High speed pipe lining method and apparatus

High speed pipe lining is accomplished by supporting a length of pipe to be lined between spindles in a lathe-type apparatus and rotating the pipe at a speed sufficient to afford a G-force of the order of 10-15 G's. A rather fluid concrete mixture comprising gap-graded sand is introduced into the interior of the rotating pipe using a cantilevered trough. The rotational speed of the pipe is then increased substantially to afford a force of the order of 35-50 G's, and the pipe is subjected to high amplitude axial vibrations for a period of time of the order of one minute or less. The resulting concrete lining is highly compacted, quite dense and hard, and has a smooth surface.

BACKGROUND OF THE INVENTION 
This invention relates generally to methods and apparatus for lining or 
coating the interior of hollow objects, and more particularly to the 
lining of cast iron pipe and the like with concrete. 
It is common to apply concrete or similar corrosion-resistant linings to 
the interior surfaces of metal pipe to prevent corrosion and rusting and 
the undesirable contamination of water carried by the pipe. The most 
practical way to apply such linings is to use a centrifugal process in 
which lining material is introduced into the interior of a length of pipe, 
and the pipe is rotated about its longitudinal axis. The rotation causes 
the lining material to be spread over the interior surfaces and to be 
compacted to produce a relatively smooth coating on the interior surfaces. 
Considerable difficulty is encountered, however, in providing satisfactory 
concrete linings in pipe, particularly in long sections, e.g., twenty 
feet, of large diameter, e.g., forty inches, pipe. This is due, in part, 
to the inability to rotate the pipe at a sufficiently high enough speed to 
produce good compaction of the concrete so that shrinkage is minimized and 
so that voids or other defects do not result. As the concrete cures, 
shrinkage may also cause the lining to separate partially from the 
interior surfaces and permit voids or stress concentrations to develop in 
the lining, rendering it easily broken. Typically, concrete is introduced 
into the pipe by a slinger while the pipe is stationary. This necessitates 
using a concrete mix which is rather thick and not very flowable, i.e, 
somewhat dry, so that the concrete will stick to the pipe wall. The pipe 
is then rotated for a short period of time at a speed high enough to 
smooth out the concrete but low enough to avoid removing excessive water 
from the concrete. If too much water is removed, the concrete will not 
cure properly and the resulting lining will be powdery. 
Conventional centrifugal lining apparatus supports the pipe section on 
spaced pairs of rollers which engage the peripheral surface of the pipe 
and which are driven to impart rotation to the pipe. It is practically 
impossible, however, to produce pipe which is perfectly round and 
balanced. Any out-of-roundness will cause the center of mass of the pipe 
to deviate from the access of rotation, and as the pipe is rotated, forces 
are produced which tend to lift the pipe from the rollers. To maintain the 
pipe in contact with the rollers, it is necessary to exert a downward 
force on the top of the pipe, as by using holddown rollers. Even with 
holddown rollers, as the pipe speed increases, lateral vibration and 
motion of the pipe due to out-of-roundness may become quite large. If the 
vibration becomes excessive, it may wreck the apparatus, and, in any 
event, a point is quickly reached where the force necessary to hold the 
pipe on the rollers exceeds the rim strength of the pipe. In addition, the 
lateral vibrations and bouncing to which the pipe is subjected interferes 
with the ability of the concrete mixture to spread uniformly and smoothly 
over the interior surface of the pipe and is detrimental to the resulting 
lining. As a result, the maximum speed at which the pipe may be rotated is 
substantially less than that desired to produce good compaction of the 
concrete. 
It is desirable to provide pipe lining apparatus and methods which avoid 
these and other disadvantages of known methods and apparatus, and it is to 
this end that the present invention is directed. 
SUMMARY OF THE INVENTION 
The invention affords high speed pipe lining methods and apparatus which 
enable pipe to be lined rapidly and efficiently and which produce linings 
which are smooth, uniform, highly compacted and substantially void and 
defect free. The linings produced are rugged and durable, and pipe lined 
in accordance with the invention may be immediately handled without the 
excessive care required in handling pipe lined by conventional methods and 
apparatus. 
Briefly stated, in accordance with the invention, a length of pipe to be 
lined is supported at its ends by a mechanism formed to rotate about an 
axis corresponding to the longitudinal axis of the pipe. The pipe is first 
rotated at a low speed about its longitudinal axis while depositing within 
the interior of the pipe uniformly along its length a predetermined 
quantity of lining material, the speed being selected to be such that the 
lining material is spread evenly about the interior surface of the pipe. 
The rotational speed of the pipe is then increased to a substantially 
higher speed and the pipe is subjected to vibrations in a direction 
parallel to the longitudinal axis of the pipe so as to compact the lining 
material. 
More specifically, the mechanism which supports and rotates the pipe may be 
a lathe-type mechanism comprising movable spindles which engage and 
resiliently support the ends of the pipe. The lining material may be 
deposited within the interior of the pipe by a trough inserted axially 
into one end of the pipe. The rotational speed of the pipe while the 
lining material is being deposited therein is preferably such as to afford 
a centrifugal force of the order of 10-15 G's. The trough is removed from 
the pipe, and the rotational speed is then increased so as to afford a 
force of the order of 35-50 G's. The longitudinal vibrations imparted to 
the pipe during its high speed rotation may be effected by a striker 
member supported on one of the spindles which is arranged to repetitively 
strike the end of the pipe supported by that spindle. After about 30-60 
seconds of high speed rotation and vibration, the vibration is stopped and 
the pipe is allowed to slow to rest. 
Preferably, the lining material is concrete which is formed with gap-graded 
sand. The sand may comprise approximately equal quantities of fine and 
coarse particles, the diameters of which may be in a proportion of the 
order of 8:1. The gap-graded sand enables a given fluidity in the concrete 
mixture to be achieved with less water than required with non-gap graded 
sand, and the substantially higher rotational speeds achievable with the 
invention produce good compaction of the concrete and afford a smooth 
lining surface. Furthermore, the high speed rotation removes a substantial 
percentage of the water from the concrete mixture, so that, although the 
mixture is rather fluid when it is introduced into the pipe, after 
rotation the concrete is fairly hard. The longitudinal vibrations imparted 
to the pipe during high speed rotation produce thorough mixing of the fine 
and coarse sand particles in the concrete, and cause the fine particles to 
fill the interstices between the coarse particles. This helps to eliminate 
any voids in the concrete and produces a denser, more compact lining. 
Other features and advantages of the invention will become apparent from 
the description which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The invention is particularly well adapted for applying concrete linings to 
long sections of large diameter cast iron pipe and the like, and will be 
described in that context. However, as will become apparent, this is 
illustrative of only one utility of the invention. For example, the 
invention is also applicable to applying linings to other objects, as well 
as to centrifugal molding operations. 
FIG. 1 illustrates a high speed pipe lining apparatus in accordance with 
the invention for applying a lining to the interior of a length or section 
of pipe 10. As shown, the apparatus includes a lathe-type mechanism 
comprising a drive spindle arrangement 12 and a tail spindle arrangement 
14 adapted to engage and support pipe 10 at its ends and to rotate the 
pipe about its longitudinal axis. Each spindle arrangement comprises a 
spindle frame 16 which is supported for movement in the axial direction of 
the pipe on guide shafts 18 which are mounted on a suitable support 20. 
Rotatably supported within the spindle frame of the drive spindle 
arrangement is a drive spindle 22 adapted to be rotated by a motor 24 and 
drive belts 26 about a longitudinal axis corresponding to the axis of the 
pipe. The drive spindle includes a spindle extension 28 which is formed to 
enter the bell or spigot end 30 of the pipe. The spindle extension carries 
a striker member 32 adapted to strike repetitively the bell end of the 
pipe to impart longitudinal vibrations to the pipe, the striker member 
being driven by a ram 34 mounted on a slide carriage 36, as will be 
described in more detail hereinafter. 
The tail spindle frame similarly rotatably carries a tail spindle 40 which 
has a spigot end plate 42 adapted to simulate the bell end of a pipe 
section and to receive the tail end 44 of the pipe. 
A section of pipe to be lined is rolled on a pair of spaced rails 50, which 
are supported on appropriate foundations 52 and extend normal to the 
longitudinal axis of the pipe (normal to the plane of the drawing), to a 
location between the head and the tail spindles. The pipe section may then 
be raised by a pair of V-shaped (in a plane transverse to the longitudinal 
axis) pipe lift devices 54 which are operated by an appropriate hydraulic, 
pneumatic or other actuating mechanism 56. The V-shaped pipe lifts center 
the pipe in the transverse direction (normal to the plane of the drawing) 
with respect to the spindles, and raise the pipe so that its longitudinal 
axis corresponds substantially to the longitudinal axis of the spindles. 
The spindle frames are then moved axially toward each other, in a manner 
to be described, so that the spindles engage the ends of the pipe. The 
pipe lifts are then lowered out of the way, leaving the pipe section 
supported on the spindles. 
Concrete lining material may be introduced into the interior of the pipe 
section by inserting a cantilevered trough 58 into the interior of the 
pipe through the tail spindle 40. The trough may be carried on a movable 
trough car 60 which rides on tracks 62 that extend parallel to the 
longitudinal axis of the pipe. The trough is preferably rotatably 
supported on the trough car by appropriate rotary supports 64, and the 
trough may be connected to a rotary actuator 66 which rotates the trough 
about its longitudinal axis. Rotary actuator 66 may be a hydraulic 
actuator, for example, powered by a hydraulic power unit 68 carried on the 
trough car. The trough car may be driven back and forth along the tracks 
by an electric motor, for example, (not illustrated). The trough may be 
charged with a predetermined quantity of concrete lining material by 
pumping the concrete from a source 70 through a line 72 which discharges 
into the trough. The quantity of concrete loaded into the trough is 
calculated based upon the dimensions of the pipe to give a predetermined 
lining thickness, and the concrete is evenly distributed in the trough 
along the length of the trough. 
As will be described in more detail shortly, upon a section of pipe being 
loaded into the spindles and the trough being charged with concrete, motor 
24 is started to begin rotation of the drive spindle and the pipe, the 
tail spindle rotating by virtue of its engagement with the pipe, and the 
trough is inserted axially into the interior of the pipe. With the pipe 
rotating at a first, low, speed, sufficient to afford a centrifugal force 
of the order of 10-15 G's, for example, the trough is slowly rotated by 
actuator 66 to dump the concrete into the interior of the rotating pipe. 
The concrete, which is evenly distributed along the length of the trough, 
is dumped uniformly along the length of the pipe, and the centrifugal 
force causes the concrete to flow and spread uniformly over the interior 
surface. The trough is removed from the pipe and the rotational speed of 
the pipe is increased substantially to a second, high speed, sufficient to 
afford a force of the order of 35-50 G's, for example. While rotating at 
the higher speed, ram 34 is actuated to cause striker 32 rapidly and 
repetitively to strike the bell end of the pipe to produce longitudinal 
vibration of the pipe. High speed rotation and vibration is continued for 
a predetermined period of time such as thirty to sixty seconds, for 
example, after which the pipe is allowed to slow gradually to rest. The 
pipe lifts are then raised to support the pipe and allow the spindles to 
be retracted from the pipe ends, and the pipe is lowered onto the rails so 
that it may be rolled out of the way to make room for the next pipe 
section. The concrete lining is then preferably cured in a steam oven. 
This puts some of the moisture removed during high speed rotation back 
into the concrete, and ensures that sufficient moisture is available to 
hydrate the concrete so that it cures properly. 
Surprisingly remarkable results have been achieved using the invention. It 
has been found that the concrete lining is extremely smooth, uniform and 
quite hard immediately after removing the pipe section from the apparatus. 
In part, this is due to the rather high rotational speed to which the pipe 
is subjected during lining, which speed is substantially greater than the 
rotational speeds possible with conventional apparatus of the type 
previously described which employs rollers engaging the peripheral surface 
of the pipe. As a result, substantially higher centrifugal forces are 
applied to the concrete, which causes the heavier particles in the 
concrete to be centrifuged toward the pipe wall and brings the finer 
particles, such as cement, to the inside of the lining. This causes better 
compaction of the concrete and produces a lining having a smooth surface. 
In addition, a larger percentage of the water content of the concrete is 
removed through centrifuge action. (Upon being released from the spindles, 
the water, which is collected in the bottom of the pipe, runs out onto the 
floor.) As a result, the concrete lining formed is dense, hard, and quite 
compact. Thus, it is not as fragile as the linings produced by 
conventional lining apparatus. Accordingly, the pipe may be immediately 
handled without the same degree of care which would ordinarily be required 
to prevent damage to the uncured lining. 
FIGS. 2 and 3 illustrate the drive spindle arrangement of the invention in 
more detail. As shown, the drive spindle frame 16 may comprise a central 
hollow cylindrical member 80 connected to a pair of somewhat triangularly 
shaped (see FIG. 3) transversely extending front and rear brackets 82 and 
84, respectively. The lower ends of the front and rear brackets may be 
connected together by cylinders 86 slidingly disposed on guide shafts 18, 
and support plates 88 may extend between the brackets and between the 
cylindrical member 80 and cylinder 86. As best shown in FIG. 2, guide 
shafts 18 may be supported at their front and rear ends by pillow blocks 
90 mounted on supports 20. A linear actuator 92 may be mounted on one 
support, e.g., the rear support, and may have its movable shaft 94 coupled 
to an ear 96 attached to the lower end of front bracket 82 of the spindle 
frame. Actuator 92, which may be either a hydraulic, a pneumatic, or an 
electric actuator, for example, serves to translate the spindle frame 
axially back and forth on guide shafts 18 to enable the drive spindle to 
engage and disengage the bell end of the pipe. 
As is further shown in FIG. 2, drive spindle 22 may also comprise a hollow 
cylindrical member which is rotatably supported within cylindrical member 
80 of the spindle frame by tapered roller bearings 100. To enable the 
drive spindle to be rotated by motor 24, a multiple groove sheave 102 may 
be disposed about the external peripheral surface of the spindle 22 
adjacent to a rear end plate 104 and connected by a plurality of V-belts 
26 to a mulitiple groove tapered bore sheave 106 located on the motor 
shaft 108. Motor 24 is mounted on a base 110, one side of which may be 
pivotally connected at 112 to the tops of spindle brackets 82 and 84 and 
the other side of which may be connected to the spindle brackets by an 
adjustment mechanism 114 (see FIG. 3), which may comprise a bolt and nut 
arrangement, to enable adjustment of the tension in the V-belts. Spindle 
extension 28, which may be connected to a front end plate 116 of the drive 
spindle, may be a tubular member having a rear flange 118 (for connection 
to end plate 116) and an annular dish-shaped front piece 120 sized to fit 
within and support the bell end 30 of the pipe, as shown in FIG. 2. 
The drive spindle and the spindle extension may have disposed within their 
interiors transversely extending circular plates 124 which slidingly 
support a coaxially disposed striker rod 126 that is adapted to engage 
striker member 32. The striker member, which may comprise an elongated 
rectangular bar, as shown, may extend radially across the inner diameter 
of the spindle extension and through a pair of diametrically opposed 
longitudinally extending slots 130 in the wall of the spindle extension. 
The striker member is selected to have a length sufficient to enable it to 
extend beyond the external surface of the spindle extension and to engage 
the end of the pipe, and it may be held within slots 130 during rotation 
of the spindle by a pair of plates 132 having a length corresponding to 
the inner diameter of the spindle extension which are bolted on opposite 
sides of the striker member, as best shown in FIG. 3. The striker member 
may also be biased toward engagement with the end of the pipe by 
adjustable spring assemblies 134 located between the striker member and 
flange 118 of the spindle extension. Spring assemblies 134 also serve to 
absorb recoil forces on the striker member during longitudinal vibration 
of the pipe. 
As previously noted, striker member 32 is driven by ram 34. As shown in 
FIG. 2, slide carriage 36 may be mounted on a support 133 which is formed 
to enable the ram to be inserted coaxially into the rear end of the drive 
spindle and to engage striker rod 126. The ram may be moved in and out of 
the drive spindle by a positioning mechanism 136, which may comprise a 
hydraulic cylinder, for example, connected between support 133 and the 
slide carriage. Ram 34, which may be similar to a standard concrete 
breaker, is preferably hydraulically operated and may be, for example, a 
Kent model KHB-302 hydraulic ram capable of delivering 1200 blows per 
minute at a force of 410 ft-lbs. per blow. When the ram is moved into 
engagement with striker rod 126 and actuated, ram rod 140 of the ram 
reciprocates axially at 1200 cycles per minute, causing striker member 32 
(via the intermediate striker rod 126) to strike repetitively the bell end 
of the pipe and impart a high amplitude axial vibration to the pipe. It 
has been found that the frequency is not as important as the amplitude of 
the vibration in producing good compaction of the concrete. The amplitude 
of the vibration imparted to the pipe is a function of the impact force 
per blow of the ram, which can be controlled somewhat by controlling the 
hydraulic fluid pressure supplied to the ram. In general, better results 
are obtained with higher amplitudes. Striker member 32 and striker rod 126 
rotate with the drive spindle. However, the ram does not. 
The tail spindle arrangement may be generally similar to the drive spindle 
arrangement, as shown in FIG. 4 wherein the same reference numerals are 
used to designate elements which are similar to the drive spindle 
arrangement. The tail spindle arrangement may comprise a hollow 
cylindrical member 40 rotatably supported by tapered roller bearings 100 
within a tubular cylindrical member 80 of the tail spindle frame 16. The 
spindle frame may be moved axially back and forth on guide shafts 18 by a 
similar frame translation mechanism 92 as employed for the drive spindle 
frame. The tail spindle differs from the drive spindle in that it is not 
formed to enable it to be driven, but simply to rotate freely in the 
spindle frame. Spindle end plate 42 comprises a cup-shaped annular end 
piece 144 which is formed to receive the tail end 44 of the pipe and to 
simulate the internal configuration of the bell end of the pipe. 
Referring to FIG. 2, the internal surface of the bell end of standard pipe 
of the type with which the invention is employed may include circular 
grooves for receiving resilient gaskets, as of rubber, for sealing the 
connection between adjacent pipe sections. As shown in FIG. 4, a first 
annular gasket 148 may be disposed within a groove in the annular end 
piece 144 of the tail spindle so as to engage the external peripheral 
surface of the tail end 44 of the pipe section 10 received within the end 
piece, and a second annular gasket 150 may be positioned within the end 
piece so as to engage the circular end wall of the tail end of the pipe 
section. Similar gaskets 148 and 150 are preferably positioned within the 
bell end 30 of the pipe which is to be lined, as shown in FIG. 2. These 
gaskets resiliently support the pipe on the drive and tail spindles, 
particularly in the longitudinal direction, and assist in reducing the 
vibrational forces imparted to the spindles during lining. Gaskets 150, 
which as shown in FIGS. 2 and 4 have an inner diameter which is smaller 
than the inner diameter of the pipe, also conveniently serve as end stops 
for the concrete lining 152 deposited within the pipe and help ensure that 
the ends of the lining are straight and uniform. 
Referring to FIGS. 1 and 5, trough 58 which is employed for depositing 
concrete lining material into the interior of the pipe may comprise an 
elongated tubular member having a longitudinal slot 160 therein which 
extends from the free end 162 of the trough toward its rear end (the end 
adjacent to trough car 60) for a distance corresponding to the length of 
the pipe section to be lined. As best illustrated in FIG. 1, the walls of 
the tubular trough preferably taper so that the wall thickness decreases 
from the rear of the trough toward its free end. This reduces the weight 
of the trough and increases its strength so that vertical deflection is 
minimized when the trough is charged with concrete lining material. To 
assist in uniformly distributing the concrete lining material along the 
length of the trough, an elongated upright baffle plate 164 may be 
disposed within the trough, as shown. The baffle plate, which extends 
longitudinally from the free end of the trough to a first transverse 
baffle plate 166, may be selected to have a height corresponding to the 
level of the predetermined quantity of concrete required to give a desired 
lining thickness, and the top of the baffle plate may be used as a 
reference level for charging the trough with the predetermined quantity of 
concrete and for ensuring that the concrete is uniformly distributed along 
the length of the trough. 
To enable the trough to be employed for lining different lengths of pipe, 
additional transversely extending baffles 168 spaced uniformly a 
predetermined distance apart may also be disposed within the trough. 
Baffle 166 may be located 18 feet, for example, from the free end of the 
trough, which corresponds to a standard pipe length, and baffles 168 may 
be spaced at six inch intervals, for example, up to 20 feet, which 
corresponds to another standard length. Depending upon the length of pipe 
being lined, the appropriate number of compartments between the baffles 
may be filled with concrete. Of course, the amount of concrete with which 
the trough is charged may also be metered to ensure that the desired 
predetermined quantity of concrete is used. The required quantity can 
readily be calculated from the dimensions of the pipe and the thickness of 
the lining to be formed. 
The operation of the invention has been described previously. There are 
several factors which are responsible for the remarkable results achieved 
by the invention. These include the high rotational speeds and the axial 
vibrations imparted to the pipe during lining, which result in better 
compaction of the concrete and, accordingly, a denser, harder and smoother 
lining. Although high speed rotation and vibration of the pipe will 
produce satisfactory linings, the quality of the lining produced is also 
influenced by the concrete mixture employed. It has been found that 
significant advantages accrue by employing a concrete mixture which 
comprises gap-graded sand, i.e., sand composed of particles or grains 
having sizes which lie in a small number of distinctly different size 
ranges, such as coarse and fine particles. The centrifugal forces imparted 
to the concrete mixture during rotation of the pipe cause the heavier 
components of the mixture to be centrifuged against the pipe wall, and 
allow the lighter components of the mixture, such as cement and water, to 
move toward the inside of the pipe lining. With gap-graded sand, the axial 
vibrations imparted to the pipe during high speed rotation cause the sand 
particles to fall over each other and allow the fine particles to fill the 
interstices between the coarse particles. This forces additional water and 
cement out of the concrete mixture, and produces a smoother, more densely 
compacted lining. 
Another advantage of using gap-graded sand is that less water and cement 
are required in the mixture. With gap-graded sand, the percentage of voids 
between sand particles is smaller, and less cement and water is required 
to fill these voids. Moreover, a desired fluidity can be obtained with 
less water. It is necessary that the concrete mixture initially deposited 
within the pipe be sufficiently fluid, i.e., flowable, so that it spreads 
uniformly over the interior of the pipe prior to high speed rotation. A 
preferred concrete mixture which has been used quite successfully in the 
invention comprises gap-graded sand which is composed of approximately 
equal quantities of only coarse and fine particles, the ratio of the 
diameters of which is of the order of 8:1, a sand to cement ratio of the 
order of 3.5-4:1 with a ratio of 3.65:1 being preferred, and a moisture 
content of the order of 12%. The initial rotational speed of the pipe when 
the concrete mixture is introduced is of the order of 10-15 G's, as 
previously noted, with 15 G's being preferred. At these speeds, some 
compaction of the concrete is produced when it is deposited into the pipe, 
but the speeds are also low enough to allow the concrete to spread 
uniformly over the interior surfaces of the pipe and to settle with good 
knitting of the components of the concrete. Because of the rather fluid 
nature of the concrete mixture, at speeds less than approximately 5 G's 
the mixture does not stay on the pipe wall very well. At speeds greater 
than approximately 20 G's, the mixture does not spread as uniformly nor as 
smoothly as at lower speeds, and 15 G's has been found to produce 
consistently good results. 
It has likewise been found that high speed rotation sufficient to produce a 
force of the order of 35-50 G's produces very good compaction of the 
concrete and results in a smooth, tough lining. The amount of time at 
which the pipe is rotated at high speed and vibrated has not been found to 
be particularly critical and may be of the order of 30-60 seconds, for 
example, with 45 seconds being preferred. 
The foregoing operating parameters were derived by employing the invention 
to apply 3/8 inch thick concrete linings to 1,000 mm, 20 foot long 
sections of pipe, and these parameters may vary to some extent depending 
upon pipe size. 
The G-force applied to the lining is related to the rotational speed in RPM 
and pipe diameter in inches according to the following relationship. 
EQU (Pipe RPM).sup.2 .times.Diameter=70400.times.G's 
For lining 1000 mm pipe the drive spindle may have an outer diameter (OD) 
of the order of 32 inches, sheave 102 may have an OD of the order of 36 
inches, and sheave 106 on the motor may have an OD of the order of 14 
inches. Motor 24 may be a 100 HP DC motor rated at 1150 RPM, 230 VDC, 356 
A full load. This produces a maximum drive spindle rotational speed of the 
order of 447 RPM, which for 1000 mm pipe corresponds to a maximum G-force 
of the order of 117 G's. The lathe-like spindle rotating apparatus of the 
invention securely holds the pipe and rotates it about its longitudinal 
axis, and out-of-roundess of the pipe does not substantially limit the 
rotational speeds attainable with the apparatus. 
As will be appreciated from the foregoing, the invention provides a highly 
advantageous method and apparatus for applying concrete linings to pipe. 
It is readily adaptable to lining pipe of different diameters from about 
18 inches to 72 inches, for example, as well as to pipe of different 
lengths. In fact, different diameter pipe may be readily accomodated 
simply by appropriately changing the drive spindle extension 28 and the 
tail spindle end plate 42. Using the apparatus of the invention, a 
concrete lining may be applied to pipe in a matter of two to three 
minutes. 
While a preferred embodiment of the invention has been shown and described, 
it will be appreciated by those skilled in the art that changes may be 
made in this embodiment without departing from the principles and spirit 
of the invention, the scope of which is defined in the appended claims.