Hi, I am sure this has probably come up before, given diesels reclassicaltion in 2015. However in a discussion recently with another H&S professional regarding x3 diesel generators (3500lt bunded tanks) at a new site I recently visited, they mentioned that a DSEAR assessment was only required on diesel tanks when it was in volumes above 20,000lt..... I've been searching all over the HSE website, reading industry pieces and scracting my head a lot since trying to fact-check this statement, but can't find anything that states there is a minimum amount before a DSEAR Assessment is triggered. I'm no specialist in DSEAR, but I knew the flashpoints had been lowered in CLP meaning diesel now fell under DSEAR, however, in terms of min vols - this is new one to me!

Anyone out there with any experience of diesel generators, similar to this site and the requirements to undertake a DSEAR assessment on it? Is there a min.vol. before the assessment is triggered?

Thanks very much.

As Alfasev suggests, minimum volumes before you have to do something are to do with COMAH, not DSEAR.  The quantity of flammables is obviously important to the DSEAR assessment and will influence how much effort you expend on both the assessment and the control measures, but there is no minimum quantity below which there is an exemption from the legal requirement to control fire and explosion risks!

Just to clarify - diesel DOES require a DSEAR assessment, even though low risk. It is classified as 'flammable' so DSEAR applies. You can't just dismiss it and say no assessment required.

There are 2 standards for assessing the Zones that you could use.

EI15 – Energy Institute Code of safe practice for area classification for flammable liquids

According to EI 15 diesel is a category C, Class III(1) – flashpoint  55oC + and handled below flash point.

Section A1.2 Mists or sprays & Section A1.4 Class II and III products, in summary say the following

Assuming UK conditions and the diesel cannot increase in temperature or become pressurised (other than from a low head of pressure in a storage tank), as you have already identified.

Provided the diesel stays at least 5oC below its flash point, which it will in the UK  - a hot day is circa 35oC, then EI15 says that hazardous area classification isn’t required for Class III diesel products in a storage installation.

For a spray leak to be of much concern the resulting spray cloud would have to be so dense as to be difficult to see through. At an attended fuel tanker off load, shut down would be expected to very quick by the tanker driver.

Personally I’ve never seen a tanker loading operation suffer a ruptured hose when off loading etc, small liquid drips/dribbles but nothing serious.

I used to work for an organisation that sprayed diesel into the exhaust of an aircraft engine – no ignition, no problems.

BS60079-10-1 Explosive atmospheres

If you plug in diesel properties to the various formula in BS60079-10-1 April 21 edition for either a pool release or spray release.

Assume a 5m dia pool, molecular weight circa 180kg/kmol, diesel vapour pressure circa 5kpa, static pressure for a tank of circa 0.3bar (5psi) results in-

Liquid pool evaporation Qg = 4,69 x 10^-7 m3/sec volumetric   release rate from the pool i.e. very little evaporation of the liquid

Road tanker leak

Spray release treated as a vapour for a 1mm area hole (Table B1), equation B5, Wg = 2.84x10^-8 kg/sec mass release from the tanker hose

For a ‘Secondary’ grade release – a reasonable assumption for a tanker loading. Assume outdoors location, with a wind speed of 0.3m/s (Table C1) . Dilution is confirmed as ‘HIGH’

‘Availability’ should be at least ‘Fair’, more likely ‘Good’. Not ‘Poor’ for an outdoors case.

Hazardous area distance, for a ‘Heavy Gas’ is much less than 1m

The overall result gives a ‘Non hazardous’ zone, as expected.

Or if it goes onto a surface that will heat it above its flash point of 55 DegC, where it will give off a flammable vapour. You would then still need an ignition source for there to be a problem.

The stuff (diesel and similar ie Kerosene heating oil flash point of 57 DegC) is exactly the same as before the definition changed from 55 to 60 DegC, so likely all the controls you had in place before are still good. It’s just they were just outside the definition and are now inside it. You should really have a document (DSEAR assessment) to confirm it is all good.

now I get it!

The thing with general H&S people trying to look at DSEAR issues is that the two pieces of guidance which would help people get an idea are not HSE documents, but a BS and an industry guidance document. They cost £400 & £168, so £568, so not exactly peanuts. Yes, aimed at those experts as above, but are also useful for the generalist H&S people whose jobs skirt around the edges of DSEAR. Those that would like to have knowledge of when to bring experts in and when they can deal with simpler things themselves or just have questions like the OP.

H&S guidance in all forms should be either free or reasonable cost price, IMHO.

Chris