[ leak detection ]
Hydrogen gas safety standards and best practices Part 2 : detection technologies
Part 1 of this series addressed the safety considerations and challenges with industrial storage of gaseous hydrogen . Part 2 focuses on the most up-to-date technologies and best practices to be used when implementing a robust hydrogen leak detection system for an industrial facility . New technologies are continually being developed to deliver faster and more reliable detection . However , all have strengths and weaknesses that should be considered in the context of the specific application before implementation .
By Milad Eskandar , Daniel Brosig and Matt Russell , Gas Cleaning Technologies LLC , and John Boyle , John Boyle Consulting LLC
Leak sensor types and efficacy
Detecting leaks is not only important to minimize hydrogen losses , but also to prevent potential fires or explosions , especially indoors , due to its wide flammability limit range and low ignition energy . Various types of hydrogen sensors and leak detector technologies exist , and while none of them provide perfect detection , a combination of different technologies along with routine inspections is the best way to ensure safe operation .
The National Fire Protection Association ( NFPA ) requirements call for the detection of gaseous hydrogen inside hydrogen equipment enclosures ( HEE ) that include hydrogen generation , compression , or processing equipment . This detection must be interlocked to the mechanical ventilation system and initiate ventilation at a rate of 0.0051 m 3 / sec / m 2 ( 1 scf / min / ft 2 ) of floor area in the enclosure when the hydrogen concentration is measured at a minimum of 0.4 vol %. Alternatively , mechanical ventilation can be continuously running and not be linked with the hydrogen detection system . The detection system must also be linked to the emergency shutdown system ( ESS ); detection of hydrogen at 1 vol % ( 25 % of its lower flammability limit [ LFL ]) or higher must result in the activation of the ESS . 1 There are no other requirements for hydrogen detection from NFPA . However , standards vary from country to country and state to state . Care should be taken to ensure local norms and standards are being followed .
Hydrogen gas point detectors are useful to be placed in indoor locations or near storage areas where hydrogen can accumulate . A good rule of thumb is to place this type of sensor in the highest draft-free location in the room or enclosure , 30 cm ( 12 in ) or more below the ceiling to avoid elevated temperatures . 1 These sensors can also be used outdoors when combined with hydrophobic screens to protect from rain . It is important to note that point sensors do not measure hydrogen concentration over an area but only in the immediate vicinity where the sensor is located as they rely on diffusion of hydrogen towards the sensor . In outdoor and well-ventilated areas , hydrogen concentration is likely to be highly diluted by air ; therefore , it may not be possible for point detectors to adequately identify a leak . For this reason , it is recommended that point sensors be placed as close as possible to potential leak sources in these situations . Most point sensors also require routine calibration with standard gas mixtures .
Hydrogen Tech World | Issue 9 | April 2023 37