Low protection level:
The valve-specific motor provided by the electrical equipment manufacturer has a fully enclosed squirrel-cage structure, with a short-term intermittent working mode (10 minutes) and self-cooling function. According to GB 4942.1-85 requirements, the minimum protection level is IP44, and the maximum protection level is IP68. The required protection level varies depending on the valve's operating conditions and environment. A low protection level will cause the motor's interior to get damp or for foreign substances such as dust to invade, resulting in a decrease in the insulation resistance and eventual damage.
Improper packaging, transportation, and storage:
The electrical equipment packaging for the valve should have measures to prevent rain, moisture, and dust. The packaging should be sturdy and reliable. During transportation, there should be measures to prevent rain. After the product arrives at the site, it should be stored in a ventilated and dry place and not be stored outdoors. It is prohibited to conduct debugging or maintenance during rainy weather. After the debugging is completed, all fastening parts should be tightened to ensure that all electrical components are sealed and reliable.
The valve assembly has two important parameters.
The opening and closing torque value should include the actual working torque of the valve plus the torque of the valve itself. The magnitude of the opening and closing torque affects the usage of the valve. A large torque is prone to damage, while a small torque is prone to leakage. There should be sufficient margin in the selection and matching (generally, it is required to be more than 1.1 to 1.3 times the actual operating torque of the valve).
② The travel position control is related to the valve opening and closing diameter, the duration of opening and closing, and the structural form. The motor used for the valve electrical assembly is a dedicated motor with short-term working cycle, lasting for 10 to 15 minutes. If a high load is applied during the short-term working period, it may cause the motor to overheat, resulting in a decrease in insulation level and potential damage.
The valve electrical assembly does not match the motor model:
The selected motor model does not match the requirements of the electrical equipment. The actual output torque does not leave sufficient corresponding margin, and it is prone to cause damage to the motor during overload operation.
Electrical protection failure, poor quality of electrical components: The microswitches inside the valve electrical assembly are key components of the control mechanism. When the valve exceeds its stroke position, the microswitches cut off the power supply, providing overload protection. Most electrical assembly manufacturers connect stroke and torque protection in series. When the stroke or torque exceeds the limit, the microswitches promptly cut off the AC contactor coil control power, thereby cutting off the main circuit of the motor.
Improper installation and use during debugging:
The valve electrical assembly is divided into two types: horizontal installation and vertical installation. In the vertical installation, the tail end of the motor is at the bottom. When the rubber seal of the wiring sleeve fails, the lubricating oil in the cavity will enter the motor through the cable outlet, which may cause the windings to short circuit and damage the motor.
According to JB 8528-1997, the rotation direction of the handwheel of the electric device should be consistent with the rotation direction of the output shaft. Clockwise rotation is for closing the valve, and counterclockwise rotation is for opening the valve. If the actual rotation direction of the motor does not conform to the specified direction, then any two phases of the three-phase power supply need to be replaced (just by swapping them). Otherwise, due to reverse phase, the protective measures will fail, causing damage to the motor.
③ Since the dedicated motor for the valve operates under a high-load short-duration working condition, if the continuous debugging time exceeds the rated time, it will cause the motor to overheat and be damaged.
The electrical assembly of the valve does not match the valve connection: The electric assembly of the multi-turn valve is divided into two types: torque type and thrust type. The torque type mostly adopts three-jaw connection or key connection, and the valve assembly does not bear axial thrust. The thrust type mostly uses threaded connection and can withstand large axial thrust. In order to avoid interference between the valve assembly and the valve connection, it is necessary to limit the appropriate gap between the upper part of the valve mating surface and the valve assembly. Ensure that the worm gear installed on the output shaft does not shift axially, ensure that the center meshing plane of the worm and worm gear has a good meshing effect, and ensure that the transmitted torque reaches the rated output torque value.
The temperature control protection system of the motor is malfunctioning.
The motor is equipped with a temperature control switch. When the valve motor is subjected to excessive torque or operates for a long time, the motor temperature rises and exceeds the set temperature value. At this point, the temperature control switch immediately cuts off the control circuit, thereby protecting the motor.