Which Shut Off Valves Should Be Open and Which Closed: A Comprehensive Guide
Introduction
- The correct setting of the globe valve can ensure the safety of the production process, improve the efficiency of the fluid passing through the pipeline, extend the life of the equipment, reduce the harm of the water hammer effect, and meet the requirements of the industry standard.
- If the globe valve is not installed correctly, it will first endanger production safety, then reduce production efficiency, and finally lead to economic losses.
- The purpose of this guide is to show the reader how to maintain the correct condition of the valve, especially opening and closing
Understanding Shut Off Valves
A. Definition and Function
- The globe valve is a valve that adjusts or shuts off the flow of fluid by moving the Disc or Plug vertically, completely closing the fluid, or completely opening the flow adjustment。
- When you are maintaining equipment and pipes, use the stop valve to completely isolate the medium for maintenance, or in the event of an emergency, prevent further disorderly flow of the medium。
B. Common Types of Shut Off Valves
- The globe valve is divided into three parts according to the structural characteristics Angle Globe Valve，Y-Pattern Globe Valve，Straight Globe Valve
- Angle Globe Valve：the valve body is L-shaped，reduces elbow requirements and can be used directly in pipe steering;Y-Pattern Globe Valve:The valve body channel and the pipeline axis are 45°~60° oblique Angle, streamlined design.Suitable for asphalt, heavy oil;Straight Globe Valve:Import and export coaxial.Steam system, high pressure water supply pipeline.
Valve Settings in Different Systems
A. Plumbing Systems
- Water Supply Lines: When there is water leakage or emergency, and when going out need to close the valve, the rest of the time can be opened normally valve.
- Drainage Systems: Check valves need to be set up in the drainage system to prevent the backflow of sewage to contaminate the medium, but also to avoid odors and clogging.
B. Heating and Cooling Systems
- Boiler Systems: The main steam valve is fully opened after the heating pipe, and then the water supply valve can be automatically or manually switched to the water level, and the blowdown valve should be operated under low load.
- Air Conditioning Systems: Install an expansion valve at the inlet of the evaporator and adjust the expansion valve with a pressure gauge or thermometer
C. Industrial Applications
- Chemical Processing Plants: First of all, consider the compatibility of the chemical liquid and the valve material to avoid chemical reactions. Second, consider the sealing grade and anti-cross contamination.
- Oil and Gas Pipelines: Different valves should be selected according to different scenarios of pipeline use. For example, submarine oil pipelines are recommended to choose all-welded ball valves to avoid the risk of leakage.
Emergency Situations
A. Water Leaks
- When a leak occurs, first close the valve closest to the upstream of the leak and the valve closest to the downstream. If the leak still occurs, close the main pipeline valve.
- If it is a pipeline leak, you can choose a pipeline repair device for emergency repair, if it is a valve leak, it is immediately replaced。
B. Gas Leaks
- When a gas leak occurs, first close the main pipeline valve, place the gas in the pipeline to further spread, and then close the upstream and downstream valves at the leak until they are all closed.
- Operators shall carry out personal safety protection, evacuate non-operators, initiate emergency plans and organize on-site treatment teams.
C. Fire Emergencies
- The globe valve is both a “switch” and a “fuse” in the fire extinguishing system, and its reasonable setting should follow the principle of “accurate partition, fast response, and reliable redundancy”. The combination of automated control and manual intervention minimizes the risk of fire spread while avoiding system failure due to valve failure.
- Maintain valve regularly to keep valve in full working condition。
Maintenance and Inspection
A. Regular Maintenance Tasks
| Maintenance cycle | Critical maintenance task |
| Daily | 1. Visual inspection of leakage (stem, flange） 2. Manual valve slight rotation test |
| Weekly | 1. Soap water to detect gas sealing 2. Clean up the surrounding environment of the valve |
| Month | 1. Remove and check the packing letter or bellows to seal 2. Manual test of the safety valve |
| Each Season | 1. Calibrate the travel and flow error of the regulating valve 2. Clean the filter and the drain valve |
| Year | 1. Complete valve (corrosion, crack) 2. Pressure seal test |
| Special Situation | 1. Check for neutral / associated heat after extreme weather 2. Rinse and verify after the system modification |
| Record | 1. Maintenance data entry (failure rate analysis) 2. Dynamic adjustment of spare parts inventory 3. Training on emergency operation procedures |
B. Inspection Checklists
Problem of leakage
Stem or flange leakage: due to aging packing or loose bolts, it is necessary to tighten the gland or replace the corrosion resistant packing (such as graphite). When the seat seal fails, grind the sealing surface and install a filter to intercept impurities. The steam leakage of the safety valve needs to be ground offline or the spring replaced.
Safety Precautions
A. Personal Protective Equipment (PPE)
Chemical resistant gloves (e.g. Nitrile/neoprene) – resistant to contact with corrosive media;Goggles/full cover – prevent splashing liquid, particulate damage to the eyes;Anti-smash and anti-puncture safety shoes – prevent heavy objects from falling or sharp objects from stabbing;Gas mask/respirator (for toxic gases) – with suitable filter box;Flame-retardant protective clothing – protects against burns in high temperature or flammable environments.
B. System Depressurization
- First close the upstream and downstream valves, then open the pressure relief valve/exhaust valve to relieve the pressure in stages, then drain the residual liquid/residual gas, and finally confirm the pressure value.
C. Lockout-Tagout Procedures
- Lock the valve and hang a “Do not operate” warning sign to prevent misopening and avoid what danger。
Conclusion
The correct setting of the globe valve requires: ① material adaptation (such as cast steel for steam, Hastelloy for chemical industry); ② Main valve near the risk point (boiler, fire division); ③ Double valve isolation + pressure relief before maintenance; ④ Automatic interlock + manual redundancy in high-risk scenarios; ⑤ Check the tightness regularly according to API/ASME. Illegal operation (working with pressure, single valve isolation) is liable to leak or burst. When in doubt, consult engineers and refer to NFPA/ISO standards to ensure safety and efficiency.