Cryogenic liquids potential hazards

The potential hazard associated with expansion of liquid to gas is substantial for hydrogen, as it is for other cryogenic fluids. Careful attention must be given to the location of relief devices in liquid hydrogen handling systems. 

Cryogenic liquids have large expansion ratios, some as much as 900 or more to 1 (see Figure 4.22). Because of this expansion ratio, if the cryogenic liquid is flammable or toxic, these hazards are intensified because of the potential for large gas cloud production from a small amount of liquid. As the size of a leak increases, so does the size of the vapor cloud. 

This chapter describes many of the potential hazards associated with compressed gases and cryogenic liquids, and presents some of the requirements and guidelines for their safe handling, use, and transportation. However, the information is not complete with respect to all... 

Examples of gases commonly handled as cryogenic liquids include oxygen, nitrogen, argon, neon, hydrogen, and helium. Liquefied natural gas (LNG), liquid methane, and liquid carbon monoxide are also handled as cryogenic liquids. The consequences from extreme cold and other potential hazards that accompany these products are ... 

Because of the potential hazards resulting from the extremely low temperatures of cryogenic liquids, all personnel using them must be properly trained in the use of specialized equipment designed for the safe storage, transfer, and handling of these products. 

Compressed gases and cryogenic liquids in containers pose certain potential hazards when being transported. Containers can leak or be damaged in transport. Hazards can be created from the containers themselves when subject to impact from a vehicle accident, when the container is not properly secured in a vehicle, or when the product being transported is released from its container exposing people or the environment to the hazardous materials. 

Due to the potentially hazardous nature of many compressed gases and cryogenic liquids during manufacture, storage, transport, and use, there is an essential need for effective, informed, and timely emergency response ... 

As with cylinder valve connection philosophy, the intent of standardizing transfer connections is to minimize the proliferation of connection types for the same application and to avoid potentially hazardous cross-connections. Standard transfer connections for the applications described above consist of a fixed-end coimec-tor at the termination point, a hose nut, a head-piece, and, in the case of cryogenic liquids, a gasket. 

More detailed information is available in CGA P-14, Accident Prevention in Oxygen-Rich and Oxygen-Deficient Atmospheres [12], and CGA P-12, Safe Handling of Cryogenic Liquids. [10] The Compressed Gas Association also publishes a brief safety bulletin, CGA SB-2, Oxygen Deficient Atmospheres which can serve as a means to emphasize to personnel the potential seriousness of this invisible hazard. 

The increase in the size and production capacity of air separation plants, has led to a growing capacity of cryogenic liquid storage installations at production sites. Therefore, considering the potential hazards associated with liquid products has become a fundamental issue to address, together with the estimation of the effects of a major release of liquid on the local environment, and the development of preventive measures. 

OCCUPATIONAL SAFETY NOTE LNG Is a cryogenic material and presents a potential safety hazard due both to the extremely cold temperature of Its liquid and the flammability of Its vapor. Personnel Inspecting such systems should exercise utmost caution Including the wearing of proper eye protection, gloves and clothing. 

---