Back in May 2020 and January 2021, I posted the first two parts of this three-part series on the hazards of Liquid Nitrogen. These articles were prompted by the OSHA and State Fire Marshal cases involving fatalities at cattle and human sperm bank businesses. Then, in January of this year, we had the GA Food plant LN2 incident, where six (6) workers lost their lives during a release of N2. So, needless to say, these two articles got a lot of attention, and yesterday, after OSHA’s news release of their nearly $1M in citations to the GA business and its sanitation contractor and installer, I was reminded by a friend that I never posted Part III – Use and Handling. So here we have the “code requirements” on the use and handling of LN2. This section of the code is broken down into these specific requirements:
- Cryogenic fluid systems
- Pipng
- Indoor use
- Outdoor use
- Filling and dispensing
- Vehicle loading and unloading areas
| 5505.1.1 Cryogenic fluid systems. Cryogenic fluid systems shall be suitable for the use intended and designed by persons competent in such design. Equipment, machinery and processes shall be listed or approved. |
All system components must be either LISTED or specifically approved for use with LN2.
| 5505.1.2 Piping systems Piping, tubing, valves, and joints and fittings conveying cryogenic fluids shall be installed in accordance with the material-specific provisions of Section 5501.1 and Sections 5505.1.2.1 through 5505.1.2.6. 5505.1.2.1 Design and construction Piping systems shall be suitable for the use intended through the FULL RANGE OF PRESSURE AND TEMPERATURE to which they will be subjected. Piping systems shall be designed and constructed to provide ADEQUATE ALLOWANCE FOR EXPANSION, CONTRACTION, VIBRATION, SETTLEMENT, AND FIRE EXPOSURE. |
A competent designer MUST show that ALL of these elements have been satisfied.
| 5505.1.2.2 Joints Joints on container piping and tubing shall be threaded, welded, silver brazed, or flanged. |
Joints represent potential weak points in a system if they are not properly designed and constructed. Friction joints are NOT allowed on liquid cryo piping.
| 5505.1.2.3 Valves and accessory equipment Valves and accessory equipment shall be suitable for the intended use at the temperatures of the application and shall be designed and constructed to withstand the maximum pressure at the minimum temperature to which they will be subjected. |
This sets the basic criterion for approval, which requires valves and any accessory equipment to be able to withstand the MINIMUM TEMPERATURE AT THE HIGHEST OPERATING PRESSURE. This will ensure that the valves can withstand the most critical forces to which they may be subjected during normal operation.
| 5505.1.2.3.1 Shutoff valves on containers. Shutoff valves shall be provided on ALL CONTAINER CONNECTIONS except for pressure relief devices. Shutoff valves shall be provided with access thereto and located AS CLOSE AS PRACTICAL to the container. 5505.1.2.3.2 Shutoff valves on piping. Shutoff valves shall be installed in piping containing cryogenic fluids where needed to limit the volume of liquid discharged in the event of piping or equipment failure. Pressure relief valves shall be installed where liquid is capable of being trapped between shutoff valves in the piping system (see Section 5503.2). |
This section requires shutoff valves on all container connections. This allows isolation of the container to prevent a large release. It is critical that shutoff valves NOT be placed before or after pressure relief devices.
NOTE: Although I have written numerous articles explaining how this can be done – MOST organizations do not have the operational discipline to manage a Car-Seal program at the level it requires to ensure we do NOT defeat a PRD.
Shutoff valves are required at STRATEGIC LOCATIONS within the piping systems where a large release may be possible. Because piping systems vary so much, there is no single solution based on either use or process layouts. There is an additional requirement for pressure relief devices (i.e. hydrostatic relief valves) to be installed where shutoff of the flow could potentially cause a buildup of pressure between the source and the shutoff valve (i.e. blocked-in liquid scenario).
| 5505.1.2.4 Physical protection and support Piping systems shall be supported and protected from physical damage. Piping passing through walls shall be protected from mechanical damage. |
This requires a level of protection from physical and other damage where piping is either exposed or passes through elements, such as walls and floors, that are subject to movement. These requirements, along with the others, are intended to increase the reliability of the piping and associated processes.
| 5505.1.2.5 Corrosion protection Above-ground piping that is subject to corrosion because of exposure to corrosive atmospheres, shall be constructed of materials to resist the corrosive environment or otherwise protected against corrosion. Below-ground piping shall be protected against corrosion. |
A possible failure mode of piping is the weakening of the piping system caused by external corrosion. The extent of corrosion protection required will depend on the piping material used, the particular climate, or, in the case of the underground installations, the soil condition and content of the soil. In some areas, this may be a significant problem whereas in others it may not. Corrosion-resistant construction materials are the preferred means of managing this risk.
| 5505.1.2.6 Testing. Piping systems shall be tested and proven free of leaks after the installation as required by the standards to which they were designed and constructed. Test pressures shall be not less than 150 percent of the maximum allowable working pressure where hydraulic testing is conducted or 110 percent where testing is conducted pneumatically. |
I think I have beaten this horse long enough. I counted 17 articles over the past 15 years on the ASME B31 series of piping RAGAGEPs, and discussing their construction requirements! This section sets the testing criteria for either a hydraulic test or a pneumatic test.
| 5505.2 Indoor use Indoor use of cryogenic fluids shall comply with the material-specific provisions of Section 5501.1. 5505.3 Outdoor use Outdoor use of cryogenic fluids shall comply with the material specific provisions of Sections 5501.1, 5505.3.1, and 5505.3.2. |
The code does not provide detail on the specifics of indoor use. That is contained in NFPA 55 which I will discuss in PART IV.
| 5505.3.1 Separation Distances from lot lines, buildings, and exposure hazards shall comply with Section 5504.3 and the material-specific provisions of Section 5501.1. |
Because use is more hazardous than storage, the basic separation requirements found in Tables 5504.3.1.1 and 5504.3.1.2.1 would apply in addition to any of the restrictions found in the referenced standards in Section 5501.1.
| 5505.3.2 Emergency shutoff valves Manual or automatic EMERGENCY SHUTOFF VALVES shall be provided to shut off the cryogenic fluid supply in case of an emergency. An EMERGENCY SHUTOFF VALVE shall be located at the source of supply AND at the point where the system enters the building. |
This section establishes the requirement that emergency shutoff valves be provided and readily available during an emergency for on-site personnel or local emergency response personnel. Essentially, the ability must exist to BOTH shut down the cryogen supply and shut off the supply at the point where it enters the building. Pressure relief devices will be necessary where liquid could be trapped between the source and the emergency shutoff valve at the entrance to the building (see the commentaries to the definitions of “Emergency shutoff valve,” “Emergency shutoff valve, manual” and “Emergency shutoff valve, automatic” in Section 202 and to Section 5505.1.2.3.2 for further information).
| 5505.4 Filling and dispensing Filling and dispensing of cryogenic fluids shall comply with Sections 5505.4.1 through 5505.4.3. |
Filling and dispensing can cause fluid release due to the connections and disconnections involved in these processes. This will address the LOCATION AND CONSTRUCTION of dispensing areas, the approval of loading and unloading activities, and controls on the amount of fluids dispensed into stationary tanks. All of these requirements focus on preventing an unwanted fluid release and possible physical damage or personal injury.
| 5505.4.1 Dispensing areas Dispensing of cryogenic fluids with PHYSICAL OR HEALTH HAZARDS shall be conducted in approved locations. Dispensing indoors shall be conducted in areas constructed in accordance with the International Building Code. |
This section focuses on the dispensing of fluids with physical or health hazard ratings, such as flammability or toxicity. This section also references the IBC for construction requirements, primarily to determine whether a Group H occupancy is required. This specifically relates to whether the MAQs of Nitrogen have been exceeded.
| 5505.4.1.1 Ventilation. Indoor areas where cryogenic fluids are dispensed shall be ventilated in accordance with the requirements of the International Mechanical Code in a manner that captures any vapor at the point of generation. Exception: Cryogenic fluids that can be demonstrated not to create harmful vapors. 5505.4.1.2 Piping systems Piping systems utilized for filling or dispensing of cryogenic fluids shall be designed and constructed in accordance with Section 5505.1.2. |
In addition to the basic ventilation requirements for the indoor storage of cryogens, this section requires that vapors be captured at the source; therefore, special ventilation would be required at the point of fill for the dispensing operation. These ventilation requirements appear to be for normal operation rather than emergency operation. There is an exception if the amount and type of gas would not be sufficient to create a hazardous situation.
| 5505.4.2 Vehicle loading and unloading areas Loading or unloading areas shall be conducted in an approved manner in accordance with the standards referenced in Section 5501.1. |
Generally, loading, unloading, dispensing, and filling operations have a high potential for creating a hazardous situation if not properly conducted. This section ensures that the areas are constructed and operated as required by approved standards.
| 5505.4.3 Limit controls Limit controls shall be provided to prevent overfilling of stationary containers during filling operations. |
Overfilling cryo tanks is a SERIOUS hazard, so the code REQUIRES Hi-LEVEL controls to prevent overfilling. In my mind, a control is an interlock that PREVENTS the overfilling; however, I have had some crazy discussions where the AHJ required only a hi-level alarm. I design for BOTH: a high-level alarm at 80-83% and a Hi-Hi Level Alarm and Interlock at 85%.
| 5505.5 Handling Handling of cryogenic containers shall comply with Sections 5505.5.1 and 5505.5.2. 5505.5.1 Carts and trucks Cryogenic containers shall be moved using an approved method. Where cryogenic containers are moved by hand cart, hand truck, or other mobile device, such carts, trucks or devices shall be designed for the secure movement of the container. |
This section focuses on portable containers and the prevention of fluid leaks. Carts and trucks used to transport cryogenic containers shall be designed to provide a stable base for the transported commodities. They shall include a means of restraining the containers to prevent accidental dislodgement. If carts, hand trucks, or similar methods are chosen, they must be able to safely and securely transport the containers. This includes restraining containers during transport.
| 5505.5.2 Closed containers Pressurized containers shall be transported in a closed condition. Containers designed for use at atmospheric conditions shall be transported with appropriate loose-fitting covers in place to prevent spillage. |
This section recognizes that pressure-containing containers can be moved safely when properly closed. Containers designed for use at standard atmospheric pressure require only an appropriate cover to prevent fluid from escaping.