Tuesday, 28 December 2010

The Holiday Season Proves to be Otherwise

It was not exactly going to be a surprise that my holiday would be interrupted. The company, in its infinite goodness, gave me friday 24th december to monday 3rd january inclusive... But questions were asked as to how far away I'd be, and I've got a heap of contact numbers and a bucketful of keys made ready for emergencies. Last job on thursday was to put together a rapid-response toolkit for quick grabbing, on the workshop table.

First call was on christmas day... A security man had spotted water seeping under a door. I told him where to find a stop-valve, and went briefly the following day, to check, split water pipe, water off, concrete floor, no real damage. Note it down for my return.
Boxing day.. or the day after christmas... My boss calls to say the security guy's called him to report a hissing sound on another site. He's been out there, in the dark, and found what he thinks is a slight leak on a fire-sprinkler, so he's turned the main valve off, and we arrange to meet early on monday morning.
Oh my. Fire sprinklers.

That particular mill has a system that's currently air-filled. That's because of the risk of freezing in unheated areas. The fire sprinklers are little brass things mounted on pipes, high up, all over the place. You'll have seen them, even if you don't know what they are. Factories, supermarkets, hospitals, hotels, airports, schools, all manner of larger buildings have them.
Usually there's a little glass phial visible, filled with liquid (often, but not always, red).
In the event of a fire, that little phial starts to get hot. The liquid in it, usually an alcohol mix, expands as it gets warmer, just as the red alcohol in a thermometer does. There's a bubble of free space to allow a certain amount of expansion, but at a set-point, (for the red bulb, 68 degrees C, or 155 degrees F), the bulb breaks. When in position, the bulb was holding a little brass cone in place, which in turn was holding back the water (or in our case, air)... Ploosh!
In theory, an air-filled system is immune to freezing.
Before winter, we drained the pipework, and filled the system with compressed air. in theory, all the piework is installed sloping toward the drainpoints, so it all empties.
In practice, a few lengths of pipe seem not to have emptied, ice has formed in the pipe and expanded. The weakest part is the brass cone under the sprinkler bulb. Ice forces past it and deforms it.

The sprinkler, thank heavens, does not activate because the pipe is plugged with dirty black ice. (Black? yes, because the iron pipe corrodes a little, but theres not a lot of  oxygen available, so the more common form of red iron oxide,   Fe2O3, is not found, but black iron oxide, magnetite,  Fe3O4   is abundant).
When it becomes a problem is when it melts.
Because then, air in the pipes will hiss out, carrying some filthy water, until the pressure back in the control valves drops below the trigger point... Then, in seconds, a valve will drop, a boost pump will kick in, and about fifty tons of water will all try to race to the break-point.

The ones I photographed were the easy ones, only about 8 feet up, in an office.
The tricky ones are 25 feet up just under the roof. I have to unscrew them, thaw the plug of ice in the hole with a gas torch, then screw a fresh one in, wrapping the threads in ptfe tape to seal them. One hand for the wrench, one hand for the pipe, one hand for the gas torch, and one hand to hang onto the ladder. Oh. I see there's a problem there, then. Oh well.

And it was going well, until one of the high-level ones started to hiss very ominously. And then a sound of rushing thunder... "But valve number two's turned off... even if the valve's dropped it can't fill, surely...."
"Oh shit!" yells my boss, abandoning his ladder-footing position and setting off at a run to the sprinkler house, where armageddon has kicked in.
My ladder's leaning on nothing, really. Just a three-inch piece of roof truss. And the foot's on a fairly slick concrete floor. And there was nowhere to attach a safety harness. And my safety man's left at a run. Just as the water gets there, in my face. Boom! 100 gallons per minute is the design rate. Out of a tank that had 9" of ice on the top. And black too. And it's trying to pluck me off the ladder, and I can feel the ladder moving...
I have never, ever, gone so fast down a ladder. Apart from being drenched to the skin in freezing black water, and the temperature being still below freezing, and the snow falling outside... I felt quite lucky, considering the other possibility.

I go open the big drain valves, and a fire door to outside, and gradually the water slows.
My fingers don't work.

I set off outside and up to the sprinkler house, where bells are jangling and a siren warbling, my boss is busy turning valves, as I shut down the alarms and the boost pump.
He's swearing and just a bit agitated.
Why? Because the sprinkler layout plan, kept in the sprinkler house, as required by the fire authorities and the insurance, clearly states that valve-set two covers the area in which we are working. Valve set two was off, and no water was flowing.
But valve-set one was at full blast.
Just  a few weeks ago the system had its annual check and service. How is it that for YEARS, since their installation, perhaps, the valves have been labelled wrongly? Why haven't the pros who do our alterations, and maintenance pointed it out? because the only way we're ever going to find out is at the wrong end of an emergency.
So the job that was to take a couple of hours of my holiday became a full day. With wet clothes, and below freezing temperatures. Yes, I have waterproofs, and no, they were on another site. as were my dry clothes.

Do you want to hear about today?
6" pipe, 150 pounds per square inch pressure, at the top of the tower, boom!......
Waterfall down six flights of stairs.... And I'm going uphill in the dark, because the water's blown all the lights. All I can see in my head-torch's beam is falling water... Up to the top of the stairs, then up a steel  ladder, in a waterfall. Toward the thunder.
This time, though, I'm in waterproofs.

Best pic I could get, looking up at the bottom of the sprinkler tank, the joint by the bend had failed, and this was  after I'd shut the water off. I've never tried to calculate how many tons of water are up there, the other side of that inch or so of iron. um....
Quick calculation gives me about sixty tons

It was a problem that required me to return to ground level, and try turn a valve in a basement off. But the valve's stiff, rusted up, ancient. It has been off earlier this year though, I know it works. I just need more leverage, a wrench, maybe.
Although I hate carrying it, my 48" "Record" wrench comes into its own at a time like this.

Good thing too, or I'd have had to use a bigger one.
I think the biggest I've got is the seven foot chain-wrench. and you can slip a few extra feet of scaffold pole on the end if you really need to be brutal. The downside of that chain wrench is that I can just carry it, but not without cursing.

Tomorrow? still officially on holiday, I'll be in at work by eight. I suppose I'll get paid, or get a few days off in lieu.