WO2006124589A2

WO2006124589A2 - Launching system

Info

Publication number: WO2006124589A2
Application number: PCT/US2006/018431
Authority: WO
Inventors: Donald S. Demich
Original assignee: Pwi Consultants Ltd.
Priority date: 2005-05-12
Filing date: 2006-05-12
Publication date: 2006-11-23
Also published as: WO2006124589A3

Abstract

A method for launching multiple tools within a pipeline in embodiments of the invention may include one or more of the following steps: (a) stopping fluid flow within the pipeline, (b) opening a trap door, (c) draining a trap, (d) inserting a first tool into the trap, (e) coupling a second tool to the trap door, (f) shutting the trap door, (g) resuming flow within the pipeline to carry the first tool down the pipeline, and (h) releasing the second tool at a predetermined time.

Description

LAUNCHING SYSTEM

Field of the Invention

This invention relates to a new or improved launching system for introducing tools into a pipeline. Specifically, the present invention relates to launching at least two tools in a pipeline without having to drain a pipeline trap for each tool.

Background of the Invention

Pipelines are well-known in the art and there are various reasons to pig a pipeline. After the pipeline is built, it is desirable to run pigs to remove any debris present in the line. For example, in crude oil pipelines, wax removal or control is important to maintain line efficiency. Likewise, in wet gas pipelines, liquid removal and removal of debris in the pipe are also important.

Pig launchers are used to launch a pig into a pipeline, and pig receivers are used to receive a pig after it has made a successful run. The pipeline is normally segmented into sections, and a pig trap is fitted at the start and end of each section. The pig trap is similar to an air lock or a torpedo launch tube. It is isolated from the pipeline by a valve, so it can be depressurized to load the pig. Once loaded, the trap door is closed and the trap is pressurized. With the main trap valve open, oil or gas flow can be directed behind the pig to push it into the pipeline. The reverse process applies at the other end of the line, when the pig is received. By way of background and with reference to Figure 1, a prior art pigging procedure will be described. During normal operation valve 1 is open and valves 2 and 3 are shut to create a trap 12. Trap 12 then remains empty of any material flowing in pipeline 10. During an inspection, an operator inserts a tool, e.g., a pig 14 into trap 12 through trap door 16. After door 16 is shut, valve 2 and 3 are opened and valve 1 is shut. Then whatever fluid is running through pipeline 10 travels through trap 12 and carries pig 14 down through pipeline 10. The pig then cleans the pipeline as it travels and/or relays information relating to the integrity of pipeline 10 out to an operator as it travels down pipeline 10.

Often it is desirable to have more than one pig travel down pipeline 10. For example, during nitrogen purges it is preferable to have about 1500 feet between two pigs traveling down pipeline 10. If pipeline 10 has a flow rate of 3.0 miles an hour, then at present, the operator launches the first, pig then pump for 5 ¹A minutes and then shuts down pipeline 10 to isolate, drain, and load the second pig for launch. Typically it takes about an hour to isolate, drain, and load the second pig. Then the pipeline operator is notified to start up the flow of pipeline 10 again which can take several minutes to hours to get the line back to normal flow. This pipeline downtime is very expensive for the pipeline owner. Not only is there a cost in the manpower it takes to drain trap 12 twice and load the pigs, but also there is a substantial cost in loss of throughput on pipeline 10.

There is a need for a launching system wherein at least two pigs can be launched into the pipeline without the need to drain or otherwise stop of the flow of the pipeline in order to launch each pig.

Summary

A pipeline trap door in embodiments of the invention may include one or more of the following features: (a) an actuator coupled to the trap door, and (b) a receptacle on a front end of the actuator for holding and releasing a pipeline tool.

Brief Description of the Exhibits Figure 1 illustrates a pipeline trap known in the art.

Figure 2 illustrates a pipeline trap incorporating a launching system according to an embodiment of the present invention. Detailed Description of the Invention

The following discussion is presented to enable a person skilled in the art to make and use the present teachings. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the present teachings. Thus, the present teachings are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the present teachings. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of the present teachings. The following introductory material is intended to familiarize the reader with the general nature and some of the features of the present teachings.

The present invention provides a launching system wherein at least two tools, e.g., pigs, can be simultaneously loaded into and held within a pipeline trap for launching without the need for stopping the flow of the pipeline for each launch. The pipeline only needs to be drained once when the tools are initially loaded into the pipeline. As used herein, a pig is any device or tool that moves through the inside of a pipeline, e.g., for the purpose of cleaning, dimensioning, or inspecting.

The launching system is preferably configured as or is a part of a trap door to a pipe trap. With reference to Figure 2, the present invention discloses a trap door 20 which is configured as a pig launching system. A preferred pig launching system is shown in FIG. 1. The launching system includes a trap door 20, which can be replaced with an existing trap door of a pipeline system. The trap door 20 includes an actuator which is connected to the trap door using any known mechanism. For example, the actuator can be connected to the trap door through a center swing arm.

Various types of actuators are feasible for use with the trap door 20 and these may be mechanically, electronically or hydraulically operated. In preferred cases, the actuator is a hydraulic actuator. The hydraulic actuator preferably comprises a cylinder having a front end and a rear end. The front end is positioned inside of the pipeline trap whereas the rear end is positioned outside of the trap door and pipeline. The front end is configured to both retain and release one or more pigs. For example, in some embodiments, the front end has a receptacle that connects to or otherwise holds a portion of a pig and releases the pig with hydraulic pressure. When the pig is to be released into the pipeline, the hydraulic actuator pushes the pig into the pipeline flow, thereby launching the pig.

In operation, an operator removes the trap door 20, drains the trap 22 and inserts a first pig 30 into the trap 22. The first pig 30 is placed in a position so that once the pipe flow is resumed, the pig will be carried down the pipeline. The operator then inserts one or more pigs into the trap 22 and connects them to the door 20 so that they are not yet carried down the pipeline once flow is resumed. In the illustrated Figure 2, a second pig 32 is inserted into the pipeline and connected to trap 22. In preferred embodiments, the pig 32 is connected to the trap door 20 through an actuator 26, preferably a hydraulic actuator or ram. The actuator 26 is connected to the trap door 20 and has a receptacle 27 on its front which holds and releases a pig. In preferred embodiments, the receptacle holds a single pig. However, in other embodiments, the receptacle holds one or more pigs. Once the one or more pigs are connected to the trap door 20, then the flow of the pipeline is resumed. Preferably, the pipeline valves (e.g., valves 1, 2, and 3) are properly positioned to route whatever fluid is in pipeline 28 through the trap 22. The first pig 30 (that is not connected to the trap door) is taken away down pipeline 28. The operator then waits an appropriate time based upon the rate of the fluid flow and then releases a second pig 32 by activating the actuator 26. Second pig 32 would then also be carried down pipeline 28. A launching system of this nature eliminates the need to drain the trap twice and allows the pipeline personal to launch at least two pigs at any given time.

The operation of the launching system can also be accomplished by a control circuit so that an operator need not always be present at the pipeline site. For example, the control circuit can be programmed to cause launching of the pigs held in place inside of the pipeline at desired intervals. In cases where a hydraulic ram is used, the control circuit can cause hydraulic activation of the ram at a desired time.

The present system may be utilized in most all locations, including under water, and is suitable for all types of pigs, including foam pigs, cup pigs, sphere pigs, an scraper pigs. Pigs having a variety of functions can also be used. For example, cleaning pigs, data collecting pigs and others can be used. In some cases, ultrasonic pigs can be provided to detect the conditions of the internal pipeline, for example by giving a reading of pipewall thickness and detecting cracks. The pigs can also be of any suitable size and shape and preferably have a diameter corresponding to that of the pipeline. A discussion of pigs suitable for use with the invention will now be described. Sealing Pig

Sealing pigs are often used during hydrostatic testing of pipelines to fill the line with water and then de-water the line. Removing condensate and water in wet gas systems, water from product pipelines or separating dissimilar products in a products pipeline, are other applications. Sealing pigs can be spheres, solid cast polyurethane pigs, or mandrel type pigs with sealing cups or discs. Foam Pig

Foam pigs, better known as Polly-Pigs, are often manufactured from open cell polyurethane foam. The foam is of various densities ranging from light density (2 lbs/ft³), medium density (5-8 lbs/ft³), to heavy density (9- 10 lbs/ft³). Although normally found in a bullet shape, they can have concave ends, flat ends, or bullet noses on both ends. The Polly-Pig can be bare often foam or coated with a 90- durometer polyurethane material. The coated pigs may have a spiral coating of polyurethane, various brush materials or silicon carbide coating. If the pig is of bare foam, it will typically have the base coated. The standard Polly-Pig length is typically twice the diameter. Some advantages of Polly-Pigs are that they are compressible, expandable, light weight, and flexible. Polly-pigs generally travel through multiple diameter pipelines, go around mitered bends, and short radius 90° bends. They generally make abrupt turns in tees so laterals can be cleaned. They generally also go through valves with as little as 65% opening. Polly-pigs are often also inexpensive. Polly-pigs are often used for line proving (proving a pig will pass through the line), drying and wiping, removal of thick soft deposits, condensate removal in wet gas pipelines and pigging multiple diameter lines. Polly-pigs coated with a wire brush or silicon carbide are often used for scraping and mild abrasion of the pipeline. Mandrel Pig

Mandrel pigs have a metal body (steel or aluminum) and are often equipped with seals (scraper cups or discs) to provide the differential pressure to propel the pig in the pipeline. For cleaning the line the pig is equipped with wire brushes or polyurethane blades. One advantage of the mandrel pig is that it can typically be either a cleaning pig, sealing pig or a combination of both. The seals and brushes can be replaced to make the pig reusable. Cleaning pigs are often designed for heavy scraping and can be equipped with wire brushes or polyurethane blades. These pigs are often designed for long runs. Bypass holes in the nose of the pig control the speed or act as jet ports to keep debris suspended in front of the pig. Cleaning Pig

Cleaning pigs are often used to remove accumulated solids and debris from the walls of the pipeline. This is normally paraffin in crude oil pipelines. When inhibitors are used in a gas pipeline, the solvents in the inhibitors often evaporate, forming a gunk on the pipe walls which can be removed by cleaning pigs. Cleaning pigs are often also used in conjunction with chemical treating of the lines to disturb the corrosion sites and remove water, microbes, corrosion products, and food for microbes. Cleaning pigs are also often equipped with brushes or blades to do the cleaning.

Cleaning pigs are often designed to remove solids or accumulated debris in the pipeline. This increases the efficiency and lowers the operating cost. They often have wire brushes to scrape the walls of the pipe to remove the solids. Pigs 14" and smaller normally use rotary wire wheel brushes. These brushes are often easy to replace and inexpensive. Special rotary brushes are often used on some larger pigs. Larger pigs typically have wear compensating brushes. These brushes can be individually replaced as needed and are often mounted on either leaf springs, cantilever springs, or coil springs. The springs push the brushes against the pipe wall. As the wire brushes wear, the force of the spring keeps it in contact with the pipe wall compensating for the brush wear.

There are many different brush materials available. The standard brushes are often made of fine or coarse carbon steel wire. For pipe lines with internal coatings, Prostran is generally the material of choice. Some service requires a stainless steel brush. Special brush designs such as the pit cleaning brush are also available. When soft deposits of paraffin, mud, etc., need to be removed, the urethane blade is an excel-lent choice. The blade design is interchangeable with the brushes. Bypass ports are often installed in the nose of the pig or on the body. These ports are generally used to control fluid bypass. If the ports are on the body of the pig, the flow will generally also flow through the brushes and keep them clean. As the fluid passes through the ports on the nose of the pig, it helps keep the debris in front of the pig stirred up and moving. Plugs are often used to regulate the bypass. The sealing elements are often either elastomer cups or discs. They are often used as a combination cleaning and sealing element to remove soft deposits. Cups are often of standard or conical design. Specialty cups are also available for some applications. The cup and disc material is normally manufactured from a polyurethane material which gives outstanding abrasion and tear resistance but is limited in temperature range. Neoprene, nitrile, EPDM, and Viton are often available for higher temperature applications. Batching Pig

Batching pigs are often used to separate dissimilar fluids such as various grades of gasoline, heating oils, etc., in multiple product pipelines. These pigs are often unidirectional if they have scraper cups and bidirectional if equipped with discs. Displacement Pig

Displacement pigs displace one fluid with another. They can be bidirectional or unidirectional in design. They are often used in the testing and commissioning phase of the pipeline, i.e., hydrostatic testing, line fills and de-watering, etc. Line evacuation and abandonment is another application for the displacement pig. Gauging Pig

Gauging pigs are often used after constructing the pipeline to determine if there are often any obstructions in the pipeline. It assures that the ovality of the line is within accepted tolerance. The gauging plate may be mounted on the front or rear of the pig and is made of a mild steel or aluminum. The plate may be slotted or solid. The outside diameter of the plate is 90-95% of the pipe's inside diameter. Profile Pig

A profile pig is a gauging pig with multiple gauging plates, usually three plates. One plate is mounted on the front, one in the middle, and one on the rear of the pig. It is normally used before running an ILI (In Line Inspection) tool to assure the tool's passage around bends and through the pipeline. Dual Diameter Pig

There are many miles of dual diameter pipelines crossing the country side. The lines are normally two pipe sizes different, i.e., 4" x 6", 8" x 10", etc. The mandrel pig is usually fitted with solid discs for the smaller line and slotted discs for the larger line. If it's a cleaning pig, the brushes will generally support it in the line and keep the pig centered. The Polly-Pig is also widely used in this application. Transmitter Pig

Occasionally pigs will get stuck in a line. The location of the stuck pig can be found by using a detector pig with a transmitter in its body. The transmitter will emit a signal so it can be located with a receiver. After the pig is located, the line can be dug up and the pig removed. Transmitters will normally mount into a mandrel, solid cast, or Polly-Pig. Specialty Pigs Many applications require special pigs. Manufacturers in the pigging industry have made special pigs for many applications. A pinwheel pig which uses steel pins with hardened tips was developed to remove wax and scale from a pipeline. A magnetic cleaning pig was developed to pick up ferrous debris left in the pipeline. Solid Cast Pigs Solid cast pigs are often of various designs and are often usually made of polyurethane; however, neoprene, nitrile, Viton, and other rubber elastomers are often available in smaller size pigs. They are often considered sealing pigs although some solid cast pigs are often available with wrap around brushes and can be used for cleaning purposes. The solid cast pig is available in the cup, disc, or a combination cup / disc design. Most of the pigs are often of one piece construction but several manufacturers have all urethane pigs with replaceable sealing elements. ^■

Because of the cost to redress a mandrel pig, (material and labor), and to transport them, many companies use the solid cast pig up through 14" or 16". Some solid cast designs are often available in sizes up to 36". Solid cast pigs are often extremely effective in removing liquids from product pipelines, removing condensate and water from wet gas systems, and controlling paraffin build-up in crude oil systems. Spheres

Spheres have been used for many years as a sealing pig. There are four basic types of spheres; inflatable, solid, foam, & soluble. The soluble sphere in usually used in crude oil pipelines and contains a micro crystalline wax and amorphous polyethylene which act as a paraffin inhibitor. Although the sphere will normally dissolve in a few hours, the dissolving rate is a function of fluid temperature, fluid movement, friction, and absorbability of the crude. If the line has never been pigged, it is a good idea to run the soluble pig. If it hangs up in the line, it will not obstruct the flow. The inflatable sphere is typically manufactured of various elastomers

(polyurethane, neoprene, nitrile and Viton) depending on the application. It has a hollow center with filling valves which are often used to inflate the sphere with liquid. Spheres are often filled with water, or water and glycol and inflated to the desired size. Depending on the application and material, the sphere is inflated l%-2% over the pipe inside diameter. As the sphere wears from ser-vice, it is resized, extending its life. In small sizes the sphere can be manufactured solid, eliminating the need to inflate it. The solid sphere sometimes does not have the life of an inflatable sphere because it cannot be resized.

Spheres can also be manufactured from open cell polyurethane foam. They can be coated with a polyurethane material to give better wear. For cleaning purposes they can have wire brushes on the surface. The advantages of the foam sphere are often that they are often light weight, economical, and do not need to be inflated.

Spheres in general are often easy to handle, will negotiate short radius 90's, irregular turns and bends. They typically go from smaller lateral lines to larger main lines and are often easier to automate than other styles of pigs.

Spheres are often commonly used to remove liquids from wet gas systems, water from product pipelines, batching dissimilar products, meter prover service, paraffin control in crude oil pipelines, and hydrostatic testing and de-watering after pipeline rehabilitation or new construction.

Claims

What is claimed is:

1. A method for launching multiple tools within a pipeline comprising the steps of: stopping fluid flow within the pipeline; opening a trap door; draining a trap; inserting a first tool into the trap; coupling a second tool to the trap door; and shutting the trap door.

2. The method of claim 1, further comprising the step of resuming flow within the pipeline to carry the first tool down the pipeline.

3. The method of claim 2, wherein the second tool is coupled to the trap door by an actuator.

4. The method of claim 3, wherein the actuator is a hydraulic actuator.

5. The method of claim 3, wherein the trap door has a receptacle to hold and release the second tool.

6. The method of claim 5, further comprising the step of releasing the second tool at a predetermined time.

7. The method of claim 6, wherein the second pig is released by activating the actuator.

8. The method of claim 7, wherein the second pig is carried down the pipeline by the fluid flow.

9. A pipeline trap door comprising: an actuator coupled to the trap door; a receptacle on a front end of the actuator for holding and releasing a pipeline tool.

10. The trap door of claim 9, wherein the actuator is a hydraulic actuator.