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Dräger and PAUS breathe new life into mine rescue market

Dräger, Goldcorp (now Newmont), and PAUS Maschinenfabrik GmbH have come up with a new mine safety solution that, they say, is bringing rescue units safely, reliably, and as close as possible to emergency sites underground.

As underground mines go deeper in search of reserves, the distance mine rescue teams must travel in case of an emergency continues to increase.

In many emergency situations underground, only ventilation and drainage systems remain operational as mines look to avoid further incidents. All other infrastructure (the power supply, operation of technical and general vehicle traffic, etc) are shut down.

In this situation, mine rescue teams are forced to walk to the scene with all their equipment. Injured personnel are brought to collection points where first aid is provided, while evacuation to the surface must be organised.

“Depending on the specific situation and the extent of the emergency, the rescue services must immediately switch on their own breathing equipment after descending into the shaft and walking to the emergency site,” PAUS says. “In doing so, they consume part of the volume of the breathing mixture (compressed oxygen) contained in the breathing equipment. As a result, the longer they travel to the emergency scene with their breathing equipment switched on, the less breathing mixture – and, thus, working time reserves – remains for solving the main tasks, for clarifying the location and possible causes of the emergency, for searching for injured persons and for bringing the victims from the danger zone to the exits of the mine for evacuation.”

PAUS says a significant improvement of the operational conditions and increase in the work productivity of the rescue teams has come about with the cooperation of specialists from Dräger and Goldcorp, together with PAUS. The MRV 9000 Mine Rescue Vehicle is the result, a unit developed to deliver the rescue units safely, reliably and as close as possible to the emergency site.

The high operational reliability of the MRV 9000 in underground mines is ensured by the robust construction of the basic vehicle (from PAUS’ MinCa 18A series) and the life support system of Dräger, which is engineered down to the smallest detail, the companies say.

Design and technical features of the MRV 9000

The base of the MRV 9000 is the two-axle PAUS MinCa 18A vehicle which has been tested at mine operations over several years.

In its standard version, the MRV 9000 mine rescue vehicle is fitted with a Deutz TCD 2012 Stage 3a (Stage 5 available) diesel engine with a power of 95 kW, water cooling and exhaust gas turbocharging. Able to consume various fuel qualities, the MRV 9000’s exhaust gases are cleaned with a powerful filter.

The engine’s control system reduces machine downtime, according to PAUS. For example, in a situation where low lube oil pressure or overheating of the coolant is detected, the engine’s power will, first, reduce and then, second, completely stop to protect the unit. The real-time engine status is displayed to the driver on the large dashboard display.

The MRV 9000 is equipped with a customisable fire extinguishing system and, in each of its designs, if the engine compartment catches fire, the engine automatically stops operating and the extinguishing medium, such as foam, water spray or powder, is automatically or manually injected into the engine compartment. Hand-held fire extinguishers with around 10 kg of extinguishing medium are within easy reach, according to PAUS.

The hydrostatic four-wheel drive of the MRV 9000 provides high tractive power via planetary gears and the suspension provides excellent road grip when driving on rough and bumpy roads, according to PAUS. Optimum handling and fuel consumption are maintained at speeds of up to 35 km/h; even on ascending or descending gradients with up to 40%.

The design of the independent suspension of the front axle (steering axle) Clark 212 and the rear axle Clark 112 is identical, PAUS says. It consists of two springs and two shock absorbers each, two steering rods and two triangular bars each with a tie rod lever attached to the vehicle frame. The maximum load capacity of an axle is 8 t, which ensures excellent stability of the vehicle frame with a permissible total weight of the MRV 9000 of 11 t, PAUS explains. For the wheels of the vehicle off-road tyres of 9.00-R20 size with a load capacity of 4 t each are used.

The two-door driver’s cab with an additional seat is separated from the rescue cassette. The rescue cassette has six seats, a left-hand access door and an additional rear door. All eight seats, equipped with safety belts, are dimensioned so mine rescuers equipped with a tool kit and breathing equipment on their back – eg Dräger PSS BG4 Plus – can sit. The driver’s cab and the cassette of the MRV 9000 are pressurised and are equipped with built-in safety systems in compliance with ROPS and FOPS standards, which protect the driver and the other passengers of the vehicle against injuries, vehicle roll-over or heavy falling objects. In addition, a hatch is installed in the middle of the body roof as an additional emergency exit for the mine rescuers. All doors of the vehicle are airtight and sufficiently wide for easy and safe entry and departure of the mine rescuers with full equipment. In addition, the driver’s cab is equipped with a hydraulic tipping device. This makes it easy to carry out technical maintenance or repairs with the help of the raised cabin, according to PAUS.

The steering system of the vehicle is equipped with a Danfoss steering booster. In the case of a malfunction, the vehicle can still be steered using an emergency steering mechanism.

The brake system of the MRV 9000 is a hydraulic dual-circuit system. By pressing the brake pedal, all multi-disc oil brakes on the wheels are activated. The hydrostatic drive is at the same time an additional working brake for the vehicle – when the driver takes their foot off the accelerator, the vehicle automatically brakes. This is especially effective when driving downhill. The parking brake of the Posistop system – an SAHR brake – acts on the rear wheels of the vehicle.

The vehicle’s electrical system works with direct current and a voltage of 24 V, supplied by two 12 V batteries with a capacity of 110 Ah each and an A/C generator (80 A) with a voltage of 28 V. The main switch (cutoff switch) for the electrical circuits, emergency parking and reverse gear of the vehicle is in the driver’s cab. In the engine compartment, above the driving level, there are switch boxes with relays and the fuses for the electric circuits, all of which are protected from moisture and dirt in insulated enclosures, but easily accessible for maintenance. All indicators of the status of the vehicle’s power units have LED lighting, while the vehicle is equipped with powerful front headlights and bright rear lights with flashing direction indicators.

The unit comes with a width of 2.2 m, height of 2.64 m, length of 6.15 m, a wheelbase of 3.26 m and ground clearance of 260 mm. It also has a turning radius of 3.7 m (inner) and 7 m (outer).

Design and technical features of the life support system

The MRV 9000 is equipped with an integrated life support system to allow mine rescuers to safely reach the emergency site and evacuate injured personnel. Filtered air is injected into the driver’s cab and rescue cassette for breathing during the entire journey.

“The technical basis for the reliable functioning of the integrated system was provided by the specialists of the PAUS company, who developed the airtight construction elements of the driver’s cabin, cassette, all welds of the wall elements, the roof, the anti-slip floors and the special sealing of all doors and hatches,” it said. “The technological basis and structure of the filling system, developed and installed by the specialists of the Dräger company, includes the following elements: compartments for storage of the cylinders with the oxygen-air mixture for breathing; panels for controlling the supply of the air mixture; safety valves that drain the air from the driver’s cab and the cassette and prevent the ingress of contaminated mine air; gas detectors that control the condition of the air and signal the exceedance of the permissible limits of the concentration of hazardous gases in the driver’s cab and the cassette.”

The life support system can operate in two modes: Cleaning the air and feeding the air mixture into the cassette and into the driver’s cab; and flushing the cassette and the driver’s cab to displace infiltrated contaminated mine air.

In the cleaning mode, used during much of the rescue operation, the air mixture from the cylinders is continuously fed through pipes into the operator’s cab and the cassette via flow regulators. These regulate the amount of air supply, which depends on the number of pit rescuers in the cab and cassette. According to the standard, approximately 40 litres/min per person must be supplied to remove carbon dioxide or dangerous gas mixtures exhaled via the safety valves, with used oxygen returned to the atmosphere.

The combination of the system components enables the constant maintenance of an overpressure of at least 100 Pa in the driver’s cab and in the cassette, as well as the reliable prevention of the penetration of dangerous methane. The quality control of the air (the concentration of О2, СО2, СО) and the humidity in the driver’s cab and the cassette of the MRV 9000 is carried out with Dräger’s multi-channel gas detectors from the X-am series (4). After the mine rescue team leaves the vehicle, the composition and air supply are adjusted to the minimum permissible value with the help of the control elements, PAUS explains.

Yet, because contaminated mine air still enters the driver’s cab and the cassette through the door openings after the mine rescuers have left the vehicle, the flushing mode with air supply up to 1,000 litres/min is switched on to displace it via valves. When the gas measuring devices register the normal defined quality of the air, the mine rescuers and the victims to be evacuated can switch off their respirators.

The reserve of the breathing mixture, compressed to 300 bar and stored in six cylinders with a capacity of 50 litres each, is stored in two chambers with three cylinders each. This block with three cylinders is connected to the control units in the driver’s cabin and in the rescue cassette by a reducing valve, which cuts the pressure of the mixture, and stainless steel pipes. The results of the continuous measurement of the actual pressure and air volume in the cylinder block are registered on a special monitor in the driver’s cab.

With this information, it is possible to determine exactly the timeframe of operation of the unit of mine rescuers arriving in the mine for the elimination of the emergency. The block of three cylinders is installed in such a way there is no possibility to separate it from the reducing valve in the storage chamber, while refilling is possible with the use of an optionally available refuelling unit.

The set of six air cylinders with a capacity of 50 litres each is adequate for:

  • Moving a unit of six mine rescuers (two in the driver’s cab, four in the cassette) to the emergency location within 60 minutes;
  • Performing work in the emergency zone by five mine rescuers (one member of the unit remains in the driver’s cab) for 120 minutes; and
  • The return of the unit of mine rescuers with six people (together with three injured personnel) within 60 minutes.

With such a capacity in six cylinders, it is permissible to switch on the purging mode as follows:

  • In the driver’s cab, three times for a period of three minutes each time; and
  • In the cassette, three times for a period of eight minutes each time.

In this way, the mine rescue vehicle can allow the rescue team four hours of transportation in an atmosphere unsuitable for breathing.

The MRV 9000 mine rescue vehicle can optionally be equipped with a wide range of additional equipment, which includes around 20 different setups, Paus said.

“The use of the innovative MRV 9000 vehicle radically improves the working and operating conditions for the rescue units: both the minimisation of the travel time to the site of operation, the effectiveness of the medical emergency response, and the search and evacuation of victims and their transport to the stationary medical facility significantly increase the chances of rescue for accident victims,” PAUS said.