Electric trains down pits..

[colly0410]

I know electric trains using overhead power cables were used down Gedling pit. Did many other pits use them? How did they get round the M&Q act re intrinsic safety of sparking ect? I presume they can only be used on intakes only..

[John]

Apr 29, 2014 5:11:57 GMT -5 colly0410 said:

I know electric trains using overhead power cables were used down Gedling pit. Did many other pits use them? How did they get round the M&Q act re intrinsic safety of sparking ect? I presume they can only be used on intakes only..

They had special regulations written for them...It was the NCB who made all their collieries safety lamp, some mines had never recorded methane, but for standardization all were brought under the umbrella of safety lamp. Clifton used naked lights up until the early 50's, so workmates told me, although smoking had been banned for years underground.
Even when I started my apprenticeship, I recall on motor that was not flameproof, infact it had an "open frame", it was the main stone head drift haulage motor near pit bottom.

Even today, you can find special regulations as passed by Parliament, online, Boulby has some I wasn't aware when working there, One I knew, which was the No1 shaft winder, as it hasn't a detaching hook, it has a balance rope on top of the skip and in the tower is a "knife" which will slice the rope of the balance rope in the event of a dangerous overwind.
There is another to do with diesel engined LHD vehicles.

If you do a search you should come up with a few regs regarding bare wire overhead trolley installations at some collieries, even though they are now long closed. Use the search criteria "overhead bare wire trolley regulations"

[John]

Got me thinking of special regulations that were passed way back, I recall when "Free neutral" was approved on a limited scale. The M&Q Act, electricity in mines of coal and shale, required the star point of all transformer secondary's be solidly grounded via the mines main earthing system. BUT, during the late 1950's into the 1960's the NCB engineering branch was encouraging manufacturers to come up with Sensitive Earth Leakage systems to reduce earth fault currents to as low as possible, especially on coal face equipment.

Two systems emerged, one within the framework of the Act, known as "restricted neutral" and the other "free neutral" which violated the law by having the neutral point "ungrounded" It was known as multi point earthing, as each GEB had an inductor installed with it's star point solidly earthed as protection, but the transformer had a spark gap. The purpose of the spark gap was in case the high voltage winding developed a fault, it would break down the spark gap rather than charge the secondary windings with high voltage.

B&F marketed this system with their sensitive earth leakage installed GEB's I think from memory they were the SM2 2x's . Ititially they had to have special regulations draughted by Parliament for the equipment to be installed at named Collieries, but the Chief HMI went along with the design as it represented a new major safety factor...

Also, the maximum allowed voltage on portable machinery at the coal face back then was 660 volts AC, but now SEL was available, exemptions were readily granted for the new 1100 volt standards the NCB wanted to instal.

Cotgrave had very poor floor conditions, so was granted an exemption to have the M/G transformer mounted on the monorail with the GEB's, in fact it was mounted just feet away from the ripping lip, with an inch thick steel plate to protect it from shot firing, with the provision that a high voltage circuit breaker was installed at the last transfer point and the conveyor attendant authorized to shut the power off via telephonic instructions from either the electrician or Deputy of the district.
They also had a flexible wired armoured cable feeding the transformer from the last leg of double wired armoured cable, another dispensation from the M&Q Act.

[Wheldale]

I read a paper about Westoe colliery years ago, they had a system installed in the 80's as they were way out under the North Sea. I believe the loco could travel at speeds of around 25 mph.

[John]

Apr 29, 2014 12:58:16 GMT -5 Wheldale said:

I read a paper about Westoe colliery years ago, they had a system installed in the 80's as they were way out under the North Sea. I believe the loco could travel at speeds of around 25 mph.

But would HMI allow them to travel at 25mph?? One of the problems with standard loco and rope haulage manriders is floor lift under the rails... They overcame the actual danger of derailment by using captive rail design. I'm sure there were systems using captive rails that exceeded 25MPH..

I've been in battery personnel carriers going flat out, around 20MPH, and it's pretty scary when they left the rails, same with 14MPH rope hauled manriders, kind of jars all the fillings out your teeth until it comes to a dead stop. LOL

[John]

Apr 29, 2014 12:58:16 GMT -5 Wheldale said:

I read a paper about Westoe colliery years ago, they had a system installed in the 80's as they were way out under the North Sea. I believe the loco could travel at speeds of around 25 mph.

But would HMI allow them to travel at 25mph?? One of the problems with standard loco and rope haulage manriders is floor lift under the rails... They overcame the actual danger of derailment by using captive rail design. I'm sure there were systems using captive rails that exceeded 25MPH..

I've been in battery personnel carriers going flat out, around 20MPH, and it's pretty scary when they left the rails, same with 14MPH rope hauled manriders, kind of jars all the fillings out your teeth until it comes to a dead stop. LOL

[Wheldale]

A few links here, but not much to go on.

www.healeyhero.co.uk/rescue/individual/Bob_Bradley/Bk-5/B5-1983-P1.html

www.dmm.org.uk/colleng/5208-01.htm

[John]

The link on the Healey site looks like a captive rail system, so chances of a derailment are almost zero, and check the difference between it and the American video, how the two systems are different, the all covered NCB manrider and loco and the totally open US loco.. No chance of anyone being able to come into contact with the NCB overhead wire, I'll bet the M&Q Act required the rails to be bonded across the fishplates too.

[John]

Just looked at the DMM site link, I was right about rail bondings, again though, an old set up probably pre 1954 Act...I'll have to see what the Act stated, but I'll bet it laid down tough rules.

[rob52]

Apr 29, 2014 9:46:30 GMT -5 John said:

"Got me ... "Free neutral" was approved on a limited scale. The M&Q Act, ... required the star point of all transformer secondary's be solidly grounded via the mines main earthing system. BUT, during the late 1950's into the 1960's the NCB engineering branch was encouraging manufacturers to come up with Sensitive Earth Leakage systems to reduce earth fault currents to as low as possible, especially on coal face equipment.

Two systems emerged, ..."restricted neutral" and the other "free neutral" which violated the law by having the neutral point "ungrounded" It was known as multi point earthing, as each GEB had an inductor installed with it's star point solidly earthed as protection, but the transformer had a spark gap. The purpose of the spark gap was in case the high voltage winding developed a fault, it would break down the spark gap rather than charge the secondary windings with high voltage."

I have a couple of "Papers" you might want to chase up from the "Mining Technology" Journal.
Author/s MINING TECHNOLOGY ISSN: 0026-5276. Year Vol Issue Pgs
Holmes J. EARTH FAULT CURRENT LIMITATION FOR COAL FACE ELECTRICAL SUPPLIES 1974, 56 640 Pgs 48-52
Elliott C Earth Leakage Protection - Past and Present 1976, 58 673 Pgs 444-451
Gray G.W. PHASE SENSITIVE SHORT CIRCUIT PROTECTION 1978, 60 690 Pgs133-136
Lord H., Pearson F.K. ULTRA-SENSITIVE INSTANTANEOUS FAULT PROTECTION FOR CAGE INDUCTION MOTOR SUPPLIES. 1980, 62 715 Pgs 219-223
Mittra D.K., Chatterjee T.K. Incipient earth fault detection cum early warning instrumentation system for longwall coal face electrical distribution networks operated on insulated - neutral system 1991, 73 848 Pgs 244-246

AMEE & AMEME had discussions on this at length at Annual Conferences and in papers published in "The Mining electrical & mechanical engineer" ISSN: 0374-373X. You want access to "The Mining electrical & mechanical engineer" by Association of Mining Electrical and Mechanical Engineers. IMM Durham House, NCM UK Library or Durham Mining Museum in the UK may be able to help you.
The Mining electrical & mechanical engineer
NCM UK
DMM UK

Electrotechnology in Mining
Nenad Marinovic
Hardcover, Elsevier Science Ltd
isbn-10: 0444882723, isbn-13: 9780444882721
=>> also worth a look


Rob

[John]

I'll check them out later Rob, thanks..

I should mention though, I missed out "restricted neutral" which was also making it on the scene in the 1960's in the UK coal industry, but had been known for many years. It was the common way of reducing fault current in Australian collieries when I started there in 1979.
Combined with SEL was probably the best of the two options, ie multi point free neutral and restricted neutral.

Biggest problem with free neutral/multi point earthing, was when a fault occurred on say the shearer cable, ALL GEB's tripped out on earth fault, caused the electrician a few headaches staying within the law.....LOL Unless it was an obvious fault or one that locked out the offending GEB.
If all boxes reset, it left the electrician two choices, one to stay legal by testing ALL outgoing circuits with a megger, or saying stuff it and let everything go..... More often than not, it was start cutting again and see what happens...LOL