material 14 along discharge line 22a. Pump 50 then pumps the material through coil 48. When spray guns 60 are inoperative, pump 02, designated 54, forces the material out of the

lines

62 and 64 through bypasses 70 and back to line 65. This cycle can be repeated continuously. It should be noted that beyond the bypass, line 52 serves to recirculate continuously small excess volume produced by pump 50and not taken into pump 54. This excess goes from line 52 to 65 to 22a.

The heat exchanger 40 comprises a generally rectangular structure having thermally insulated walls. The insulation 41 can be of any thermally insulating material such as asbestos or fiberglass. The body of the structure is filled with a heat transfer material 42 that can be heated to elevated temperatures. Coil 48 passes through the hot heat transfer material 432 thus transferring heat from the heat transfer material to the material passing through coil 48. Any kind of oil capable of being heated to approximately 475 F. may be utilized in the heat exchanger as the heat transfer material. In the presently preferred embodiment of the invention, heat transfer oil is used in the heat box.

As shown in FIG. 4, extending horizontally into the heat box 40 are heater elements or rods 44. As many heating elements as are required may be inserted into the heater box 0. The heater rods comprise a hollow metallic housing which may he rectangular or cylindrical in cross section and which contain an electrical heating element capable of heating the surrounding heat transfer material to a desired temperature. When all the heater elements are operating, the heat transfer material is maintained at a temperature such that a viscous material passing through coil 43 will be maintained at an elevated temperature (less than that of the heat transfer oil temperature) such that the viscosity of the viscous material will be lowered sufficiently to make it sprayable. lt is, of course, within the scope of the invention to apply heat in any manner to heat exchanger 40, for example electrical coils that are protected could be placed on the bottom or the side of the container or the heating tubes could be placed vertically into the container. Also coal or gas flames could be used to heat the box 40. The heating elements 44 are thermostatically controlled so that when the desired heat transfer oil temperature is attained, they will shut off until a second lower sensing temperature is attained. Then heater elements will again come on to bring the oil up to the original temperature level.

Coil 48, FIG. 4, which can be a conventional heat exchange coil terminates at,discharge pipe 52 which is connected to a pump 54, FIG. 1. Pump 54 has a capacity to provide a pressure of 3,000 pounds per square inch to the material leaving the heater box through discharge tube 52. When coal tar is passed through the heat exchanger 40 which is at an elevated temperature, the coal tar leaves the box through tube 52 at a temperature of approximately 270 F. and a viscosity sufficiently low for spraying. One kind of tar used has at 270 F. approximately the same viscosity as SAE I40 weight oil at 72F. Temperature-sensing element 57 at discharge pipe 52 causes heaters 44 to be cut out if the temperature of the materials goes above 270F. Material heater box 40 is forced along conduit lines 56 and 58 by pump 54 to spray guns 60. When the guns are not in use, the thixotropic coal tar or other material is forced by pump 54 through bypass 70, and then through

return lines

62 and 64 to line 65. Line 52, FIG. 1, contains a bypass 55 which is designed to operate at 1,000 p.s.i. Thus, when pump 54 is shut off or is not working and only pump 50 is working, and providing 1,000 p.s.i. pressure, material passes through line 22, through pump 50, through coils 48, through discharge line 52, through bypass 55, and through lines 65 back to line 22. This cycle is continued until spraying is commenced. The material passing through this cycle is heated as it passes through heat box 30. it can be observed that only a small amount of material is actually being heated while cycling. This material is then ready to be immediately sprayed when pump 54 is activated. When pump 54 is activated, the 3,000 pound pressure created moves material through line 22, through separator 53 and through manifold 53a, through pressure hoses 56 and 58, to spray guns 60. When pump 54 is activated, pump 50 supplies a greater volume (9 gallons per minute) than pump 54 is capable of pumping (7 gallons per minute). The excess material pumped by pump 50 (2 gallons per minute) continues to recirculate through bypass 55 and returns to line 22, thus combining warm material with cold material coming from container 10 and thus increases the efficiency of the heat exchanger 40. Spray gun 60 can be of any commercially available type. When the spray gun is not in use, hot material passes through a bypass valve 70 and returns via

lines

62 and 64 to the intake vantageous in that solvents can be reclaimed and recycled thus making the process more economical.

In operation, a thixotropic viscous material 14 is loaded into container by placing containers of the material at opening 12 which has a ledge 13. The vibrator 39 and auger 30 are then turned on at predetermined revolutions per minute such that a drum of thixotropic coal tar is vibrated and its contents empty into container 10. Continued vibration of container 10 then levels off the material therein and prevents cavitation. The material is urged through discharge line 22, through pump 50, and through heat exchange coils 48 which pass through heat exchanger 40. The temperature of the heat transfer material in the heater box is maintained at maximum 300F. While passing through heat exchange coils 48, material 14 is heated to a temperature of approximately 270F. Pump 54 supplying a pressure of 3,000 pounds per square inch forces the material (whose viscosity is now sufficiently low for atomizing through a spray gun) through separator 53 and manifold 53a and through high-pressure lines 56 and 58 to spray guns 60 where the material may be sprayed. lf spraying is to be discontinued for a short time, spray guns 60 are shut off and the material is returned through bypass valves 70 along

lines

62 and 64 to return line 65. This material is then circulated through line 65 and line 22a through pump 50, through coil 48 in heater box 40 through discharge line 52 and through bypass 55 which opens at 1,000 pounds per square inch. The temperature in the heater box is also maintained at maximum of 300 F., thereby maintaining material that is being circulated through the box at 270F. This material is then ready to pass through pump 54 and to be sprayed immediately upon reactivating spray gum 60.

in a typical operating run, drums of coal tar are emptied into container 10 by any convenient means and preferably by lodging them to a ledge 13 at opening 12 in container 10. Feed screw 30 is then turned on. Shaft 39 is next caused to rotate which causes container 10 to vibrate. This vibration helps to empty the highly viscous thixotropic material out of the drums and into the container. Next, the heating elements in the heat exchanger are activated and the temperature of the oil is brought up to approximately 270-300F. The first pump 50 is then turned on. This pump urges material from tank 10 through discharge line 22a and through heating coils 48 in the heat box out through discharge line 52, through bypass 55, through return line 65 back into line 220. This cycle is continued until spraying is to be commenced. The second pump 54 is then activated. Activation of pump 54 forces material leaving the heat exchanger 40 through line 52 and through lines 58 and 56 to spray guns 60. Two gallons of material per minute continue to go through bypass 55. When two spray guns are used, 7 gallons per minute of thixotropic coal tar at 270 F. can be sprayed. When spray guns 60 are deactivated, the thixotropic coal tar is returned through

lines

62 and 64 to return line 65 and is then continued cycling through the 1,000 pound per square inch pump and the heat exchanger and through pumps 54, separator 53, lines 56 and 58, bypass 70 and back through

lines

62 and 64. Then coal tar is sprayed onto any pipeline surfaces or any other surfaces to be sprayed and temperature in the heat box is thermostatically maintained at approximately 300F. The heat exchanger 40 can be shut off shortly before the spraying operation is complete. Next, pump 54 and pump 50 are shut off and feed screw 30 is shut off. The material in lines 58 and 56 which solidifies still contains solvents when it cools and may be ejected by the 3,000 pound pump at the start of the next run. it is also within the scope of the invention to provide heating mantles for hoses 56 and 58. These can be activated prior to starting a run (if a material low in solvent has been used in a prior run) to aid in ejecting cooled material from lines 56 and 58.

it is apparent from the foregoingthat the invented thixotropic coal tar spraying device has many advantages. One such advantage is that coal tar can be sprayed at a temperature of approximately 270 F. or lower. At that temperature some solvents are still retained in the coal tar and this makes it particularly useful for spraying steel pipe lines which are unprimed, the solvent serving to wet the steel and causing better adhesion between the coal tar and the steel pipe. Another advantage of the invented device is that coal tars having viscosities in excess of 1,500,000 centipoise can be processed by the apparatus without applying high temperatures because of the application of vibration which decavitates the material and lowers viscosity before it is pumped through the heat exchanger. Yet another significant advantage of the present device is that because of the lower temperatures required for spraying the coaltar, no noxious fumes are given off by the coal tar as is the case with prior art devices where temperatures of 475 or higher are used to lower the viscosity. Furthermore, spattering of coal tar when sprayed, is a common occurrence on pipeline -jobs and when the prior art methods using viscous materials at temperatures of over 475 F. are used, it becomes extremely hazardous since coal tar for example at these temperatures and its fumes will cause severe burns on the skin of anyone in the vicinity. However, when only 270 F. temperature is used, the process is far less hazardous to an operator.

lclaim:

1. Apparatus for storing and spraying a viscous thixotropic material at a temperature substantially below the normal temperature employed for spraying, said apparatus comprising:

a. a container for storing a quantity of said material at ambient temperature, having a discharge port;

b. means for reducing the viscosity of at least that portion of said material adjacent the outlet of said container comprising means for vibrating at least said portion to thereby provide a material which is pumpable at a temperature substantially lower than the temperature at which it is pumpable if not vibrated;

c. heat exchange means for heating said material only to a temperature substantially below the normal temperature required for spraying said material if it is not vibrated;

d. spray means connected to the discharge of said heat exchange means for spraying said material; and

e. means for pumping said material from said container through said heat exchange means to said spray means.

2. The apparatus as defined in claim 1, wherein material passing through said heat exchange means is heated to above 200 F. and below 280 F.

3. The apparatus of claim I, and means for recirculating material from the discharge of said heat exchange means to the intake of said heat exchange means.

4. The apparatus of claim 1, and solvent condenser means between said heat exchange means and said spray means.

5. The apparatus of claim 1, wherein said material is coal tar, said normal temperature is about 450-600 F. and said lower temperature is about 270 F.

6. The apparatus of claim 1, said vibrating means comprising a feed screw adjacent said discharge port for directing material to and through said discharge port.

7. The apparatus as defined in claim 6 wherein said feed screw has a weight .interiorly connected to one side thereof so that said feed screw rotates eccentrically.

8. A method of spraying a thixotropic viscous material at a temperature substantially below the normal temperature required for spraying comprising:

reducing the viscosity of thixotropic viscous material by:

a. vibrating said material, and

b. heating said material to a temperature substantially lower than the temperature required to achieve a sprayable viscosity without vibration; and

spraying said material at substantially said temperature.

9. The method of claim 8, said material being coal tar and said temperature to which it is heated being about 270 F.

10. A method of spraying a thixotropic viscous material comprising the steps of:

vibrating and decavitating a thixotropic viscous material;

heating said viscous material until its viscosity is lowered sufficiently to permit spraying; and

spraying the heated material onto a workpiece.

Claims

2. The apparatus as defined in claim 1, wherein material passing through said heat exchange means is heated to above 200* F. and below 280* F.
3. The apparatus of claim 1, and means for recirculating material from the discharge of said heat exchange means to the intake of said heat exchange means.
4. The apparatus of claim 1, and solvent condenser means between said heat exchange means and said spray means.
5. The apparatus of claim 1, wherein said material is coal tar, said normal temperature is about 450*-600* F. and said lower temperature is about 270* F.
6. The apparatus of claim 1, said vibrating means comprising a feed screw adjacent said discharge port for directing material to and through said discharge port.
7. The apparatus as defined in claim 6 wherein said feed screw has a weight interiorly connected to one side thereof so that said feed screw rotates eccentrically.
8. A method of spraying a thixotropic viscous material at a temperature substantially below the normal temperature required for spraying comprising: reducing the viscosity of thixotropic viscous material by: a. vibrating said material, and b. heating said material to a temperature substantially lower than the temperature required to achieve a sprayable viscosity without vibration; and spraying said material at substantially said temperature.
9. The method of claim 8, said material being coal tar and said temperature to which it is heated being about 270* F.
10. A method of spraying a thixotropic viscous material comprising the steps of: vibrating and decavitating a thixotropic viscous material; heating said viscous material until its viscosity is lowered sufficiently to permit spraying; and spraying the heated material onto a workpiece.