In the world of hazardous materials, evacuating them from their primary (and secondary) containment system plays a KEY role in performing maintenance/servicing on the system SAFELY. For example, opening a process/system that contains hazardous materials FIRST has to be evacuated of that hazardous material, and this evacuation to a “safe place” should be done through a Manual “Spring-Loaded-CLOSED” valve (e.g., a deadman valve). And this valve just may save a life?
I have participated in the development of these energy isolations and “evacuations” hundreds of times over my career. From Day 1, I was taught that these evacuations are done through a Manual “Spring-Loaded-CLOSED” valve (e.g., a deadman valve). These valves got their slang name from the Railroads back in the 1880’s, as the design found its way into the locomotives’ controls. Should something happen to the engineer, the throttle would spring back to the OFF position and stop the train, street car, and even elevators.
A recent video was shared with me that is a perfect example of when a deadman valve could have prevented a tragic outcome. Had this evacuation been done through a deadman valve, the worker simply would have let go off the spring-loaded handle, and the valve would have closed very quickly.
Manual “Spring-Loaded-CLOSED” valves (e.g., deadman valves) are considered to be a PASSIVE engineering control; as such, they require NO ENERGY or intervention to perform their safety function. This feature is excellent when designed, installed, OPERATED, and appropriately maintained.
But like any safety device, we have seen “human ingenuity” DEFEAT these safety valves. It’s sort of like wearing your fall protection because you’re required, but not tying off! We have seen these valves secured in their OPEN positions with duct tape, baling wire, rope, coat hangers, nails, etc. Sure, the valve is being used as “required,” but it is useless once its design is DEFEATED.
These valves have begun to find their way into codes and standards.
The IFC, CHAPTER 50 HAZARDOUS MATERIALS—GENERAL PROVISIONS includes fail-safe valves in its basic piping design for hazardous materials.
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5003.2.2.1 Design and construction. Piping, tubing, valves, fittings and related components used for hazardous materials shall be in accordance with the following: 1. Piping, tubing, valves, fittings and related components shall be designed and fabricated from materials that are compatible with the material to be contained and shall be of adequate strength and durability to withstand the pressure, structural and seismic stress and exposure to which they are subject. 2. Piping and tubing shall be identified in accordance with ASME A13.1 to indicate the material conveyed. 3. Manual valves or automatic remotely activated fail-safe emergency shutoff valves shall be installed on supply piping and tubing and provided with ready access at the following locations: 3.1. The point of use. 3.2. The tank, cylinder or bulk source. 4. Manual emergency shutoff valves and controls for remotely activated emergency shutoff valves shall be clearly visible, provided with ready access and identified in an approved manner. 5. Backflow prevention or check valves shall be provided where the backflow of hazardous materials could create a hazardous condition or cause the unauthorized discharge of hazardous materials. Exceptions: 1. Piping for inlet connections designed to prevent backflow. 2. Piping for pressure relief devices. |
The IFC list the use of these valves in an “exception” found in CHAPTER 60 HIGHLY TOXIC AND TOXIC MATERIALS.
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6004.2.2.7 Treatment systems. The exhaust ventilation from gas cabinets, exhausted enclosures and gas rooms, and local exhaust systems required in Sections Exceptions: 1. Highly toxic and toxic gases—storage. A treatment system is not required for cylinders, containers and tanks in storage where all of the following controls are provided: 1.1. Valve outlets are equipped with gastight outlet plugs or caps. 1.2. Handwheel-operated valves have handles secured to prevent movement. 1.3. Approved containment vessels or containment systems are provided in accordance with Section 6004.2.2.3. 2. Toxic gases—use. Treatment systems are not required for toxic gases supplied by cylinders or portable tanks not exceeding 1,700 pounds (772 kg) water capacity where a gas detection system complying with Section 6004.2.2.10 and listed or approved automatic-closing fail-safe valves are provided. The gas detection system shall have a sensing interval not exceeding 5 minutes. Automatic-closing fail-safe valves shall be located immediately adjacent to cylinder valves and shall close when gas is detected at the permissible exposure limit (PEL) by a gas sensor monitoring the exhaust system at the point of discharge from the gas cabinet, exhausted enclosure, ventilated enclosure or gas room. |
PLEASE take note that this “exception” is NOT a “passive system” as the automatic closing fail-safe valves are actuated by a gas detection system, making them an “active system”.
But it is the use of the Manual “Spring-Loaded-CLOSED” valves (e.g., deadman valves) that I want to shine light onto. These valves are a MUST when transferring a hazardous material from an engineered containment system via a “temporary” arrangement. Things can go wrong in these “temporary” arrangements and when they do, their consequences can be severe. The simple ability to let go of a valve handle to STOP flow to this “temporary” arrangement and walk/run away can save a life.