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Ames Procedural
Requirements

APR 1700.1

COMPLIANCE IS MANDATORY


Ames Health and Safety Manual

Chapter 15 - Cryogenic Safety

Table of Contents

15.1 Overview
15.2 References
15.3 Definitions
15.4 Responsibilities

15.4.1 Supervisors
15.4.2 Safety, Health and Medical Services Division
15.4.3 Employees

15.5 Handling Cryogenic Liquids

15.5.1 Personal Protective Equipment
15.5.2 Containers and Equipment

15.6 Oxygen Alarm System

15.7 Explosion and Fire Prevention

15.8 Liquid Oxygen And Hydrogen

15.9 Appendices

Appendix A: Physical Properties of Low-Temperature Liquefiable Gases
Appendix B: Job Analysis Worksheet
Appendix C: Safety Rules for Handling Cryogens


15.1 Overview

This chapter is to provide safety information and requirements for cryogenic materials.

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15.2 Reference

  1. CGA P-121-1993,, Compressed Gas Association, Inc., Safe Handling of Cryogenic Liquids, Arlington, VA, CGA, 1993.
  2. 29 CFR 1910, Subpart H. Hazardous Materials Part 103, Hydrogen, Part 104, Oxygen, Subpart S, Electrical: Part 307 Hazardous (classified).
  3. NSS 1749.16, NASA Safety Standard for Hydrogen and Hydrogen Systems.

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15.3 Definitions

Cryogenic Liquids - A liquid with a normal boiling point below- 130 degrees F

Dewars - Insulated storage tanks designed specifically to store cryogenic fluids

Pressure Relief Devices - Used to prevent pressure buildup in a system if it exceeds a pre-determinated amount.

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15.4 Responsibilities

15.4.1 Supervisors

  1. Ensure that a job hazard assessment is performed to identify the hazards
  2. associated with the proposed use of cryogenic materials. (See Appendix B)
  3. Ensure that the potential for oxygen deficiency has been evaluated for the Safety, Health and Medical Services Division for locations where cryogenics are used or stored.
  4. Ensure that the lab safety plan (if required) includes hazard assessments, personal protective equipment assessment and emergency procedures specific to the hazards presented by the cryogenic materials.
  5. Ensure employees completed Cryogenic Safety Training prior to work with cryogenics.
  6. Provide on the job training for specific operations and hazards associated with cryogenic materials. Maintain records of on the job employee training.
  7. Perform and document periodic visual inspections of work areas and alarm systems to ensure that safety controls are being used, and are effective.

15.4.2 Safety, Health and Medical Services Division

  1. Assist in the preparation of the hazard assessment and oxygen deficiency evaluation.
  2. Provide cryogenic safety training.

15.4.3 Employees

  1. Comply with the safety requirements outlined in this chapter, the hazard assessment and applicable regulations.
  2. Use the personal protective equipment required in this chapter and the hazard assessment.
  3. Report any potential safety hazard to the responsible supervisor.
  4. Attend all required cryogenic training.
  5. Prior to each shift, perform visual inspection of work area and alarm systems where cryogenic materials are used.

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15.5 Handling Crogenic Liquids

15.5.1 Personal Protective Equipment

The minimum required PPR for handling anything that is, or may have been, in contact with croygenic materials includes:

  1. Safety glasses
  2. Loose fitting gloves that after appropriate ventilation for the task.
  3. Other PPE selections maybe used if approved in writing by the supervisor.

15.5.2 Transport of Cryogenic Liquids

Cryogenic dewars shall not be accompanied by the personnel when transported by elevator. An oxygen deficient atmosphere could occur if The cryogen released in the elevator.

15.5.3 Containers and Equipment

  1. Follow all requirements in the Ames Pressure System Safety APR (Locate number from Carla) and other NASA Directives, such as 8710.5 NASA Safety Policy for Pressure Vessels, Pressurized Systems.
  2. Use only equipment rated for use with cryogens and designed for the intended products, pressure and temperature.
  3. Relief valves must be rated to vent at a pressure no more than 10 percent above the design pressure of the line or the downstream equipment involved.

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15.6 Oxygen Alarm System

All permanent oxygen detection systems must be supervised by NASA Dispatch.

A supervised system may be allowed only with review and approval of the Safety, Health and Medical Services Division.

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15.7 Explosion and Fire Prevention

  1. Smoking and open flames is not permitted in areas where flammable cryogens (hydrogen), etc. for oxygen are used or stored.
  2. Do not use fuels, oils, or allow grease to build up on materials that will come in contact with liquid oxygen. A shock sensitive mixture may form.
  3. Electrical equipment approved for hazardous locations shall be required.
  4. Liquid hydrogen should avoid contact with air. Oxygen from air will condense in the liquid hydrogen creating a potential explosion hazard.
  5. Fighting cryogenic fires required professional firefighters.

15.8 Liquid Oxygen and Hydrogen

Follow all requirements in the NASA NSS 1740.16 (Hydrogen) and NSS 1740.15 (Oxygen).

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15.9 Appendices


15.9.1 Appendix A: Physical Properties of Low-Temperature Liquefiable Gases

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Appendix B: Job Analysis Worksheet

3. Cryogenics

Cyrogenics is a field that uses or studies materials at extremely low temperatures. According to the National Institute of Standards and Technology, the term applies to any work conducted at temperatures lower than -150 degrees Centigrade (-238 degrees Fahrenheit).

Cryogenics uses gases that liquify at extremely cold temperatures, including nitrogen, oxygen and helium.Cryogenic liquids require cautious handling. The liquid gases can make carbon steel, plastics and other high-strength materials fracture or shatter with ease. Contact with eyes or the skin can cause serious frostbite injuries. Flesh sticks to super-cooled materials, even nonmetallic materials, and trying to remove skin stuck to any frozen material can tear flesh.

Skin exposed to a cryogenic liquid or gas should be restored to normal body temperature by running warm liquid over it. The warming liquid should never exceed 112 degrees Fahrenheit and the affected body parts should never be rubbed. Victims should get emergency care as quickly as possible.

A less obvious danger from cryogenic liquids comes when they warm and while reverting to a gaseous state, displace oxygen. Breathing oxygen-deficient air can cause dizziness, nausea, vomiting, unconsciousness and confusion. Depending on how rapidly the gas expands, unconsciousness can occur without being preceded by any of these warning symptoms. For this reason, cryogenic liquids should always be used in open, well-ventilated areas. If that is not possible, use air monitoring devices to measure oxygen levels and signal when oxygen drops to dangerous levels.

An oxygen-supplying respirator, such as an airline respirator with an egress bottle or a self-contained breathing apparatus (SCBA) is essential when working in an oxygen-deficient atmosphere. Cartridge-style respirators will not help. Persons overcome by loss of oxygen should be moved to a well-ventilated area immediately. Rescuers may need an SCBA to avoid falling victim themselves. If breathing is difficult, oxygen should be supplied. If breathing has stopped, artificial respiration should be administered.

While transferring and handling cryogenic liquids, always wear chemical splash goggles and face shields. Wear gloves made to withstand extremely low temperatures. The gloves should fit loosely so they can be thrown off quickly. Wear long-sleeve shirts and trousers to protect all parts of the skin. Pant legs should go over the tops of footwear so spills cannot get into boots or shoes.

When cryogenic liquids warm up, the huge amounts of gas they are capable of producing can cause explosions or vessel ruptures. For this reason, the liquids should never be kept in plugged or covered containers. Use containers made specifically for cryogenic liquids, such as Dewar flasks. These consist of one flask inside another with a space in between providing insulation. The insulation keeps the liquid from warming quickly and causing rapid gas expansion. Even though Dewar flasks are made to withstand the stress of extreme temperature changes, they should be filled very slowly to protect the containers from excessive internal stress. They should not be filled past 80 percent of their capacity to allow for gas expansion.

Because cryogenic liquids can boil at room temperatures, causing eruptions and splashes, tongs should be used to remove anything immersed in the liquid. For more information, see EZ Facts� document No. 290, How to Work Safely with Cryogenics. Go to: http://www.labsafety.com/refinfo/ezfacts/ezf290.htm. For a selection of cryo-related products, go to: http://www.labsafety.com/search/results.asp?prodKeyword=Cryo.

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Appendix C: Safety Rules for Handling Cryogens

Liquid, vapor, or low-temperature gas will produce effects on the skin similar to a burn. This will vary with temperature and exposure time. Vapors issuing from cryogenic liquids can damage tissue including the eyes, which can be damaged by an exposure to cold gases too brief to affect the skin.

  1. Stand clear of boiling and splashing cryogenic liquid and its vapors. Boiling and splashing always occur when filling a warm container or when inserting warm objects into the liquid. Always perform these operations slowly to minimize boiling and splashing.
  2. When transferring, cool the receiving container to prevent splashing.
  3. Never allow any unprotected part of your body to touch uninsulated pipes or vessels that contain liquefied gases; the extremely cold metal may stick fast and tear the flesh when you attempt to withdraw from it.
  4. Use tongs to withdraw objects immersed in liquid, and handle the tongs and the object carefully.
  5. Do not drop materials into cryogenic liquids. Violent boiling can splash liquid onto personnel and equipment.
  6. Avoid breathing vapors from any cryogenic materials.

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