US3041204A - Internal conduit coating method and apparatus - Google Patents

Description

L. W. GREEN June 26; 1962 INTERNAL CONDUIT COATING METHOD AND APPARATUS Filed March 24, 1959 INVENTOR. dam/0 M 5?:[4/

United States Patent r 3,041,204 INTERNAL CONDUET COATING METHOD AND APPARATUS Leland W. Green, Malibu, Calif. (1710 Santa Monica Blvd, Santa Monica, Calif.) Filed Mar. 24, 1959, Ser. No. 801,631 4 Claims. (Cl. 117-97) This invention relates to method and apparatus for coating the inner surface of pipes or conduits with any desired fluid material such as sealing and caulking compositions, rust and corrosion inhibitors, paint, or the like. My device and process are particularly adapted for employment in rigid conduits which are too long for conveniently passing therethrough a cable-attached pipe-contacting head and hence resort has been had in the past to various plug-type heads which are in effect blown through the conduit by air pressure. These have proven unsatisfactory in various ways, especially in becoming wedged in bends or against minor projections of the conduit wall, as well as being diflicultly adjustable to variations in pipe diameter. In addition to the diificulty of dislodging them when stuck, there is the further result that even when these heads pass through, such obstructions or variations along the pipe surface will affect the uniform thickness and coverage of coating material spread by the contact heads; in fact, if they pass through too easily, considerable areas of conduit may not be coated at all.

Accordingly it is an object of the present invention to provide an improved device and method-for applying coating material to inner conduit surfaces, so as to. produce a more uniform film coat in a quicker and more satisfactory manner.

Another purpose resides in the provision of a fluidpropelled, deformable contact head of novel construction, particularly adapted to negotiate bends in the line and pass other obstructions. In addition, should my contact head become lodged in the line, as by an impassable obstruction, it is more readily dislodged and its direction more readily reversed for withdrawal than is the case with conventional fluid-propelled, plug-type heads.

A further advantage resides in the provision of means for balancing the inner pressure of my deformable contact head against pressure of the propelling fluid, and of selectively varying the difference between the two pressures to adapt to various operating conditions, including reversal of the direction of flow, such changes being effected by means of air compression and release mechanisms connected along the conduit.

Yet another advantage arises from employment of different types of special purpose, deformable conduit-engaging spheres which may be interchangeably coupled to a novel connector member. In particular, the immediate coating driving sphere of one form of my assembly is formed with a peripheral band of axially-directed metering grooves which spread parallel ribbons of coating material along the inner conduit face. The following sphere, coupled to the pressurized metering sphere by a connector shaft so as to resemble a dumbbell, is a smoothing or wiping sphere which by its contact with the conduit face spreads out and merges the coating ribbons so as to form a continuous uniform film.

Other objects and advantages of the invention will be apparent from the following description and claims, the novelty consisting in the features of construction, combination of parts, the unique relations of the members and the relative prop'ortioning, disposition, and operation there of, all as more completely outlined herein and particularly pointed out in the appended claims.

In the drawings, which form part of the present specification:

3,041,204 Patented June 26, 1962 FIG. 1 is a vertical longitudinal sectional view taken through a conduit section being internally coated by fluid moved between two pairs of my deformable spheres shown in elevation, with the lead sphere seen entering an enlarged section of conduit at the right, and particularly showing how its outer contacting surface adjusts itself to the increased inner circumference of the pipe;

FIG. 2 is an enlarged perspective view of the rear driving pair of spheres shown in FIG. 1, particularly showing the metering grooves about the lead sphere of the pair;

FIG. 3 is a longitudinal section taken through a bend or curved portion of a conduit, particularly showing how a pair of my spheres, seen in elevation, accommodate themselves to pass the bend; and

FIG. 4 is a vertical axial section through one of a connected pair of my spheres which is adapted to be filled with pressurized air, with portions shown in elevation.

The conduit 10 illustrated in FIG. 1 represents a rigid pipe, such as a petroleum pipeline which may be laid across sections of the country between successive pumping stations (not shown) disposed along the line, from which stations the flow of fluid through successive sections of the conduit may be controlled. From time to time it may be desirable to clean out one or more of such sections and recoat its inner surface. Accordingly air (or other gas) is supplied to the line from a suitable source, such as pump 12, through an inlet line 14 and pressure regulator 16 to a section of the conduit which is sealed off from the preceding section as by a diaphragm or apertured disk plug 18. Adjacent the further terminal of the section, a similar annular closure 20 is provided with air outlet 22 and flow regulator 24 by which the outflow of fluid from the conduit section ahead of the traveling coating assembly can be regulated; or conversely a back-pressure may he built up thereagainst. Alternately, in the event of an insurmountable stoppage of the coating assembly in the conduit, due to an obstruction in the line, a reversing pressure can be built up by blowing air in through the line 22.

Essentially my process comprises moving a body of liquid or semi-fluid coating material 26 axially along the conduit while it is contained between two pairs of my deformable spheres 28, 30 the whole being propelled or driven by the rearward pair which in turn is activated by air pressure. Accordingly coating material 26 is moved along the inner face of the conduit, the volume of coating material thus held between the two pairs of spheres gradually diminishing as it is spread along the pipe until the two pairs of compacting spheres approach each other within the line. a

The spheres of the pair 30 particularly illustrated in FIGS. 3 and 4, are connected to provide an'essentially dumbbell-shaped unit which consists of a front element 32 and a rear element 34, each of which is hollow and her or rod 36 here shown as of rigid construction and hexagonal in transverse section. The connector is formed 'at each end with a threaded end portion'38 of reduced cross section which is mounted in an internally threaded metal insert 39 to which the elastomeric material of the sphere is bonded. The connector 36 is provided'with two stepped cylindrical faces 40, 41 inwardly of the threaded end portion 38, the latter-being bounded at its inner end by a shoulder 42. An annular flange 44 mounts on the connector in abutting relation with the shoulder and provides a semi-spherical inner face 45 provided with a ribor ridge 46 adapted to seat in the outer face of the sphere. A seal 48 of the O-ring type completes the assembly. The connector can thus be interchangeably of pipe length must be constant.

3 coupled at either end to any one of the spheres, thus perrnitting comparative ease of replacement or substitution of one spherical unit for another.

Diametrically opposite the mounting of the connector tube, each sphere is provided with another annular internally threaded insert 50 mounted in the wall of the sphere, the material of the sphere being bonded to the peripheral surface of the insert. A valve body 52 formed by an external head or flange portion 54 provided with hexagonally disposed flat surfaces for engagement by a wrench, and an inwardly projecting tubular portion 56 carrying a shorter, externally threaded collar 58 is threadedly mounted in the insert 50. Adjacent the body flange 54, an annular abutment shoulder 60 of somewhat restricted diameter is disposed in lateral registration with an aluminum crush washer so as to press it against the outer face of the ball-mounted insert 50 by tightening the valve body. Within a tapped, centrally apertured, outwardly projecting externally threaded nipple 64, there is threadedly mounted a conventional valve unit 66 (similar to that used in a pneumatic tire) the release pin 8 projecting outward and being receivable in a closure cap 70 (FIG. 1).

As seen particularly in FIGS. 1' and 2, the driving pair of spheres or driving unit 28 is constructed of a forward pressurized sphere 76 and a rear unpressurized sphere 78 secured together by a connector rod 84 which may be of the same construction as the rod 36 previously described. The interior of sphere 78 has its hollow interior open to the atmosphere of the conduit through one or more openings 80.

The lead sphere 76 is designed to perform a metering function being for that purpose provided with a peripheral band of axially aligned, parallel slots or grooves 86 extending for a short distance along that portion of the sphere which even when somewhat deformed by pressure of the conduit thereagainst, presses against the inner face of the conduit uniformly about the circumference. Consequently the coating material 26 flows rearwardly through each groove as the sphere is blown forward, the depth of coating material passed through each groove corresponding to the channel depth of the grooves which in turn is regulated by the internal pressure in the sphere. In this connecton, sphere 76 may be constructed generally the same as the spheres 32 and 34. The following or trailing sphere 78 performs a smoothing or trowelling action in flowing together the adjacent ribbons of coating composition so as uniformly to cover the entire inner face of the conduit. It will be apparent of course that the amount of pressure in the metering sphere 76 must be balanced against the wiping force of the following sphere, that is, the latter must not be so collapsible or inelastic as to fail to wipe the entire pipe circumference. For this reason, a steel expansion band may be disposed within the sphere, although this is not shown.

In the operation of the pipe coating apparatus, a body of coating material 26 is initially trapped between the two units or assemblies 28, 30, and air or other gas is supplied under pressure behind the driving unit 28 to propel the entire train forward. Escape of air from the pipe ahead the leading or driven unit 30 is controlled by the valve 24.

The factors involved in the control of the processes are: velocity of the train through the pipe; drive pressure; control or back pressure; pressure exerted on coating material; diameter of pipe; friction; viscosity of coating material; and internal pressure in spherical elements.

Of the above factors viscosity can be considered constant. The pipe diameter may be variable and the friction will be variable. The factors of drive pressure and back pressure are controllable while the internal pressure in the spheres is preselected to suit the conditions to be encountered.

In order to attain uniform coating thickness, the amount of material metered by sphere 72, per increment The amount of coating material so metered is proportional to the pressureon the 4. coating material and the increment of pipe length is a function of the velocity of the train, therefore these two factors must be kept constant, or if variations occur, compensation effects must be introduced. The velocity is proportional to the drive pressure minus the back pressure but is influenced by the unknown friction factor. The pressure on the coating material is equal to the drive pressure minus the friction of units 28. Control of these parameters is accomplished by the pressure regulator 16 in the inlet line to maintain the drive pressure at a fixed value, while back pressure gas is vented through flow regulator 24 which passes a certain volume at a given rate irrespective of the pressure.

A functional analysis of the system under various operational conditions follows:

Case I .--Sm00lh Conduit of Constant Diameter Friction will be constant; drive pressure is regulated and constant, therefore the velocity is constant. As a result of the latter being constant, back pressure will be constant as will the pressure on the coating material, hence the coating will be of constant thickness.

Case 2.Obstructi0n in the Line As spheres 32 and 34 respectively meet the obstruction, the velocity is abruptly reduced and consequently the back pressure drops. The pressure regulator 16 maintains the drive pressure at original value and the pressure on the coating fluid increases, since friction is reduced by decrease in velocity. This will result in greater compressive force on sphere 76 forcing it outward against the conduit wall, with a consequent squeezing of the metering notches 86 on its periphery; thus a reduction in the amount of coating material compensates for reduced velocity. Also since the back pressure is decreasing, the net pressure or differential or driving force across the train increases. This action continues until the spheres 32, 34 are forced past the obstruction after which the velocity will be restored, the regulators will react and the system returns to normal.

When unit 28 meets the obstruction, the velocity will again be reduced, back pressure will drop as a consequence of the flow regulator action resulting in a reduction of pressure on the coating fluid. Metering requirements under these circumstances are self-compensating since reduced coating material demand because of lower velocity is offset by the reduction of pressure on the coating fluid. The reduction of back pressure and hence pressure on the coating material provides an increased driving force across unit 28 to ultimately force it past the restriction after which equilibrium will be restored as before.

Case 3.Transiti0n From Smooth to Rough Conduit The analysis of this condition parallels that given under case 2 except that the reactions will be of less magnitude and when equilibrium is established the back pressure will be lower to compensate for increased friction in the rougher pipe.

Case 4.Transition to Conduit of Slightly Different Diameter As spheres 32 and 34 successively enter the larger section they will expand into the increased diameter, and continue to bear against the wall, but with less force, the friction force will consequently be reduced. Since the displacement is greater in the larger diameter back pressure will increase since the flow regulator 24 will allow only a fixed rate. This compensates for the change in friction factor and since the drive pressure is constant, no change in velocity will occur.

When sphere 76 encounters the larger section it will also expand and further reduce friction, but any increase in velocity will be offset by an increase in back pressure. The expansion of sphere 76 will cause a corresponding widening of the metering slots to supply additional coating material for the larger circumference and constant coating thickness is maintained.

The action of the train encountering a section of reduced diameter would result in converse compensating effects.

I claim:

' l. A conduit-coating device, comprising a'pair of resilient hollow spheres adapted to be moved along the interior of a conduit in sliding registration with its inner perimeter and thus propel an adjacent quantity of coating material ahead of it through the conduit so as to coat the same, said spheres being axially spaced apart by a radially restricted connector member, one of said spheres being formed with a peripheral series of generally axially directed grooves disposed about its conduit-contacting circumference so as to meter ribbons of conduit-adhering coating material therethrough, said one of said spheres being constructed and arranged for receiving and holding pressurized fluid in its hollow interior. I

2. The device of claim 1 in which said other sphere has its interior open to the conduit atmosphere so as to serve as a spreading agent for the coating ribbons.

3'. A conduit-coating device, comprising a hollow, inflated, resilient sphere adapted to be moved along the interior of a conduit in sliding engagement therewith and to propel ahead of it a quantity of coating material, said sphere being formed with a peripheral series of axially directed grooves disposed evenly about the conduit-contacting surface, a trailing spreader member behind said sphere,

and said spreader member.

and a connector member extending between said sphere 4. The method of coating the interior of a conduit,

which comprises entrapping a fluid body between a first pair of resilient, spaced and connected hollow, conduitengaging'spheres, and a second pair of resilient, spaced and connected, hollow conduit-engaging spheres, providing and maintaining internal pressure in the spheres of said first pair and the leading sphere of said second pair, moving said pairs of spheres and said fluid body by applying fluid pressure behind said second pair, and maintaining back pressure against the leading sphere of said first pair by providing a closure in the conduit ahead of the leading sphere and venting air from the space in the conduit between the leading sphere and the closure at a constant rate of flow.

References Cited in the file of this patent UNITED STATES PATENTS 1,485,577 Witten Mar. 4, 1924 1,703,463 Weigel Feb. 26, 1929 1,746,071 Cotton Feb. 4, 1930 1,796,338 Moore Mar. 17, 1931 2,106,004 Inglee Jan. 18, 1938 2,445,645 Stephens July 20, 1948 2,480,358 Curtis et a1 Aug. 30, 1949 2,851,061 Bernard et a1. Sept. 9, 1958 FOREIGN PATENTS 381,307 Great Britain Oct. 6, 1932

Claims (1)

1. 4. THE METHOD OF COATING THE INTERIOR OF A CONDUIT, WHICH COMPRISES ENTRAPPING A FLUID BODY BETWEEN A FIRST PAIR OF RESILIENT, SPACED AND CONNECTED HOLLOW, CONDUITENGAGING SPHERES, AND A SECOND PAIR OF RESILENT, SPACED ENGAGING SPHERES, AND A SECOND PAIR OF RESILIENT, SPACED AND CONNECTED, HOLLOW CONDUIT-ENGAGING SPHERES, PROVIDING AND MAINTAINING INTERNAL PRESSURE IN THE SPHERES OF SAID FIRST PAIR AND THE LEADING SPHERE OF SAID SECOND PAIR, MOVING SAID PAIRS OF SPHERES AND SAID FLUID BODY BY APPLYING FLUID PRESSURE BEHIND SAID SECOND PAIR, AND MAINTAINING BACK PRESSURE AGAINST THE LEADING SPHERE OF SAID FIRST PAIR BY PROVIDING A CLOSURE IN THE CONDUIT AHEAD OF THE LEADING SPHERE AND VENTING AIR FROM THE SPACE IN THE CONDUIT BETWEEN THE LEADING SPHERE AND THE CLOSURE AT A CONSTANT RATE OF FLOW.

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