PNEUMATIC CONTROL MACHINE FOR AUTOMATION OF POLYETHYLENE PRODUCTION

A pneumatic control computer for use in automatic polyethylene production is described. Ethylene under 1500 atm pressure is used as a raw material. Polymerization takes place in the reactor at 200--250C with a small quantity of initiator. The polymer and gas residues formed are subsequently channeled into a separator unit, where polymer and ethylene being returned to the reactor are extracted. The control computer ('auto-operator') regulates all process parameters, implements process control logic, starts and stops the control process, and has emergency protective features. The computer uses approximately 360 analog and discrete pneumatic elements. Deviation of basic parameters beyond their allowable operating range is indicated on the control panel, which also contains a temperature signal panel indicating reactor temperature distribution. Two polymerization processes may be controlled by such a machine. The basic characteristics are: input and output signals are compressed air (0.2 - 1 atm) and electrical relay signal 70 pneumatic and 25 electrical input signals, 30 output signals, are available, the temperature signal panel contains 12 points corresponding to different temperatures. The machine measures 1.7 x 1.7 x 1.7 m. During four years of use, only 35 pneumatic elements needed replacement, which supports the assertion of a high reliability index. Edited machine trans. of Pribory i Sistemy Upravleniya (USSR) n6 p29-31 1967.