Today's KNOWLEDGE Share :Importance of Permeation test on COPV

Today's KNOWLEDGE Share

Guidance on sorting out Hydrogen Permeation issues on Type 4 Cylinders:

I think I can throw some light on the H2 permeation that creates more concern in recent months in the H2 storage systems market.

Post COVID the hydrogen market boom takes place in the world market and there are a few challenges rising up especially looking at increased pressure requirements that range from 350-700 bar for H2 type 4 cylinders when compared with working pressure on CNG type 4 cylinders.

Hydrogen is the lightest element and it has highly volatile, escapes faster and disperses rapidly before it forms a flammable concentration level.When compare with other gases,hydrogen rises 2 times faster than Helium and six times faster than natural gas at 72km/hr (20m/sec).Volumetric flammable hydrogen concentrations in air starts at 4% and the explosive hydrogen concentrations starts at 18.3%.

The H2 type 4 cylinders factor of safety also increases and need to withstand upto 2000 bar in the burst test in order to meet the stringent international standard ECE R134 for H2 cylinder requirements.The winding time will increase and thickness of the cylinders (from 20 mm to 40 mm) too increase based on the design parameters.There are still many developments can be made with existing epoxy resin system to improve better heat resistance,toughness,strength,chemical resistance etc.In the coming years we can witness lots of changes in the improved Epoxy resin system that can offer better barrier resistance to H2 permeation.

The current type 4 manufacturers should form a team of experts and start focus on adding cost effective additives that will show better result in the prevention of H2 permeation on type 4 cylinders for the overall operations.There's still some certified well known Type 4 cylinder companies do struggle with Gas Permeation on their Type 4 cylinders in the world market.To solve this,the gas chemistry,liner material,epoxy,additives chemistry has to be understand completely to land up with the right solutions that will yield very good results on permeation over the years.

A allowable H2 permeation range that states in grams per day has to be calculated on your cylinder to see where your type 4 cylinders stand on Hydrogen Permeation range. And the better the permeation your composite structure offers,the excellent performance of type 4 cylinders one can witness while in operation for more than 20 years.

While designing your prototype Type 4 cylinders,the main priority you have to give on the Barrier properties of the cylinders as a permeation test is going to give you a lot more problems with your cylinders in the coming years as the certification will be more stringent than today's one.

Muthuramalingam Krishnan

Credit (Photo) :Hexagon Purus

#composites #hydrogeneconomy #type4cylinders #epoxy #carbonfiber #COPV