Pig launcher
An apparatus ( 10 ) for launching one or more pigs ( 5 ) for cleaning of production flow lines, or tubing, on the sea bed is shown. The apparatus includes a lifting frame ( 1 ) retaining a charging pipe ( 3 ) which is able to carry a train of pigs ( 5 1 - 5 10 ) resting stand-by in the charging pipe ( 3 ), a plurality of valves (V 1 -V 4 ) which on the one side is in fluid communication with the charging pipe ( 3 ), and on the other side is in fluid communication with a high pressure drive fluid different from the production flow, a connecting means ( 2 ) for connecting of the apparatus ( 10 ) to a closable pipe sub leading to the production flow line to be pigged, and an actuatable piston ( 4 ) which is able to displace the train of pigs within the charging pipe ( 3 ).
1. An apparatus ( 10 ) for launching one or more pigs ( 5 ) for cleaning of production flow lines, or tubing, on the sea bed, said apparatus comprising:
a support frame ( 1 ) carrying a charging pipe ( 3 ) to carry a train of pigs ( 5 1 - 5 10 ) resting stand-by within the charging pipe ( 3 );
a plurality of valves (V 1 -V 4 ), which on one side are in fluid communication with the charging pipe ( 3 ), and on the other side are in fluid communication with a high pressure drive fluid different from the production flow;
a connecting means ( 2 ) for connecting of the apparatus ( 10 ) to a pipe hub, leading to the production flow line to be pigged;
an actuatable piston ( 4 ) to displace the train of pigs within the charging pipe ( 3 ); and
a drive pig ( 6 ) arranged between the piston ( 4 ) and a closest adjacent pig ( 5 10 ), wherein
the drive pig ( 6 ) is in sealing contact with an internal wall of the charging pipe ( 3 );
the drive pig ( 6 ) is remote controlled actuatable by operation of said plurality of valves (V 1 -V 4 ) that apply drive fluid in predetermined volume when the valves open for advancement of the train of pigs, and applies drive fluid during launching of the pig ( 5 1 ) in front; and
during shifting functional activities the drive fluid can be communicated:
a) into the charging pipe ( 3 ) in an area just behind the drive pig ( 6 ) when positioned in its initial position,
b) into the charging pipe ( 3 ) in an area just behind a foremost pig ( 5 ), and
c) into/out from the charging pipe ( 3 ) at both sides of the actuatable piston ( 4 ).
2. The apparatus according to claim 1 , wherein the actuatable piston ( 4 ) is influenced by a spring ( 7 ) abutting a plate ( 3 a ) extending laterally of the charging pipe ( 3 ).
3. The apparatus according to claim 2 , wherein the charging pipe ( 3 ) has stopper means ( 3 b ) impeding the actuatable piston ( 4 ) to pass an inlet for drive fluid into the charging pipe ( 3 ) according to point c) above.
4. The apparatus according to claim 1 , wherein the actuatable piston ( 4 ) includes two lands of different diameter, where the lands define a volume there between, which volume is in communication with an accumulator or volume compensator.
5. The apparatus according to claim 1 , wherein the operable valves are in the form of a master valve (V 1 ) in the line from the source of high pressure fluid, a three-way valve (V 2 ) with branch off (B 1 ) and a valve (V 3 ) to the charging pipe ( 3 ) according to point a) above, and a branch off (B 2 ) and a valve (V 4 ) to the charging pipe ( 3 ) according to point b) above, in addition to two branch offs (B 3 ) and (B 4 ) to the charging pipe ( 3 ) according to point c) above.
6. The apparatus according to claim 1 , wherein the charging pipe is designed in a curved shape to reduce a requirement to space.
7. The apparatus according to claim 6 , wherein the charging pipe is designed in a U-form.
8. The apparatus according to claim 7 wherein the curved charging pipe has a somewhat enlarged diameter in the curved areas in order to limit deformations in sealings of the pigs ( 5 ) during long term storage within the curved areas.
9. The apparatus according to claim 6 , wherein the charging pipe ( 3 ″) is designed in a helical configuration.
10. The apparatus according to claim 9 wherein the curved charging pipe has a somewhat enlarged diameter in the curved areas in order to limit deformations in sealings of the pigs ( 5 ) during long term storage within the curved areas.
11. The apparatus according to claim 6 , wherein the curved charging pipe has a somewhat enlarged diameter in the curved areas in order to limit deformations in sealings of the pigs ( 5 ) during long term storage within the curved areas.
12. The apparatus according to claim 1 , wherein the drive fluid is selected from the group consisting of: methanol ethyl glycol), pure methanol or mineral oil.
13. The apparatus according to claim 1 , wherein a circuit for high pressure fluid to be applied to the charging pipe includes a relieving safety valve, a pressure gauge with transmitter and a pig detector.
14. The apparatus according to claim 1 , wherein a chamber ( 8 ) is an independent chamber separate from the charging pipe ( 3 ′).