Answered some questions about the need for anything other than basic services on Workplacelaw.net and have just had a perfect real life example of the need to follow the BS5306-3 service regime.
For the first time in a while I've had to use extinguishers on real (non training) fires. On the first (overheated HGV brakes) all went well.
The second was for a burning grit bin - didn't want to pull a pump away as it was night and it might have something better to be available for (e.g. dwelling fire).
Got out the extinguisher, only been in place for 3 days after replacing the ones used on the HGV. An Amerex 5lb ABC powder, basic serviced by me (gauge test, weight, etc), in date for extended service (just!) carried out by a 3rd party.
Pull the pin, give it a quick squeeze, nothing other than a 'pop' and small gust of D/P. For the whole duration of putting out this melting bin with constant squeezing & releasing of the handles and shaking all I got were gusts of powder, and then pops & spurts. I eventually get the job done but wonder what went wrong.
I get the first clue bringing in the extinguisher at home - under sodium street lights I couldn't see this but now I saw the powder was brilliant white. Now although there is no standard scheme of pigmentation for powder, if it's white you can be 99% sure it's BC Powder.
Someone had mixed the powder, filling an ABC extinguisher (acidic ammonium phosphate) with BC powder (alkaline sodium bicarbonate). All the manuals give horror stories against doing this and I've found outthe hard way - increased pressure (the pops) and worse moisture generation (poor discharge). Opening it up revealed a powder that was full of claggy lumps.
The Morals of this story-
Don't mix powders - it's not a back covering 'just in case' in the manuals.
Do extended services - they are not just a money making exercise - I'd done every possible check for safety & operability during my basic services, but the only way you will know if an extinguisher will work correctly is when you set it off- the discharge test & detailed examination of an extended service does this for you - you don't want to find out it doesn't work when it's a real fire!
