Rank: Forum user 
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HI folks
one for the comah specialists. would a seperation of 250m be classed as sufficient for 100kg of Hydrogen and at the other end 8 tons of LNG? there are no distances given in the acop
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Rank: Forum user
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Failing any other guidance being available, you need to identify your accident scenarios.
Some sort of leak and jet fire seems one of the main consequences.
You can only work out the size of the resulting flame and hence heat radiation by making a mathematical model. Normally this is done using the PHAST software.
Heat radiation above 12.kw/m^2 would be of concern. Above 35kw/m^2 would be a big problem.
What pressure & temperature is the hydrogen stored at? And the LNG?
With out looking up the CoMAH values is 100kg of H2 enough to bring you in to COMAH and/or 8 tones of LNG?
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Rank: Super forum user
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Potts
Should be more than sufficient, not least as generally compatible - i.e. both flammable - the exception would be potential domino effect but your quantities are relatively small.
Well sub COMAH - thresholds for lower tier 5 tonnes for hydrogen, 50 tonnes for LNG.
If you were above threshold HSE would define 3 consultation zones based on "Representative Worst Case Major Accident" in essence the worst case scenario - a hazard rather than risk based approach which the Buncefield Major Accident Investigation Board has told them to move away from. Quantified Risk Assessment already routinely used to assess Seveso sites that store flammables (as well as toxics) in the Netherlands.
For each of these the RWCMA would probably be a BLEVE of 50% of the largest container assuming horizontal, 90% if vertical. Plenty of explanation and illustration if you google BLEVE
Limit of Outer Zone beyond which you can in effect do anything would be at 500 thermal dose units, involving a dangerous dose of thermal radiation for vulnerable people, and equivalent to 4.9 kw/m2 for 1 minute.
You are not going to get an Outer Zone anything like 250m as regards your quantities.
You might get some actual numbers at the RIVM site, but you would need to get someone to translate from the Dutch.
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Rank: Forum user
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As Peer says, well outside of CoMAH limits
Hydrogen 5tonnes or 50 tonnes
LNG 50 tonnes or 200tonnes
Tier 1 / Tier 2 categories
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Rank: Forum user
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Thanks everyone, I have someoone doing a Dsear risk assessment, but reading through the Comah Acop came acros the 2% rule and was intrigued to know if this would apply. unfortunately there are no distances, hence the question. we also have Diesel and an ammonia tank on site and even including these we are well below comah
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Rank: Super forum user
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A PS
British Compressed Gases Association Code of Practice CP33 "The Bulk Storage of Gaseous Hydrogen at Users's Premises" (Revision 1: 2012) sets out minimum recommended horizontal distances from various features in "Table 1" (which is actually a graphic not a table). Doesn't mention LG but recommends minimum 8m from LPG tanks and 5m from flammable gas cylinders.
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