Pig launchers
are used to launch the pig into the pipeline, and pig
receivers are used to receive the pigs after they have made
a successful run. The choice of these pig traps will depend on
the type of pig to be run and pipeline design conditions.
Provisions in the station design should include handling
equipment for pigs 20" and larger. Caution should be taken for
liquid spillage from the pig traps.
Typical Pig Launching Procedures
The operational sequence
described below is for general information only. It is not
intended, nor should it be used, to train pigging system
operators. Operating procedures will vary from one pipeline
company to another. The following pig launching procedures can
be used as a guideline for developing operating procedures.
Since company policies vary
regarding whether the pig launcher is left on stream or isolated
from the pipeline after the pig is launched, the operator should
verify that the trap is isolated from the pipeline and
depressurized before commencing any part of the launch
procedure.
- Make sure that the isolation valve and
the kicker valve are closed.
- In liquid systems, open the drain valve
and allow air to displace the liquid by opening the vent
valve. In natural gas systems, open the vent and vent the
launcher to atmospheric pressure.
-
When the pig launcher is
completely drained (0 psi), with the vent and drain valves
still open, open the trap (closure) door.
- Install the pig with the nose firmly in
contact with the reducer between the barrel and the nominal
bore section of the launcher.
- Clean the closure seal and other
sealing surfaces, lubricate if necessary, and close and secure
the closure door.
- Close the drain valve. Slowly fill the
trap by gradually opening the kicker valve and venting through
the vent valve.
-
When filling is
complete, close the vent valve to allow pressure to equalize
across the isolation valve.
- Open the isolation valve. The pig is
ready for launching.
- Partially close the main line valve.
This will increase the flow through the kicker valve and
behind the pig. Continue to close the main line valve until
the pig leaves the trap into the main line as indicated by the
pig signaler.
- After the pig leaves the trap and
enters the main line, fully open the main line valve. Close
the isolation valve and the kicker valve.
- The pig launching is complete.
Typical Pig
Receiving Procedures
The operational sequence described below
is for general information only. It is not intended, nor should
it be used, to train pigging system operators. Operating
procedures will vary from one pipeline company to another. The
following pig receiving procedures can be used as a guideline
for developing operating procedures.
Since company policies vary regarding
whether the pig receiver is left on stream or isolated from the
pipeline, the operator should verify whether there is any
internal pressure in the receiving trap before starting any part
of the receiving procedures.
- Make sure the receiver is pressurized.
- Fully open the bypass valve.
- Fully open the isolation valve and
partially close the main line valve.
- Monitor the pig signaler for pig
arrival.
- Close the isolation valve and bypass
valve.
- Open the drain valve and the vent
valve.
- Check the pressure gauge on the
receiver to assure the trap is depressurized (0 psi).
- Open the trap closure and remove the
pig from the receiver.
- Clean the closure seal and other
sealing surfaces, lubricate if necessary, and close and secure
the trap (closure) door.
- Return the receiver to the original
condition.
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