Apparatus and method for withdrawing samples from a unit of a polymerization plant

A method for withdrawing samples from a unit of a polymerization plant having a sampling nozzle by an apparatus comprising:

• a sampling valve for connecting to the sampling nozzle;
• a first sample collection tank having a gas discharge conduit and a solid discharge port;
• a transfer conduit operatively connected at a first end to the sampling valve and at a second end to the first sample collection tank;
• a first control valve mounted on the transfer conduit downstream of the sampling valve, thereby controlling the flow of a sample of a polymerization material into the transfer conduit;
• a second control valve mounted on the transfer conduit downstream of the first control valve and upstream of the first sample collection tank, thereby controlling the flow of the sample into the first sample collection tank;
• a third control valve mounted on the gas discharge conduit of the first sample collection tank;
• a second sample collection tank, located below the first sample collection tank and connected to the first sample collection tank via a fourth control valve mounted on the solid discharge port and the fourth control valve having a locking device;
• a solid discharge conduit connected to a discharge port at the bottom of the second sample collection tank;
• a fifth control valve mounted on the solid discharge conduit and the fifth control valve having a locking device;
• a sixth control valve mounted on the solid discharge conduit downstream of the fifth control valve;
• and
• a flushing system for flushing the conduits and the valves;
• wherein
• the locking devices of the fourth and fifth control valves are operable by a single key,
• the single key is extractable from the locking devices only when the locking devices are locked, and
• the single key opens one of the fourth and fifth control valves only with the other of the fourth and fifth control valves is closed;
• and
• the unit being operated at a pressure P1 above the pressure P2 of the apparatus;
• the method comprising the steps of:
• a. setting the valves in the closed position and keeping the single key of the locking devices of the fourth and fifth control valves inserted in the locking device of the fifth control valve;
• b. opening the first, second and third control valves and flushing the valves, the transfer conduit, the first sample collection tank and the gas discharge conduit with a cleaning gas provided by the flushing system;
• c. closing the third control valve and opening the sampling valve to withdraw the sample from the unit of a polymerization plant and transferring the sample via the transfer conduit to the first sample collection tank;
• d. detecting that the sample is present in the first sample collection tank;
• e. opening the third control valve to remove gas and vaporizable liquid from the sample collected in the first sample collection tank;
• f. extracting the single key from the locking device of the fifth control valve;
• g. inserting the single key in the locking device of the fourth control valve and opening the fourth control valve, whereby the sample collected in the first sample collection tank is discharged under gravity into the second sample collection tank;
• h. closing the fourth control valve and extracting the single key from the locking device of the fourth control valve;
• i. inserting the single key in the locking device of the fifth control valve and opening the fifth control valve;
• and
• j. opening the sixth control valve, whereby the sample collected in the second sample collection tank is discharged through the discharge conduit.