1. System Overview
The CARGOPRO (CARGOCONTROLSYSTEM) system mainly consists of four subsystems: a liquid level telemetry system, a valve remote control system, an independent high-level and high-high-level alarm system, and a large-tank water ingress alarm system. It can monitor the entire ship's cargo control system.
We use GEFanuc90-30 and VersaMaxMicro series PLCs as the system control units, VersaMaxRemoteI/O as the remote station for signal acquisition, and general bus protocols such as GeniusBus, ModBus, and Profibus as the internal communication protocols. We also communicate with the industrial control software iFix through the TCP/IP network protocol to achieve human-machine interaction.
2. System Solution
The system diagram of the entire CARGOPRO system is shown in Figure 1:
Figure 1 CARGOPRO System Diagram
2.1 Liquid Level Telemetry System
The liquid level telemetry system adopts a distributed acquisition and centralized control design concept, detecting and alarming the liquid level in the corresponding compartments, the temperature of the liquid cargo tanks, and the draft at the four corners. Due to the variety and wide distribution of signals, special attention is paid during acquisition; therefore, all signals are acquired through GE VersaMax Remote I/O modules installed in various acquisition boxes to ensure the accuracy of the acquired signals. The GE VersaMax Remote I/O modules communicate with the PLC master station installed on the cargo control console via GE's Genius Bus protocol, sending the acquired signals to the PLC's CPU module. After processing by the CPU, the control signals are sent to the GE VersaMax Remote I/O modules via Genius Bus, enabling remote control.
The host computer portion of this system includes an industrial PC, a switch, a printer, and software. The industrial PC communicates with the PLC master station via TCP/IP protocol, enabling information exchange between the monitoring software HMI/SCADA iFix and the PLC. Operators can use the iFix software to monitor all measurement points in real time and process alarm information.
2.2 Independent high-level and high-high-level alarm systems
This system collects independent alarm signals to trigger alarms for high and very high liquid levels in compartments such as cargo tanks, sewage tanks, and ballast water tanks. It employs an independent VersaMaxMicro series PLC as the controller and a QuickPanelView series touchscreen as the HMI, forming a relatively independent control system that displays and controls the corresponding alarm signals.
The touchscreen, acting as an HMI, communicates with the PLC controller via the ModBus bus protocol. All alarm signals are displayed and the operator can control the system entirely on a single touchscreen, making the entire system extremely streamlined.
2. 3. Flooding alarm system for the main cabins
The system utilizes the principle of pressure-based liquid level measurement, converting pressure signals into 4-20mA current signals, which are then sent to the VersaMaxMicro series PLC control station on the control panel. The PLC control station communicates with the QuickPanelView series touchscreen via TCP/IP to display and control alarm signals. The entire system can independently display liquid level, alarm signals, and provide control.
2.4 Valve Remote Control System
The valve remote control system consists of a cargo control console with a GEFanuc90-30 series PLC control master station, a solenoid valve box with a VersaMaxRemoteI/OPLC acquisition and control station, a dedicated industrial computer for valve remote control, a hydraulic power pump station, a solenoid valve box (including emergency valve blocks), hydraulic valves, a hand-cranked pump, and an emergency hand-cranked pump. The valve remote control device uses an electro-hydraulic drive to control the operation of the solenoid valves, enabling remote control of the opening and closing of valves in the cargo oil and ballast tank pipelines. Valve opening and closing operations and valve position indications are displayed on the dedicated valve remote control screen on the cargo control console.
The hydraulic remote control valves can be switched on and off at the PLC control master station on the cargo control console. The valve on/off indicators are red for closed and green for open; the valve opening indicator also provides opening degree indication and control. The solenoid valve box PLC control station is connected to the cargo control console PLC master station via GeniusBus. Based on the operational requirements of the cargo control console PLC control station, it controls the corresponding solenoid valves. Through the instantaneous energization and locking function of the solenoid valves, it controls the oil inlet and outlet direction, achieving the purpose of opening and closing the valves. All valve position indications and opening degree control signals of the remote control valves are sent to the solenoid valve box PLC control station, and then transmitted to the cargo control console PLC control station via GeniusBus.
The host computer component includes an industrial PC, a switch, a printer, and software. The industrial PC communicates with the PLC master station via TCP/IP protocol, enabling information exchange between the monitoring software HMI/SCADAiFix and the PLC, and realizing valve control, status display, alarm history recording, and query.
3. System Features
To maximize system security and stability, we utilize GE PLCs for control and signal acquisition modules. Employing a distributed acquisition and centralized control principle ensures accurate and convenient acquisition and control of various signals. Compatibility with multiple common bus protocols, such as GeniusBus and ModBus, significantly increases system scalability. Furthermore, modular design divides the system into independent modules with different functions, facilitating modification and expansion. This allows for customized solutions tailored to specific customer needs. Multiple human-machine interfaces, such as IPCs, touchscreens, and MIMIC boards, ensure convenient and quick access to information and control by operators.
4. Conclusion
The CARGOPRO system has been applied to multiple ships due to its extremely high safety and stability and user-friendly human-machine interface, and has passed the ship inspection of multiple classification societies.
