The frozen saline ball-type cut-off valve gets stuck frequently

There is a quality issue with the valve; replace it directly. Try our company’s shut-off valves

Where exactly is the quality issue? Is it the material or the design style? What do you think about the selection process? What are the special designs of your company’s cut-off valves for chilled brine?

Add me on WeChat to chat; the phone number is on the left

Specifically, it’s either impossible to open or impossible to close; in most cases, it’s impossible to open. When frozen brine reaches the valve, ice forms when the salt concentration is below the eutectic concentration and the temperature is below the salt precipitation temperature but above the eutectic temperature. It must have frozen.

Nothing was to the point except for the 5th floor. In some cases, whether it’s FC or FO, there is a problem with the valve getting stuck when trying to open or close it… The specific cause has been identified: the PTFE gaskets used in the valve cores are of domestic manufacture, lack toughness, are brittle, which leads to saltwater leakage. Once saltwater leaks out, the water evaporates, and the salt particles cause the valve stem to get stuck. In some cases, the valves are installed horizontally, and even end up inside the cylinder, which further causes sticking issues. Imported PTFE gaskets have been submitted at present. The following is my summary of cut-off valve fault diagnosis. This method cannot address the root cause but only provides temporary relief. The fundamental solution is to replace the gasket or clean it. Fault diagnosis of cut-off valve (broken01): 1. On-site, verify that production is not affected; check the automatic operation status of the valve, ensure the gas supply pressure is at 0.4 MPa, there is no leakage, and the gas source is free of water, along with conducting other visual inspections. 2. Use on-site buttons for manual switching to observe the valve’s operation. 3. If the valve operates normally, with quick switching and proper positioning, check the solenoid valve and DO signal. 4. If the valve cannot move to its full position unilaterally or moves slowly, then: 4.1 The valve can be opened fully quickly, but it cannot be closed completely, or the closing speed is very slow. 4.1.1 The valve is of FC type; it does not close when there is no air supply, and it operates in the air-open mode. This type of valve opens under air pressure and closes due to the pull of a spring. It might be that the air pressure inside the cylinder cannot be discharged quickly, such as due to a blocked exhaust hole in the silencer, or a blockage in the air passage of the solenoid valve. After ruling out this possibility, it is usually due to insufficient spring tension, and the spring needs to be replaced ； 4.1.2 The valve is of the FO type; it does not open when there is air supply, and it is of the air-shut type. This type of valve closes under air pressure and opens due to the force of a spring. In this case, increasing the air supply pressure slightly may help to see if there is an improvement. It is usually due to the valve body getting stuck; increase the air pressure. If there is a noticeable improvement, move it several more times, and this will generally resolve the issue. If the air supply pressure is increased, there is no improvement: the valve still cannot close fully or does so slowly. However, when the air pressure is released, it opens completely quickly. This could be due to a damaged seal in the cylinder allowing air leakage, or severe sticking of the valve body. 4.2 The valve can be closed fully quickly, but it cannot be opened completely, or the opening speed is very slow. 4.2.1 The valve is of FC type; it does not close when there is no air supply, and it operates in the air-open mode. This type of valve opens under air pressure and closes due to the pull of a spring. In this case, increasing the air supply pressure slightly may help to see if there is an improvement. It is usually due to the valve body getting stuck; increase the air pressure. If there is a noticeable improvement, move it several more times, and this will generally resolve the issue. If the air supply pressure is increased, there is no improvement: the valve still cannot close properly or does so slowly. However, it can close quickly when the air pressure is released; this may be due to a damaged seal in the cylinder allowing air leakage, or severe sticking of the valve body. 4.2.2 The valve is of the FO type; it does not open when there is air supply, and it is of the air-shut type. This type of valve closes under air pressure and opens due to the force of a spring. It might be that the air pressure inside the cylinder cannot be discharged quickly, such as due to a blocked exhaust hole in the silencer, or a blockage in the air passage of the solenoid valve. After ruling out this possibility, it is usually due to insufficient spring tension, and the spring needs to be replaced ； The valve cannot move to its full position on its own; generally, the valve body is not severely stuck and the solenoid valve is not damaged either, so it’s likely that the issue can be resolved smoothly. 5. The valve openings and closings are very slow and do not reach the full position. If the valve operated by manual buttons responds, and the switches can be moved, the action is slow and it cannot reach the full travel distance. It is usually due to long-term disuse, which causes severe sticking of the valve body. In such cases, one option is to switch to using a handwheel to turn it several times, or directly connect the air supply to the cylinder to see if that improves the situation. If there is no improvement, the valve body needs to be disassembled to inspect the valve core and sealing surfaces, followed by cleaning and lubrication. 6. The valve switches do not respond at all. First, check the manual/automatic switch to see if it is in automatic mode. Control whether the video signal is output effectively, such as confirming video operations. The solenoid coil can be removed, and a non-magnetic screwdriver can be used to check whether there is any attraction on the coil during switching. Alternatively, operate the switch on the computer; if audible sounds of the coil closing and opening can be heard on-site, then the coil is functioning properly. After confirming that the coil is functioning properly, check the solenoid valve. During the coil switching process, check whether exhaust is coming from the exhaust port; if there is exhaust, the solenoid valve is functioning properly. Alternatively, disconnect the solenoid valve from its valve body and check by turning the coil on and off to see if the valve operates synchronously. After confirming that the solenoid valve is also functioning properly, it is usually due to blockage in the valve body; proceed with the subsequent steps as described in point 5.

The presence of salt can cause blockages in the gas pathways and solenoid valves, which is very problematic. If air seeps into the pneumatic device through the packing chamber, it’s not just a packing issue; it’s likely that the poor precision of the packing chamber’s construction, excessive gaps, and insufficient smoothness of the valve stem are all factors that can lead to the ball valve sticking. Based on what you’ve described, it should be the case that most ball valves cannot be closed. If a ball valve is in the closed position and its seal is intact, then the fluid won’t get into the packing chamber; unless there is an internal leak in the valve itself, in which case it will not be able to be opened or closed. Another possibility is that you are using a floating ball valve, which has only single-sided sealing, which is why fluid can leak into the packing chamber. If the problem persists even after replacing the packing in the valve, it is recommended to switch to a fixed ball valve with double-sided sealing; this should resolve the issue. Of course, good filler should still be used.

The temperature and pressure range for which pure PTFE seals can withstand stress is limited. To accommodate different temperature and pressure conditions, various substances are added to PTFE to improve its performance for use in such varied environments. Therefore, when selecting a valve, it is necessary to take into account the temperature and pressure of the operating conditions, as well as the properties of the medium used, in order to make an appropriate choice. Simple PTFE gaskets are not a panacea.