Author Topic: Scraper boxes  (Read 995 times)

Offline pwhole

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Re: Scraper boxes
« Reply #25 on: July 21, 2021, 02:55:57 pm »
Phil, if you look carefully at the photo of Dave Williams, he is wearing defenders. You can just see the orange pivots on his helmet through the condensation that the slusher has chucked out.

Haha, yes, I stand corrected! Seems sensible to wear them really with that racket going on. To be honest I wouldn't mind a ten-min audio recording of one of those operating at full bore - you could have some fun with that on a computer :)

I had a close shave a few years ago load-testing some abseiling rails, lifting up a 600 kg weight-box with a Tirfor clone. The entire front end of the casting broke off the winch, the mechanism collapsed, the weight box hit the floor (luckily only a few inches up, but only a few inches from my feet), and the lifiting cable twanged up into the roof and nearly took out my colleague, who was moving the abseil trolleys along for testing. The winch was rated for at least 800kg, so that was pretty shit all round. At least we got to go home early. I doubt they bought a better-quality winch as a replacement.

Offline Mark

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Re: Scraper boxes
« Reply #26 on: July 21, 2021, 03:35:23 pm »
I'm finding all this fascinating, but that was my main thought in all this - what happens if it goes wrong? As in, the scraper just gets totally jammed? Presumably there's only so much load the pulley anchors can take? The winch guy seems awfully vulnerable in that situation. Also the noise operating these things in an enclosed space must be close to unbearable? I'm not seeing many ear-defenders, but is that as they were already deaf? I know Mark can still hear though, so maybe not :)

As I recall, you had to keep a lot of pressure on the lever to get the rope to move, if the bucket got stuck it just stopped, you couldn't apply enough pressure to keep the drum turning & break the rope, (each drum had a sort of band brake/clutch thing) which you had to pull really hard to make things move

It was a case of crawling down the heading and freeing the bucket when things came to a stop,

I don't remember it being particularly noisy more of a rumble than a screaming air motor, I do however struggle with my hearing now, particularly when there is a lot of background noise.


Offline LJR

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Re: Scraper boxes
« Reply #27 on: July 21, 2021, 06:21:23 pm »

As I recall, you had to keep a lot of pressure on the lever to get the rope to move, if the bucket got stuck it just stopped, you couldn't apply enough pressure to keep the drum turning & break the rope, (each drum had a sort of band brake/clutch thing) which you had to pull really hard to make things move


True, which is why you will notice Dave Williams has two bits of scaffold tube stuck over the handles to get more leverage!

Offline Kevin_Williams

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Re: Scraper boxes
« Reply #28 on: Yesterday at 09:06:11 pm »
A couple of further points on operating a scraper at Redburn. If the bucket got stuck and the return pulley was tending to pull out the usual practice was to place a stick of powder against the rock that prevent the bucket moving.

I am aware of the bad practice whereby a miner helped the bucket to move by standing and bouncing on the back end of it. To prevent him him falling over he was holding onto the return rope. With the rope moving in both directions either side of the return pulley it was just a matter of time before an accident occurred.

If the rope broke while operating the machine you would stop the machine simply by releasing the brake band. If the rope was repairable this would be done correctly using u-bolt rope clamps (or incorrectly by tying a reef knot in it). Should a rope repair feed into the scraper drum it might cause problems which meant that the rope was replaced.

Later on at Geevor rope guards were mounted onto the unit that prevented the rope whip-lashing over the machine. 

 

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