Hose + Coupling World December 2021 Sample - Page 44

TECHNICAL ARTICLE
a ) WEH H70 ( 70 MPa / 700 bar / 10,000 psi ) b ) WEH H35 ( 35 MPa / 350 bar / 5,000 psi ) c ) Walther H70 ( 70 MPa / 700 bar / 10,000 psi ) Figure 5 : Main types of hydrogen nozzles and locking mechanisms . 10
The reason for a locking mechanism on the nozzle lies with the fact that the hydrogen being delivered is a gas , see Figure 5 . The dispenser has the gas at a certain pressure ( 700 or 350 bar ), which is then equalized with the pressure in the tank . As gas leaking from the connection wastes hydrogen , and also poses a safety risk the connection between the hose and the tank has to be secure . It works like this : a Toyota Mirai , for example , has a tank capable of holding approximately 5 kg of H 2 at 700 bar ; but if the tank is half-full , and you connect a 350 bar hose , you will not be able to fill up the rest . As the pressures in the dispenser and in the tank will be the same , no hydrogen will flow . 10 In this situation , the tank you connect to would need to have a minimum of 700 bar to fill the car tank .
Material Selection
Material selection for the inner tube poses some interesting challenges for the designer . Hydrogen molecules are very small and prone to leak easily through cracks , poor connections , or even some solid materials , as opposed to other common gases at equivalent pressures . Although hydrogen is generally non-corrosive and does not react with the materials used for hoses , at certain temperature and pressure conditions it can diffuse into a metal lattice causing a phenomenon known as ‘ hydrogen embrittlement ;’ this ultimately causes the steel reinforcement to fail .
Fuel cells are also very sensitive to contaminants and the inner tube material should not be a source of them . “ Contaminants derived from fuel cell system component / structural materials , lubricants , greases , adhesives , sealants , and hoses have been shown to affect the performance and durability of fuel cell systems .” 11
To ensure the integrity of the hose , hoses for hydrogen delivery should be assembled by the manufacturer and pressure tested to 1.5 times the rated pressure . 12 They should be documented with serial number , test pressure , test date , and first date of service . It is highly advised that hydrogen hoses assemblies should also , “ be discarded after 12 months of use or immediately after any mechanical abuse such as a breakaway incident .” 12
Final Thoughts
The general public will be responsible for handling hoses and nozzles during refueling . Considering the pressures involved and the characteristics of the gas , it comes as no surprise that hydrogen stations are subject to strict regulation and standards . Some of them are generic ( such as Local and state fire and building codes ), but there are already some very specific .
• NFPA 2 - Hydrogen Technologies Code
• ANSI / CSA HGV 4.2-2013 - Hoses for Compressed Hydrogen Fuel Stations , Dispensers and Vehicle Fuel Systems
• ISO 19880-5:2019 Gaseous hydrogen — Fueling stations — Part 5 : Dispenser hoses and hose assemblies
Moving forward , it will be important to understand the unique requirements of hydrogen hoses and how to safely and efficiently maintain and operate them .
References
1 . Hydrogen Fuel Cell Engines and Related Technologies Course Manual , Module 2 : Hydrogen Use , available at https :// www . energy . gov / eere / fuelcells / downloads / hydrogen-fuel-cell-engines-and-related-technologies-course-manual 2 . https :// www . eia . gov / energyexplained / hydrogen / use-of-hydrogen . php 3 . https :// www . epa . gov / ghgemissions / sources-greenhouse-gas-emissions 4 . Schneider , J . et al , Hydrogen Fueling Standardization : Enabling ZEVs with " Same as Today " Fueling and FCEV Range and safety , available at : https :// h2tools . org / sites / default / files / 2019-08 / paper _ 256 . pdf 5 . https :// www . energysage . com / electric-vehicles / charging-your-ev / charging-a-tesla / 6 . https :// www . eia . gov / energyexplained / hydrogen / use-of-hydrogen . php 7 . Hydrogen Fuel Cell Engines and Related Technologies Course Manual , Module 4 : Fuel Cell technology , available at https :// www . energy . gov / eere / fuelcells / downloads / hydrogen-fuel-cell-engines-and-relatedtechnologies-course-manual 8 . https :// h2tools . org / sites / default / files / 2019-08 / paper _ 256 . pdf 9 . https :// www . bridgestone . com / technology _ innovation / hydrogen _ hose / 10 . https :// www . toyota . com / content / ebrochure / 2021 / mirai _ fueling _ V11 . pdf 11 . Bahman Zohuri , Hydrogen Energy : Challenges and Solutions for a
Cleaner Future , Springer Nature , 1st ed . 2019 , ISBN-10 : 3319934600
12 . Hydrogen Fuel Cell Engines and Related Technologies Course Manual , Module 10 : Maintenance and Fueling Facility Guidelines , available at https :// www . energy . gov / sites / default / files / 2014 / 03 / f11 / fcm10r0 . pdf
ABOUT THE AUTHOR
Davi Correia is a Senior Mechanical Engineer who has worked at a major Brazil-based oil company for the last 15 years . Correia is part of multi-disciplinary team that provides technical support for topside piping and equipment of production platforms . During this period , he began to work with materials and corrosion , and later moved to piping and accessories technology , where he has become one of the lead technical advisors on valve issues . Correia was part of the task force that revised the IOGP S-562 standard , and wrote the S-611 standard . Correia has a master ' s and a doctor ' s degree in welding by the Universidade Federal de Uberlandia .
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