HCU16 HART connected device isolation barrier

Description

HCU16 HART connected device isolation barrier

HCU16 HART connected device isolation barrier

The HCU16 HART connection unit – see Figures 4.4 & 4.5 – provides a connection interface between the field wiring and the onward link to the host/system control for non-hazardous areas. It also provides a take-off point for the HART signals to the maintenance system. Connections to the field signals and the system are via screw-clamp terminals and the link to the BPHM64 is via a 20-way ribbon cable. Each channel has three terminals: +ve, -ve and a transmitter supply terminal (Tx +) – see Figure 4.5.

The HART signal has to be terminated with an impedance of approximately 240W. Positions are provided on the circuit board to fit parallel resistors (normally 250W), or an appropriate series resistor to raise the impedance if it is < 240W. This unit can be used with analogue outputs if the system’s current signal is compatible with HART communications. The HCU16 is supplied fitted in a carrier for DIN rail mounting. The footprint of the carrier is 150 x 125mm and the height from the top face of T-section DIN rail is approximately 55mm.

Many systems have 4-20mA analogue outputs that are not compatible with HART data because their impedance is normally too low for the HART to operate correctly. In addition, the noise generated by the analogue output can sometimes interfere with the HART data, or sometimes the HART signal can even affect the stability of the current signal. The HCU16AO HART connection unit – see Figure 4.6 & 4.7 – enables HART signals to be used in current output loops, in non-hazardous areas. It has 16 isolated channels, each with a low-pass filter in series with the current signal from the system.

This has virtually no effect on the 4-20mA signals but presents a suitable high impedance (> 240W) to the HART signals for their detection and measurement. As with the HCU16, the HART data is transferred to the BPHM64 HART multiplexer interface via a 20-way ribbon cable. Field and system connections are made via pluggable 8-way, screwclamp terminals, in 4 groups of 4 channels. The HCU16AO is supplied in a carrier for DIN rail mounting. Overall footprint of carrier: 275 x 125mm. Height from top of DIN rail to top of screw connectors: 58mm.

Previous experience has shown that power plants attach great importance to DCS hardware maintenance management, but do not have corresponding or incomplete management methods for software. If anyone on site can modify the configuration, the software cannot be copied, backed up, and managed in a timely manner, which is very dangerous for the operating unit. Therefore, both software and hardware should be managed simultaneously, and the management of DCS system software and application software should be standardized. Software modifications, updates, and upgrades must comply with the approval authorization and responsible person system. Before modifying, updating, or upgrading the software, it should be backed up; After modifying the logic, the DPU program needs to be backed up once. Strictly regulate the usage permissions of the dedicated keyboard for the operator station to avoid misoperation. The software versions of each workstation must be checked clearly, and it is necessary for each station to maintain consistency. Various software that has not been tested and confirmed is strictly prohibited from being downloaded to the running DCS system for use. Targeted DCS system antivirus measures must be established.

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