REGULATING VALVE APPLICATIONS TEMPERATURE CONTROL of a BATCH PROCESS with Electrical Time Sequence Programmer (Solenoid Pilot)
PURPOSE:
For accurately controlling temperature of a batch process where on-off operation is to be electronically controlled.
OPERATION:
Operation is similar to that of the pressure and temperature combination pilot-operated regulator whereby the temperature (PT) pilot senses the temperature of the heated product (e.g. water) and appropriately modulates the flow of steam. Pressure is limited by the pressure (PP) pilot. The solenoid valve (PS-pilot) is electronically activated to control on-off operation of the batch process.
INSTALLATION GUIDELINES:
(see Figure 12)
• The temperature and pressure pilots should be set individually, starting slowly and gradually with the PT-pilot. • For optimum operation and service life, maintain recommended minimum piping straight runs before and after the PRV. Inlet pipe diameters could be 1-2 sizes larger and outlet pipe diameters 2-3 sizes larger than the end connections of an appropriately sized Regulator. The purpose of increasing the pipe size downstream of the regulator is to keep the steam velocity constant on both sides of the regulator. • The pressure sensing line should slope downwards, away from the regulator, to prevent condensate from entering the pilot. • Eccentric reducers, if required, are used on valve inlets to prevent accumulation of condensate which could become entrained with high-velocity steam, possibly resulting in dangerous waterhammer. • While a separator is appropriate for protection of the Regulator, it is not always required, as a properly sized drip leg with steam trap may be sufficient. It is recommended for systems where steam is known to be “wet” and the entrained moisture could affect valve performance and/or result in component damage. • Consider low-cracking pressure (1/4 PSI opening pressure) check valves after steam traps when discharging into condensate return lines. Check valves eliminate the possibility of condensate backing up through the steam trap into the system. • The vacuum breaker and auxiliary air vent located at the top of the jacketed kettle vessel promotes proper drainage and optimum heat transfer. The vacuum breaker allows system equalization with atmospheric air to allow gravity condensate drainage when vacuum is formed from condensing steam. The air vent improves heat-up times and overall heat transfer by expelling accumulated air on start-up. • A safety relief valve (SRV) is appropriate where applicable codes dictate their requirement, or anywhere protection of downstream piping and equipment from over-pressurization is desired. Consult the factory for appropriate SRV sizing guidelines.
106
www.watsonmcdaniel.com •• Pottstown PA • USA • Tel: 610-495-5131
Made with FlippingBook - Online magazine maker