Accurately capturing mechanical loads in high-stress underground mining equipment is a major technological challenge. Armoured face conveyors (AFCs) in longwall mining operate under extreme conditions, facing complex dynamic forces that analytical models cannot reliably predict. This article, authored by Jörg Wittkamp, presents a novel telemetric measuring system, ENCOL-Ex®, developed by Grünewald GmbH in cooperation with Thiele GmbH & Co. KG, for continuous tensile force measurement directly within a moving chain link during operation.
The ENCOL-Ex system acquires real-time data in the top strand and wirelessly transmits accumulated data in the bottom strand to a receiver unit connected to surface infrastructure. This article outlines the structural constraints, electrical architecture, cyclical measurement workflow, and upcoming final validation at the Polish Zaklad Górniczy Janina coal mine.
Introduction and problem statement
Maximising equipment availability and operational safety is central to underground mining engineering. In longwall coal mining using shearer loaders, AFCs (chain scraper conveyors) undergo extreme physical stress. High-performance chains must sustain static tensile loads for material transport while absorbing unpredictable, dynamic peak stresses from blockages, uneven loading, sprocket polygonal effects, and complex friction.
Traditional load determination relied on theoretical models and indirect measurements, such as drive motor electrical power draw. However, these methods fail to capture actual internal force distribution, particularly during multi-strand or asymmetric loading. To bridge this gap, Thiele partnered with Grünewald to develop an integrated sensor system that measures physical tensile force directly at the point of action – inside the moving chain link itself – within hazardous, explosion-prone environments.
Requirement profile and technological background
Thiele sought to quantify real operational chain stresses to inform product design, material selection, and lifetime predictions. Grünewald brought extensive expertise in specialised underground mining sensors, including flow, pressure, temperature, level, and tilt sensors, as well as stationary load monitoring.
Grünewald focuses on customised mechanical integration and flexible signal outputs while adhering to strict mine safety standards. Their equipment holds international explosion-proof certifications, including ATEX, IECEx, and regional approvals (MA in China, MSHA in the US, EAC, and Queensland IECEx). This safety expertise formed the baseline for project ‘Intelligent Chain’, designated ENCOL-Ex.
System architecture of the ENCOL-Ex system
The ENCOL-Ex system seamlessly integrates into standard conveyor geometries. The functional prototype is tailored for twin-strand armoured face conveyors running in parallel line pan profiles beneath shearer loaders.
The architecture comprises three primary components:
- Measuring links (sensor units): Modified high-strength chain links containing miniaturised measurement electronics, acting as autonomous sensing and transmitting units.
- Receiver unit: A stationary unit near the auxiliary drive at the discharge end for wireless data reception and signal processing.
- Surface data infrastructure: Fixed cabling that routes aggregated measurement data from the receiver to the surface control room.
For validation and redundancy, the test system employs four active measuring links (two per strand with a staggered offset), enabling continuous cross-validation of force profiles.
Operating principle and cyclical measurement sequence
Transmitting data from a moving chain without slip rings or cables requires a cyclical workflow aligned with conveyor kinematics.
Top-strand measurement phase
In the top strand, the link actively conveys coal under maximum tensile load. Internal sensors record elastic link deformation, and embedded electronics digitise the signals. Because dense coal loads cause severe radio attenuation inside the closed pan channel, data is temporarily stored in local memory within the link.
Bottom-strand idle and transmission phase
Upon passing the return sprocket into the bottom strand, the empty chain returns toward the main drive under minimal load. To preserve battery life, the link automatically enters a software-controlled sleep mode, deactivating the sensors.
As the link reaches the end of the bottom strand near the stationary receiver, a trigger pulse wakes the electronics. Within this short window, stored top-strand data is transmitted via wireless telegram to the receiver. A new measurement cycle then begins upon re-entering the top strand.
Data processing and surface visualisation
The receiver processes incoming radio packets and displays real-time tensile forces and load asymmetries on a rugged local display at the longwall face. This allows operators to promptly correct chain misalignment or overloading. Simultaneously, data is transmitted up the mine shaft to a centralised surface database for logging and analysis.
Energy management and energy harvesting
The measuring links are currently powered by high-efficiency, encapsulated primary batteries, achieving a six-month operating lifespan via bottom-strand sleep mode and optimised transmission power.
Future developments aim for complete energy autonomy by replacing batteries with an energy harvesting module. This module will capture ambient conveyor vibrations to charge an internal supercapacitor, powering the electronics and wireless transceiver maintenance-free.
Final field validation
Following laboratory testing, final field validation will occur at TAURON Wydobycie S.A.’s Zaklad Górniczy Janina (ZG Janina) coal mine in Libiaz, Poland. Its demanding geological conditions and high longwall output provide an ideal testbed for assessing mechanical durability, RF signal stability, and thermal resilience under real operating conditions.
Summary and outlook
The ENCOL-Ex system by Grünewald and Thiele advances mining transparency by measuring tensile forces directly inside moving chain links, closing a critical gap in conveyor condition monitoring.
Following field validation at ZG Janina, final ATEX and IECEx certification will enable global deployment in underground mining. The resulting real-time insights will empower mine operators to implement predictive maintenance, minimise unscheduled downtime, and improve overall mining efficiency.