Operating conditions in chemical plants that require dual valves
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1. For equipment used to handle hydrocarbons, toxic gases, and chemically hazardous substances, when the operating pressure or temperature exceeds certain values, double valves should be installed on the pipelines connected to such equipment. 2. Dual valves should be installed for equipment that needs to be shut off for cleaning or maintenance during the operation of the unit. 3. Double valves can be used for heat exchangers that may experience failures due to salt deposition, severe scaling, corrosion, or other reasons. 4. A dual valve is not required for the bypass of control valves; a dual valve can be used only when severe corrosion or scaling is suspected, or when failure might occur for other reasons and manual adjustment of the bypass valve over an extended period is necessary. 5. All shut-offs on the hydrogen pipeline, including pressure gauge valves and sampling valves, shall employ dual valves. 6. For liquid butane and lighter hydrocarbons, dual valves must be used for sampling and purging. 7. All pipelines on the liquid chlorine storage tank shall be equipped with double valves. 8. In certain intermittent chemical manufacturing processes, if a substance might leak in during the reaction, it could lead to explosions, fires, or serious quality issues; therefore, double valves should be installed on the pipelines carrying such media, along with a vent valve on the pipeline between the two valves. 9. Double valves should generally be installed on the blowdown pipes of industrial boilers. 10. In the design of high-pressure pipelines, dual valves must be installed; this is necessary regardless of the pipeline diameter, in order to prevent leakage of the medium. The valves should be installed closely together to reduce the number of fittings and facilitate operation. 11. When the process system pipelines are connected to the company’s utility pipelines, dual valves must be installed, with a drain valve added between the two valves. 12. Sampling valve switches are used frequently and are prone to damage; therefore, two valves are generally installed on the sampling tube – one as a shut-off valve and the other for sampling. 13. For large-diameter pipes, which are difficult to clean thoroughly, a drain pipe at the lowest point should be installed, along with a double valve or a single valve followed by a blind flange. 14. The drain pipes of towers and vessels should be equipped with double valves during normal operation. 15. When discharging hazardous materials, double valves should be installed.
1. Equipment used to handle hydrocarbons, toxic gases, and chemically hazardous substances under certain operating pressures or temperatures requires double valves to be installed on its connection pipelines. 2. Devices that need to be shut down for cleaning or maintenance should be equipped with double valves. 3. Heat exchangers prone to failure (such as salt deposition, scaling, corrosion, etc.) can be equipped with dual valves. 4. A bypass for the control valve generally does not require a dual valve, unless manual adjustment is needed for an extended period due to a malfunction. 5. Double valves should be used at all isolation points on the hydrogen pipeline, including pressure gauges and sampling valves. 6. Double valves must be used for sampling and discharge of liquid butane and lighter hydrocarbons. 7. All pipelines of the liquid chlorine storage tank shall be equipped with double valves. 8. In batch chemical production, where there is a risk of hazardous material leakage, the relevant pipelines should be equipped with double valves as well as vent valves. 9. Industrial boiler drain pipes should be equipped with double valves. 10. High-pressure pipelines should be equipped with double valves to prevent leaks, and the double valves should be connected tightly. 11. Double valves and drain valves shall be installed at the connections between the process system pipelines and the utility pipelines. 12. Two valves should be installed on the sampling tube, as it is prone to damage due to frequent use. 13. Large-diameter pipes should be equipped with a low-point drain pipe, along with a double-valve or single-valve arrangement along with a blind flange. 14. Drain pipes for towers and containers should be equipped with double valves during normal operation. 15. Double valves should be used to drain hazardous materials completely. .