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The chapter has been generally revised and updated to reflect field and recent developments in hydrogen generation and fire protection.

This replaces WSOM Chapter B-45, issuances 68-21 and 69-51, dated July 15, 1968 and October 31, 1969, respectively.

Issue Date Org. Code NATIONAL WEATHER SERVICE Part Chap.
5-18-81 OA/W512 Operations Manual B 45

1. Purpose. The purpose of this chapter is to establish National Weather Service (NWS) policies and procedures necessary to conduct a safe hydrogen program at Weather Service facilities.

3. Scope. The policies and guidelines presented herein are limited to bottled hydrogen gas and the use of generating equipment.

4.1 New and Reconstructed Upper Air Facilities. Hydrogen gas shall be used at all new and reconstructed upper air facilities whenever and wherever possible.

4.2 Bottled Hydrogen Gas versus Locally Generated Hydrogen Gas. The determination of source of hydrogen gas to use for balloon inflation shall be made on the basis of operational and economic feasibility.

4.3 Helium Gas Substitutions. Helium gas shall be substituted for hydrogen gas at facilities judged to be unsafe for hydrogen. Judgments are to be made by the NWS region safety manager on the basis of technical merit. Helium gas may also be used as a backup should local weather conditions make the use of hydrogen gas dangerous. Such a judgment is left to the meteorologist in charge/official in charge (MIC/OIC).

4.4 Protective Clothing Not Required. Protective clothing shall not be required and will not be provided. Experience has shown that such clothing is cumbersome and can therefore create a hazardous condition. (Protective clothing, however, shall be used whenever potassium hydroxide, KOH, is being handled during all hydrogen generator maintenance and cell filling operations.)

5. Responsibilities and Authority. The NWS regional safety representatives shall be responsible for the continuous evaluation of safety at NWS facilities. MIC/OIC's are responsible for all aspects of safety, including carrying out recommended changes in procedure as well as any technical change that can be handled locally. To assist in this safety task, OIC's may designate a local safety representative to work with the safety manager to assure safe operation on a daily basis. Such duties shall be considered collateral duties.

6. Interim Plans and Policies. During the interim, between the issuance of this chapter and a review of procedures by the safety manager. guidelines established by sections 7 to 10, below, shall apply. These deal with siting, construction, and fire extinguishment; balloon inflation procedures; record keeping and maintenance; and emergency procedures.

7.l Codes and Standards. All facilities shall comply with the National Fire Protection Association (NFPA) Codes and Standards. The minimum distance in feet for a hydrogen system, in separate building or in a special room which is part of or attached to any purpose building, shall be as specified in NFPA N0. 50A, Table 2 (for hydrogen system less than 3000 cubic feet, 10 feet to a wood frame or protected wood frame building or structure).

7.2 Hydrogen Housing. All buildings housing hydrogen cylinders or generators shall be well ventilated. The purpose of this order is to assure that maximum advantage is taken of hydrogen's most vital safety property: its ability to disperse to a non- flammable mixture in air in a matter of seconds. Inlet and outlet openings to hydrogen buildings shall have a minimum total area of one (1) square foot per 1000 cubic feet of room volume and shall be directed to the open air. Ceilings of inflation buildings with radomes above the inflation building shall be gas-tight to prevent hydrogen from entering the radome.

7.3 Storage of Flammable Materials. Generally, flammable materials shall not be stored in rooms where hydrogen gas is stored. A minimum distance of 50 feet between hydrogen and fast burning solids, such as lumber, excelsior, or paper, is specified. A minimum distance of 50 feet between hydrogen and air compressor intakes or inlets to ventilating or air-conditioning equipment is specified. A minimum distance of 25 feet between hydrogen systems of less than 3000 cubic feet and vent or fill openings of below-ground flammable and combustible liquid storage tanks is specified. A minimum distance of 10 feet between hydrogen system of less than 3000 cubic feet and up to lO00 gallons of flammable and combustible liquids above-ground storage tanks or up to 15,000 cubic feet of flammable gas storage is specified; 25 feet for larger storage capacity.

7.4 Electrical Equipment. Electrical equipment shall meet Class I, Division 2, Group B specifications, described in the National Electrical Code (NEC).

7.5 Physical Safety of Hydrogen Equipment. Hydrogen systems shall be securely fastened, electrically grounded, and protected from damage due to falling objects.

7.6 New Construction. All new constructions of hydrogen facilities shall be of nonflammable materials, where feasible.

7.7 Fire Extinguishers. At cold weather stations, an ABC dry chemical extinguisher shall be used in the fill room. Halon 1301 or 1211 extinguishers may be used in the radome room and in any other room with extensive electrical equipment. As a precaution against static electrical shock, plastic or fiber nozzles of extinguishers should be grounded to the metal handle or body of the extinguisher. At stations where ambient temperature does not drop below 0EF, either Halon 1211 or C02 extinguishers may be used at locations with extensive electrical equipment. Hydrogen fires are not normally extinguished until the supply of hydrogen has been shut off. Reignition may occur if a metal surface adjacent to the flame is not cooled. The fire protection provided shall be determined by an analysis of local conditions. Hydrogen flames are PRACTICALLY INVISIBLE, 80 special care must be taken to assure that the fire i8 extinguished.

7.8 Hydrogen Cylinders. Where bottled gas is used, only cylinders meeting U.S. Department of Transportation regulations may be used.

7.9 Manifolding. Hydrogen cylinders shall not be manifolded under any circumstances. Further, only valving approved for hydrogen by NFPA or the American Gas Association may be used. Such valves are normally a diaphragm type. Whenever possible, stainless steel tubing with stainless steel swage10ck fittings will be used in hydrogen systems.

7.10 Pressure Regulation. Pressure regulators may be either the single or double stage type provided they are Underwriters Laboratories (UL) or Factory Mutual (FM) approved.

7.11 Grounding. Grounding straps shall be provided around the fill bench to assure passive grounding of the operator during filling operations. This requirement is particularly vital when relative humidity is below 50 percent. Ground straps shall be provided for balloons and shall be used during the fill operation and shall remain connected to the balloon while it is secured to the fill bench awaiting release. A passive grounding strap arrangement is also recommended around the drain port of the hydrogen storage tank employed by generator units.

7.12 The Balloon Fill Nozzle. The balloon fill nozzle shall be grounded to a co on ground with the frame of the building and the remainder of the fill system. The grounding system shall have a resistance of less than 25 ohms.

7.13 Electrical Components. Interior wiring, light switches, and light fixtures shall be of the explosion-proof type, for Class I, Division 2, Group 8 locations, described by NEC.

7.14 Spark-Proof Tools. Spark-proof tools shall be used in making all repairs and adjustments near hydrogen tanks and generators. However, it should be noted that even the so-called "spark-proof" tools can provide an invisible spark sufficient to ignite hydrogen gas. Consequently, all repair activities should be carried out carefully and thoughtfully.

7.15 Fiberglass Instrument Shelters (Radomes). Radomes shall be vented at their apex, where feasible, as a redundant safety feature in the event of failure of gas tight seals between the fill room and radome.

7.16 Smoking. Smoking is absolutely prohibited within a distance of 25 feet in or near buildings where hydrogen is stored or generated. "Hydrogen No Smoking" warning signs shall be posted on all exterior sides of the Inflation Shelter and at least one sign in all interior spaces.

7.17 The Hydrogen Safety Switch. At stations where fill-line freeze-up is not a possibility, the hydrogen safety switch shall be used. Where line freeze-up is likely to occur, the switch need not be used; however, the inflation process shall be closely observed.

8. Balloon Inflation. In general, balloon inflation procedures should be designed for ease of execution and a minimum handling of the balloon. The basic idea is that less complexity and handling will produce fewer balloons with pinhole leaks.

8.1 Inflation Equipment - Hydrogen Tanks. Stations using bottled hydrogen shall inflate balloons using only one tank at a time; this tank shall be kept within the storage room at all times. It shall be properly secured to prevent it from falling.over. A single-stage preset regulator valve or a UL approved multistage regulator shall be attached to the tank and gas routed to the inflation room via special piping at low pressure. If separate regulator hose and nozzle systems are used for inflating raob and pilot balloons, single tanks may be connected to each system provided both systems are not operated simultaneously. Valves are to be kept closed on all tanks not being used for inflation. A tank being used for inflation shall have its valve closed as soon as the inflation process is complete. When a tank cap cannot be removed or the valve opened using normal pressure, the faulty tank should be returned to the supplier. Use only proper tools to remove caps or open valves. Tank valves shall be kept closed while attaching or removing a regulator or supply line to or from the tank. Whenever a leak is suspected, test for escaping hydrogen gas by using a solution especially formulated for detective leaks through the formation of bubbles. Ordinary soap solutions are not reliable. Should a leak be discovered, that tank should be taken outdoors immediately and discharged; notify the supplier that the tank is faulty.

8.2 Inflation Equipment - Hydrogen Generators. The intelligent and safe use of hydrogen generators requires special training. Operators of hydrogen generating equipment shall be certified as soon as' practicable by satisfactory completion of the NWS operator's training course. Untrained operators shall be carefully supervised while operating the equipment until they become fully qualified. MIC/OIC's are responsible in their administrative capacity for seeing that all operators have been properly trained.

8.3 Inflation Procedures. Raob balloons will be inflated to provide nozzle lifts in accordance with existing instructions. Pilot balloons will be inflated to provide a slightly lower nozzle lift when using hydrogen instead of helium (see Federal Meteorological Handbook No. 5, Table B1-l). A separate set of nozzles and weights for use with hydrogen should be available. The nozzles; weights, cutoff valve, regulator, and tank should be connected to a common electrical ground by an electronics technician (ET3. The MIC/OIC shall require that all grounds be inspected visually by the operator before each filling and at least semi-annually by a station ET and the results of the inspection be recorded. Before inflating a balloon, purge any air in the system by bleeding a small quantity of hydrogen slowly through the hose and nozzle. Inflate the balloon at a slow rate to reduce the possibility of static buildup and spontaneous ignition. In temperatures below freezing, ground the balloon with a ground strap. Maintain' the balloon in a grounded condition while it is secured awaiting release. When high gusty winds make balloon removal from the inflation building difficult, consider using helium (He) gas for inflation. If a leak is detected any time during the hydrogen filing process, immediately shut off the flow of hydrogen and dispose of the balloon.

9.1 Ground Equipment. As a general rule, only emergency maintenance should be performed on tracking equipment during balloon inflation periods. Should an emergency repair become necessary during an inflation period, inflation shall stop, the balloon disposed of without its measurement package, and maintenance carried out before further balloon inflations. If possible, the presence of personnel in roof-top radomes or on the roof of the inflation building should be avoided during balloon inflation and release periods. Orientation checks required by Federal Meteorological Handbooks No. 3 and 5 should therefore be completed before starting the balloon inflation process.

9.2 Hydrogen and Helium Cylinders. Cylinders shall be inspected upon arrival to assure that they have been pressure tested in accordance with American Society of Mechanical Engineers pressure vessel codes. A pressure test is required every 5 years. The date of the last test is stamped on the cylinder. MIC/OIC's are not required to accept delivery of cylinders which have not been tested within the previous 5 years and indeed should not do so. Cylinders which will go out of date in the near future should be used first.

9.3 Hydrogen Generator Maintenance. Regional Directors are to establish maintenance, recording and report procedures, and formats to assure safe operation of the hydrogen generator unit. The establishment of such items is to be based on the experience gained within their own regions. This requirement recognizes the ability of each region to formulate a solution to its problems based on its own unique circumstances. As a minimum, checklists should be established and the required safety check and maintenance should be thoroughly carried out by responsible persons within the time limits established for the various elements of equipment. It must be emphasized that such procedures shall be subject to review and final approval of the regional safety representative. At some future date, changes and formalization to a uniform format may be made by the safety representative in consultation with the Regional Director.

10. Emergency Procedures. Each region is to establish a set of emergency procedures to deal with such events as balloon leaks, system leaks,and fires. OIC's shall insure that all persons affected are trained in emergency procedures. These shall be reviewed and updated in consultation with the safety representative. In general, the standard procedure for dealing with hydrogen fires is to close off appropriate valves and let the hydrogen gas burn itself out.

11. Recommended Improvements to Balloon Inflation Buildings. The following improvements are recommended for implementation as soon as practicable.

1. Protect ground wires in the generator room with removable rubber coverings. These are commercially available.

2. Ground the overhead barrier below the fiberglass instrument shelter to the building ground.

3. Change the fill hose to one which is braided with metal and grounded on the inside.

5. In the colder climate, construct an array of grounding straps around the work station and each emergency switch so that the operator can be grounded without recourse to actions beyond the normal filling routine. The grounding straps can be built on site and consist of a simple spring-supported brass rod array (see exhibit B-45-l).

6. In the colder climates , change the nozzle configuration to a removable type. Have the operator attach the balloon to the removable nozzle in a warm room.

7. In colder climates, provide localized heating at the fill station; preferably a radiant heating arrangement (see exhibits B-45-l and B-45-2).

8. Cover the sharp, bottom edge of overheat roller doors with a rounded rubber or neoprene astragal.

12. Recommendations for Hydrogen Generators. The following changes are recommended for implementation as soon as practicable.

1. Color code the hydrogen system including the generator unit, lines, valves and components in accordance with the American Standards Association "Scheme for the Identification of Piping System," A13.1:

The proper color may-be applied to the entire length of the pipe or in bands 8 to l0 inches wide near valves, pumps, and at repeated intervals along the line. The name of the specific material is stenciled in black at readily visible locations, such as valves and pumps Arrows should be painted on each pipe or tube to show the direction of flow of the gas or liquid.

2. Undertake a change of all lines to stainless steel tubing to prevent leaks due to corrosion.

3. Change all fittings to swagelock to reduce the chances of leakage at joints and for ease of maintenance.

4. Change valves to a toggle-type to assure automatic closure (one-quarter turn ball valves on sampling lines are permitted).

5. Place a water trap in the generator line just after the check valve on the hydrogen storage line. See point 7, drawing BD-238, Stuart Electrolyser Manual.

6. Replace the S tube on the floating bell with a flexible plastic hose, as illustrated in exhibit B-45-3.

8. Replace the metal line at the inlet to the compressor with a clear plastic tubing.

ABC Refers to A, B, or C fires

Type A = ordinary combustion

Type B = liquid/chemical

Type C = electrical

AGA American Gas Association

ASME American Society of Mechanical Engineers

Class I, Division 2, Group B Spaces where flammable gases are stored or used (NEC)

CO₂ Carbon Dioxide

DOT U.S. Department of Transportation

ET Electronics Technician

FM Factory Mutual Insurance Company

H2 Hydrogen

He Helium

ICC U.S Interstate Commerce Commission

MIC Meteorologist in Charge

NFC National Electrical Code (NEC) (NFPA 70)

NFPA National Fire Protection Association (NFPA)

NWS National Weather Service

OIC Official in Charge

E2 Oxygen

UL Underwriters Laboratories

ABC	Refers to A, B, or C fires
	Type A = ordinary combustion
	Type B = liquid/chemical
	Type C = electrical
AGA	American Gas Association
ASME	American Society of Mechanical Engineers
Class I, Division 2, Group B	Spaces where flammable gases are stored or used (NEC)
CO₂	Carbon Dioxide
DOT	U.S. Department of Transportation
ET	Electronics Technician
FM	Factory Mutual Insurance Company
H2	Hydrogen
He	Helium
ICC	U.S Interstate Commerce Commission
MIC	Meteorologist in Charge
NFC	National Electrical Code (NEC) (NFPA 70)
NFPA	National Fire Protection Association (NFPA)
NWS	National Weather Service
OIC	Official in Charge
E2	Oxygen
UL	Underwriters Laboratories