In the water conservancy and hydropower industry, hydraulic check butterfly valves have been widely used as valves to protect the safe operation of water pump units and water turbine units. Hydraulic check butterfly valve products are also becoming more and more perfect, and are used in unattended pumping stations of large-scale water delivery projects. The new PLC control heavy hammer hydraulic control check butterfly valve is a major update on the basis of existing products, making the whole machine structure more compact, network control functions more complete, and on-site debugging work easier and more convenient.
The hydraulic system of the unrenewed heavy hammer hydraulic check butterfly valve is designed based on the working performance of conventional hydraulic components. There are many pipes between hydraulic components, many leaks, large oil resistance, and the overall volume of the hydraulic station is huge. At the same time, the design of the electrical system is not conducive to large-scale water delivery projects to flexibly change the system working conditions according to the usage. Therefore, when designing the new PLC control heavy hammer hydraulic control check butterfly valve (Figure 1), the hydraulic system and the electrical system were redesigned to make the unified coordination performance of the two more perfect and more suitable for the working environment of large-scale water conservancy systems.
Introduction to the update of the control system
1. Structural features
The butterfly valve is used in the normal temperature water system with a large diameter, so the butterfly plate is designed as a double-plate truss structure, which has a large flow area, good rigidity, and low flow resistance. It can also meet the sealing requirements of working conditions under large pressure changes. The sealing material selects conventional soft seal or high-performance metal seal according to the impurity content of the water medium. Due to the working nature of the butterfly valve, it is required to be more rigid than the butterfly valve used under ordinary working conditions.
2. Hydraulic system
Take the butterfly valve applied to the water pump system as an example. When the water pump is stopped, in order to avoid the reverse flow of the medium, the pump rotor will rotate in the reverse direction and exceed the maximum number of revolutions allowed by the pump, which will cause the unit to run away. The flow velocity will not rise too high under the action of the valve flow resistance, which protects the safety of the unit, completes the closing act in the slow closing stage, prevents the formation of water hammer, and protects the safety of the pipeline system. Taking into account the difference between the design and actual use conditions, the adjustment range of the hydraulic system’s fast and slow closing angle and time has been appropriately increased (Figure 2), and the integrated hydraulic block is used to minimize the leakage point and effectively eliminate the hydraulic control butterfly valve. The leakage problem.
3. Electrical system
The electrical control adopts Schneider programmable logic controller PLC analog module, FDPS switching power supply, MSC106~43 signal processor, and uninterruptible power supply UPS and other components to ensure that the butterfly valve in the unattended pump station fails It can be normal and guarantee the safety of the working system.
The programmable controller PLC analog module is the central component of the electrical system. The controller can be written using a variety of general-purpose programming programs and can be modified and adjusted repeatedly. Through the input control program, the action sequence of the butterfly valve is controlled, which can satisfy the user The operating requirements. With multiple adjustment points, the opening and closing setting procedures can be modified according to the actual situation of the site to ensure that the butterfly valve can automatically open and close in two stages of fast and slow according to the set time and angle. The control program is equipped with a lock program. During use, only a valid password can be entered to change the parameters, avoiding misoperation by non-workers and further ensuring the safety of the working system.
The uninterruptible power supply UPS is placed in the electric control box, and the power supply is automatically switched when the power fails. Ensure that the valve can also complete the normal closing action during a power failure to ensure the safety of the system.
Renewal of packing for large diameter ultra-high temperature butterfly valve
The first test is to compress the packing in a simulated stuffing box, put it in a heat treatment furnace and heat it to 816°C, and then take it out after holding it for 48 hours. Not like oxidation failure. It is confirmed by analysis that conventional fillers need to be filled with corrosion inhibitors to prevent pitting corrosion of the valve stem of Cr13 material. It is the corrosion inhibitors that cause the fillers to fail at high temperatures. Considering that Inconel X-750 stem material does not have a tendency to pitting corrosion, it is not necessary to add corrosion inhibitors in the packing. The filler without corrosion inhibitor was pressed into the simulated stuffing box. After being heated to 816℃ and kept for 48 hours, the gray-black filler did not change color, and the elasticity of the filler did not change. Only the part in contact with air showed obvious oxidation. In order to improve the high-temperature performance of flexible graphite, the filler made of flexible graphite without corrosion inhibitor and high-temperature anti-oxidation board is pressed tightly in the simulated stuffing box. After heating to 816 ℃ and holding for 48 hours, the gray-black filler has no Discoloration, the elasticity of the filler does not change, and the part in contact with air is slightly oxidized. This preliminarily confirms the reliability that the packing temperature can reach 816°C in the compressed and sealed state. After many trials and improvements, an ultra-high temperature flexible graphite packing was made.
The hydraulic principle of the PLC-controlled heavy hammer hydraulic check butterfly valve is advanced, and the hydraulic components ensure zero leakage of the hydraulic station, making the whole machine safe and reliable. The protection level of the electrical system has reached IP67 or higher, and there will be no malfunction in extreme wet conditions, ensuring the safety of personnel and the reliability of system operation to the greatest extent. Due to the good harmony of the whole machine, the electro-hydraulic control system has complete functions. It can be operated as a stand-alone system for independent control, or it can be networked with a central computer through a spare contact to realize linkage operation with pipeline equipment such as water pumps and turbines.
The successful development of the large-caliber ultra-high temperature butterfly valve mainly solves the problems of the selection of the body material, the design of the butterfly valve sealing structure and the valve stem sealing structure, and the ultra-high temperature packing is selected through the experiment, which is the valve for the catalytic cracking unit system of the petrochemical industry. The design and manufacturing have gained experience.
About the author: Song Jiyang, male, from Tieling City, Liaoning Province, Position: Engineer