Method for cementitious coating of pipe and forms for use therewith

Metal pipe sections are welded together at the job site and then progressively coated with concrete by a traveling coating machine moving along the length of the pipe. After the coating operation the pipe is supported on forms having an upper concave portion shaped to receive the curved pipe. After the coating has hardened the pipe can be removed from the forms and installed. Apertures in the forms allow fluid to drain from the coating. Curved shims containing apertures aligned with those in the forms may be used to accommodate smaller pipe diameters.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates broadly to the coating of pipe, and more 
particularly to a method and means for coating pipe with cementitious 
material. 
2. Description of the Prior Art 
Pipes are often coated before being installed in order to provide certain 
qualities not possessed by the uncoated pipe. This is particularly true in 
the case of metal pipes, which are normally coated with asphalt or plastic 
material to protect against corrosion and are also sometimes coated with 
granular material to provide shock resistance. In addition, if the pipes 
are to be used in a wet environment, such as in river crossings and 
off-shore oil wells, or even in moist environments such as marshy grounds, 
they are normally coated with concrete to weight them down so as to 
protect against buoyancy or upward movement of the installed pipes. 
When coating metal pipe with concrete, individual sections of pipe are 
normally coated by hand or by a sprayed fluid concrete mixture. In either 
case, the end portions of the pipe are left uncoated and are placed on end 
support stands to support the pipe section while the concrete is curing. 
After the coating is cured, the coated pipe sections are strung together 
on the pipe right-of-way and the pipe ends are welded together to form a 
continuous length of pipe. The uncoated end portions of the pipe sections 
are then also coated with concrete and, after curing, the pipe length is 
ready to be installed. 
This procedure requires a great deal of time and can substantially delay 
the laying of the pipe line. Even if the application of concrete to the 
pipe lengths is carried out at the job site instead of at a plant or yard 
site, the double application of concrete to the pipe still extends the 
duration of the coating process. The coating procedure could obviously be 
shortened by coating the pipe in a single operation, but the prior art has 
not heretofore provided a way of accomplishing this. Although coating 
machines have been developed for applying asphalt and epoxy corrosion 
resistant materials to continuous lengths of pipe, the same concept has 
not been used to apply cementitious coatings to continuous lengths of 
metal pipe, presumably because of the unique problems involved in applying 
thick layers of cementitious material and the difficulty in supporting the 
coated pipe during the relatively long curing process without damaging the 
coating. 
The choices offered, therefore, are to either coat the pipe sections 
individually in the slow conventional manner in order to allow the coating 
to cure prior to connecting the pipe in the field, or to coat the pipe 
after connecting the sections together, but only at the great risk, if not 
the certainty, of damaging the concrete coating while supporting the pipe 
as it is curing. 
It would obviously be advantageous to be able to substantially shorten the 
cementitious coating process without adversely affecting the quality of 
the coated pipe for the reasons discussed above. 
SUMMARY OF THE INVENTION 
This invention involves a method for coating pipe with a layer of 
cementitious material by connecting a plurality of pipe sections together 
to form a length of pipe, progressively coating the length of pipe with 
the cementitious material, supporting the coated pipe on support forms and 
curing the cementitious coating material while the pipe is supported on 
the forms. 
In a preferred embodiment the support forms comprise concave support 
surfaces on which the pipe rests. The curvature of the concave surface 
substantially matches the curvature of the outer surface of the coating so 
that the support forms uniformly contact the coating and hold the pipe 
securely to help the coating maintain uniform shape and thickness as it 
cures. Shims can be used in the concave portion of the form to accommodate 
coated pipe of lesser diameter, and both the main portion of the forms and 
the shims may be provided with apertures to allow fluid to drain from the 
cementitious material as it cures. The details of the design of the form 
may vary depending on the material used to fabricate the form and the size 
and weight of the coated pipe. 
The actual coating operation preferably is performed by a coating machine 
that travels along the length of the pipe after the sections of pipe have 
been welded together. As the machine moves along the pipe, the portions 
that have just been coated are lowered to the support forms described 
above so that the fresh coating can retain its cylindrical shape during 
curing. This operation does not interfere with the usual pipe laying 
practices and permits the pipe to be laid in the trench or other final 
installation location as soon as the coating has sufficiently cured. 
Accordingly, it is an object of the present invention to provide a method 
of coating a pipe which will enable cementitious coatings to be applied to 
the entire length of a pipe rather than having to leave the end portions 
uncoated to allow the pipe sections to be later welded together. 
Another object of the invention is to provide a method of applying a 
cementitious coating to a length of pipe comprised of pipe sections which 
have been connected together, and supporting the coated pipe so that the 
coating is not damaged but retains its intended shape and dimensions. 
A further object of the invention is to provide a support form for 
receiving and supporting the freshly coated pipe which allows for drainage 
of fluid from the coating and securely holds the pipe in place during the 
curing process. 
These and other objects of the invention, as well as other features and 
benefits thereof, may be ascertained and more fully understood from the 
following description when read in conjunction with the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 of the drawing, sections of metal pipe 10 which have 
been welded together at their ends to form welded connections 12 are shown 
resting on supports 14. The supports 14 will have been distributed along 
the right-of-way of the pipe line at intervals appropriate to the size and 
weight of the pipe to be supported, and in this case are shown adjacent 
the trench or ditch 16 in which the pipe eventually will be laid. They may 
be comprised of any suitable and convenient materials, such as, for 
example, brick, sand, wood or even mounds of earth from the job site. The 
pipe sections will have been positioned in end-to-end relationship along 
the right-of-way and will have been bent by a conventional pipe bending 
machine to contour the pipe to the designed alignment. The welding 
operation will then have been carried out in any conventional manner, 
typically using a line-up clamp to align the adjacent ends of the pipe 
sections to provide the proper gap and spacing for the weld to be made. As 
the welding of adjacent pipe sections is completed, the supports 14 are 
placed under the pipe to support it as needed, resulting in the 
arrangement shown in FIG. 1. 
As shown in both FIGS. 1 and 2, a conical bull plug 18 has been attached to 
the leading end of the leading pipe section 10 by any convenient means, 
such as by welding or clamping. This facilitates entry of the pipe into a 
traveling coating machine 20 which includes drive wheels 22 above the pipe 
10 and support wheels 24 beneath the pipe. The drive wheels 22 are driven 
through a suitable engine and power take-off arrangement 26, the 
connection of which to the drive wheels is not shown since the details 
thereof do not form part of the invention. The selection of a suitable 
engine and power take-off arrangement as well as the connection to the 
drive wheels is well within the knowledge of one skilled in the mechanical 
arts. 
To start the coating machine on the pipe, the drive wheels 22 will be 
rotating in a clockwise direction as viewed in the drawing, and the 
coating machine 20 will be held by a boom 28 at a height to enable the 
bull plug 18 to enter the machine between the leading drive wheel 22 and 
leading support wheel 24. The pipe 10 will have been raised to the proper 
elevation by a suitable lifting device 30 carried on a self-propelled cart 
or vehicle 32. Engagement of the leading drive wheel 22 first with the 
bull plug and then with the pipe will cause the coating machine 20 to 
begin to travel along the pipe as if the pipe were a track. Continued 
movement of the machine will result in the pipe engaging the trailing 
drive wheel 22 and trailing support wheel 24 and entering the coating 
chamber or mold box 34. 
A suitable cementitious material, such as concrete, would be fed 
continuously into the coating chamber by a hopper, not shown, which would 
move with the coating machine along the length of the pipe. The 
cementitious material would be charged to the chamber in the space between 
the pipe and the interior surfaces of the chamber and would be subjected 
to vibration and packing elements to compact the material. As the pipe 
exits from the chamber, the force of the incoming cementitious material 
causes the material to exit with the pipe through a suitably shaped 
opening concentric with the pipe to in effect extrude the coating onto the 
pipe. If desired, power spools 36 can wrap wire mesh around the coated 
pipe for purposes of reinforcement. A plastic wrap may also be introduced 
from power spools to aid in adhering the concrete to the pipe before it is 
deposited on the forms, to help maintain the thickness of the coating and 
to promote the curing of the concrete. 
As shown in FIG. 3, as the coating operation continues the lifting 
mechanism 32 and the coating machine 20 move along the length of the pipe 
toward the right of the drawing, the coating machine coating the pipe as 
it travels. Note that support forms 38 have been set in place on the 
supports 14 after the coating machine has moved past the supports 14. It 
is necessary in accordance with the invention to use the forms 38 to 
support the freshly coated pipe in order to properly support the green 
coating and the weight of the coated pipe P during the curing process. 
Although the support forms 38 are illustrated as resting on the supports 
14, it is not essential that the support forms be placed in this manner. 
For example, as shown in dotted lines, they could be placed directly in 
the trench 16 if desired, and the coated pipe P deposited directly thereto 
from the coating machine. 
Referring now to FIG. 4, the form 38 comprises a bottom surface 40 
connected by side walls 42 to a concave support surface 44. Although shown 
as flat, the bottom surface 40 may be of any shape determined to be best 
suited for the terrain or for being positioned on top of the supports 14 
referred to in connection with FIGS. 1-3. The form is of solid 
construction and typically would be comprised of a suitable plastic 
material having enough strength to support the weight of a portion of the 
coated pipe. A number of apertures 46 are provided in the form, extending 
from the support surface 44 through the bottom surface 40 to allow 
drainage of fluid from the coating or of any other substance that might 
otherwise accumulate on the concave surface 44. 
The concave surface 44 is designed to have the same radius of curvature as 
the radius of curvature of the pipe coating. The extent to which the 
curved support surface 44 extends upwardly will vary according to such 
considerations as the diameter of the coated pipe and the thickness and 
type of coating, but in general the support form 38 will be designed to 
support the weight of the coated pipe and to support the green coating 
material so it can hold its shape and thickness during the curing period. 
Forms designed for a relatively large diameter coated pipe can also be 
used for smaller diameter coated pipes by employing a curved shim 48, the 
convex surface of which conforms to the curvature of the support surface 
44 of the form 38 and the concave surface of which conforms to the 
curvature of the smaller diameter coated pipe. The shim 48 would also be 
provided with apertures aligned with the apertures 46 in the form 38. The 
use of shims reduces the expense of the support forms since the shims are 
less costly than another set of smaller forms would be. 
The form 38, with the shim 48 in place, is shown in FIG. 5 with a portion 
of a coated pipe P supported thereon. As can be seen, the concrete coating 
52 of the coated pipe is supported on the shim 48, but would of course be 
supported directly on the support form 38 if the shim were not used. It 
can be seen that the aligned apertures 46 and 50, being located at the 
bottom of the concave support surface of the form, provides for drainage 
of fluid or other substances which may otherwise accumulate during the 
curing process. The bottom surface 40 of the support form is shown to be 
flat in order to be adequately supported by the flat support surface. As 
mentioned above, if the support surface on which the form 38 rests were of 
a different shape, the bottom surface of the form could be designed 
accordingly. 
If desired, additional support blocks, such as bricks of suitable size, may 
be placed at intervals on the concave support surface of the support forms 
when setting the forms in place so that when a portion of freshly coated 
pipe is deposited thereon the brick will penetrate the coating and provide 
a support surface against which the pipe 10 can directly rest. This 
arrangement is shown in FIG. 5 wherein blocks 54 have been incorporated 
into the pipe coating by the method just described. This would not be 
done, of course, if plastic wrap has been applied to the coating as the 
coated pipe exits from the coating machine. 
A modified support form comprised of metal is shown in FIGS. 6 and 7 as 
comprising a concave support section 56 containing apertures 58. Spaced 
along the length of the support section 56 are support bases comprising 
upright side walls 60 integrally formed with a flat bottom support wall 
62. The side walls 60 may be attached to the concave support section 56 by 
any suitable means but are illustrated as being welded to the upper side 
edges of the support section at 64. Also welded to the upper side edges of 
the support section at 66 are angled plates or lips 68 which extend out 
from the concave support section at an angle to facilitate entry of the 
coated pipe into the support form. Lugs 70 may be provided at the ends of 
the support forms to enable the forms to be joined together as by bolting 
or other means to provide more uniform support, prevent shifting of 
individual supports, maintain the elevation of adjacent concave support 
surfaces constant and speed up the process of collecting the support forms 
after the pipe is laid. 
The curing process of the pipe coating may be carried out according to 
conventional practice. The coating may have to be periodically moistened 
if weather conditions require it or suitable additives may have to be 
included in the coating mix to accommodate high or low temperatures. The 
use of support forms during the curing process, however, does not require 
any change from normal curing procedures. 
It will now be appreciated that the present invention provides a simple yet 
highly effective means for applying and curing a cementitious coating to a 
length of pipe. The ability to coat the joined sections in the field as 
opposed to first having to coat individual pipe sections up to their end 
portions and then having to coat the end portions themselves in a separate 
process yields a considerable savings in time and labor. The use of a 
coating machine to continuously apply the coating greatly speeds up the 
coating process. Further, the use of the support forms of the present 
invention to receive the freshly coated pipe directly from the coating 
machine and to hold the coated pipe in place for the duration of the 
curing process maintains the coated pipe in stable condition and allows 
the coating material to drain. 
While the principles of the invention have now been made clear in the 
illustrated embodiments and in the foregoing description, it will be 
obvious to those skilled in the art that modifications of structure, 
arrangements, proportions, elements, materials and components used in the 
practice of the invention which are particularly adapted for specific 
environments and operational requirements may be made without departing 
from those principles. The appended claims are therefore intended to cover 
and embrace any such modifications within the limits only of the true 
spirit and scope of the invention.