This document is no longer a CPR. This document implements the requirements of Corporate procedure ESH100.2.IS.18, Handle Cryogenic Fluids Safely.

IMPORTANT NOTICE: A printed copy of this document may not be the document currently in effect. The official version is the online version located on the Sandia Restricted Network (SRN).

GN470100 – SAFE HANDLING OF CRYOGENIC FLUIDS

Subject Matter Expert:  Roger Shrouf
GN470100, Issue D
Revision Date: October 31, 2008; Replaces Document Dated: December 14, 2007
Review Date: October 16, 2006

Change History

• Applicability and Ownership
• Training
• Cryogen Hazard Awareness
• Design for Safety
• Personal Protective Equipment (PPE)
• Cryogenic Liquid Handling Equipment
• Materials of Construction
• Oxygen Monitors
• Operational Concerns
• Waste Disposal
• ES&H Documentation and Reporting/Notification
• Points of Contact
• Related Hazards and Activities
• References
• Attachment
• A - Hazards Associated with Inert Cryogenic Liquids
• B - Example Valve Sequencing Instructions for an LN₂ Fill Station

APPLICABILITY AND OWNERSHIP

For purposes of this document, Members of the Workforce are:

• Sandia employees.
• Sandia contractors.

This document applies to all operations that use cryogenic fluids in either open or closed handling operations and supplements MN471000, Pressure Safety Manual.

Although this document addresses cryogenic safety issues in general, it primarily focuses on, and gives specific examples of, the inert cryogenic fluids of liquid nitrogen, liquid helium, or liquid argon. Liquid nitrogen is the most frequent cryogenic application at SNL.

A thorough evaluation of the safety of a cryogenic application may require a joint effort involving safety engineering, industrial hygiene, and facilities organization(s) for design and maintenance. Division ES&H Teams provide assistance in establishing the appropriate reviews.

The ES&H Teams and Safety Engineering Department (10322) is responsible for the development, approval, revision, and administration of this document. Forward suggestions for improvement to the manager of the ES&H Teams and Safety Engineering Department.

TRAINING

Requirements

Managers shall ensure that Members of the Workforce complete the required training identified below prior to performing the indicated work activity or fulfilling the indicated role. Untrained Members of the Workforce may temporarily work under the direct supervision of an appropriately qualified Member of the Workforce if the conditions/limitations of such work are documented (e.g., specific activities and duration) prior to performing the work.

• Complete the appropriate training as required in MN471000, Pressure Safety Manual, Chapter 2, "The Pressure Safety Program."
• Before beginning operations involving cryogenics, be trained on site-specific procedures for safe operations, including training on:
• Applicable operating procedures.
• Original equipment manufacturer's procedures.
• Valve sequencing checklists.

Note: Members of the Workforce whose activities involve the use of cryogenic fluids may use SF 2001-PQF, Pressure System Operator Qualification Form (Word file/Acrobat file), to document their qualifications, such as training.

See HR100.2.1, Identify and Complete Sandia Required Training for all Members of the Workforce for the corporate Sandia Required Training Policy.

CRYOGEN HAZARD AWARENESS

Requirements

• Be aware of the hazards related to the equipment.
• Know the methods for controlling those hazards.
• Follow the proper operating procedures applicable to the equipment.

Cryogenic burns can be serious. Members of the Workforce shall select the appropriate level(s) of protection commensurate with their application. Considerations include:

• The eyes are especially sensitive and require protection from splashes or sprays of cryogenic fluids.
• Fingers (or hands) are also frequently involved in accidents.
• Large quantities or pressurized streams of cryogenic liquids present a higher level of hazard.

The use of PPE is discussed in "Personal Protective Equipment (PPE)."

Guidance

DESIGN FOR SAFETY

Requirements

Cryogenic system owners shall be responsible for the design, operation, and maintenance of laboratory cryogenic systems and shall verify that:

• All apparatus for handling cryogenic liquids is constructed of compatible materials and designed according to the requirements of MN471000, Pressure Safety Manual, and other applicable industry standard requirements.
• Pressure relief is provided for all applicable spaces, such as where cryogenic liquids can be trapped.
• Relief valves vent to safe locations.

Guidance

Specific operator aids, such as valve sequencing checklists, are encouraged. Technical work documents (TWDs) may be needed in cases where the level of hazard or operational complexity warrants; see ESH100.2.GEN.3, Develop and Use Technical Work Documents.

PERSONAL PROTECTIVE EQUIPMENT (PPE)

Requirements

Engineered controls should be the primary means of worker protection. Where engineered controls may not be complete or feasible, workers shall wear the appropriate PPE to augment any engineered controls in place. Members of the Workforce shall wear:

• PPE where there is a reasonable potential for injury that could be prevented by the use of such protective equipment.
• The appropriate levels of protection commensurate with the level of hazard associated with a given activity.
• Safety glasses with side shields or indirect vented style goggles, as a minimum, for the open handling of cryogens.
• A face shield when the application involves more severe splashing or potential exposure to pressurized sprays of liquids or cold gases.

Note: Consult with the appropriate division ES&H team to determine the need for utilizing a face shield.

• Insulating gloves to protect the hands when the potential exists for injury from exposure to cryogenic liquids, cold gases, or surfaces cooled to low temperatures (e.g., uninsulated transfer lines and tubing).

Note: Gloves should be loose fitting and easy to remove in the event that liquid is spilled into the glove. Trapping a liquid cryogen in contact with the skin, such as within a glove, shoe, or boot, will result in cryogenic burns. Cryogenic aprons and sleeves are also available for additional protection.

• Safety shoes when there is a reasonable potential for foot injury from lifting or rolling heavy dewars or other equipment.
• Hearing protection during transfer operations generating high noise levels.

Note: Consult the appropriate Industrial Hygiene team member to determine the need for hearing protection.

Members of the Workforce shall not wear:

• Open-toed shoes or sandals when handling cryogenic fluids.

Note: Certain types of personal attire (e.g., shorts) also increase the risk of exposure to cryogenic liquid hazards and are not recommended.

Guidance

• Dewar filling operations where Members of the Workforce could be exposed to pressurized sprays or splashing.
• Making or breaking of connections where residual amounts of liquid or gas under pressure may be encountered.
• Inserting probes or other instrumentation into liquid baths producing rapid boiling of the cryogenic liquid.

Cryogenic system owners should be involved in the design of cryogenic fluid handling systems, such as fill stations, to verify that systems are designed to minimize exposure to the liquids, gases, and cold surfaces.

The handling of cryogens within closed systems with the controlled venting of liquids or boil-off gases may not require the use of PPE. Each system should be carefully evaluated for potential exposure to personnel. The system integrity and layout, as well as the frequency of making and breaking connections should be taken into consideration. Remember to vent system pressure before breaking connections. Consider using PPE (eye and hand protection) when breaking connections in order to prevent exposure to residual amounts of liquid or cold gases.

CRYOGENIC LIQUID HANDLING EQUIPMENT

Requirements

• Members of the Workforce use only equipment intended for cryogenic service during activities involving cryogens.
• Commercial equipment is not modified in a fashion that could defeat the designed safety features of the equipment or otherwise create an unforeseen hazard, such as inadequate venting of cryogen spaces.
• All spaces of a vessel or piping system containing cryogenic liquids shall have adequate pressure relief.

Note: consumer products, such as Thermos^® bottles, are not approved for cryogenic applications. Although the container itself may hold cryogenic liquid in an adequate manner, the lid, even when loosely applied, does not allow for proper venting of boil-off gases.

• Piping and connections for pressurized cryogenic liquid handling systems are constructed of safe materials and maintained in leak free, good condition, including dewars, flex lines, tubing, valves, fittings, brazed joints, transfer equipment, and pressure relief valves. Failures involving these components could result in exposure of personnel to pressurized sprays of the cryogenic liquid.
• Pressure relief is provided for any piping segment that has the potential to trap cryogenic fluids (i.e., cryogenic fluid trapped between closed valves).
• Pressure relief is provided for any sections of a dewar containing cryogenic fluid.
• Pressure relief is provided in vacuum insulation spaces to address potential leakage of cryogenic fluids into the vacuum space.

Guidance

Figure 1. Pressure Relief Locations.

MATERIALS OF CONSTRUCTION

Guidance

OXYGEN MONITORS

Guidance

OPERATIONAL CONCERNS

Requirements

• Only operate systems for which they are trained and authorized, e.g., laboratory personnel shall not operate or modify house systems.
• Validate that applicable valves are labeled in agreement with drawings or checklists and readily accessible to laboratory and emergency response personnel.
• Pay attention to unusual behavior of equipment that may signal a malfunction or a potential hazard. These include elevated pressure, the unexpected formation of frost on components, excessive or unusually frequent refill cycles, or the failure of a system to purge or vent per normal operations. See Figure 1 in Attachment A for discussion of LN₂ house systems.
• Transfer cryogenic liquids slowly and at low pressure to minimize the splashing and boil-off of liquid, insert transfer lines slowly to minimize boil-off of cryogen liquids and the resultant pressure increase, and check the pressure on storage dewars before starting transfer procedures.
• Pump or purge air out of transfer lines and experimental apparatus before transferring cryogenic liquids, especially LHe.
• Keep containers for cryogenic liquids clean and free of contamination from fuels, oils, and greases.
• Verify that open LN₂ dewars have insulating covers or loose fitting stoppers to reduce the condensation of air into the LN₂ while still allowing for venting of the LN₂ gas. See Attachment B for example valve sequencing instructions for an LN₂ fill station.
• Continuously attend manually operated valves during operation.

Note: Hazardous quantities of cryogenic liquids can be released into lab spaces or into building exhaust systems when manual valves are left unattended. When pre-cooling house LN₂ piping lines, consider where the liquid and the resultant boil-off gas is going and at what point will it begin to collect as a liquid and present a hazard. The overflow of cryogenic liquids may present an immediate hazard to personnel and facilities.

• Use cryogenic liquids only in well-ventilated areas or with local exhaust ventilation.

Note: Both system design and operational practices should be used to limit accidental releases of cryogenic liquids. Consider the use of small volume sources (as opposed to large volume house sources) of cryogenic liquids as a way to limit accidental releases.

• Wear the appropriate PPE for a given application as determined by the potential for exposure to the hazards. PPE s hall be consistently used during cryogenic liquid operations.
• Secure cryogenic dewars from physical damage. Consider, where applicable, the potential for seismic activity or strong winds pushing a dewar across the dock pad, or the potential for damage by vehicle traffic.
• For transport of cryogenic dewars in elevators, allow only individuals associated with the transport of the dewar into the elevator at the time of transport.

At the conclusion of operations, Members of the Workforce shall verify that appropriate valves are shut off.

In the event of an emergency, Members of the Workforce shall:

• Evacuate or not enter the area when oxygen monitors indicate a lack of oxygen.
• Notify personnel in surrounding areas who may be affected.
• Seek medical attention for any injuries or cryogenic burns.
• Report the event, as appropriate (see "ES&H Documentation and Reporting/Notification").

WASTE DISPOSAL

Requirements

• Dump liquid cryogens into any drain.
• Accumulate liquid cryogens in significant quantities in areas not appropriate for that purpose.

Note: Even relatively small quantities can damage equipment or facilities, such as crack floor tiles, damage water pipes, and damage electrical insulation on wiring. Also, consider the hazard presented by the boil-off gas when any significant quantities of a cryogenic liquid are released.

Guidance

ES&H DOCUMENTATION AND REPORTING/NOTIFICATION

Requirements

For SNL designed and assembled systems, the system owner shall compile a data package according to the requirements in MN471000, Pressure Safety Manual.

Guidance

Any significant accidental releases should be reported to the appropriate manager and center ES&H coordinator. Notification through an emergency or nonemergency hotline may be appropriate, depending on the severity of the release. Any personnel in the vicinity who could be exposed to the hazards of the release should also be notified. A predetermined point of contact, such as the person responsible for ordering the product, could also be useful because the schedule for re-ordering may be affected by large volume releases.

Note: Incidents that are reported to the nonemergency hotline are useful in tracking and analyzing accident and failure scenarios, determining trends, and changing engineering configuration or procedures.

Commercial (off-the-shelf) vessels may be used as is, but available owner or operator manuals should be retained for reference as part of the system data package.

POINTS OF CONTACT

Guidance

For assistance on cryogenic fluid applications, including safety engineering, industrial hygiene, and the facilities engineering and maintenance organization(s), Members of the Workforce should contact the appropriate Division ES&H Team. The organization’s pressure advisor may also provide assistance.

Members of the Workforce should contact facilities organizations, such as the Mechanical and Civil Engineering Department, for assistance with the design, installation, maintenance, and modification of LN₂ house systems.

RELATED HAZARDS AND ACTIVITIES

Hazards and activities related to the use of cryogenic fluids include:

REFERENCES

Requirements Source Documents

10 CFR 851, Worker Safety and Health Program.

29 CFR 1910.101, Compressed Gases

49 CFR 173.316, Cryogenic Liquids in Cylinders

ANSI/ASME B31.3, Process Piping

ASME Section VIII Division 1

CGA Publication P-12, Safe Handling of Cryogenic Liquids

*NFPA 55, Standard for the Storage, Use, and Handling of Compressed Gases and Cryogenic Fluids in Portable and Stationary Containers, Cylinders, and Tanks

*Public Law 91-596

*International Fire Code (IFC)

Implementing Documents

SNL, MN471000, Pressure Safety Manual

Related Documents

British Cryogenics Council, Safety Panel, Cryogenics Safety Manual

Edeskuty, F. J., and W. F. Stewart, Safety in the Handling of Cryogenic Fluids

Timmerhaus, K. D., and T. M. Flynn, Cryogenic Process Engineering

Roger Shrouf, rdshrou@sandia.gov
Al Bendure, aobendu@sandia.gov

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