Appeal 33432

OSMC 301.4

Appliances regulated by this code shall be listed and labeled for the application in which they are installed and used, unless otherwise approved in accordance with Section 105.

The defueling vent stack assembly and other components at the roof will provide protections per non-permit applicable standards and exceptions in the fire code and building code. There are no listed and labeled assemblies for hydrogen gas.

The Daimler Corp 42 repair garage for hydrogen powered trucks includes de-fueling of the trucks. The direct de-fueling will be by a vent stack through the roof with a direct connection to the tank. The entire garage area is also provided with continuous negative mechanical ventilation.

The proposed design is for the de-fueling vent stack to be voluntarily designed to CGA 5.5 standards, referenced by NFPA 2, and continuous ventilation throughout the garage that creates a negatively pressurized repair garage. Additional protection will be by the ventilation fans being listed for Class I Div 2 requirements. Listed and labelled appliances for hydrogen do not exist, because special impacts on appliances by hydrogen only really occur when hydrogen is contained.

The repair garage will service hydrogen fueled trucks. Appliances in the garage will not be able to be listed and labeled for hydrogen gas use, as such a standard to list appliances does not exist. Equivalent protection will be provided by the appliances being designed per CGA 5.5 (standard for hydrogen vent systems), the garage being provided continuous and emergency rate negative ventilation, and the exhaust fans meeting Class I Div II protection ratings.

The intent of the code is to provide adequate protection to prevent hydrogen gas from igniting and any other potential impacts hydrogen may have on appliance components. There are no known impacts on materials from hydrogen that is at atmospheric temperature and pressure, as hydrogen moves to fast to have any chemical impacts, unless it is heated or under pressure. Therefore there are no standards to list appliances towards.

Protection from ignition is provided by negative pressurization and additional protection by the exhaust fans being Class I Div 2 rated. The attached Technical Opinion report provides details, but the largest tank on a truck is 3,723 cu.ft. of gas with a continuous ventilation rate of 1.6 cfm/s.f. for the 20,600 s.f. space, approx. 33,000 cfm, with an emergency ramp ventilation rate to 4 cfm/s.f., approx. 82,400 cfm, providing very fast exhaust of hydrogen gas, preventing the gas from getting close to LFL density, and meeting the code requirements of OSSC 406 and OFC 2311.

The vent stack assembly voluntarily designed per CGA 5.5, lack of standards to list appliances for hydrogen gas, continuous and emergency rate negative ventilation of the garage with standby power, and Class I Div 2 rating of the exhaust fans that can exhaust the entire contents of a single tank failure very quickly provide equivalent protection for listed and labeled appliances and request approval of this appeal.

OSSC §414.7.1 (OFC 5003.2.3)

Equipment, machinery and required detection and alarm systems associated with the use, storage or handling of hazardous materials shall be listed or approved.

The defueling vent stack assembly cannot be listed for hydrogen use. There are no listing criteria for equipment for hydrogen gas.

The Daimler Corp 42 repair garage for hydrogen powered trucks includes de-fueling of the trucks. The direct de-fueling will be by a vent stack through the roof with a direct connection to the tank. The entire garage area is also provided with mechanical ventilation.

The proposed design is for the engineered vent stack assembly be composed as shown in the engineering drawings, voluntarily designed per the requirements of CGA 5.5. Additional protection will be provided by testing prior to building occupancy for de-fueling.

Hydrogen is a lighter than air gas that is being used in a repair garage. The provisions of OSSC 406 and OFC 2309 and 2311 will be followed. Trucks with hydrogen gas tanks will be driven into the garage for repair. Prior to any work commencing on the fueling system, the tanks will be de-fueled. The hydrogen tank will be connected to a vent stack assembly that will allow the hydrogen to escape to air above the roof.

The vent stack assembly is not directly covered in these code sections. Additional protection for the de-fueling vent stack will be that the vent stack will be designed voluntarily per CGA 5.5 (Standard for hydrogen vent systems), referenced by NFPA 2, the hydrogen technologies code. NFPA 2 is not an applicable standard that can be used for permitting, but is a standard that can be used for guidance. Testing of the completed assembly for leaks will be conducted before being used for de-fueling.

The basis of the vent stack assembly is outlined on Pages 10-13 of the attached stamped Technical Opinion and engineered in the submitted drawings, including calculations showing that the stack pipe will meet the requirements of CGA 5.5 based on the proposed height/diameter ratio of the vent. The pipe is designed to withstand the forces encountered if the hydrogen catches fire. CGA 5.5 states the following, as the basis the design requirements in CGA 5.5 anticipates:

“It is not uncommon for the exhausting hydrogen to ignite. If designed in accordance with this standard, the vent stack provides adequate level of safety in the event of a hydrogen fire at the vent stack exit.”

Voluntarily following the design guidelines of CGA 5.5 with testing when the assembly is completed, will provide protection beyond what the applicable code requires, meet the intent of the code for safety of hydrogen vent systems, and therefore request approval of this appeal.