A Mine of Knowledge – Underground Inspections at a Potash Plant

Dec 13, 2020 Safety at work / Industrial Inspection
It’s 5:30 a.m. in the Rhön Mountains, somewhere between Bad Hersfeld and Eisenach. On the outskirts of a little town called Philippsthal in eastern Hesse (near Werra), a well-lit shaft headframe towers into the rainy sky. Beneath the surface of Philippsthal is Europe’s largest underground mine; the shaft forms part of the Werra potash plant, which is owned and operated by the German mining company K+S. K+S is one of the largest salt producers in the world; in Philippsthal, it mines some 15 million metric tons of potassium salt (“potash”) per annum.
Standing in front of the plant gate are Rainer Stuckhardt, his brother Axel Stuckhardt, and Jan Odeh, experts from the DEKRA Kassel branch. Twice a week, they – as well as another colleague – drive down into the potash mine to check the 1,150 mining vehicles underground: light vehicles on Tuesdays and heavy machinery on Fridays. The shifts are changing over at the mine this morning: some 80 miners from the night shift are making their way up through the shaft in conveyor baskets, while the early shift is speeding down 750 meters underground. In the locker room – the mine’s large changing area – the workers are busy changing into, or out of, their work clothes. Each miner (mostly men, but also a few women in a separate locker room) has two metal baskets for their street clothes and belongings – one for clean clothes and another for dirty ones. These baskets hang on chains from the ceiling.

Down the Shaft

The miners greet the DEKRA experts, who stand out thanks to their green overalls among the miners all dressed in white or blue, with “Glück auf!” (“good luck”, a German miners’ greeting). Once Rainer Stuckhardt and his colleagues have donned their helmets, safety shoes, and goggles, they descend into the depths at 12 meters per second. The mine cage, which is open at the sides, speeds past the surrounding layers of rock.
Although it was cold and windy on the surface, it’s a comfortable 26°C down in the potash mine. The dusty salt in the air immediately settles on the skin – you can taste it on your lips. The mood underground is friendly, direct, and informal. Axel Stuckhardt explains that the miners’ greeting Glück auf comes from the word auftun (English: “to find”), so they’re essentially wishing each other luck in finding new deposits. This greeting also implies a wish for getting out of the mine safely and with your health at the end of your shift.

A Chamber of Salt

Awaiting underground is a labyrinth of subterranean streets that humans formed in the salt using explosives, picks, and shovels. The area of the potash mine is approximately the size of the city of Munich, with a diameter of around 80 kilometers. The streets aren’t lit – only the 14 actual mining areas have lighting. Everything is covered by a layer of white salt. In a huge two-hectare chamber of salt (the central workshop), the DEKRA experts meet Florian Brandau, the man in charge of the Werra underground mine. Scheduling the annual inspections of the mining vehicles – including blast hole drilling trucks, explosive-loading vehicles, ridge anchor drilling trucks, loaders, so-called robbers, and off-road vehicles – is quite complicated. “Of course, we actually need the vehicles in the sections where salt is mined. They only come here to the central workshop or to the maintenance areas for DEKRA inspection,” says Brandau. There are ten smaller workshops closer to the mining areas.

Inspection Checklist

“All of these mining vehicles need to be inspected by experts annually under Germany’s General Federal Mining Regulation,” explains Rainer Stuckhardt, before he begins inspecting the blast hole drilling truck using a hammer, wire brush, and crack spray. He cleans the salt off certain areas with the wire brush, for example welded connections at joints and beams, to check for any cracks. The mining vehicles hardly rust at all underground, as there is not enough moisture. Things are, of course, different aboveground, but the vehicles spend virtually no time up there: they are disassembled into their individual parts, taken down in the shafts, and reassembled below. Most of them never see the light of day again, with the exception of the cars, which need to be disposed of on the surface.

“All these mining vehicles need to be inspected by experts annually under Germany’s General Federal Mining Regulation.”

Rainer Stuckhardt
Rainer Stuckhardt works through his checklist point by point; even the tires, which are operated at a pressure of 8 bar down here, are given a blow with the hammer. If something needs to be repaired, the DEKRA experts make a note of it in their inspection report. The inspection date of the fire extinguishers in every vehicle is also a part of the overall inspection. Any defects have to be repaired, of course. And the workshop is completely equipped to do so: there’s a welding station, multiple cleaning stations, and gas stations. The replacement parts stored here are worth a total of ten million euros.

Underground Blasting

On the edge of the mining area, the miners drive gouge bits up to 2,000 meters horizontally into the rock to obtain information about the further course of the deposits and to plan mining operations. But how does the salt make it onto the conveyor belts and get aboveground? The potassium salt is “shot out”: explosive-loading vehicles insert detonators and granulate up to seven meters deep into the salt. A special drilling pattern ensures that the wall then collapses forward in a V-shape. Extremely flat wheel loaders with shovels that can hold up to 21 metric tons of material take the salt to the so-called “crusher plants,” where it is then crushed and transferred to the conveyor belts. What doesn’t come down in the explosion is peeled from the ceiling by the robber.
Including the aboveground factory, around 4,400 people are employed at the Werra plant. “The salt is primarily used for fertilizers,” explains Florian Brandau. But it is also used in the manufacture of plastics (e.g. Lego and lunch boxes). The Werra plant also has its own production facility, where the salt is refined for medical applications, such as for saline or dialysis solutions.