Published in the March 2014 International Coal News Magazine

I frequently get asked for the golden rules, so I decided it was time to update the list with a “back to basics” look at best practice on a longwall.

I should point out that these basic rules work for everyone from the sharp end of the business (the coal face) to everyone outbye, which includes engineers of all disciplines, managers, technicians, consultants, suppliers and CEOs (and accountants).

Rule 1

The hydraulic pumps are the heart of the longwall system. Without the correct pressure and flow, the roof support system will not function correctly and the longwall roof will be damaged, resulting in roof falls and downtime.

Check your OEM’s recommended operating pressure. Never operate your longwall with reduced pressure and flow and never operate with only one pump running.

Rule 2

The high pressure guaranteed set system is there to “top up” the hydraulic pressure and “guarantee” the correct setting load in the support legs.

If you have a high-pressure system fitted on your longwall, never operate under normal conditions with it turned off.

Rule 3

In longwall mining, we often continue to produce coal with broken or faulty equipment. The majority of engineering breakdowns are usually readily fixed within a few shifts but how big is a roof fall and how long will it take to fix it? A day? A week? Several months?

Do not turn engineering problems into mining problems. The consequences are many times more expensive and hazardous to the longwall crews who have to fix them.

Rule 4

There is no such thing as a nearly straight longwall face. It’s straight, or it is bent.

Keep the longwall straight. If it is bent, fix it.

Rule 5

When the supports are in yield, the supports are lowering and the roof is coming down with the canopy. That leads to fractures in the roof and bed separation in the overlying strata, resulting in broken roof and roof falls.

If the supports on the longwall face are yielding, do not stop. Keep cutting until the yielding event has ceased.

Rule 6

Armoured face convyeor creep is one of the most destructive forces on a longwall. Once out of control is will accelerate and get much worse before it gets better. Constant vigilance is required. The rate of creep is more important than how far offline it is.

Measure the AFC creep every shear and record it accurately.

Rule 7

Horizon control is critical to successful longwall operations. Everything on a longwall has to follow the path that the shearer cuts. Changes in horizon should be made in small steps.

If the AFC angle looks wrong, it probably is. Fix it rather than try and keep going. It will take eight to 12 shears to fix up a bad cut.

Rule 8

The supports on a longwall should be advanced as close as practicable behind the shearer. Longwall rates of cutting are determined by how quickly the pumps can advance and set the supports to the correct pressures, not by shearer speed.

If the support advance falls behind, slow down the shearer.

Rule 9

The gate end areas of the longwall are the areas of high stress. The supports in this area must be advanced once the driveframes are pushed over.

Do not leave supports back at the main and tailgate ends of the longwall.

Rule 10

Longwall operations require high levels of maintenance to remain effective. Gone are the days when changing legs could be left to the end of a block of coal. Every hydraulic leak and bypass is downgrading the system.

Regular maintenance is essential to longwall health.

Remember that poor practice today may not manifest itself until tomorrow or the next day. We cannot always see the results of our actions immediately.