News
News
Solenoid valves and valve terminals boast robust designs, powered by an electromagnetic field around a movable core known as the armature. This setup enables precise regulation of gas and liquid flow within systems. Solenoid valves VOFC and VOFD, compliant with the latest SIL classification, ensure a failure probability rate of 2.41 E-4 and a safe failure fraction of 75%. Studies indicate a maximum of one faulty operation per 2,410 cycles when operated correctly.
However, despite their reliability, solenoid valves are susceptible to complexities inherent in mechanical products. Understanding and addressing these issues promptly can prolong device lifespan and maintain peak performance. Here are common challenges to watch for:
If a pneumatic valve suddenly stops functioning, rust accumulation could be the culprit. This inhibits the valve from returning to its failsafe position when power is cut. Contamination of stainless steel may occur during grinding, polishing, or machining, embedding carbon steel in 430 stainless steel plungers without proper cleaning or dressing. Upon dismantling, visible signs of rust on the armature assembly within the core tube (solenoid valve mounting spot) may be observed.
To prevent this issue, avoid using cleaning chemicals that can get trapped in crevices, solenoid tube cores, and dead-end lines. Instead, clean equipment like process pipework with water. Consider installing a magnetic descaler unit upstream for additional protection.
By addressing maintenance needs promptly and employing preventive measures, you can mitigate potential issues and ensure the longevity and reliable performance of solenoid valves.
A coil can malfunction or remain inactive even after the power supply is disconnected due to various factors:
- Incorrect voltage application.
- High gas or liquid temperatures.
- Improper installation with the solenoid not in a vertical upright position.
- Inadequate heat dissipation through ventilation.
- Spikes or electrical surges.
- Damage to the tube or armature.
To address this issue, replace the faulty components and investigate potential causes of short circuits. Install the correct type of coil compatible with the voltage/frequency requirements. Inspect for moisture presence and clean if necessary. If the solenoid coil is completely burnt, replacement is necessary.
When operating, a solenoid valve might produce excessive noise during its opening and closing cycles. This noise can manifest as buzzing or thumping sounds, often caused by hydraulic shocks, humming, or high differential pressure leading to pulsations in the pressure line.
To address this, consider using a slower valve, such as a ball valve. Increasing the diameter of the piping can also help reduce the velocity of the media, thereby minimizing noise as inlet pressure decreases. Installing a water hammer arrestor can further dampen these sounds. Additionally, maintaining proper flow and fluid pressure is essential, and replacing the alternating current frequency with a rectifier coil may be necessary.
Common issues like leakage, valve failure, damaged seals, faulty power supplies, and the presence of dirt particles can lead to solenoid valve complications if left unaddressed. Fortunately, troubleshooting these problems is relatively straightforward due to the valve's simple design with few parts. Vigilance and prompt action are key to preventing significant malfunctions over time.
Slide gates and diverter valves utilizing pneumatic actuators (air cylinders) necessitate appropriately matched pneumatic solenoid valves. These solenoid valves regulate the airflow to the ports of the air cylinder, enabling the opening or closing of a slide gate or the switching of a diverter. Solenoid valves come in various configurations based on factors such as port size, flow factor, and application environment.
As a general guideline, a single coil solenoid valve is recommended for slide gates, while a double coil solenoid valve is preferable for diverter valves. When a single coil solenoid valve is linked to a slide gate, it is configured to open the gate when energized and close it when de-energized. This setup ensures that the slide gate closes automatically in the event of power loss, a feature known as "fail closed."
On the other hand, a double coil solenoid requires a momentary electrical signal to reposition the blade. Once positioned, the blade remains in place until the opposite coil receives another signal. In the event of a power outage, the blade maintains its last position, ensuring continuity of material flow. This functionality is referred to as "fail last position."
Efficient air flow is essential for achieving optimal performance in pneumatic systems. Each solenoid valve is rated for flow in liters per minute or by a flow coefficient (Cv) or flow factor (Kv). It's crucial that the rated airflow of the solenoid valve aligns with the air demand requirements of the bulk handling valve manufacturer for the air cylinder. When purchasing solenoids locally, ensure that the airflow and other specifications perfectly match those specified by the valve manufacturer. Using a solenoid valve with lower flow capacity can lead to performance issues such as chattering and sluggish blade actuation.
Solenoid valves come in various environmental ratings to suit system requirements. In North America, it's essential to consider UL listings and NEMA ratings for solenoid valve coils to ensure suitability for the operating environment. In the European Union, compliance with ATEX standards is necessary for both the solenoid valve body and coils when used in hazardous locations. Other regions may adhere to internationally recognized standards like IECEx or require country-specific ratings such as GOST-R. Additionally, the Ingress Protection (IP) rating, indicating the level of protection against dust and water ingress, should be taken into account.
Common symptoms of solenoid valve issues in pneumatic systems include inconsistent actuator movement, air leaks, and difficulty in reaching set pressures, which can often be resolved by checking for debris, ensuring proper electrical connections, and replacing worn or damaged seals. When utilizing an air flow solenoid valve to activate a gate or diverter, it's important to account for potential power failures, which often result in the loss of plant air. To mitigate this risk and ensure sufficient compressed air is available to close a gate in such scenarios, customers may consider incorporating an air fail-safe device. This device acts as a reserve air tank and comes equipped with an air filter, pressure gauge, check valve, and fittings. The size of the tank should correspond to the volume requirements of the air cylinder powering the gate. The check valve guarantees that there is adequate air in the reserve tank to close the blade once. The air tank can be mounted remotely, up to 25 feet from the gate. Investing in an air fail-safe serves as a cost-effective insurance policy, particularly when it's crucial to halt material flow promptly during an unexpected loss of plant air.
