Keywords: Butterfly Valve, Heavy Hammer, New Technology Application
The heavy hammer butterfly valve is a sophisticated device composed of several key components including the butterfly valve body, hydraulic bypass valve linkage, heavy hammer, release mechanism, manual or electric pump, rack drive cylinder, and an electronic control system (as shown in Figure 1). The oil from the pump is directed into the rack drive cylinder, where the piston moves to rotate the gear on the main shaft of the butterfly plate, opening the valve and lifting the heavy hammer to its highest position. A pawl on the weight is locked by the spindle lock, which is controlled by an electromagnet and holding device. In the event of an accident, the electronic control system triggers the release of the electromagnet, allowing the heavy hammer to drop and close the butterfly valve automatically.
The hydraulic system uses a two-stage throttling method to regulate the closing speed of the butterfly valve. Initially, the closure is slow to reduce the rate of speed increase, followed by a faster stage to manage the water pressure rise effectively. This process is illustrated in Figure 2.
One of the key technical features of this system is its dual-purpose hydraulic design, which allows for compact assembly and ease of operation. Even without external power, the system can rely on gravity storage to shut down safely. It also includes automatic protection mechanisms that trigger shutdowns in case of over-speed, bearing overheating, or generator demagnetization. The valve offers two-stage closure, ensuring a safe and controlled operation. The electromagnet-controlled locking mechanism is both reliable and requires minimal operating force.
Main technical parameters for the D741-10 heavy hammer butterfly valve include a working pressure of 1 MPa, available diameters ranging from φ400 to φ1200, a maximum head of 100 meters, and a rated head of 145 meters. The opening time is approximately 5 minutes manually or 1 minute with electricity, while the fast-closing phase lasts 5–10 seconds and the slow-closing phase ranges from 10–50 seconds. The over-speed protection range is adjustable up to 1.8 times the rated speed.
This type of valve has been successfully applied in hydropower plants such as the Chaitan Hydropower Plant in Linhai City, Zhejiang Province, and the Pingyang Hydropower Plant. These installations feature a hybrid power station setup with a pressure tunnel of 1100 meters and a 2.6-meter diameter. The system has demonstrated excellent performance, with 100% correct operation during 203 opening and closing cycles. Electric opening takes about 55 seconds, and the fast-closing time is set at 5 seconds to limit speed rise to within 40%, followed by a slower closure to manage water pressure increase to 21%.
In the event of an emergency shutdown due to over-speed, the system automatically releases the heavy hammer when the speed exceeds 1.4 times the rated value, preventing further damage and improving safety.
In conclusion, the heavy hammer butterfly valve significantly enhances equipment reliability, reduces operational labor, and lowers maintenance workload. It also eliminates the need for backup DC power supply, especially in isolated or low-manpower operations. By using a two-stage closure, it ensures that both the unit's speed and water pressure remain within acceptable limits, offering a more economical and reliable solution compared to traditional methods like artificial resistance.
Bimetallic conical twin screw and barrel
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