Valves and flow equipment for the polymer industry

Polymer production and processing plants operate with monomer, solvent, catalyst, additive, resin, polymer mixture, steam, thermal oil, chilled water, glycol, nitrogen, compressed air and auxiliary fluid lines. Valve selection is based on chemical compatibility, pressure, temperature, viscosity, volatility, possible presence of solids or deposits and sealing requirements.

Polymerisation, mixing, heating, cooling, transfer, dosing, storage and cleaning processes require a defined function for each valve. Correct sizing helps limit excessive flow velocity, pressure losses, flow fluctuations and wear on seats, sealing elements and internal parts.

Typical applications

• Monomer, solvent, catalyst, inhibitor and chemical additive lines.
• Transfer and dosing of resins, polyols, isocyanates, latex and polymer mixtures.
• Polymerisation reactors, mixing tanks, recirculation lines and feed lines.
• Thermal oil circuits for controlled heating of reactors, pipework and tanks.
• Steam networks for heating, cleaning and auxiliary thermal processes.
• Chilled water, glycol and cooling water lines for heat exchangers and condensers.
• Nitrogen systems for purging, blanketing, inerting and oxygen removal.
• Venting, relief, draining, sampling and bypass lines.
• Auxiliary compressed air networks for pneumatic actuators and control instruments.

Equipment selection criteria

• Compatibility of body, seat, stem, gasket and packing materials with the fluid.
• Operating pressure, design pressure and valve differential pressure.
• Operating temperature, cleaning temperature and thermal variations during start-up or shutdown.
• Viscosity, density, volatility and risk of solidification, gelling or deposit formation.
• Possible presence of granules, fillers, fibres or suspended solids.
• Required flow rate and allowable pressure drop.
• Isolation, control, non-return, relief or overpressure protection function.
• Seat, stem and connection tightness requirements.
• Actuation method: manual, pneumatic, electric or self-acting.
• Connection to PLC, DCS, SCADA or process safety system.

Indicative equipment

• Isolation valves for monomers, solvents, resins, nitrogen, steam and auxiliary fluids.
• Control valves for flow, pressure, temperature or level regulation.
• Bellows-sealed valves or special stem sealing arrangements for reduced external leakage.
• Pressure reducing valves and pressure regulators for steam, nitrogen, air and auxiliary gases.
• Check valves for protection of pumps, compressors and dosing systems.
• Safety and relief valves for reactors, tanks, heat exchangers and pipework.
• Steam traps and condensate equipment for steam lines.
• Line strainers for protection of control valves, pumps, nozzles and instruments.
• Pneumatic and electric actuators for remote or automatic operation.

For each application, the fluid composition, pressure, temperature, flow rate, viscosity, risk of deposits or solidification, installation point and valve function in the control system should be reviewed. These data define the valve type, nominal size, pressure class, construction materials, sealing arrangement and suitable actuation method.