Today the performance requirements of process plants are becoming increasingly difficult to satisfy. In fact, without process control it is difficult to operate most modern processes safely and profitably. To understand the process dynamics and its behavior Apex has developed compact setups. These setups are easy to operate and self-educative. Some of the products are computerized and work with specially developed interactive software. We hope one will find the theoretical knowledge in its best practical performance with the Apex products. The control valve characteristic set up is designed to understand basic principles and operation of pneumatically actuated control valves. The stand-alone type set up consists of different type of control valves, cylindrical overhead tank, receiving tank, rotameter, pump and other components mounted on supporting structure.
[...] Maintenance and troubleshooting Drain the set up regularly after shutdown. Use clean and soft water for the set up. Problems and causes: Some of the problems and probable causes are given below. Pump discharge Air trap due to insufficient water in receiving tank. Impeller chocking. Rotameter flow Air trapped in rotameter. (Refer Commissioning: Flow circulation) Closed vent valve on the overhead tank. Closed regulating valves at the inlet of control valves. Insufficient pump discharge Dirt particles. Pressure drop measurement Respective hose cock closed. [...]
[...] Open the regulating valves (provided at the inlet of control valves). Keep open the vent valve (fitted to the overhead tank at the top of the set up) and ball valve (fitted in the overflow line from overhead tank to receiving tank). Switch on the pump. Close the vent valve and ball valve, when water overflows to receiving tank. Open the ball valve and vent valve when rotameter lifts to its maximum range. Repeated above step till air from rotameter is removed. [...]
[...] Pneumatic leakage or insufficient pressure. Diaphragm breakage. Experimentation Working of the set up: Water from receiving tank is pumped to overhead tank and re-circulate. Water from overhead tank flows through the control valve. Water flow is measured using rotameter and the water inlet pressure at the control valve is measured in terms of water column. The control valve stem travel is adjusted by air regulator resulting change in flow through the control valve. As outlet of control valve is open to atmosphere, pressure at valve inlet is considered as pressure drop across the valve. [...]
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