US3791842A

US3791842A - Process of applying powder to a rotating object

Info

Publication number: US3791842A
Application number: US00129869A
Authority: US
Inventors: D Neal
Original assignee: Midwestern Specialties Ltd
Current assignee: Midwestern Specialties Ltd
Priority date: 1971-03-31
Filing date: 1971-03-31
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12

Abstract

A method of spraying powder from nozzles onto the outer periphery of the pipe while the pipe is rotated about its longitudinal axis. The spray nozzle or nozzles are spaced from the outer periphery of the pipe and at the optimum angle with respect to the transverse or cross-sectional configuration of the pipe for providing the most efficient and complete coating or covering of the object.

Description

Unite States Patent Neal Feb. 12, 1974 1 PROCESS OF APPLYING POWDER TO A 3,407,099 10/1968 $611611 117/1054 ROTATING OBJECT 3,439,649 4/1969 Probst et a1 1 17/17 3,155,545 11/1964 Rocks et a1. 117/17 [75] Inventor: D nnis Neal, Tulsa, a 3,581,922 6/1971 Versoy 117/17 2,428,991 10/1947 Ransburg 117/17 [73] Assgnee" g g Tulsa 3,536,514 10/1970 La Fave 61. a1 117/17 1 Fi1ed= 31, 1971 Primary Examiner-William 1). Manin Appl. No.: 129,869

U.S. Cl ..l17/16,117/17,117/18, 117/20,117/21,117/24,117/105.4,118/310, 118/314,118/315,118/316,118/320,

Int. Cl B05b 5/2, 844d 1/94 Field of Search. 117/16, 17, 20, 21, 24,104 R, 117/105.4, 18; 118/621, 627, 308, 310, 311, 312, 314, 315, 316, 320, 630

References Cited UNITED STATES PATENTS Stanley et a1. 117/17 Assistant ExaminerM. Sofocleous Attorney, Agent, or Firm-William S. Dorman 5 7 ABSTRACT A method of spraying powder from nozzles onto the outer periphery of the pipe while the pipe is rotated about its longitudinal axis. The spray nozzle or nozzles are spaced from the outer periphery of the pipe and at the optimum angle with respect to the transverse or cross-sectional configuration of the pipe for providing the most efficient and complete coating or covering of the object.

6 Claims, 12 Drawing Figures PAIENT'EB rm 1 2 I974 sum 1 or z .g A y Fig 4 Fig. 5

Fig 3 DENNIS NEAL INVENTOR.

WMJW

ATTORNEY Pmarim 3.791.842

SHEET 2 [IF 2 so so 2 y l 2 O E 50 2 a 4 5 e 7 s 9 060 90 I20 150 DISTANCE IN INCHES LOCATION,

DEGREES SEPARATION 7 Fig. 8

50 60 60 5 U 2 5 5 E 50 6 so E 50 LL c: IJJ LL NUMBER OF GUNS ORIENTATION, AIR PRESSURE, PSI

DEGREES Fig. 9 Fig.10 Fig. 11

so u Z 2: U I so it DENNIS NEAL INVENTOR.

20 3o 40 so so 70 BY LINEAR SPEED, FT./M|N. A E

Fig. 12

ATTORNEY PROCESS OF APPLYING POWDER TO A ROTATING OBJECT This invention relates to improvements in coating objects and more particularly, but not by way of limitation, to a method of applying powder to the surfaces of a rotating object.

It is well known that the service life of pipes, whether disposed underground or otherwise, is hampered or greatly lessened due to the element surrounding the pipe. For example, the underground or buried metallic pipes are subjected to a great amount of external corrosion which results from a natural flow of electric current caused by the reaction between the metal surfaces and chemicals in the soil or water surrounding the structure. The electric current will flow from the metal to the adjacent soil and back to the metal, thus making the metallic structure an anode at the point where the current leaves the metallic structure and as the current flows from the pipe, minute particles of the metal are carried into the soil, thereby causing pitting of the pipe. This is commonly called electrolysis and over a period of time the pipe may become severely damaged and require replacement. This is particularly disadvantageous with very large diameter pipe lines which are used for transporting natural gas at high pressures. weakening of the pipe due to corrosion or other reasons can lead to explosions, causing severe damage and occasionally loss of life. i

There are several methods utilized today for reducing the damage due to corrosion or electrolysis, such as eathodic protection, or external coating of the pipe for protection thereof. The external coatings are applied to either buried structures or to those structures disposed above the ground, and are generally considered to be advantageous for several reasons in that the coating may provide a more universal and lasting protection for the pipe than the cathodic protection method. However, many of the coatings presently available have certain disadvantages in that the comparatively rough handling of the pipe during installation, and the like, frequently chips the coating or breaks the coating and as a result deterioration of the metal can result. Common practice is to both coat the pipe and protect the pipe cathodically. Cathodic protection, however, frequently causes the coating to fail. Consequently, there has been a great study and effort put forth in the development of coatings for pipe, and particularly plastic coatings which will overcome these disadvantages. For example, one such coating known under the trade name Nap- Gard has been developed by the Napko Corporation which has proven to be extremely efficient and desirable for the exterior coating of the pipe. This particular coating material is tough and has a great resistance to deterioration under cathodic protection. Nap-Gard is a high molecular weight cross linked polymer whose basic polymeric structure consists of linearized phenolic type units, further described in the Napko Industrial Coating Division publication SA-258 dated April 1967. This coating material requires the application of two coats of material, with one of the coatings preferably being the application thereof in powdered form. Of course, it will be apparent that the coating must be applied to the external surface of the pipe in a manner for completely covering thereof to produce the necessary protection of the pipe, and as a result it is extremely important to apply the powdered form thereof in an efficient manner for a complete covering of the surface being coated.

The present invention contemplates a novel method of applying powder to a rotating object. such as a pipe rotating about its longitudinal axis, in a manner wherein a complete and efficient coating or covering of the object is assured. The powder is sprayed onto the outer periphery of the object through nozzles or spray guns which have been particularly spaced and arranged with respect to the distance from the object to assure an efficient application of the powder. lt is to be noted that the efficiency of the coating is the percentage of powder delivered from the guns which actually adheres to or stays on the object. The distance of the guns from the object has a major effect upon the coating efficiency and is directly related to the spray pattern. In addition, the location of the banks of guns significantly affects the efficiency of the coating, whereas the specific number of the guns appears to have a relatively minor effect on the coating efficiency. The orientation of the guns also produces a major effect on the coating efficiency, and an orientation of the guns leading into the direction of rotation of the object greatly improves the coating efficiency. In addition, whereas air pressure has a slight by definite effect on the efficiency, it is noted that the efficiency is greater with the use of lower air pressure. The lineal speed of the rotating object appears to be a major effect of the coating efficiency, it is considered that this may be somewhat illusionary, since the efficiency increase related to lineal speed may be the result of less repulsion of the particles from the surface having a thinner, more diffuse coating. Furthermore, the electrostatic charge is also a major condition in the effect of the coating efficiency. Thus, in the present method of applying powder to a rotating object, careful selection of the spacing between the guns, the distance of the guns from the object, and the angular disposition of the guns or orientation of the guns with respect to the object are particularly selected to produce an efficient application of the powder not heretofore attainable.

It is an important object of this invention to provide a novel method of applying powder to a rotating object such as a pipe section being rotated about its longitudinal axis.

lt is another object of this invention to provide a novel method of applying powder to a rotating object by spray guns wherein the spacing of the guns with respect to the object is particularly selected for optimum efficiency of the coating of the object.

Another object of this invention is to provide a novel method of applying powder to a rotating object by spray guns wherein the spacing between the guns is particularly selected for optimum coating efficiency.

Still another object of this invention is to provide a novel method of applying powder to a rotating object wherein an angular position or orientation of the guns with respect to the object is particularly selected for optimum coating efficiency.

A further object of this invention is to provide a novel method of applying powder to a rotating object which is simple in operation and efficient in results.

Other and further objects and advantageous features of the present invention will hereinafter more fully appear in connection with a detailed description of the drawings in which:

FIG. 5 is a schematic side elevational view of one type of spray gun depicting a spray pattern as used during the application of powder in accordance with the invention.

FIG. 6 is a schematic plan view of a pair of adjacent spray guns depicting a spray pattern as used during the application of powder in accordance with the invention.

FIGS. 7 through 12 are graphic representation of the experiments relating to coating efficiency as related to:

FIG. 7 distance of guns to object;

FIG. 8 angular separation of banks of guns;

FIG. 9 number of guns;

' FIG. 10 angular orientation of each gun with respect to object;

FIG. 11 driving air pressure for guns; and

FIG. 12 linear speed of outer periphery of pipe past guns.

The experiments resulting in the present invention were conducted on 30 inch diameter pipe which was cleaned prior to the coating operation, and a coating similar to that disclosed in the Richard C. Stanley et al. co-pending applications Ser. No. 52,638, filed July 6, 1970, entitled Method for Coating Pipe, now Pat. No. 3,687,706; and Ser. No. 56,822, filed July 21, l970, entitled Method and Means for Coating Pipe, now Pat. No. 3,687,704 and with which I am familiar, was the basis for the experimentation in the application of the powder to the outer periphery of the pipe. The pipe was checked by proper personnel for acceptability, and the rate at which pipe could be properly cleaned was determined and correlated to the wheelabrator formula 1 sq. ft./HP/min. for white metal cleaning.

The cleaned pipe was heated over the 4 inch by 4 inch row of Blu-Surf burners, and the time required to heat the pipe to a temperature of 450 F. was measured. The effects of pipe rotation rate, the effects of the distance of the pipe from the burner, the effects of the wall thickness of the pipe on the heating rate were also determined. A family of curves was then generated using this data to show heating rates for different wall thicknesses and different pipe diameters. The tests and experiments of the powder application were then conducted to determine the effect of several application variables on the efficiency of the coating. As hereinbefore set forth, the efficiency of coating is the percentage of powder delivered from the guns which actually stays on the pipe. The following variables were studied during the experimentation:

l. The distance of the gun from the outer periphery of the pipe. 2. The location of the banks of guns around the outer periphery of the pipe.

3. The number of guns. 4. The orientation (or angular dispostion) of the guns (leading or trailing the direction of pipe rotation.

5 5. The air pressure utilized in the guns.

6. The electrostatic charge.

The guns in each bank of guns were spaced longitudinally along the pipe on 9 inch centers, and each of the above variables was evaluated separately, as will be hereinafter set forth in detail.

With regard to the iocation of the gun banks, and referring particularly to FIGS. 1 and 8, reference character 10 schematically indicates a pipe diameter, reference character 12 indicates a first or top bank of guns, and reference character 14 schematically indicates a second or bottom bank of guns. As hereinbefore set forth, the guns in the

banks

12 and 14 are spaced longitudinally along the pipe 10 on 9 inch centers, and the location of the

banks

12 and 14 around the pipe 10 with respect to each other were tested at a plurality of angular positions therebetween, with the location of the banks being indicated by positions on clock. As shown in FIG. 1, the top bank 12 is located at or 12 oclock, whereas'the bottom bank 14 is located at 240 in the clockwise direction, or 8 oclock. The graph depicted in FIG. 8 shows the correlation between coating efficiency and the location of the banks of guns as referenced by degrees of separation.

The coating efficiency appears to be affected significantly by the positioning or location of the

gun banks

12 and 14 around the outer circumference of the pipe 10, and as clearly shown in FIG. 8, the optimum efficiency was obtained with a spacing of substantially ninety degrees therebetween. This was a rather surprising result, and the data were determined through the use of only two banks of guns. It is admitted that the use of three banks of guns may provide different results.

The number of guns provided appears to have a minor effect on the coating efficiency, as shown in FIG. 9. However, it is believed that this may be due to the effect of the position of the guns in the different banks of guns rather than any real effect due to the number of guns.

The distance of the guns from the outer periphery of the pipe, however, has a major effect on the coating efficiency, as is clearly shown in FIG. 7. The distance of the guns from the pipe is also directly related to the spray pattern as shown in FIGS. and 6. The experimental data shows a marked improvement with the guns spaced 5 inches from the outer periphery of the pipe, and at a greater distance than the 5 inches, the spray patterns from adjacent guns overlap causing severe turbulence. As shown in the graph in FIG. 7, the optimum distance appears to be from 4 /2 inches to 5 inches for guns spaced on 9 inch centers. Of course, guns on different center line spacing would have different optimum distances.

Referring particularly to FIGS. 5 and 6, the nozzles or

spray tips

16 and 18 are longitudinally spaced with respect to the pipe with the

centerlines

20 and 22 thereof, respectively, spaced substantially nine inches apart. The spray patterns from the

nozzles

16 and 18 are shown in side elevation in FIG. 5 and in plan view in FIG. 6 as indicated at 24 and 26, respectively. It will be readily apparent that in FIG. 6, that the

spray patterns

24 and 26 begin to overlap at a distance of approximately four and one-half inches forward or away from the outer extremity of the

nozzles

16 and 18, as shown at 28. At a distance of 5 inches from the

nozzles

16 and 18 there is a slight overlapping of the spray patterns, but the coating efficiency is relatively high, even at the 5 inch distance from the pipe.

With regard to the angular position or orientation of the guns with respect to the pipe, FIGS. 2, 3, 4 and 10, depict a variety of gun orientations. As shown in these Figures, the pipe is indicated as being rotatable about its longitudinal axis in a clockwise direction as indicated by the arrow A. The gun, indicated schematically at G is depicted in FIG. 2 as being positioned normal to the pipe, whereas the gun G is orientated from the normal position at a negative angle a leading into the direction of rotation in FIG. 3, and at a positive angle a trailing the direction of rotation in FIG. 4.

The orientation of the guns has a major effect on the coating efficiency, as particularly shown in FIG. 10. An orientation leading into the direction of rotation markedly improves the coating efficiency. This effect was not optimized, however, and it is possible that even better results may be obtainable. It appears likely that the optimum angle of the guns depends on two factors, namely the rate of pipe rotation and the distance of the guns from the pipe.

As shown in FIG. 11, the air pressure utilized in conjunction with the nozzles or guns appears to have a slight but definite effect, with better coating efficiency being obtained at the lower air pressure. It should be noted that the general level of efficiency is much higher in these data points because the pipe was coated at a lineal speed of approximately 67.7 feet per minute during this particular testing operation.

As will be seen from an inspection of FIG. 12, the lineal speed of the pipe moving past the guns appears to have a major effect upon the coating efficiency. However, this is believed to be somewhat illusory since the coatings obtained were not complete but barber poled. It is believed that this increase in efficiency is caused by less repulsion of the powder particles from the surface of the pipe with the thinner more diffuse coating, a phenomenon demonstrated by Resins Technical Center. Under normal conditions it is doubtful if this improvement in efficiency will actually be observed.

The testing also indicated that electrostatic charge has a major effect upon the coating efficiency, causing a difference of approximatcfl fiper ceglhgisglgr e v iHEiTE e tFaf EYTaFQ particles are required when this type of equipment is used.

Based on the results of this testing of powder application or coating of rotating objects with powder it has been found that a relationship exists between coating efficiency and the location of the banks of guns around the outer periphery of the pipe; the spacing of the guns from the pipe; and the orientation of the guns with respect to the pipe. These results were surprising since there has been nothing in the prior art to indicate that these variables would produce such an increase in coating efficiency. An orientation of the guns in a negative angular direction, or leading into the direction of the rotation of the object being coated, in combination with a spacing between the guns related to the distance of the guns from the outer periphery of the pipe whereby only a slight overlapping of spray patterns is achieved, and further consideration being given to the circumferential location of the gun banks around the outer periphery of the pipe provides a coating efficiency in the application of powder to a rotating object not heretofore obtained.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.

What is claimed is:

I. A process of applying powder to a rotating object which comprises utilizing at least one bank of spray guns for applying the powder to the outer periphery of the object, disposing each bank of spray guns circumferentially about the outer periphery of the object with respect to the rotational axis of the object, spacing the guns longitudinally along the length of each bank, locating each bank of guns at a selected distance from the outer periphery of the object with relation to the longitudinal spacing between the guns of each bank so that there is a slight overlap of spray pattern of the powder from adjacent guns of each bank, orientating the angular position of the guns in a negative angular direction leading into the direction of the rotation of the object and spraying the powder onto the object while rotating the object about its longitudinal axis.

2. A process of applying powder to a rotating object as set forth in claim 1 wherein there are two banks of spray guns, said banks being circumferentially spaced around the outer periphery of the object approximately apart.

3. A process of applying powder to a rotating object as set forth in claim 1 wherein the orientation of the guns is approximately 15 leading from the normal into the direction of rotation of the object.

4. A process of applying powder to a rotating object as set forth in claim 1 and including placing an electrical charge on the particles of the powder being applied to the object.

5. A process of applying powder to a rotating object which comprises utilizing a pair of banks of spray guns for applying the powder to the outer periphery of the object, disposing the banks of guns circumferentially around the outer periphery of the object at a spacing of approximately 90 between the banks, spacing the guns longitudinally along the length of the banks, placing the guns at a selected distance from the outer periphery of the object in coordination with the longitudinal spacing between the guns whereby the spray patterns of the adjacent guns of each bank slightly overlap upon impinging the outer periphery of the object, orientating the angular position of the guns in a plane perpendicular to the longitudinal axis of the object at an angle of approximately 15 from the normal leading into the direction of rotation of the object, and spraying the powder onto the object while rotating the object about its longitudinal axis.

6. A process of applying powder to a rotating object as set forth in claim 5 and including placing an electrical charge on the particles of the powder being applied to the object.

i i I I! k

Claims

2. A process of applying powder to a rotating object as set forth in claim 1 wherein there are two banks of spray guns, said banks being circumferentially spaced around the outer periphery of the object aPproximately 90* apart.
3. A process of applying powder to a rotating object as set forth in claim 1 wherein the orientation of the guns is approximately 15* leading from the normal into the direction of rotation of the object.
4. A process of applying powder to a rotating object as set forth in claim 1 and including placing an electrical charge on the particles of the powder being applied to the object.
5. A process of applying powder to a rotating object which comprises utilizing a pair of banks of spray guns for applying the powder to the outer periphery of the object, disposing the banks of guns circumferentially around the outer periphery of the object at a spacing of approximately 90* between the banks, spacing the guns longitudinally along the length of the banks, placing the guns at a selected distance from the outer periphery of the object in coordination with the longitudinal spacing between the guns whereby the spray patterns of the adjacent guns of each bank slightly overlap upon impinging the outer periphery of the object, orientating the angular position of the guns in a plane perpendicular to the longitudinal axis of the object at an angle of approximately 15* from the normal leading into the direction of rotation of the object, and spraying the powder onto the object while rotating the object about its longitudinal axis.
6. A process of applying powder to a rotating object as set forth in claim 5 and including placing an electrical charge on the particles of the powder being applied to the object.