In August/September, OEMs and equipment suppliers made presentations to the recently formed ACARP Longwall Automation Steering Committee (see separate article, URL below). In this first of a series of articles detailing the current state of longwall automation from the point of view of OEMs, Mick Webster, DBT Australia manager automation, spoke to ILN about DBT's current research into automation. Among DBTs many initiatives will be the introduction into Australia within the next two months of training in a mobile test laboratory which simulates the use of the equipment underground.
DBT claims to be the world leader in longwall automation. The company's main offering is the PM4 system which automates roof supports based on shearer position. In Australia, ten longwall faces are currently fitted with DBT's PM4 system. Of these, four run shield automation consistently, five run shield automation partially and one does not run shield automation at all due to local workforce issues. All installations are technically capable of operating in full automation. A number of reasons such as poor mining conditions or insufficient training prevent this.
"At DBT we believe we've got the shield automation 90% there, based on a reliable shearer position," Webster said. "What's missing to achieve full face automation - this is everyone's conclusion, not just DBT's - is really, 'where is the longwall in 3D space?', which goes back to the shearer. You can decide where the shearer is with inertial navigation or some other method, but to do that with the shields is impractical."
Site specific features DBT has plugged onto its system for some Australian mines include pressure monitoring for wind blast warning, pressure monitoring for strata monitoring, and control of shearer speed based on AFC loading.
"Our Australian focus on development is consolidating what we've got - making it simpler, more user-friendly and applying it to different applications where some mines may have a different style of cutting for instance," Webster said.
DBT's current focus in automation is directed to the movement and control of roof supports based on a given shearer position: "In this regard we are a long way forward with our PM4 system which provides software custom written to suit various sequences of operation. Our immediate development thrust is to simplify the 'system management' features with improved menu systems and also system management from the gate end or surface. This will not impact on our current ability to run full automation without recourse to gate end control computers. Development is also under way to provide more flexibility in control of individual functions."
Unlike other systems the PM4 has many parameters which can be easily changed on the face to give operators the opportunity to optimise the system for changing mining conditions.
Future hardware development will include faster processors and larger RAM to improve the versatility and provide for improved maintenance diagnostics and greater scope for face information management and data logging systems. Tighter integration with other longwall control systems and features such as AFC control and audio communication is also under development.
But the obstacles to full longwall automation are far from being purely technical, as Webster notes. In the past these have included lack of acceptance by the operators, inadequate operator experience, poor maintenance regimes, and poor mining conditions.
One of the less obvious problems is that a highly automated face requires higher levels of maintenance utilising well trained, well educated maintenance staff. Says Webster: "The concept of a manless face is impractical because you then need people on the face to maintain it, and also to observe mining conditions. The logistics of shield maintenance increase with the amount of sensors you put onto each shield."
Webster pointed out that a typical longwall face of 150 roof supports might include 3500 plug and socket connections, 720 solenoids and 600 transducer devices. Whilst the PM4 system is optimised to reduce the number of cable and hose connections, and the equipment is reliable, as the age of a system increases the quantity of items dictate that there will be maintenance issues.
Another problem is the impact of entrenched work practices on the introduction of automation. Webster said there were some mines where the workforce refused to use the automation features because they believed they could do it better manually. Due to the flexibility of the PM4 system it is possible to run a face with two people using manual multiple batching of shields. Linked to this is the requirement for operators to fully understand the various operating parameters to get the best out of the equipment's sophisticated tools.
To help overcome this latter problem, Webster will introduce, in the next two months, a training test laboratory to simulate the equipment underground. The system will include a simulated face of 40 roof supports, with simulated AFC and shearer operations for training operators.
"More importantly, I want to create a training module called Systems Management. What happens when you want to change the settings to do something differently? Which parameters do you change and what is their interaction with other parameters?"
