Discuss the operating procedures for valves

I’ve never heard that valves have specific operating procedures!

Valves in the chemical industry are the simplest and most commonly used. Do not apply excessive force when opening or closing them; turn the handle half a turn after full opening.

1. Preheat the steam valve before opening it. 2. After the valve is fully open, turn it half a turn in the opposite direction. 3. For valves with visible stems, remember the fully open and fully closed positions to avoid hitting the dead center. 4. When using the pipeline for the first time, open and close the valve several times to flush it. 5. For certain types of media, the valve should be closed again after it has cooled down, at an appropriate time

During seasons with low temperatures below 0°C, for valves that are not in use, it is essential to prevent freezing; the plug at the bottom of the valve should be removed promptly to drain any accumulated water inside. Insulation measures should be taken for valves that cannot be excluded from operation and those that operate intermittently. The valve packing gland should not be tightened too much; it is sufficient for the valve stem to rotate freely. Tightening it excessively increases the friction on the valve stem and raises the operating torque. When the valve is in operation, it is generally not permissible to replace or add packing under pressure; otherwise, it may lead to medium leakage and pose a danger. For valves that operate at high temperatures, when the temperature rises above 200°C, the bolts expand due to heat, which can lead to poor sealing of the valve. In such cases, it is necessary to \"heat-tighten\" the bolts; however, this should not be done when the valve is in its fully closed position. To prevent the valve stem from getting stuck and making it difficult to open again. Operation and use of valves: After the valves are installed, operators should be able to become familiar with the structure and performance of the valves as well as their driving mechanisms. They must be able to correctly identify the direction in which the valves open, the indicators of opening degree, and other signaling elements, and they should be capable of operating the valves skillfully and accurately. For butterfly check valves, it is necessary to handle various emergency faults promptly and decisively. The proper operation of valve controls is crucial; track ball valves have a direct impact on their service life, and they are also related to the smooth and safe operation of equipment and systems. Operation of manual valves: Manual valves are operated using handwheels or handles, and they are widely used in petrochemical valve systems. Operators should pay attention to the following points: ◆ The direction in which the valve opens – for wedge gate valves, this is usually against the direction of the clock hands; for ball valves, it indicates that the valve is open. The clockwise direction indicates that the valve is closed. Therefore, pay attention to the direction when opening and closing the valve. ◆ The handle of the valve is designed based on the force required to operate it manually. Therefore, the valve can be opened and closed simply by manually turning the fluoroplastic-lined globe valve stem; generally, gate valves do not allow the use of levers or wrenches, or hydraulic/electric control valves, to open and close them. To prevent excessive force from damaging the sealing surfaces and other components: ◆ When closing gate valves and stop valves to the full position, turn them 1/4 turn to 1/2 turn further to ensure a better fit of the threads, thereby avoiding over-tightening that could damage the internal threads of the valve. Ball valves ◆ Gate valves and stop valves should not be used for throttling purposes, as this can lead to erosion of the valve plates and sealing surfaces, as well as vibration and leakage, which can damage the valve. ◆ When opening steam valves, do so slowly to remove any condensate water from the pipes; this helps prevent water hammer effects in bellows-type stop valves. Damaged valves and pipes ◆ Large-diameter gate valves, globe valves, and butterfly valves; some are equipped with bypass forged steel gate valves, which serve to balance the pressures on both sides of the valve and thereby reduce the force required to open it. Therefore, when starting to use it, the bypass valve should be opened first, followed by the gradual opening of the main valve. When shutting it down, the three-way ball valve requires the bypass valve to be closed first, after which the main valve can be closed gradually. ◆ After some valves are shut off, as the temperature drops, the valve components contract and minor leaks may occur at the sealing surfaces; in such cases, it is sufficient to tighten the valve slightly after it has been shut off. Operation of automatic valves ◆ Before activating a steam trap, any dirt and impurities in the pipeline must be removed to prevent the water control valve from being clogged, so that the filter valve can function properly. During operation, check the performance of the steam trap; if too much steam is discharged, it indicates that the valve is not functioning properly, while if only water is discharged, it means the valve is working correctly. ◆ Safety valves: Safety valves should be regularly tested for pressure retention, and records and markings regarding the pressure levels should be kept. Before installation, upward-mounted ball valves must pass pressure testing and pressure retention tests successfully. In the past, safety valves were adjusted offline, and production units employed scientific management methods for valve manufacturing. In recent years, some organizations have introduced online regulators for safety valves. These devices consist of mechanical, hydraulic, and electronic components, and their advantage is that they create conditions that are more in line with actual production realities, resulting in more accurate data. They also enable manual self-locking balance regulation of the valves, without disrupting production; there is no need for disassembly or transportation, and this approach increases the rate at which safety valves can be adjusted. The downside is that it can only be used with spring safety valves, and the valve stem must have threads ； For swing check valves, it is necessary to know the average diameter of the valve sealing surface ； It is not possible to clean the safety valve, grind the pressure relief and holding valves, replace parts, or conduct a gas-tightness test. If the hydraulic check valve fails to return to its original position after the safety valve activates, it will cause excessive leakage from the water pump, affecting production; immediate action must be taken to address this issue. The method involves using a hand to lift the safety valve equipped with a wrench, and opening the free-floating ball type steam trap from time to time in order to discharge dirt and other contaminants. ◆ Before activating the pressure reducing valve, open the bypass valve or flushing valve to clean the pipeline; once the pipeline is clean, close the low-temperature check valve and then activate the pressure reducing valve. Operation of other valves: Other valves are operated using electric, electromagnetic, pneumatic, or hydraulic devices to open and close them. Remote control is achieved through instruments, electric switches, etc. Therefore, operators should have a thorough understanding of the structural features and working principles of these valves, be familiar with the operating procedures, and be able to operate them independently, rather than having to carry out emergency handling in case of an accident

Different valves vary, so it’s not possible to establish general guidelines; one must refer to the manufacturer’s instructions, as different manufacturers may provide different specifications