Issues regarding the installation of SIS valves on the discharge pipeline of liquid chlorine storage tanks
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I’ve read several similar posts on the platform, but I still have some questions. I hope experienced users can help clarify them... A few days ago, experts suggested installing certain devices. We are a manufacturer that uses liquid chlorine; there are already DCS cut-off valves on the discharge pipes of the storage tanks. Liquid chlorine is transported through pipes under pressure, without the need for pumps. In the workshop where liquid chlorine is used, there is a dedicated system for vaporizing liquid chlorine, along with complete DCS and SIS systems. If a valve based on SIS is to be used for the storage tanks, then which parameters should it be linked to? The experts said it should be linked to the low liquid level in the tanks. We raised objections at that time and explained the relevant circumstances... After all, the liquid chlorine in the tanks should eventually run out, especially during long periods of shutdown for maintenance... Moreover, if there’s almost no liquid chlorine left in the tanks, what’s the point of having a valve that shuts them off automatically? Or are there other key parameters that would require the SIS valve to shut off the flow of liquid chlorine... :o
Installing SIS valves on storage tanks is primarily aimed at enhancing safety. For toxic and highly hazardous chemicals such as liquid chlorine, the use of a SIS system enables rapid shutdown of the supply in emergency situations, thereby preventing accidental leaks or other dangerous occurrences. Based on the situation you described, a low liquid level interlock for the storage tank may not be appropriate; in most cases, it is indeed desirable to use up all the liquid chlorine. More reasonable chain parameters may include pressure anomalies (too high or too low), temperature anomalies, pH value anomalies, etc., all of which are important factors affecting the safe storage and transportation of liquid chlorine. Additionally, it is also possible to consider installing a leak detection interlock that shuts off the valve immediately upon detecting a leak, in order to prevent the accident from spreading. It is recommended to communicate further with the expert team to determine the most suitable chain parameters based on actual operational and safety requirements. .
Thank you for your reply and clarification. Given the actual production requirements, I haven’t yet found suitable cascade parameters; however, the valves still need to be installed as a last resort to meet inspection requirements :)
I understand your situation. Installing valves can indeed serve as a preventive measure, helping to address potential future safety inspections or changes in regulatory requirements. Even though the most appropriate chaining parameters have not been determined yet, it is recommended to proceed with the installation first, while continuing to discuss and test with experts or security teams to find the best solution. Hope everything goes well! .
Then avoid a chain; use a one-button switch.
We are also a user of liquid chlorine; the storage tanks used for liquid chlorine indeed require a SIS interlock system. An HH level interlock should shut off the DCS feed isolation valve, an HHH interlock should shut off the SIS feed isolation valve, an LL level interlock should shut off the DCS discharge isolation valve, and an LLL interlock should shut off the SIS discharge isolation valve. The HH interlock activates the DCS emergency relief system, while the HHH interlock activates the SIS emergency relief system ； The storage tank itself also needs to be equipped with two sets of pressure relief assemblies consisting of rupture discs and safety valves!
Based on our operating conditions, a low low liquid level doesn’t seem to be very meaningful, but it can be used to interlock with high liquid levels or high pressures