US2791198A - Pipe coating apparatus including hot - Google Patents

Description

May 7, 1957 J. D. CUMMINGS PIPE COATING APPARATUS INCLUDING HOT COATING MEANS AND COOLING MEANS 5 Sheets-Sheet 1 Filed Feb. 9, 1955 INVENTOR.

ATTOR/Vf) dame: D. Cumm/nys ab WM P #5 May 7, 1957 Filed Feb. 9, 1955 J. D. CUMMINGS PIPE COATING APPARATUS INCLUDING HOT COATING MEANS AND COOLING MEANS 5 Sheets-Sheet 2 dam a: 17. (umm/n w INVEN TOR.

I ATTOR/Vfy May 7, 1957 J. D. CUMMINGS 2,791,198

\ PIPE COATING APPARATUS INCLUDING HOT comma MEANS AND COOLING MEANS Filed Feb. 9, 1955 5 Sheets-Sheet s Mam e: 17. (0/77/7707 Q IN V EN TOR.

QQXW United States Patent PIPE COATING APPARATUS INCLUDING HOT COATING MEANS AND COOLING MEANS James Dell Cummings, Houston, Tex., assignor to Crutcher-Rolfs-Cummings, Inc., Houston, Tex., a corporation of Texas Application February 9, 1955,Serial No. 487,162

12 Claims. (Cl. 118-69) This invention relates to the application of a protective coating on cables or conduits such as cross-country pipe lines commonly employed for the transmission of oil and gas. It deals with improved equipment designed to travel along a stretch of pipe line whose sections are joined on the ground beside a dug trench and to apply a tar-like substance as a sheath on the pipe as a final step preparatory to deposit of the pipe line in the trench. More particularly, the improved equipment includes a cooling mechanism arranged to trail immediately behind the coating machine and operative to quickly harden the hot, soft coating by rapidly reducing its temperature to an extent that the stiffened coating will resist running or displacement, so that the coated pipe can be placed without delay directly into its final position in the trench ready for backfilling of the trench.

In the installation of pipe lines the practice heretofore has been to prepare a trench and weld pipe sections end to end on the ground beside the trench and then apply to the metal pipe a corrosion resistant coating, as a hot fluid which gives up its heat to the surrounding air and solidifies as the coated pipe rests on supporting bolsters for several hours before being lowered into the trench and buried. Coating machines such as disclosed in Cummings et a1. Patent No. 2,692,906, dated October 19, 1954, track on the pipe and spread on the pipe a thick layer of asphalt dope in fluid form at a temperature of about 450 Fahrenheit, and also wrap the coating with spiral courses of paper, which help to hold the hot fluid is place while it is cooling to normal air temperature in the transition from a fluid to a solid. Because of the slow rate of cooling in air, there is a tendency for the hot fluid to sag or run from the top to the bottom of the pipe, and sag occurrence destroys coating thickness uniformity around the pipe circumference.

It is an object of the present invention to provide equipment to reduce the cooling time interval for quick setting and suflicient solidity of a hot fluid coating to insure a better bond to the surface of the metal pipe and a more uniform, hardened coating thickness and thereby to enable instant laying of the coated pipe as a continuing part of the machine coating operation, and which can be followed at once by backfilling to speed up the entire pipe laying job and without damage to the coating, as previously has resulted from strains imposed on cold pipe during a subsequent lowering operation.

Another object of the invention is to provide a cooling jacket surrounding the pipe and traveling in tandem to the usual coating machine as close as conveniently can be to the coating applicator shoe, with flushing spray nozzles to thoroughly and completely flood the hot pipe coating with an abundance of coolant fluid which rapidly absorbs the heat for a sudden chilling of the high temperature coating. At a travel rate of approximately sixty (60) feet per minute and with the circulation of coolant at a rate of approximately three hundred gallons per minute, the temperature of a freshly coated pipe can be decreased Patented May 7, 1957 about three hundred degrees Fahrenheit to enable the coated pipe to be dropped into the trench at once without waiting for a long cooling interval, as was heretofore required, and without the additional expense of labor and costly equipment for a deferred and separate operation of lifting the pipe from cooling bolsters and then lowering it into trench position.

A further object is to provide a pipe coating arrangement utilizing water as the coolant, which, after its absorption of heat from the coating, is collected for re-use by circulation and extraction of heat therefrom in a cooling tower mounted on a ground supported vehicle which follows alongside the cooling jacket.

A further object of the invention is to provide a cooling jacket of comparatively light weight with a coolant liquid collection and runoff arrangement to minimize dead weight water load on the cooling jacket and a jacket which does not required a built-in power propulsion mechanism but which, because of its light weight, can be easily towed by the power driven coating machine and suspended at its forward end from the coating machine, with its rearward end having a wheeled support on the coated pipe so that none of the jacket weight is impressed on the coating while it is in a displaceable, ,hot, fluid condition.

Other objects and advantages will become apparent during the course of the following specification read in the light of the accompanying drawings, wherein Figure 1 is a top plan view of the operating equipment assembled in pipe coating and cooling relation;,Fig. 2 is a side elevation of the coating machine and the cooling jacket as viewed on line 2-2 of Fig. 1; Fig. 3 is a vertical, longitudinal section of the cooling jacket assembly; Fig. 4 is a transverse section on line 4--4 of Fig. 3; Fig. 5 is a side elevation partly in section of the truck mounted cooling tower; Fig. 6 is a top plan detail view showing a tow bar steering arrangement for the cooling tower vehicle; and Fig. 7 is a section on line 7-7 of Fig. 6.

In the drawing an open trench 1 is indicated. The excavated dirt would be piled to one side of the trench, and the operating equipment here involved will track on the ground on the opposite side of the trench. The foremost of the equipment is illustrated in Fig. l as an endless track, power driven vehicle 2 having a conventional side boom structure 3 from which depends articulated linkage for mounting a series of spaced cradle rollers 4 for lifting the pipe 5 above the ground and suspending it during the coating operation. A similar power driven tractor and boom supported cradle mechanism will be used behind the coating and cooling equipment, as shown in fragment at 4A in Fig. 2. The two suspending cradles co-operate in positioning the pipe between them on a substantially straight line in spaced relation above the ground for the proper operation of applying and cooling the pipe coating. Although in Fig. 1 the axis of the pipe line is shown as extending substantially parallel to the trench, its deposit into the trench is facilitated by guiding the trailing cradle in a path closer to the trench than is the leading cradle, and in that event the axis of the pipe will extend at an incline to the direction of the trench, so that it will pay off from the trailing cradle without sharp lateral bends, directly into the trench.

Connected by a swivel tow coupling 6 at the back of the front tractor vehicle 2 is the usual tar kettle 7 supported on the ground by either wheels or endless tracks. The kettle includes a burner so that the asphalt dope placed in the kettle from time to time will be melted down and kept in a hot, fluid state for flow through a flexible pipe 8 by means of a suitable pump to the pipe coating shoes shown at 9 in Fig. 2. These shoes 9 constitute a part of the coating machine of the type shown. in the Cummings patent previously referred to. The;

pair of pumps one of which will draw hot coating fluid through the flexible pipe 8 from the tar kettle 7 and the other of which will scavenge drippings falling into the collecting trough 14 underslung by the main frame beneath the applying shoes 9 fed by both pumps. Another power take-off and variable ratio transmission will drive a rotary ring 15 which encircles the pipe at the back of the machine and carries a pair of spools 1616 from which paper strips are unwound as the ring rotates for wrapping the hot coating in spiral succession.

Immediately to the rear of the coating machine is the cooling device, which includes a cylindrical jacket formed in separable upper and lower halves 17 and 18, with the front end of the lower half connected by a pair of tow chains which extend forwardly and outwardly to clear the rotating spools 16-16 and have their forward ends connected to outriggers 2020, secured at the back of the coating machine to extend transversely at each side thereof. Supported by and projecting forwardly through the rear wall of the bottom jacket section 18 is a coolant delivery conduit or pipe 21 whose forward end terminates in a pair of arcuate branches 22, each of which is secured to the jacket section or pan 18 by brackets 23, as best seen in Fig. 4. At their upper ends and spaced on opposite sides of the pipe 5 are detachable pipe couplings 2424 for connection with arcuate branch conduits 25. A pair of seating pads 26-26 secure the pipe branches to the upper jacket section 17. These branches form a part of a rearwardly extending conduit 27 whose rear end is plugged or otherwise closed. The upper and lower conduits 27 and 21 each have a number of spaced spray nozzles 28-28 directed toward the pipe coating for delivering thereto the cooling water. An over-all length cooling jacket of about six feet has been found proper for the use of a sufficient number of nozzles to handle the volume of cooling water required to effect the desired drop in coating temperature.

After absorbing heat from the coating, the water drops freely into the bottom section 18, which serves as a collection pan and whose bottom portion 29 is centrally depressed and inclines downwardly and rearwardly to the discharge or drain pipe shown at 30.

Extending throughout the width and length of the pan 18 and at a height below the spray nozzles 28 is a strainer screen 75 of wire mesh. This holds back and may be cleaned periodically of foreign particles such as globules of dope which may become entrained in the flushing coolant and unless separated would present a clogging problem.

Extending rearwardly from the back wall of the pan 18 and above its bottom is an inclined drain tray 31 for delivering to the collection chamber any water dripping from the pipe beyond the spray nozzles. The drain tray 31 is semicircular in cross section to extend below the under side of the pipe, and at its rear end has secured to it a rubber or other similar squeegee flap 32 for Wiping engagement with the coated pipe in cleaning the same of moisture collection. Detachably bolted to the sides of the tray 31 at their rear ends are the terminal ends of an inverted U-shaped strap 33, to straddle the coated pipe and support the rearward ends of a pair of framing bars 34 whose forward ends are rigidly secured at the back of the top jacket section or pan cover 17. These longitudinal frame bars 34 mount a pair of outwardly and downwardly inclined axles on which are rotatable a pair of wheels carrying pneumatic tires 35 in relative planes which converge downwardly to ride on the cold pipe coating and support the back of the cooling jacket. The front of the cooling jacket has a pair of horns or hooks 36 which can be fitted into the bottom links of a pair of side chains 37 suspended from a bridle bar 38 on the free end of a boom 39 which projects rearwardly from a pivot connection on the frame of the coating machine. A guy wire 39 also connects to the free end of the boom 39 and leads to a winding drum 40 carried by the coating machine frame so that the boom and with it the front end of the cooling jacket may be raised or lowered in supporting the front end of the jacket. The raising and lowering adjustment of the jacket will be useful when the direction of travel is either up or down hill and it is desired to adjust the level of the bottom of the sump to insure the rapid flow of water toward the drain pipe.

For recirculation of the cooling water and for the dissipation of heat absorbed from the hot coating, there is provided a cooling tower whose inlet receives water from the drain of the sump and whose outlet is connected to deliver the cooled liquid to the coated pipe flooding nozzles. The cooling tower is mounted on a suitable vehicle, such as a motor truck 41, and it includes slotted side and end walls which rise vertically from the bed of the truck to afford a boxlike enclosure into which the liquid is sprayed for aeration and cooling in the air with in the box. The slots in the side wall and the top opening of the tower enable air circulation through the enclosure for taking the heat out of the sprayed water particles, which then drop to the floor, which is in the form of av tank or a sump. Each of the side walls of the tower may consist of a number of spaced vertical posts 42 between which extend horizontally a succession of spaced slats 43 which are set successively in downwardly and inwardly inclined parallel planes, affording shutters or water deflectors with air passages therebetween. Water to be cooled is atomized at the top of the tower by being discharged through spray heads in each of a succession of spaced transverse branch pipes 44 extending on both sides of a centrally disposed inlet conduit 45 extending across the length of the tower. In the bottom of the tower there is located a tank 46 which has side and end walls to form a storage container for the liquid coolant. The tank 46 also has a partition wall 47 which in longitudinal sectionis of a wide V-shape so that from both ends it inclines downwardly to a central region near the bottom of the tank and is connected at its lowest point with an outlet pipe 48. That space above the tank upper wall 47 constitutes a sump into which the cooled water is collected and stored at some desired predetermined level. The tank spaces below the wall 47 afford water storage chambers or reservoirs outside the cooling circuit and enable replenishment of the liquid supply as may be needed from time to time to compensate for evaporation. For increased storage capacity, vertical tank extensions 49 may project upwardly from the wall 47 and into the cooling tower space. Either float or hand operated valves 50-50 are provided for communicating the sump with the respective end storage chambers. Normally the valves 50 will be closed. If sump liquid level needs to be increased, one or both valves can be opened for water fiow'in the sump. Under some conditions, water from the sump may be transferred to the storage reservoirs, depending on relative levels and proper manipulation of the valves 50. Thus, for example, if the vehicle 41 is traveling up or down a steep incline so that either the forward or the rearward end of the sump moves below the water level in the sump, overflow and loss of cooling liquid would result. To minimize that condition, control of the valves 50 would transfer the excess water to storage until such time as replenishment is needed.

Water flow from the sump of the cooling tower is pump 50 whose pressure ,outlet is detachably joined to one end of a flexible hose or conduit 51 whose other end is detachably coupled .to the conduit 21 of the spray cooling device. A similar flexible hose 52 has one end detachably connected to the drain pipe of the cooling jacket, and its opposite end is detachably connected to the suction side of a pump 53 whose outlet leads to the spray delivery pipe of the cooling tower. Both pumps and 53 are driven from a common source of power, such as an internal combustion engine 54, through suitable power transmission mechanism, such as belting 55 or gearing. Preferably, the drive to the pumps 50 and 53 is at different speeds so that the pump 53 has a greater operating capacity for withdrawing water from the traveling cooling jacket as fast as it accumulates at the drain connection 30 so that no excess of water is carried in the cooling jacket. Also, the pump drive transmissions are separably clutchable to the engine 54, whereby the delivery from the pump 50 can be discontinued in advance of the withdrawal of water from the cooling jacket by the pump 53, whereby all the water may be returned and stored in the cooling tower when the cooling operation on the pipe coating is discontinued.

Engine power is also utilized to drive through a belt or chain 56 an electric current generator mounted on the truck beside the engine. This generator 57 supplies current for a holiday detector and marking system. The detector includes an annular coil 58 surrounding the coated pipe and suitably supported at the rear of the cooling jacket by a bracket 59 projected rearwardly from the frame member 33. A second supporting bracket 60 extends rearwardly from the drain tray 31 and mounts a valved pressure container 61 for a supply of paint under pressure. The valve is opened under control of a solenoid for discharging paint on the coated pipe as a marker of a place for a skip or holiday in the applied coating and which Will need to be remedied. The lack of coatiing on any portion of the metal pipe over which the coil 58 passes will vary the current potential in the circuit containing the coil, and that variation is utilized to actuate a conventional relay in a circuit containing the valve operating solenoid.

The truck for hauling the cooling tower could be a trailer vehicle to be pulled behind the power tractor 2, but for convenience of transporting the equipment between jobs, a power driven vehicle will be feasible. It, of course, can be driven independently of the tractor during the cooling operation, but for a more satisfactory operation and to eliminate the need for additional manpower, a tow bar arrangement may be provided for pulling the cooling tower in tnailing relation with the tractor vehicle .2. A preferred tow bar structure is shown in Figures 5, 6, and 7, in which the bar consists of a pair of separable sections 62 and 63 for detachable coupling by a pin 64. The forward end of the forward section ,62 is for coupling at the rear of the tar kettle 7. The rearward section 63 is permanently secured to the front axle 65 of the vehicle, and when the vehicle ,is operated under its own power, the forward tow bar section 62 is detached by removal of the coupling pin 64. A vertical pivot pin 66 is carried by the axle 65 to project through a head or eye at the rear of the tow bar section 63. The fit of the pin 66 in the eye is a loose one sothat suflicient play will exist for accommodating auniversal swinging action, as will be necessary to accommodate a vertical displacement by reason of uneven terrain and a relative horizontal movement when the direction of towing movement is other than straight. So that the towed vehicle will be steered to follow the "towing vehicle, the pin 66 additionally pivots a steering lever 67 .whose rear end is pivotally connected to a bracket .68 fixed to the .usual steering tie rod 69 whose opposite ends are jointed with the steering knuckles of the dirigibly mounted wheels 70 at opposite ends of the axle 65. At its front end the lever 67 is received within a vertically elongated slot in an upwardly extending boss 71 .of the tow bar 63. The lever end slidably fits with the side walls of the slot for "transmitting horizontal swinging movement of the tow bar 63 to the tie rod 69. The vertical sliding movement provided between the lever 67 and the boss 71 will accommodate the relative vertical movement of these parts, as when the two bar 63 moves vertically about its universally jointed rear end because of uneven ground surface on which the towing and towed vehicles (are then traveling.

From the foregoing description it will be seen that the equipment has been designed to travel over any type of terrain, whether the land be flat or hilly. Should a coating holiday be marked, the blank or skip may be quickly repaired or built up by hand and without necessarily stopping the continued forward coating operation. The operator who controls the rate of travel of the lead tractor and with it the dope kettle and the cooling tower and the operator who controls the advance of the coating machine, the trailing cooling jacket, and the holiday detector will co-ordinate their operations for unison movement of the ground supported and the pipe tracking equipments. Likewise, the operator of the trailing tractor will follow closely behind, with the rearward pipe suspending cradle in proper lateral relation to the forward pipe suspension cradle and the trench for paying out the cold pipe, either directly into the trench, as will be usually the practice, or on the ground beside the trench, as may fit certain situations. In any event, there is eliminated the need for a delayed cooling interval, and the traveling mechanism will harden the hot applied coating rapidly and immediately following its application to the pipe. There results a better bond with the pipe surface, a more uniform coating layer without objectionable sag, and a stiffness to resist pressure displacement, so that coated pipe may be laid and covered at once with full assurance of adequate protection against corrosion for a long life of pipe usefulness. With assurance of coating thickness uniformity, better control of the required amount of coating material applied, and without an excess to compensate for sag, enables good coverage with lesser material for an important cost savings.

What is claimed is:

1. Traveling equipment for operation on continuous pipe line at the location of its deposit in a trench, including a pair of traveling pipe line suspending cradles engageable with the ground beside the trench and spaced apart along -a length of pipe line suspended on substantially a straight line by said cradles, with the forward cradle arranged to progressively lift the pipe line and the rearward cradle arranged to pay out and deposit the pipe line in its trench during cradie travel, a coating machine tracking on the straight pipe line between said cradles and operative to apply a hot fluid coating on the pipe line during advance of the machine, mechanism in tandem travel relation with the hot coating machine and including a device for flooding a cooling liquid on the hot applied coating and a sump to collect said liquid, a ground engaging vehicle to travel alongside said mechanism, a liquid cooling structure on said vehicle, a sump for collecting the cooled liquid, a pump connected to deliver cooling liquid from the last mentioned sump to said flooding device, a second pump to return liquid to said cooling structure from the first mentioned sump, an electric generator on said vehicle, a drive engine common to said generator and said pumps, and a holiday detector to surround the coated pipe line adjacent said flooding device for travel therewith and connected for operation by current from said generator.

2. Traveling equipment for applying a protective coating on a pipe line, including in longitudinally spaced apart succession, a ground vehicle having a pipe elevating cradle, a mobile coating machine having a supporting and tracking bearing on the uncoated and cradle elevated pipe line and operative to apply thereto a hot coating material as the machine travels along the pipe line, a cooling liquid 7 delivery device trailing said machine to flood cooling liquid on the applied coating and extract heat therefrom, a liquid collecting sump forming a part of said device, a vehicle mounted liquid cooling mechanism for travel beside said device and having an inlet connected with said sump and an outlet connected to deliver cooling liquid to said device, pump means operative to recirculate said cooling liquid and another ground vehicle having a suspension cradle receiving the cooled coated pipe line.

3. In traveling pipe coating equipment, a mobile machine for applying a hot coating to a pipe as the machine advances along the pipe and means for hardening and adhering the hot coating on the pipe and promoting coating thickness uniformity circumferentially of the pipe immediate the application of the hot coating, comprising a cooling liquid delivery device trailing said coating ma chine and having a series of delivery outlets to copiously flood an excessive supply of cooling liquid on the hot coating for quickly effecting a large drop in coating temperature representative of a transition from fluidity to self sustaining solidity, a sump for collecting liquid runoff, and a vehicle mounted liquid spray cooling tower arranged to follow the advance of said coating machine and connected to receive cooling liquid from said sump and to supply cooled liquid to said liquid delivery device.

4. For cooling and solidifying a pipe coating applied as a hot fluid by a traveling coating machine, a device for flooding the hot coating with a liquid coolant, and having a coolant collecting drain pan, draft means pulling the device immediately behind the coating machine, a vehicle carried cooling tower for travel with said device, said tower having liquid spray heads at the top thereof and a cool-ant collecting sump at the bottom thereof, a coolant flow connection between said drain pan and said cooling tower spray heads and a coolant flow connection between said sump and said coating flooding device.

5. The structure of claim 4 together with a coolant storage reservoir and a valved flow connection between the reservoir and said sump for liquid coolant exchange to maintain a desired coolant level in said sump.

6. The structure of claim 4 wherein each coolant flow connection includes a pump for a forced flow of coolant.

7. The structure of claim 4 wherein each coolant flow connect-ion includes a pump for a forced flow of coolant and the pump in the drain pan connection has a larger flow capacity than the other pump.

8. Traveling cooling mechanism for solidifying a hot coating applied to a pipe by a pipe tracking coating machine, including a pipe embracing structure formed of separable top and bottom sections with the bottom section constituting a sump having a drain line therefrom, a draft connection for pulling the structure immediately behind the coating machine, a pair of coolant delivery conduits extending longitudinally of the pipe, one conduit as part of said top section and the other as part of the bottom section, and each having a series of spray nozzles directed toward the pipe coating, a coolant supply connection with one end of one conduit and a detachable flow connection joining the other end of the last mentioned conduit with an adjacent end of the other conduit.

9. In combination, a traveling coating machine to track on and to be borne by an assembled pipe line and operative to apply a hot fluid coating on the pipe rearwardly of where the machine is borne by the pipe, cooling mechanism to direct a coolant on the hot fluid coating for solidifying the same, weight suspension means carried rearwardly by the coating machine in weight transmitting connection with the front end of the cooling mechanism traveling forward immediately behind the coating machine so that the hot coating which has been applied on the pipe is free of cooling mechanism front end weight, and a weight supporting wheel mounted at the rear of said mechanism for rolling engagement on the cooled pipe coating which has already been acted on by said cooling 8 mechanism transferring the weight of the mechanism at the rear thereof.

10. Traveling equipment for protectively coating a pipe line, including a power driven vehicle having a cradle which during vehicle advance lifts 'the pipe line to suspend it above the ground for coating, a coating machine to track on the suspended pipe and apply a hot fluid coating thereon, means immediately behind the coating machine to flood a coolant on the hot coating for forcing solidification thereof, a cooler through which said coolant circulates for heat extraction therefrom, a road vehicle supporting said cooler and having a (front axle with dirigible wheels connected by a steering tie rod, a tow bar universally pivotally joined to said axle and arranged for transmitting pull from said power driven vehicle and a lever fulcrumed on the axle with a pivot connection at one end with said tie rod and a vertical slidable key connection at its other end with said drawbar, said lever transmitting horizontal swing of the drawbar to steer the road vehicle for following the path of said power driven vehicle.

l1. Traveling equipment for applying a hot fluid coating layer on a pipe line and for immediately hardening the hot coating by the forced extraction of heat therefrom, including a pair of mobile pipe carrying cradles in spaced apart relation longitudinally of the pipe line to suspend a length of pipe therebetween as the cradles advance along the pipe line, a traveling machine operative to deposit hot fluid coating on the pipe in trailing relation to the first in line of said mobile pipe suspending cradles, heat absorbing means suspended out of contact "with the hot pipe coating and for travel along the coated pipe in heat exchange relation therewith behind said hot coating machine and in advance of the last in line of said pipe suspending cradles and operative to absorb heat from said hot coating and thereby protectively harden said coating against displacement under load transfer therethrough to said last in line of the forwardly advancing cradles.

12. Mechanism for applying a protective coating on a continuous pipe line, including a ground engaging vehicle having a pipe suspension cradle by which the pipe line is progressively picked up and elevated above the ground as the vehicle travels forward along the length of the pipe line, a second ground engaging vehicle spaced longitudinally of the pipe line in rearward trailing relation behind the first vehicle and having a pipe suspension cradle for co-operation with the cradle of the first mentioned vehicle to suspend in elevated condition a length of pipe line between the longitudinally spaced vehicle cradles land to pay off said length of elevated pipe line as the second vehicle travels forward, a pipe engaging traveling machine supporting a device to apply a hot fluid coating on the elevated length of pipe line intermediate said spaced apart cradles during forward travel of themachine and having machine supporting and tracking means riding on the cradle elevated uncoated pipe line in advance of the supported coating device, cooling equipment in trailing relation with the coating machine and in advance of the rearward cradle and operative to flood the hot fluid coating with a heat absorbing medium for a rapid transition of the fluid coating to a hardened state, and means to suspend said cooling equipment out of weight bearing contact with uncooled coating.

References Cited in the file of this patent UNITED STATES PATENTS 1,941,002 Harri-son Dec. 26, 1933 1,990,711 Rolfs et a1 Feb. 12, 1935 2,022,481 Schellenger Nov. 26, 1935 2,034,755 Fuller Mar. 24, 1936 2,287,825 Postlewaite June 30, 1942 2,573,815 Smith Nov. 6, 1951 hiv-v

Images