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Cargo Tanks Pressure Monitoring System
1. Outline
Pressure in cargo tanks and vapour return line on tankers is continuously detected and monitored with electronic differential pressure transmitters and is remotely indicated at Monitoring Panel in cargo control room.
2. Constitution machinery
A Electronic Differential Pressure Transmitters：
Electronic differential pressure transmitters having built-in microprocessors function as transducers of high-performance and excellent stability. They are powered by DC10.8-45V and pressure detected is internally converted to analog signal and output 4-20mA linear signal. With an electronic differential pressure transmitter JTD920A, a measuring range can be set 0-0.75 kPa (76.5 mmAq) to 0-100 kPa (10,197 mmAq).
B Zener Barriers
Zener Barrier is a device located at a boundary between dangerous area and safe area to establish intrinsically safe system with electronic differential pressure transmitters. Zener barrier relays linear signals, which are output from electronic differential pressure transmitters in dangerous area, to devices in safe area.
C Monitor Panel System
Monitor Panel System is fitted in cargo monitoring/controlling place. It consists of 2 sections, i.e. signal receiving section and alarm section. Signal receiving section converts linear signals (4-20 mA) from electronic differential pressure transmitters to detected pressure values (-1,000-3,000 mmAq) for remote indication. When linear signals from electronic differential pressure transmitters exceeds a preset alarm value, alarm section outputs electric signal to actuate visible and audible alarms.
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