# Patent

## Title
Pipeline pig signal trigger cavity seal

## Abstract

A pipeline pig signal includes sealing means located within a lower end of the trigger cavity of the signal which prevents pipeline debris from entering the trigger cavity. The sealing means moves between a first sealing position and a second sealing position in response to the trigger moving between a non-triggered and triggered position. The sealing means may be a polymer boot, a filter arrangement, a sliding piston arrangement, or a sliding shelf arrangement.

## Background
BACKGROUND OF THE INVENTION
This invention relates generally to signals mounted on pipelines and used to indicate the passage of pipeline pigs. More particularly, the invention relates to pipeline pig signals that make use of magnet arrangements to trigger the release of a spring-loaded indicator flag. This type of pig signal is commonly referred to as a magnetic intrusive pig signal. An example of this type of signal is described in U.S. Pat. No. 7,861,665 to Rankin, the content of which is hereby incorporated by reference.
A magnetic intrusive pig signal typically includes a plug assembly and nipple combination, or a plug assembly and flange combination, that places the nipple in fluid communication with the interior of the pipeline. An o-ring or other equivalent sealing means is used to contain the pipeline pressure. Located within a cavity of the plug assembly is a trigger mechanism having polar opposite magnets. The trigger mechanism is in communication with the release mechanism of an indicator assembly that includes a flag or other device that indicates the passage of a pipeline pig. As a pipeline pig moves along the interior of the pipeline and past the magnetic intrusive pig signal, the pig urges against the trigger. This causes the lower magnet of the trigger mechanism to travel upward toward the upper magnet. As the upper magnet is repelled by the lower magnet, its mounting shaft urges against a release mechanism which activates the flag of the indicator assembly.
Although magnetic intrusive pig signals provide a number of advantages, this type of signal can be negatively affected from time-to-time by ferromagnetic debris such as metal flakes which are attracted to the lower repulsive magnet of the trigger mechanism. The debris can cause the trigger mechanism to jam because of the close fit and tolerances within the trigger cavity. Additionally, heavy waxy sludge sometimes enters the cavity and causes the trigger mechanism to jam. This can be particularly troublesome in the magnet area of the trigger cavity.
None of the prior art magnetic intrusive pig signals include means for preventing pipeline product, debris and sludge from entering the trigger cavity. Further, pig signals that employ non-magnetic trigger mechanisms have no means for preventing contamination of the trigger cavity.
SUMMARY OF THE INVENTION
A pipeline pig signal made according to this invention has a trigger cavity internal to the signal which houses at least a portion of a trigger that protrudes into an interior space of the pipeline. A sealing means is located toward a lower end of the trigger cavity and above the housed portion of the trigger. The sealing means prevents pipeline debris from entering a portion of the trigger cavity located above the sealing means.
The sealing means move between a first sealing position and a second sealing position in response to the trigger moving between a non-triggered and triggered position. This movement may come in the form of flexing to maintain fluid containment in the magnet area portion of the trigger cavity. The sealing means may be a polymer boot, a filter arrangement, a sliding piston arrangement, or a sliding shelf arrangement.
Objects of this invention are to (1) prevent ferromagnetic debris, dirt, heavy waxy sludge, and other contaminants from entering the magnet area of magnetic intrusive pig signal's trigger cavity; and (2) provide a sealing means that can be installed in and used to retrofit existing pig signal designs.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-section view of a pig signal which includes a preferred embodiment of a trigger cavity sealing means made according to this invention. The sealing means includes a rubber boot having convolutes which provides containment of a pre-injected, incompressible fluid that prevents any pipeline product, debris and sludge from entering the magnet area of the trigger cavity.
FIG. 2 is a cross-section view of a pig signal which includes another preferred embodiment of a trigger cavity sealing means made according to this invention. The sealing means includes a sliding filter pack which allows fluid to pass through it—while blocking debris—as the trigger mechanism strokes up and down as a pipeline pig passes the signal.
FIG. 3 is an isometric view of the sliding filter pack of FIG. 2.
FIG. 4A is a cross-section view of another preferred embodiment of a pig signal made according to this invention, shown in its relaxed or non-triggered state. The sealing means includes a sliding piston.
FIG. 4B is a cross-section view of the pig signal of FIG. 4A in its triggered state. The sliding piston moves downward in response to the signal being triggered.
FIG. 5 is a front elevation view of yet another embodiment of a pig signal made according to this invention.
FIG. 6 is a cross-section view of the pig signal of FIG. 5 taken along section line 5-5. The sealing means includes a sliding shelf design.
FIG. 7 is a front elevation view of the sliding shelf of FIG. 6.
FIG. 8 is a cross-section view of the sliding shelf of FIG. 6 taken along section line 8-8 of FIG. 7.
FIG. 9 is an isometric view of the magnet holder of the pig signal of FIG. 5.
FIG. 10 is a cross-section view of the magnet holder of FIG. 5 taken along section line 10-10 of FIG. 9.
FIG. 11 is still yet another embodiment of a pig signal made according to this invention. The sealing means is a sliding piston design.










Elements and element numbering used in


the drawings and detailed description
















20
Pipeline pig signal


22
Indicator assembly


24
Plug assembly


26
Nipple/lower body


27
Inner wall of 29


28
Internal cavity/trigger cavity


29
Magnet area


30
Trigger


31
Lower end


32
First magnet


33
O-ring


35
Plunger


37
Lower end


38
Groove


39
Wall of 35


40
Flag


44
Indicator assembly body


48
Second O-ring


50
Set screws


56
Second magnet


57
Upper end


71
Shaft


73
Magnet holder


80
Sealing means


81
Seal


83
Upper end


91
Filter pack


93
Filtering material


95
Plastic washers


97
Flow-through holes


101
Sliding piston


103
Shaft


105
Magnet holder


107
Inner O-ring


109
Outer O-ring


111
Bleed screw


121
Floating shelf


123
Wear ring


125
Wear ring


127
Inner O-ring


129
Outer O-ring


131
O-ring washer


133
Outer circumferential surface


135
O-ring


137
Ring back-up


141
Sliding piston


143
Inner O-ring


145
Outer O-ring


147
Shaft


149
Magnet holder


151
Bleed screw












DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Each of the preferred embodiments of a pig signal made according to this invention includes a sealing means which prevents ferromagnetic debris, dirt, heavy waxy sludge and other contaminants from entering the magnet area of the signal.
Referring to the drawings and first to FIG. 1, a pipeline pig signal 20 is illustrated which includes an indicator assembly 22 received by and releasably secured to a plug assembly 24. The pig signal is mounted to a pipeline and the indicator assembly 22 positioned in a desired clock orientation relative to the plug assembly 24 so that flag 40, when released, is visible to a pipeline operator. Set screws 50 engage a groove 38 and, when tightened against the groove, hold signal 20 in the desired orientation. (Each embodiment described herein provides this adjustable orientation means).
Plug assembly 24 receives a nipple or lower body 26 which, in turn, receives a trigger 30. Once pig signal 20 is secured to a pipeline, trigger 30 extends into the interior of the pipeline, thereby placing the interior cavity 28 of the lower body 26 in fluid communication with the interior of the pipeline. Pipeline pressure within the plug assembly 24 may be sealed off using an O-ring 33 or equivalent sealing means. O-ring 33 can include a back-up ring 137, preferably made of a TEFLON or equivalent material. A second O-ring 48 may be included which provides a seal between the nipple 26 and indicator assembly body 44 to prevent moisture and debris from entering the interior of the indicator assembly body 44 and causing corrosion or contamination of the release mechanism for flag 40. Alternatively, a breathable seal may be used in place of O-ring 48.
Trigger 30 resides within the internal cavity 28 of lower body 26. This internal cavity 28, which is fluid filled and may also be referred to as the trigger cavity 28, has a first magnet 32 located toward its lower end 31 and a second magnet 56 located toward its upper end 57. The area above first magnet 32 and below second magnet 56 is, for descriptive purposes, the magnet area 29 of trigger cavity 28. The magnets 32, 56 are opposite in polarity to one another.
As the pig moves along the pipeline and past the pipeline pig signal 20, the pig urges against the trigger 30 and causes the trigger 30 to move in axially upward within the plug assembly 24 and, therefore, the first magnet 32 to move between a first and second position toward the second magnet 56. As first magnet 32 moves toward second magnet 56, the second magnet 56 moves between a first and second position, upward and away from the first magnet 32. As the second magnet 56 continues its upward travel, flag 40 is released and pivoted into its activated position.
To prevent pipeline product, debris, and sludge from entering the trigger cavity 28, and particularly from entering the magnet area 29, sealing means 80 are provided toward the lower end 31 of the trigger cavity 28. Sealing means 80 may be a seal 81 which contains a pre-injected fluid (incompressible to balance pipeline pressure). Seal 81 prevents any pipeline product, debris and sludge from entering the magnet area 29 of the trigger cavity 28.
Seal 81 is preferably complementary in shape to the plunger 35 that moves the first magnet between the first and second position when a pipeline pig encounters trigger 30. In a preferred embodiment, plunger 35 is a frusto-conical shaped plunger whose lower end 37 urges against the opposing upper end 83 of seal 81, causing seal 81 to flex in sealing engagement with the opposing interior wall surface 27 of the trigger cavity 28 and the wall 39 of plunger 35. This flexing helps to maintain fluid containment in the magnet area 29. Seal 81 remains in sealing engagement as the plunger 35 moves between the first and second positions. No pipeline product, debris or sludge can pass through seal 81 and enter the magnet area 29. In another embodiment, seal 81 is a polymer or rubber boot with convolutes.
Referring now to FIGS. 2 and 3, an alternate embodiment of sealing means 80 is a sliding filter pack 91 arranged about the shaft 71 of magnet holder 73. Preferably, filter pack 91 is a stack of felt-type fabric layers 93 located between plastic washers 95 having flow-through holes 97. This arrangement allows pipeline fluid to pass through the filter pack 91 but not debris and sludge as plunger 35 moves between the first and second positions as trigger 30 is activated.
FIGS. 4A & B illustrate yet another preferred embodiment of sealing means 80, namely, a sliding piston 101. Sliding piston 101 is arranged about the shaft 103 of magnet holder 105. When pig signal 20 is triggered, the piston 101 slides downward as the magnet 32 moves upward. A pair of inner and outer O-rings 107, 109 provide, respectively, sealing means against the shaft 103 and the inner wall 27 of the fluid-filled magnet area 29. A bleed screw 111 allows insertion of fluid in area 29. The magnet area 29 is pre-filled with fluid and bleed screw 111 is used to bleed off the fluid until it reaches a desired level.
Referring now to FIGS. 5 to 10, sealing means 80 is a floating shelf 121. The shelf 121 includes an external O-ring 135 with optional ring back-up 137 preferably made of TEFLON or equivalent material. A wear ring 123 is positioned to surround the shaft 103 of magnet holder 105 and a wear ring 125 is positioned about the outer circumferential surface 133 of shelf 121. An inner O-ring 127 provides sealing means between shaft 103 shelf 121. An outer O-ring 129 provides sealing means between shelf 121 and the inner wall 27 of fluid-filled magnet area 29. When pig signal 20 is triggered, the floating shelf 121 moves downward as the magnet 32 moves upward. A bleed screw 111 controls the amount of fluid in area 29. An O-ring washer 131 provides sealing means for the screw 111.
Last, FIG. 10 illustrates a preferred embodiment in which sealing means 80 is an inverted sliding piston 141. As with the other sliding designs, when pig signal 20 is triggered, piston 141 moves downward as the magnet 32 moves upward. A pair of inner and outer O-rings 143, 145 provide, respectively, sealing means against the shaft 147 of the magnet holder 149 and the inner wall 27 of the fluid-filled magnet area 29. A bleed screw 151 operates similar to that of bleed screw 111.
The preferred embodiments described above are not all possible embodiments of the invention. Therefore, the scope of the invention is defined by the following claims, including elements of the claims which a person of ordinary skill in the art would consider to be equivalent to, or no more than a trivial difference relative to, the elements listed in the claims.

## Claims

1. A pipeline pig signal having a trigger in communication with an interior space of a pipeline, the pipeline pig signal comprising:
a trigger cavity internal to the pipeline pig signal and housing at least a portion of the trigger;
a sealing means located toward a lower end of the trigger cavity and above the housed portion of the trigger, the sealing means arranged to filter debris from a pipeline fluid and prevent the debris from entering a portion of the trigger cavity located above the sealing means but permitting the pipeline fluid to pass through the sealing means and enter a portion of the trigger cavity located above the sealing means.

2. A pipeline pig signal according to claim 1 further comprising the sealing means moving between a first sealing position and a second sealing position in response to the trigger moving between a non-triggered and triggered position.

3. A pipeline pig signal according to claim 1 wherein the sealing means is a filter arrangement.

4. A pipeline pig signal according to claim 3 wherein the filter arrangement is a stack of felt washers.

5. A pipeline pig signal according to claim 3 further comprising the filter arrangement being sandwiched between a pair of plastic washers having flow-through holes.

6. A pipeline pig signal according to claim 1 further comprising the pig signal including at least one magnet in the portion of the trigger cavity located above the sealing means.

7. A system for preventing pipeline debris from entering a trigger cavity of a pipeline pig signal, the trigger cavity housing a trigger in communication with a pipeline product, the system including a filter housed within the trigger cavity and located below a magnet area of the trigger cavity, the filter remaining in engagement with the trigger cavity housing as the trigger moves between a non-triggered and a triggered position, the filter arranged to filter debris from a pipeline fluid and permitting the pipeline fluid but not the debris to pass through the filter and enter the magnet area.

8. A pipeline pig signal according to claim 7 further comprising the filter moving between a first sealing position and a second sealing position in response to the trigger moving between a non-triggered and triggered position.

9. A pipeline pig signal according to claim 7 wherein the filter is a stack of two or more felt washers placed adjacent to one another.

10. A pipeline pig signal according to claim 9 further comprising the two or more felt washers being sandwiched between a pair of plastic washers having flow-through holes.

11. A pipeline pig signal having a trigger in communication with an interior space of a pipeline, the pipeline pig signal comprising:
a trigger cavity internal to the pipeline pig signal and housing at least a portion of the trigger;
a filter arrangement including a stack of two or more felt washers sized to span a width of the trigger cavity and placed adjacent to one another and sandwiched between a pair of plastic washers having flow-through holes, one of the plastic washers in the pair being located at the uppermost end of the filter arrangement and the other plastic washer in the pair being located at the lowermost end of the filter arrangement, the filter arrangement being located toward a lower end of the trigger cavity and above the housed portion of the trigger and arranged to prevent pipeline debris from entering a portion of the trigger cavity located above the filter arrangement but permitting pipeline fluid to pass through the filter arrangement and enter the portion.