Design and Application of ROV Control Panel for Diamond Wire Cutting Machine
1. Introduction
Subsea pipelines are the lifelines of offshore oil and gas fields. With the increasing number of subsea pipelines, accidents caused by reasons such as design and construction age, pipeline corrosion, and trawling by fishing boats are becoming more frequent. Once a pipeline is damaged, it poses a significant threat to the marine environment and oil and gas production, necessitating timely repair. The repair process typically involves cutting the damaged section of the pipe and then installing connectors or flanges to connect it to a new pipeline. Cutting operations are a critical part of the repair process, and diamond wire cutting machines are essential tools. However, the controllability of diamond wire cutting machines in deep water is poor, which limits repair efficiency.
2. Deep-Water Diamond Wire Cutting Machine
2.1 Cutting Machine Actuation System
The main mechanical structure of the deep-water diamond wire cutting machine consists of three parts:
The hydraulic clamps of the pipeline holding section.
The feed system that carries the cutting tool for linear feed.
The transmission system that drives the diamond wire around the rotating wheel at high speed for grinding.
2.2 Hydraulic System of the Cutting Machine
The control system of the cutting machine integrates the main part of the hydraulic circuit, with the main mechanical part only serving as the output end equipped with hydraulic cylinders, hydraulic motors, and other actuators. There are currently two main control methods for underwater diamond wire cutting machines: deck HPU (hydraulic power unit) control and Hot Stab (hydraulic stab) control. Deck HPU control requires diver assistance and is not suitable for deep-water operations due to the long hydraulic lines that hinder oil circulation, making it only applicable in shallow water. Hot Stab control connects the actuators of the cutting machine to the control oil circuit of the ROV's external working tools through a 6-channel ROV Hot Stab. However, it provides lower oil pressure and is more sensitive to high-temperature, high-pressure, high-flow environments and complex forces, making it prone to damage.
3. Design of the ROV Control Panel
3.1 Hydraulic Principle Design
The hydraulic principle design of the control panel includes the following key parts:
Pipe Holding Pressure System: To counteract the lateral vibration and marine turbulence during the cutting machine's operation, the hydraulic system provides stable oil pressure to the clamp hydraulic cylinder to complete the pipe holding and locking action. This branch uses an O-type center position directional control valve and is equipped with a pair of hydraulic-controlled check valves at the end of the hydraulic cylinder to form an interlock structure, effectively reducing the risk of system leakage.
Throttle Speed Control and Leakage Prevention: To mitigate the severe pressure fluctuations in the system caused by sudden changes in damping on the diamond bead wire, which can damage the hydraulic motor, and to meet the speed adjustment needs for different pipelines, a throttle speed control circuit is designed. The speed is adjusted by regulating the flow rate Q entering the actuator through a check throttle valve. A Y-type center position directional control valve is used, allowing the hydraulic motor to rotate under external torque to prevent damage.
Main Line Oil Pressure Compensation: A compensator is added to the main oil line to continuously provide pressure support for the system when there is no external leakage and to provide emergency pressure holding in case of leakage.
Hydraulic Control Integrated Valve Block Structure: The main structure of the control panel hydraulic system uses an integrated valve block design to avoid interfering with the normal operation of the cutting machine and to provide more convenient assembly performance.
3.2 Overall Structural Design of the Control Panel
The overall structure of the control panel mainly consists of the following parts:
The valve seat assembly integrating oil channels and various hydraulic components.
The ROV socket plate with compensator switch and ROV Hot Stab interface.
The control panel control face with control handles for each valve and pressure gauges.
The ROV handle-handle plate for the ROV's five-function manipulator to grasp the panel.
The control panel installation plate for assembly with the cutting machine.
The compensator installation plate for compensator mounting.
4. Engineering Application
The engineering application steps of the control panel are as follows:
Workers assemble the ROV control panel and the cutting machine on the deck, and the crane lowers the cutting machine to the pipeline cutting position.
The ROV is positioned, and the Hot Stab is connected to the corresponding interface on the panel. After confirming normal operation, the ROV manipulator opens the switch valve on the control panel, connecting the hydraulic system's oil circuit.
The ROV opens the pipe-holding action control valve to its working position, the clamp hydraulic cylinder piston extends, the cutting machine clamps the pipeline, and after confirming the correct pressure reading, the control valve is returned to the center position.
The ROV opens the feed action control valve to its working position, the hydraulic motor rotates forward, the feed disc moves downward, and when it reaches a position about 10 mm above the pipeline, the control valve switch is returned to the center position to pause the movement.
Open the cutting action control valve switch to rotate the diamond bead rope to the cutting speed. After confirming the overall stability of the mechanism and normal pressure, reopen the feed control valve to its working position to start cutting the pipeline.
After the operation is completed, the mechanism is sequentially reset and closed, and then recovered.
The actual manufactured control panel is shown in Figure 6. Practical application has shown that the control panel can effectively solve the deep-water control issues of diamond wire cutting machines and improve their underwater operation efficiency.
5. Conclusion
In response to the problems encountered by diamond wire cutting machines during deep-water pipeline repair, this paper proposes an ROV control panel solution, conducts hydraulic system and overall structural design, and successfully applies it in practice, promoting the progress of deep-water pipeline repair technology.
