US3591239A

US3591239A - Recycling arrangement for retarding plug formation in a shutdown slurry pipeline

Info

Publication number: US3591239A
Application number: US802617*A
Authority: US
Inventors: Paul E Titus
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1969-02-26
Filing date: 1969-02-26
Publication date: 1971-07-06
Anticipated expiration: 1988-07-06

Abstract

Method and apparatus for retarding plug formation in a shutdown slurry pipeline. Means is provided whereby slurry liquid phase within upper elevations of the shutdown line is recycled into lower portions of the line where slumping and compacting of the solid phase may occur.

Description

United States Patent Inventor Paul E. Titus Houston, Tex.

Appl. No. 802,617

Filed Feb. 26, 1969 Patented July 6, 1971 Assignee Shell Oil Company New York, N.Y.

RECYCLING ARRANGEMENT FORRETARDING PLUG FORMATION [N A SHUTDOWN SLURRY PIPELINE 4 5 Claims, 2 Drawing Figs.

US. Cl 302/14, 302/64, 302/66 int. Cl 865g 53/30 FieldoiSearch 302/14, 15, i6, 64, 66

[56] References Cited UNITED STATES PATENTS 562,232 6/! 896 Miller 1,329,967 2/1920 Greenstreet.... 2,093,970 9/1937 Longnecker 3,038,760 6/l962 Crooke Primary Examiner-Andres H. Nielsen Attorney'sThomas R. Lampe and J, H. McCarthy ABSTRACT: Method and apparatus for retarding plug formation in a shutdown slurry pipeline. Means is provided whereby slurry liquid phase within upper elevations of the shutdown line is recycled into lower portions of the line where slumping and compacting of the solid phase may occur.

PATENTEUJUL Si n 3,591, 239

INVENTOR.

P. E TITUS BY/Z HIS ATTORNEY RECYCLING ARRANGEMENT FOR RETARDING PLUG FORMATION IN A SIIU'IDOWN SLURRY PIPELINE The present invention relates to pipeline transport operations and, more particularly, to a method and apparatus for retarding plug formation by slurry solid-phase material in a pipeline during a shutdown period.

Transportation by pipeline is a major and growing industry. With the use thereof formerly confined almost entirely to movement of water, gas and petroleum products, pipelines, with the advent of slurry transport, have become useful for long and short hauls of a wide variety of raw materials and finished products.

With respect to the pipelinetransportation of materials in slurry form, problems arise when such materials are moved through pipelines inclined to go over ahill or down into a val ley. At these locations, during a planned or emergency line shutdown, the solids of the transported slurry may settle out vertically and subsequently slide down the inclined portions of the pipeline, thereby causing a compacted plug which may be very difficult to dislodge and move when line shutdown is ter' minated and transport activities are resumed.

These difficulties are most commonly avoided by laying solids-carrying or slurry pipelines so that they do not exceed a slope or angle of inclination below which sliding does not occur. Alternatively, the inclined pipeline sections are emptied at each shutdown. Obviously, these alternative prior art approaches are not always feasible or economical, especially in those situations where long and relatively steep slopes are encountered. Slopes of this nature are being encountered with increasing frequency as pipeline operations are being extended to new relatively inaccessible mountainous areas in the United States and elsewhere.

SUMMARY OF THE INVENTlON It is therefore a primary object of the present invention to provide an improved and economical apparatus and method whereby slurry solid-phase material being transported in an inclined pipeline section is prevented from forming a tightly compacted plug during a line shutdown.

This and other objects have been attainedin the present invention by providing a method and apparatus for retarding plug formation in a shutdown slurry pipeline wherein a conduit is operatively associated with the line so as to provide communication between upper elevations of the line and lower segments of the line with the conduit having pump means disposed therein. The pump means is actuated when the pipeline flow rate falls below some predetermined level to pump liquid-rich slurry material from the line upper elevations to lower points in the line. In this manner, slurry solid-phase materials slumping within the line are continually agitated so as to prevent formation of a compacted plug under the influence of gravity.

DESCRIPTION OF THE DRAWING The above-noted and other objects of the present invention will be understood from the following description, taken with reference to the accompanying drawing. In describing the invention in detail, reference will be made to the drawing in which like reference numerals designate corresponding parts throughout several views in which:

FIG. 1 is a diagrammatic view illustrating a given length of slurry pipeline which has been modified in accordance with the teachings of the present invention; and

FIG. 2 is an enlarged diagrammatic cross-sectional view in longitudinal projection illustrating an inclined portion of the pipeline section of FIG. 1 with a conduit and pump means in operative association therewith in accordance with the teachings of the present invention.

Referring now to FIG. l, a given length of slurry pipeline I1 is illustrated in the position assumed thereby as the pipeline proceeds to and from a valley formed between two bills or mountains l2 and 13. The terrain illustrated is typical of that encountered in pipeline-laying activities, although it should be understood that the teachings of the present invention may be carried out in any topographical configuration wherein a portion of slurry pipeline is inclined.

The transportation of slurries consisting of solid particles in a fluid medium by use of pipelines similar to that disclosed in FIG. 1 is quite well known, and such expedient is finding increasing use, especially in those situations where the source of raw materials is relatively remote and inaccessible from the point of delivery, which may be a suitable processing plant, for example. In the disclosed arrangement, it may be assumed for purposes of illustration that the slurry material being trans ferred through pipeline II as by means of conventional pumps (not shown) is moving through the line in the direction indicated by the arrows. However, the teachings of the present invention are, of course, applicable regardless of the direction of flow ofthe slurry.

As long as flow continues in the pipeline, the solid matter of the slurry will remain in suspension within the pumped liquid, even when the solid matter has a higher specific gravity than the liquid. If, however, the flow is stopped for any reason, i.e., the pipeline is shut down, such solid matter will settle out of suspension. In the situation where the line is horizontal or the slope of the line is insufficient to cause sliding of the settled solids, no problem is created by such settling out. Under these conditions, a liquid-rich channel remains open at the top of the line which allows the settled material to be resuspended with a minimum of difiiculty upon resumption of slurry flow.

A serious problem can exist when the pipeline must be inclined to go over a hill or down a valley, as illustrated, for example, in FIG. I. At these locations, the settling of solids followed by their sliding down the slope during a protracted shut down can result in a compacted plug of material difficult, if not impossible, to move or resuspend. In the illustrated pipeline configuration, such solids would slide downwardly into the valley formed between hills or mountains l2 and 13. The solid material would then compress under its own weight to form a plug in the valley in an obvious manner.

Such plug formation is retarded in accordance with the teachings of the present invention as follows. In FIG. 1 a conduit I4 is illustrated as being in operative association with pipeline 11 with the conduit proceeding from an upper elevation of the line, i.e., that portion of the line disposed on hill 12, to a lower portion of the line positioned in the valley lying between

hills

12 and 13. A pump 15 is. disposed at a selected location along conduit 14.

As described above, upon termination of slurry flow the slurry solid-phase material tends to settle or slump within the line. Such action results in the formation of a liquid-rich slurry mixture in the upper elevations of the line. Plug formation is retarded in accordance with the teachings of the present invention by actuating pump 15 when the slurry flow rate has terminated or fallen below some predetermined level. The pump serves to transport the liquid-rich slurry mixture down conduit 14 whereupon the mixture is introduced into the lower portions of the pipeline 1]. The introduction of the liquid-rich slurry mixture maintains the slumping slurry solid phase in continuous agitation with the result that a solidphase-liquid-phase slurry mixture is maintained with compacting and plug formation by the slurry solid-phase material being prevented. Upon pipeline restart, pump 15 is shut down and the slurry within pipeline 11 may be readily transported.

Conduit 14, rather than being connected at one downhill point of the pipeline, as diagrammatically illustrated in FIG. I, may be connected to the pipeline at a plurality of downhill locations. In FIG. 2, for example, conduit 14 is illustrated as being connected between an upper elevation of the line and a plurality of downhill pipeline locations through manifold pipes 21-24. Valve members 31-34 are operatively associated with the manifold pipes and by maintaining all four valves in an open condition the liquid-rich slurry mixture being conveyed thrpugh conduit 14 by means of pump 15 may be introduced at a plurality of pipeline locations to provide a degree of slurry agitation within the line not possible with a single pipeline inlet. Still additional pipeline inlets may be provided by branching each manifold pipe so that it enters into the pipeline at a plurality of locations. With respect to manifold 24, for example, a plurality of manifold subs ll- 33 extend therefrom to the pipeline.

I claim as my invention:

1. Apparatus for selectively retarding and dissipating a plug caused by the slumping and compacting of slurry solid-phase material in a shutdown pipeline utilized to transport a slurry fluid comprising a solid phase and a liquid phase, said pipeline having at least one portion thereof inclined to the horizontal and at least a lowermost portion in fluid communication with said inclined portion where plug formation is likely to occur due to slumping and compacting of said solid phase under the influence of gravity when pipeline flow has terminated, said apparatus comprising:

means defining a flow path externally of said pipeline between said inclined portion of said pipeline and said lowermost portion of said pipeline; and

pump means operatively associated with said means defining a flow path externally of said pipeline to pump slurry fluid from the inclined portion of the pipeline to the lowermost portion of the pipeline to agitate said slurry solid phase and maintain said solid phase in suspension with said liquid phase at said lowermost portion.

2. The apparatus according to claim 1 wherein said means defining a flow path externally of said pipeline includes a conduit in communication with the interior of said pipeline at at least two locations along said pipeline.

3. The apparatus according to claim 2 wherein manifold means is operatively associated with said conduit and said pipeline whereby said slurry fluid may be pumped into said pipeline at a plurality of locations along said lowermost portron.

4. A method of selectively retarding and dissipating a plug caused by the slumping and compacting of slurry solid-phase material in a shutdown pipeline utilized to transport a slurry fluid comprising a solid phase and a liquid phase, said pipeline having at least one portion thereof inclined to the horizontal and at least a lowermost portion in fluid communication with said inclined portion where plug formation is likely to occur due to slumping and compacting of said solid phase under the influence of gravity when pipeline flow has terminated, said method comprising:

establishing a flow path externally of said pipeline between said inclined portion of said pipeline and said lowermost portion of said pipeline; and

pumping slurry fluid from the portion of the pipeline lying along said inclined portion along said flow path whereby said slurry fluid is injected into the pipeline at the lowermost portion of the pipeline whereby said slurry solid phase is agitated and maintained in suspension with said liquid phase at said lowermost portion.

5. The method according to claim 4 wherein said slurry mixture is injected into the pipeline at a plurality of locations along the portion of the pipeline lying along said lower elevatron.

Claims

1. Apparatus for selectively retarding and dissipating a plug caused by the slumping and compacting of slurry solid-phase material in a shutdown pipeline utilized to transport a slurry fluid comprising a solid phase and a liquid phase, said pipeline having at least one portion thereof inclined to the horizontal and at least a lowermost portion in fluid communication with said inclined portion where plug formation is likely to occur due to slumping and compacting of said solid phase under the influence of gravity when pipeline flow has terminated, said apparatus comprising: means defining a flow path externally of said pipeline between said inclined portion of said pipeline and said lowermost portion of said pipeline; and pump means operatively associated with said means defining a flow path externally of said pipeline to pump slurry fluid from the inclined portion of the pipeline to the lowermost portion of the pipeline to agitate said slurry solid phase and maintain said solid phase in suspension with said liquid phase at said lowermost portion.

3. The apparatus according to claim 2 wherein manifold means is operatively associated with said conduit and said pipeline whereby said slurry fluid may be pumped into said pipeline at a plurality of locations along said lowermost portion.

4. A method of selectively retarding and dissipating a plug caused by the slumping and compacting of slurry solid-phase material in a shutdown pipeline utilized to transport a slurry fluid comprising a solid phase and a liquid phase, said pipeline having at least one portion thereof inclined to the horizontal and at least a lowermost portion in fluid communication with said inclined portion where plug formation is likely to occur due to slumping and compacting of said solid phase under the influence of gravity when pipeline flow has terminated, said method comprising: establishing a flow path externally of said pipeline between said inclined portion of said pipeline and said lowermost portion of said pipeline; and pumping slurry fluid from the portion of the pipeline lying along said inclined portion along said flow path whereby said slurry fluid is injected into the pipeline at the lowermost portion of the pipeline whereby said slurry solid phase is agitated and maintained in suspension with said Liquid phase at said lowermost portion.

5. The method according to claim 4 wherein said slurry mixture is injected into the pipeline at a plurality of locations along the portion of the pipeline lying along said lower elevation.