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Publication numberUS3139711 A
Publication typeGrant
Publication dateJul 7, 1964
Filing dateAug 28, 1962
Priority dateAug 28, 1962
Publication numberUS 3139711 A, US 3139711A, US-A-3139711, US3139711 A, US3139711A
InventorsSoderberg Jr Carl Richard
Original AssigneeSchlumberger Well Surv Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pipeline cleaning systems
US 3139711 A
Abstract  available in
Images(4)
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Claims  available in
Description  (OCR text may contain errors)

y 7, 1954 c. R. SODERBERG, JR 3,139,711

PIPELINE CLEANING SYSTEMS 4 SheetsSheet 1 Filed Aug. 28, 1962 INVENTOR.

waadi 4M ATTORNEY y 7, 1964 c. R. SODERBERG, JR 3,139,711

PIPELINE CLEANING SYSTEMS Filed Aug. 28, 1962 4 Sheets-Sheet 2 INVENTOR.

f m id ATTORNEY July 7, 1964 c. R. SODERBERG, JR 3,139,711

PIPELINE CLEANING SYSTEMS Filed Aug. 28, 1962 4 Sheets-Sheet 3 WMK/JMV ATTORNEY 7, 1964 c. R. SODERBERG, JR 3,139,711

PIPELINE CLEANING SYSTEMS 4 Sheets-Sheet 4 Filed Aug. 28, 1962 INVENTOR.

ATTORNEY United States Patent 3,139,711 PIPELINE CLEANING SYSTEMS Carl Richard Soderberg, .112, Old Greenwich, Conn, as-

signor, by mesne assignments, to Schiumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed Aug. 28, 1962, Ser. No. 219,977 9 Claims. (Cl. 51317) This invention relates to methods of determining the effectiveness of cleaning operations conducted in pipelines, and more particularly to determining the effectiveness of sand cleaning operations conducted in a pipeline and also determining the pipeline flow conductivities for commercial operations from low pressure flow tests.

A significant operating cost in the transmission of gas by pipelines is the compressor power required to overcome friction losses in the line. This friction loss is largely dependent upon the smoothness (or roughness) of the internal surface of the line. A system of decreasing the internal roughness of a pipeline heretofore has been developed in which sand is propelled through the pipeline under controlled conditions. By decreasing the internal roughness of the pipeline the flow conductivity is increased so that the required horsepower is decreased for a given flow or, conversely, a larger flow of gas can be transmitted through a given line for a given horsepower.

In the sand cleaning of pipeline, for each operation, a slug or given amount of sand is propelled through a section of a pipeline, say ten miles in length, by a controlled gas flow. The slug of sand is formed by supplying sand and gas to the section of line, cutting off the sand supply at a preselected point of operation and continuing the gas flow to drive the thus formed sand slug through the line. For each operation, the line is initially at atmospheric pressure and a number of operations are generally required to clean the interior of the line. One of the problems in sand cleaning is to determine when the interior of the line is clean.

In another type of sand cleaning operation, sand is continuously supplied through the line under controlled conditions to obtain the desired cleaning action. Again, it is necessary to know when the cleaning operation is completed.

Heretofore, it was customary to judge the cleaning process as finished when the color of the sand, as it exits from the line, approaches the color of the sand introduced at the inlet of the line. However, this is not always a reliable standard and this judgment can be in error. Thus, after the line is reconnected for commercial operation and a flow test indicates the cleaning operation was inadequate, considerable expense is incurred if the line must be reopened for further cleaning. Also, heretofore there has been no way to determine what relative elficiency or flow conductivity changes the cleaning operation accomplishes or what efficiency or flow conductivity might be expected when the line is replaced in commercial operation.

Accordingly, it is an object of the present invention to provide new and improved methods of cleaning a pipeline to a determined extent before a line is reconnected.

It is a further object of the present invention to provide new and improved methods of cleaning a pipeline to a determined extent to obtain a measured flow conductivity after internal cleaning of a line and before reconnecting the pipeline.

A further object of the present invention is to provide new and improved methods of cleaning a pipeline to a determined extent where internal cleaning operations on the interior of a pipe have been satisfactorily accomplished.

The present invention is exemplified by a method of performing internal sand cleaning: of a pipeline comprising the steps of: flowing gas at a relatively low pressure at a determined flow throughput into one end of a section of pipeline which is open at its other end to the atmosphere, measuring the inlet pressure in the pipeline to derive from a prescribed relationship therebetween, the initial flow conductivity of the section of pipeline, scouring the interior of the section of pipeline with abrasive action to decrease its relative roughness; flowing gas at low pressure into the section of pipeline open to the atmosphere after such scouring at a determined flow throughout, measuring the upstream or inlet pressure and thereby determining the flow conductivity of the section of pipeline; and comparing the initial flow conductivity with subsequently obtained flow conductivities until such subsequent flow conductivities are substantially constant whereupon such scouring is discontinued.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 is an overall organizational view of apparatus suitable for performing the method of the present invention shown connected to a pipeline;

FIG. 2 is a perspective sectional view of apparatus shown in FIG. 1;

FIG. 3 is a perspective sectional view of apparatus shown in FIG. 1;

FIG. 4 is a perspective sectional view of apparatus shown in FIG. 1;

FIG. 5 is a plot of a relationship of variables in gas transmission; and

FIG. 6 is a plot of a relationship of variables in gas transmission.

Because the present invention is related to established gas transmission techniques, the considerations involved in conventional gas transmission techniques are set forth as background for understanding the present invention in Section I entitled Gas Transmission Considerations. A pipeline cleaning system and apparatus for practicing the present invention are next set forth in Section II entitled Pipeline Cleaning System. Section III- sets forth the basis for Flow Determination.

SECTION I Gas. Transmission Considerations When a pipeline is initially designed, flow formulas for calculating capacity and pressure requirements are used. A basic flow formula for design is the Weymouth formula, which when modified to include a compressibility factor, is as follows:

(am a Pom where To use this formula in design, a value (based upon experience) is assumed for the friction factor 1. One basis 1 3 for adopting an assumed value is that the friction factor f varies as a function of diameter in inches as follows:

A more commonly used assumption for the friction factor f is that f varies as follows:

(symbols defined heretofore) Substitution of the Equation 3 in Equation 1 and using the actual efiiciency e results in a formula commonly referred to as the Panhandle formula as follows:

T 1.07881 P 2 P 2 0.5394 1 0.4605 2.6182 F.) LTZ 7 (5) d The efiiciency factor e is usually combined with the compressibility factor Z so that Equation 4 becomes:

fl 1.07881 P 2. P 2 0.5394 2 (1.4605 2.5152 Q-435.87E d where After the line is laid in place, it is tested under the prescribed pressure, temperature and gas conditions used in calculating the design for the line. In this initial test, the mass flow w of the gas can be determined by a formula as follows:

where w=lb. mass/sec.

=density of the gas, lb./ft. V=velocity (ft. per second) A=cross-sectiona1 area (sq. ft.)

The velocity can be determined, typically, by passing a slug of ammonia through a measured length of pipeline and obtaining accurate time measurements for the time required for the slug of ammonia to traversethe measured length of the line. From the mass flow w determined (Equation 8), and measurements of pressure and temperatures and the gas conditions, the efficiency factor B for the operating line is determined from Equation 5. Mass flow can also be determined by other known techniques such as a norifice run.

In any event, the parameter determined by such flow tests is the transmission factor E. The pipeline, after installation and throughout its life, will be periodically checked by flow tests to determine the transmission factor E relative to the initially measured transmission factor, the flow tests preferably being conducted each time under the same conditions. Similar flow test conditions are required because the transmission factor E is not an absolute value but is dependent uponthe particular conditions of the gas, its flow and the pipeline parameters at the time it is measured. Hence, an E factor is significant only when related to other E factors measured under similar flow and pipeline conditions. Over a period of time, the pipelines interior will deteriorate and the efficiency of flow transmission will decrease. Thus, the E factor obtained over a period of time is simply a comparison be- 7 atmosphere and an inlet end 12.

4 tween actual measurements of flow and the flow predicted by a formula such as the Panhandle Formula 5.

If the prediction formula, such as the Panhandle formula, compensates for all thermodynamic properties and accurately reflects the properties of a completely smooth pipe, the E factor will always be less than 1. Often, however, other approximations are used which do not compensate for items such as gas compressibility and the E factor can be greater than 1. However, as long as the determination of E factor is by consistent formulas and data, it will provide the desired relative indication of the performance of the pipeline.

The foregoing considerations are of particular significance in the profitable operation of gas transmission systems. The figure of merit for purposes of profitable operation is the relative E factor for a line. The ultimate purpose of sand cleaning as hereinafter described is to improve the E factor for a line'. The purpose of the present invention is to determine the point when sand cleaning operations have satisfactorily improved the E factor in terms of an economic return and to demonstrate this improvement before the line is reconnected for operation. Also, a valuable indication can be obtained before the line is reconnected of what the E factor for commercial operation will be.

SECTION II Pipeline Cleaning System Referring now to FIG. 1, an isolated section of natural gas pipeline iii comprised of a number of coupled lengths of pipes as illustrated with an outlet end 11 open to the A sand blast nozzle or head 13 may be releasably connected to the inlet end 12 in a manner which will hereinafter become more apparent. The end 14 of the pipeline from which the section 10 is isolated, is shown to the left of the inlet end 12 of section 15 and constitutes a source of supply of natural gas with sufiicient quantities and pressures for the operation of the method of the present invention. For the purpose of controlling the flow of gas from the end 14 of the pipeline, the end 14 is coupled by an eX- tension 15 to a manifold 17. A valve (not shown) may be inserted in the extension 15 to provide a shut-off control for the manifold 17 if desired. Manifold 17 in turn is provided with outlets 18 and 19 respectively having control valves 20 and 21 to control the flow of gas through the outlets. Outlet 19 from the manifold 17 is coupled to another manifold 22 which has outlets 2,3 and 24, the outlets 23 and 24 being connected to the sand supplying pct 30. Control valves 23a and 24a may be provided in the outlets 23 and 24 respectively. Outlet 18 from manifold 17 connects to a flow measuring device 65 such as a flow prover (hereinafter explained), the flow prover being connected with another manifold 25 which has outlets 26-29 connected to nozzle 13 and respectively having control valves 26a-29a. Sand supply pot 30 has mixture feed pipes 41-43 coupled to the nozzle 13, the feed pipes respectively have valves 44-46.

The flow prover 65 is connected with conventional instrumentation in the form of accurate temperature and pressure measuring devices 61, 62, respectively. Manifold 25 is provided with an accurate conventional pressure measuring device 63, and nozzle head 13 is provided with an accurate conventional pressure measuring device 64. It will be appreciated that measuring devices 61, 62, 63, 64 can be mounted in a suitable control panel and can provide a recording of measurements synchronized by means of a clock mechanism or the like.

The flow prover as illustrated in FIG. 4 comprises a tubular member 65 provided with an orifice plate 66 having a sized orifice 67. It is primarily useful where a large pressure drop can be tolerated and high upstream pressure is available. In the flow prover, the upstream pressure and temperature are measured by meter instruments 61, 62 suitably functionally attached to the member 65, and, of course, the gas gravity and flow-orifice size are known. Critical outlet flow is induced in the flow prover by exceeding the critical pressure ratio in a well-known manner so that the following relationship holds where C=coefficient for a given sized orifice Q gas flow at 14.7 p.s.i.a. and 60 F., cu. ft./hr. G=gas gravity P =upstream pressure before orifice T =upstream temperature R.

. The value of P (at gauge 61) must be greater than the downstream pressure (at gauge 63) by an amount sufficient to give critical flow. The pressure device 63 on the manifold indicates Whether the pressure drop is adequate to provide critical flow.

Referring now to FIG. 3, the nozzle 13 is comprised of a front end portion 35 with an internal diameter similar to the diameter of the pipeline to be cleaned and may include a flanged end 36 suitably arranged for a quick connect and disconnect coupling to the end of the pipeline. The front end portion 35 of the head 13 is joined by a frusto-conical section 37 to a rearward end portion 36 having a relatively larger diameter than the front end portion 35. The gas outlet pipes 26-29 from the manifold 25 are received in a rear plate 39 of the nozzle 13 with their centers disposed upon a circle having a diameter substantially equal to that of the diameter of the pipe to be cleaned, the centers being equiangularly disposed about the circle. Baffles or deflectors 41 are mounted within the nozzle 13 and disposed over the respective open ends of the gas outlet pipes 26-29 to deflect the gas circumferentially around the head so that the gas effectively travels in a spiral path within the rearward portion (shown by the arrows) and is contracted as it is passed by the frusto-conical section 37 into the front end portion 35. Mixture inlet pipes 41-43 from the sand-supplying pot 30 are inserted through the rear plate 39 of the nozzle 13 and are generally equiangularly spaced about a circle which has a diameter substantially less than the diameter of the pipeline to be cleaned. The pipes 41-43 generally lie within the periphery of an imaginary cylinder extended rearwardly from the inner wall of the forward end section 35. The open ends of the mixture pipes 41-43 are spaced slightly to the rear of the frusto-conical section 37 so that the sand and gas mixture exciting from the pipes 41-43 is picked up by the swirling gas and compressed in the frusto-conical section 37 for introduction to the inlet end of the pipeline. The pressure gauge is connected to the forward end 35 of the head 13.

The sand-supply pot 30 (FIG. 2) includes the sand and gas mixture pipes 41-43 which respectively contain valves 44-46 and include pipe sections 47-49 which extend from an upper or top portion of the pot downwardly to a point just below the bottom or lower portion of the pot. The pot 30 is generally a cylindrically-shaped, closed vessel which contains access openings (not shown) through which sand 50 may be deposited within the pot. Gas feed pipes or jets 52-54 are arranged and respectively aligned with the open, lower ends of the pipe sections 47-49 and are coupled to the gas outlet 24. The

open end of jet pipes 52 are substantially aligned with the open ends of pipes 47-49 on a common horizontal plane. Hence, gas introduced through pipe 24 and jets 52-54 may drive sand in the container upwardly through the respective pipe sections 47-49. To provide a mixing and boosting action, the pipe sections 47-49, near their upper ends, are provided with openings 56 and the gas outlet 23 is arranged to enter the pot and introduce gas into the upper portion of the pot above the sand level. Hence, gas under pressure enters through the openings 56. in the pipe sections 47-49 to further lean out the mixture of sand and gas through the pipe sections and carry the sand to the nozzle 13.

In general, the system of sand cleaning includes the following procedural steps: the pipeline 10 is cleared preliminarily by a purge of gas through the line While the end 11 is open to the atmosphere. This may be done, for example, by connecting up the head 13 and preliminarily opening the valves 26a-29a. Control valve 20 is then opened to permit flow of gas into the pipeline. After the line has been purged by the gas for a suitable length of time, the head 13 is disconnected and a pig (not shown) inserted in the end of the line. After the pig is inserted into the pipeline, the head 13 is connected up to the pipeline again and valve 20 opened to blow or drive the pig through the line by the pressure of gas from outlet 18. The pig serves to clear the line of any debris or fluid which may be in the line and also insures that there are no air pockets left in the line. After the pig is blown clear of the end of the pipeline 11, the valve 20 is closed and the line is permitted to return to atmospheric pressure.

Control valve 20 is again opened and gas permitted to flow a sufiicient time to establish a steady state flow condition. At this time, the flow conductivity of the line is determined in a manner hereinafter more fully explained in Section III.

Preliminarily to the next step of the operation, the valves 23a, 24a are opened. Valve 21 is then opened to supply gas to the container 30 which feeds sand to the nozzle 13 and simultaneously therewith or shortly thereafter, valve 20 is opened to admit gas under pressure to the nozzle 13 to drive the sand through the pipeline. The gas pressure to the pot 30 via outlet 19 is maintained greater than the pressure of the gas supply to the nozzle 13 via outlet 18 to insure the feeding of the sand to the nozzle and into the line. A given charge or amount of sand suspended in gas at high velocities is admitted to the line during a short period of time as determined by the inlet pressures, the sand supply being cut off by operating valve 21 at the end of this time period and the gas drive is continued to propel the high velocity charge of sand admitted to line entirely through the pipeline 11. After the charge of sand is entirely through the line, the gas drive valve 20 is closed and the pipeline is once again permitted to return to an atmospheric pressure. As soon as the pipeline has returned to an atmospheric pressure, the sand blasting step may be repeated. The number of sand blasting operations necessary depends upon the moisture in the line and the degree of cleaning desired. In general, the interior of the line cleans to bright surface and subsequent operations may be conducted to further hone or polish the inside of the pipeline to a smooth finish.

The precise point of completion of sand blasting operation is derived by conducting further low pressure flow tests as will hereinafter be more fully explained in Section III.

SECTION III Flow Determination With flow of gas in a pipeline, kinetic work energy changes into heat in overcoming friction. In the case of single-phase flow, such as flow of gas in pipe, this change results primarily from friction losses due to roughness of the wall of the pipe. With the exception of completely laminar flow, such losses are characterized by a friction factor f which can be defined as follows:

where 5,; all;

is the derivative representing change in pressure p per incremental length x along the pipe g is the gravitational factor in feet per second squared D is the internal pipe diameter in feet p is the density in lbs./ cu. ft.

V is the velocity in feet per second Formula 10 when integrated will give the Weymouth Formula 1.

It has been established that the friction factor f is a function of the Reynolds number (Re.) and the relative roughness where Re.=p 11 dzinternal pipe diameter (ft.) V=velocity (ft/sec.) =density (#/cu. ft.) =viscosity (#/ft. sec.)

and the relative roughness is equal to .where e is absolute roughness and d is pipeline diameter.

The dependence of the friction factor on relative roughness and flow has been thoroughly investigated and their relationship plotted'for a full range of flow values. When flow becomes completely turbulent, that is, beyond the recognized transition region between laminar and turbulent flow, the flow is no longer a function of the Reynolds number but becomes a function of the relative roughness only. Thus, at very high Reynolds numbers (above 10,000,000) the friction factor is more or less independent of the Reynolds number. In FIG. 5, a portion of a standard plot of f, Re. and

is shown where the lines plotted are relative roughness curves for the noted values of relative roughness. Note that the curve 70 represents a plot for a smooth pipe which is really a curve of zero roughness.

In accordance with the present invention, a section of the pipeline is isolated from the main line, with one end being opened to the atmosphere and the sand cleaning equipment connected to the other end of the line as shown in FIG. 1 and described in Section II.

' Valves 20, 26a-29a are operated to flow gas at a relatively low pressure into the line to establish a flow throughput which is based on the length and size diameter of the section of pipe line. In general, the flow throughput is preferably such that inlet pressures are less than 100 pounds for a line which normally operates at high pressure in the 600-700 pound pressure range. Of course, if the pipe line is normally used in such higher pressure ranges, the inlet pressure may be somewhat increased, if desired. 'In any event, the low pressure range for the present flow determination is in marked contradiction to the operating pressure ranges where conventional on line determinations are conducted. The flow throughput is precisely determined by measurements of the pressure and temperatures taken from the temperature and pressure devices 61, 62 on the flow prover. The outlet pressure is known to be atmospheric and the inlet pressure on the pipeline is measured by the pressure device 64 on the injection head 13. Other data such as the gas compressibility, the length of line between the spaced points, the diameter of the line, the specific gravity, density and viscosity of the gas, normal pressure and temperature conditions are known or easily determined in a routine manner. The flow conductivity is determinable from this data.

For example, one way of determining flow conductivity is to find the Reynolds number and friction factor (per Equations 7, 8 and 11) from the data and plot a point such as point 71 on the chart of FIG. 5. To relate point 71 to flow conductivity, all that is required is a plot of flow conductivity on the chart as a function of the Reynolds number and friction factor. This may be done by separating the thermodynamic properties used in the Panhandle formula from the flow conductivity assumptions leaving the following relationship where viscosity: .009 centipoise.

If this empirical relation is plotted in FIG. 5 for dilferent values of E, e.g., curves 72, 73, 74 for values of E=l, 0.9 and 0.8 respectively, the relative efiiciency factor B or flow conductivity of the line can be determined direct- 1y or by interpolation from the relationship of the'plotted point '71 to these flow conductivity curves 7274. In the chart, point 71 has a flow conductivity of about 0.9 or 9.1 interpolating the value between curves 72 and 73.

Next, the gas valve 20 is closed and the line permitted to return to atmospheric pressure. At this time one or more sand cleaning operations as described in Section II are performed. At such time as the color of the sand as it exists from the line approaches the color of the sand applied at the inlet, sand cleaning operations are discontinned and another flow of gas at low pressure and at a determinable flow throughput is applied to the line and measurements of the inlet pressure are made. As before, the Reynolds number and friction factor define a point 75 in FIG. 5 from which a relative flow conductivity or E of 0.96 can be determined. Sand cleaning and low pressure gas flows are then alternatively conducted until successive flow conductivities are substantially constant in value whereupon further sand cleaning is unnecessary be cause no further appreciable flow conductivity improve ments can be obtained.

Of course, such alternate cleaning and flow steps may be terminated sooner if the economic value of the expected improvement in conductivity is offset by cost of further such steps.

To relate the final flow conductivity value to an efliciency factor for a high pressure line, a relationship for the Reynolds number and friction factor is obtained from the known operating and gas conditions of the normal high pressure operation by use of Formula 1.

For example, assume the following values are normal for the commercial operation:

T =550 R. P =14.7 p.s.i.a. P =700 p.s.i.a. P =650 p.s.i.a. G=.6

;t=.009 centipoise T=550 R. d=24 L=1O miles The relationship between the Reynolds number and the friction factor 7 value can be obtained from the Formula 1.

If Formula 1 is solved using the above values except for Q, the following relationship is derived Q /T=36.4 10 Std. ft. /day (14) or, in terms of Reynolds number Re. /T=2.02 1O (15) A line function 77 can then be plotted in FIG. 5 for Equation 15.

It should be appreciated that the present invention involves the change in a parameter which is an independent variable in gas transmission. This variable is the relative roughness of the pipe which, when changed by cleaning, has the same value determined from low pressures that it will have in high pressure commercial operations. Thus, the relative roughness value (0.00001) as determined by point 75 can be used to determine the operational point 76 for high pressure operation of the trans mission line. The operational point 76 can then be related to the flow conductivity curves 72-74 to determine the operational flow conductivity value for high pressure operations. In this case, the predicted E factor would be about 0.89.

As a check on the initial low pressure test point so determined, the line, before disconnecting and clearing, can be flow tested, the Reynolds number and friction factor determined and an initial point 77a plotted on the chart of FIG. 5. This point should coincide with the operating line 77 plotted and the relative roughness value (0.0005) as determined by the low pressure flow test. The E factor for normal high pressure operation would be 0.81 and hence, the sand cleaning would increase the E factor by 0.08.

For a preferred and more direct approach to determining efficiency factor or flow conductivity changes Formula 4 can be rearranged as follows:

From this Formula 16, for a given set of conditions in which C, G, T, L, Z, T P d, P are known, a chart can be constructed of P versus P for different assigned values of E. Such a chart is shown in FIG. 6 where E values of 1.0, 0.9, 0.8 and 0.7 are reversed and correspondingly curves 80453 plotted.

Using this basis, the pipeline is disconnected and the low flow pressure test run, the values of P and P being obtained from instruments 61, 64 and plotted on FIG. 6 from which the initial value of E is determined. Next, the pipeline is cleaned and another flow test is run and points plotted for the values P and P obtained. These steps are continued until the determined efficiency or flow conductivity values remains substantially constant, whereupon it can be said that the cleaning operation is completed and the overall flow conductivity change produced by the sand cleaning is then the difierence between the initial and finally determined flow conductivity values. It will, of course be appreciated that by maintaining either P or P constant for each test that the change in the remaining value of P or P will indicate the change in flow conductivity and that when the changing value becomes substantially constant further cleaning is not necessary.

It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of this invention, numerous other arrangements may be readily devised by those skilled in the art which ill embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. A method of performing internal cleaning of pipe line comprising the steps of: flowing gas at low pressure into a section of pipe line open to the atmosphere at a determined flow throughput, measuring the upstream pressure and determining therefrom the initial flow conductivity of the section of pipe line; scouring the interior of the section of pipe line with abrasive action to decrease its relative roughness; flowing gas at low pressure into the section of pipe line open to the atmosphere after such scouring at a determined flow throughput, measuring the upstream pressure and determining therefrom the flow conductivity of the section of pipe line; and comparing the initial flow conductivity with subsequently obtained flow conductivities until such subsequent flow conductivities are substantially constant whereupon such scouring is discontinued.

2. A method of performing internal cleaning of large diameter and relatively long lengths of pipe line comprising the steps of: flowing gas at low pressure into a section of pipe line open to the atmosphere at a determined flow throughput and steady state flow conditions, measuring the upstream pressure and determining therefrom the initial flow conductivity of the section of pipe line; scouring the interior of the section of pipe line with abrasive action to decrease its relative roughness; flowing gas at low pressure into the section of pipe line open to the atmosphere after such scouring at a determined flow throughput and steady state flow conditions, measuring the upstream pressure and determining therefrom the flow conductivity of the section of pipe line; and comparing the initial flow conductivity with subsequently obtained flow conductivities until such subsequent flow conductivities are substantially constant whereupon such scouring is discontinued.

3. A method of performing internal cleaning of pipe line comprising the steps of: flowing gas at a pressure less than p.s.i.a. into a section of pipe line of known length and diameter open to the atmosphere at a determined flow throughput and at determinable gas temperature, gravity and compressibility conditions, measuring the upstream pressure and determining the initial flow conductivity of the section of pipe line; scouring the interior of the section of pipe line with abrasive action to decrease its relative roughness; flowing gas at a pressure less than 100 p.s.i.a. into the section of pipe line open to the atmosphere after such scouring at a determined flow throughput and at determinable gas temperature, gravity and compressibility conditions, measuring the upstream pressure and determining therefrom the flow conductivity of the section of pipe line; and comparing the initial flow conductivity with subsequently obtained flow conductivities until such subsequent flow conductivities are substantially constant whereupon such scouring is discontinued.

4. A method of performing internal cleaning of pipe line comprising the steps of: flowing gas at low pressure into a section of pipe line open to the atmosphere at a determined flow throughput, measuring the upstream pressure and determining therefrom the relative roughness of the section of pipe line; scouring the interior of the section of pipe line with abrasive action to decrease its relative roughness; flowing gas at low pressure into the section of pipe line open to the atmosphere after such scouring at a determined flow throughput, measuring the upstream pressure and determining therefrom the relative roughness of the section of pipe line; and comparing the initial relative roughness with subsequently obtained relative roughness values until such subsequent relative roughness values are substantially constant whereupon such scouring is discontinued.

5. A method of performing internal cleaning of pipe line comprising the steps of: flowing gas at low pressure into a section of pipe line open to the atmosphere at a determined flow throughput, measuring the upstream pressure to determine the initial flow resistance in the line and determining from the ratio of the flow and resistance, the initial flow conductivity of the section of pipe line; scouring the interior of the section of pipe line to decrease its relative roughness; flowing gas into the section of line at a determined flow throughput after scouring, measuring the upstream pressure to determine the initial flow resistance in the line, and determining from the ratio of the flow and resistance, the flow conductivity of the section of pipe line; comparing initial flow conductivity with subsequent flow conductivities until such subsequent flow conductivities are substantially constant whereupon scouring is discontinued.

6. A method of performing internal cleaning of pipe the initial 'flow conductivity of the section of pipe line;

scouring the interior of the section of pipe line to de crease its relative roughness; flowing gas into the section of line after scouring at a determined flow throughput, measuring the upstream pressure to determine the initial flow resistance in the line, and determining from the ratio of the flow and resistance, the flow conductivity of the section of pipe line; comparing initial flow conductivity with subsequent flow conductivities until such subsequent flow conductivities are substantially constant whereupon scouring is discontinued.

7. A method of performing internal cleaning of high pressure gas pipe line conduits comprising the steps of: opening one end of a pipe line section to the atmosphere and flowing gas at low pressure into the remaining end of said section at a determined flow throughput and determining from the initial low pressure flow conductivity of said section and the low pressure operating conditions, the relative roughness of the interior of said test section; scouring the interior of the section of pipe line to decrease its relative roughness; flowing gas at low pressure into the remaining end of said section at a determined flow throughput and determining from the low pressure flow conductivity of said section and the low pressure operating conditions, the relative roughness of the interior of said section; comparing initial low pressure flow conductivity with subsequent low pressure flow conductivities until such subsequent low pressure flow conductivities are substantially constant whereupon said scouring is discontinued; determining from a final low pressure flow conductivity the final relative roughness of the interior of said section.

, 8. A method of performing internal cleaning of high pressure gas pipe line conduits comprising the steps of: opening one end of a pipe line section to the atmosphere and flowing gas at low pressure into the remaining end of said section at a determined flow throughput and determining from the initial low pressure flow conductivity of said section and the low pressure operating conditions, the relative roughness of the interior of said test section; scouring the interior of the section of pipe line to decrease its relative roughness; flowing gas at low pressure into the remaining end of said section at a determined flow throughput and determining from the low pressure flow conductivity of said section andthe low pressure operating conditions, the relative roughness of the interior of said section; comparing initial low pressure flow conductivity with subsequent low pressure flow conductivities until such subsequent low pressure flow conductivities are substantially constant whereupon said scouring is discontinued; determining from a final low pressure flow con ductivity the final relative roughness of the interior of said section; and determining from said final relative roughness, the high pressure operating flow conductivity of the pipe line prior to replacing said section in operation.

9. A method of performing internal cleaning of high pressure gas pipe line conduits comprising the steps of: flowing gas at high pressure operation at normal flow throughput through a section of pipe line in place and determining the initial operating flow conductivity, of the pipe line for gas through said section with respect to relative roughness of the interior of the section, opening one end of said section to the atmosphere and flowing gas at lowrpressure into the remaining end of said section at a determined flow throughput and determining from the initial low pressure flow conductivity of said section and the low pressure operating conditions, the relative roughness of the interior of said test section; scouring the interior of the section of pipe line to decrease its relative roughness; flowing gas at low pressure into the remaining end of said section at a determined flow throughput and determining from the low pressure flow conductivity of said section and the low pressure operating conditions,

References Cited in the file of this patent UNITED STATES PATENTS 1,557,131 Armstrong Oct. 13, 1925 1,890,164 Rosenberger Dec. 6, 1932 1,939,112 Eulberg Dec. 12, 1933 2,087,694 Malmros July 20, 1937 2,627,149 MacCracken Feb. 3, 1953 2,826,006 Croft Mar. 11, 1958

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Classifications
U.S. Classification451/36, 451/51, 134/8, 134/26
International ClassificationB24C3/32, B24C3/00
Cooperative ClassificationB24C3/327
European ClassificationB24C3/32C1