Following are recommended procedures for launching pigs in pipelines equipped with industry-standard launchers. Due to varying pig styles, launcher designs, pigging applications, pipe types, propelling media, internal conditions, and other factors, these procedures should not be considered absolutes. Please consult a pig manufacturer or distributor for technical assistance for your specific application.
To ensure satisfactory pig performance, the pig must be inspected especially if it has previously been used. By measuring the outer diameter of the pig with a diameter tape or using a regular tape and dividing by 3.1416, ensure that the outer diameter of the pig is larger than the internal diameter of the pipe in order to maintain a seal against pipe wall. The pig's sealing surfaces should also be inspected for tears, cuts, uneven wear, punctures, and other damage which may affect the pig's performance. Steel mandrel pigs with spring-loaded brushes should be inspected for corrosion, fatigue and breakage. Because loose brush pieces can damage valves and instrumentation in the pipeline, all components should be inspected to ensure good working condition.
Refer to following diagram
- Ensure isolation and launch-line (kicker line) valves are closed.
- Open vent and drain valves to allow liquid displacement or vent to atmospheric pressure.
- When the pressure gauge on launcher reads zero psi, and with drain and vent valves in open position, open closure.
- Insert pig and push forward until nose or front of pig is firmly in contact with reducer.
- Close and secure closure.
- Close drain valve. Gradually open kicker valve, venting through vent valve.
- When launcher is full, close vent valve and allow pressure to equalize.
- Open isolation valve.
- Gradually close main line valve, thereby increasing flow behind pig.
- Monitor pig detector for pig passage.
- Once pig has entered main line completely, open main line valve fully.
- Close kicker and isolation valves.