Tag Technology

General notes on the application of the IndSAFE TECHNOLOGY with reference to suitability of PASSIVE vs ACTIVE vs SEMI-ACTIVE tags, as applied to different RANGE & DETECTION MODES.

NB : The exact suitability of this technology can only be fully assessed when considering a specific application.

General principles of this technology - Notes on range and detection modes:

1. PASSIVE TAGS:
   • PASSIVE tags are suitable for proximity detection applications up to 2m.
   • This makes it ideal for protecting localized trapping or entanglement points on larger machines.
   • Examples may be the entry to a crusher or baler … or a single entrapment point on a conveyer.
   • Passive tags could also provide close monitoring of machines that frequently reverse or automatically act/move with potential for impact or crush injuries.
   • PASSIVE tags are cheap,robust and maintenance free (apart from regular functional testing)
   • PASSIVE tags can be easily fitted to clothing, boots, gloves and hard-hats.
   • PASSIVE tags can NOT differentiate between individual workers.
   • The proximity sensing range is closely linked to the size of the detector coils.
   • Typically a detection coil of approximately 800 mm diameter (30 inches) will give a proximity sensing range of 2 metres.
   • Multiple coils can be used to protect larger areas.
   • Localized protection (for sensing tagged gloves, fingers etc) can be gained with coils down to only 100 mm (4 inches).
   • In all cases the detector coil must be mounted at least 1 cm clear of metallic surfaces … and further if maximum detection range is required.
   • If passive tags are to be used to protect the periphery of a moving device then the device must be capable of being completely surrounded by detectors in all its directions of movement.
   • The speed of movement is also an issue. If the tags take 250mS to detect at a distance of 1 metre then the maximum velocity of movement is less than 4m/s assuming zero stopping distance. (4m/s = 14.4 kmph) or (7 kmph with a 50cm stopping distance)

      

2. ACTIVE TAGS:
   • ACTIVE tag sensors have much greater range capabilities – up to 100m or more.
   • ACTIVE tags can be used to differentiate between workers or classes of workers.
     

     EG: A maintenance technician could wear different tags to an operator. The operator is expected to be proximal to a machine when it starts up … whereas an undetected maintenance technician could be unexpectedly caught working on or in the machine when the machine is started. A LOCK-OUT SYSTEM is needed. His tag could interlock the machine’s ability to start or move, as well as sounding a warning klaxon.

     EG: In the case of underground remote-miners, a PROXIMITY SENSOR and AUTOMATIC EMERGENCY STOP to protect both the operator and other personnel from being run over, caught in pinch-points, or crushed against shaft walls … has been put forward as needing URGENT ATTENTION.

   • ACTIVE tags require battery power.
   • ACTIVE tags cost more.
   • ACTIVE tags are physically larger than PASSIVE tags … suitable for fitting to overalls and hard-hats … but probably not suitable for attachment to boots and gloves.
   • ACTIVE tag detectors can be a single antenna of only 300mm (12 inches) length … or a larger distributed system covering a large area, possibly several kilometers long.
   • RFID tags would confer the ability to track personnel movements past local checkpoints. (e.g. This would be of strategic importance in the event of a mining emergency or mine evacuation)

An example of the effect of operational parameters on design considerations for a specific application:

e.g. The Mining Environment

Assessment of the application of this technology to underground mining will impose several design and regulatory considerations on the system. Some of these considerations will be unique from most other applications.

• All electronics and cabling may be required to be designed for operation in an explosive environment.
• This places a plethora of restrictions and requirements on the materials, construction and layout of the devices.
• Design for this environment would involve a ground-up rework of existing electronics and packaging options.
• Whilst the proximity detection technology itself is not directly impacted … EMC restriction may tighten.
• ELECTROMAGNETIC COMPLIANCE (EMC) requirements for electromagnetic susceptibility and emissions are very strict in the mining environment.
• RADIO FREQUENCY INTERFERANCE (RFI) and MAGNETIC FIELD EMISSIONS from an inductive pickup may not be acceptable in an environment containing explosives and electronic detonation control devices. If inductively coupled RF sensing methods were found to be totally unsuitable, then ACTIVE devices may be an alternative. The device and maintenance costs would increase substantially, but possibly not beyond the perceived safety value to the mining industry.
• Both the available operating frequencies … and radiated power levels … may be more limited than those available for wider commercial use.
• The ambient EMC conditions may also differ from normal environments … changing the susceptibility requirements.
• The commercial/industrial safety standards as per AS4024 are not the same as those applied in the mining industry.
• The following additional Australian Standards have been provisionally identified with reference to mining implementation of the safety device:
  
  AS 2595.1:1992 Electrical equipment for coal mines - Electrical requirements for underground mining machines and accessories - Equipment for use in hazardous areas. 
  AS 2081.1-1988 Electrical equipment for coal and shale mines – Electrical protection devices - General requirements
  AS 2381.7-1989 Electrical equipment for explosive atmospheres - Selection, installation and maintenance - Intrinsic safety
  AS/NZS 4240:1994 Remote controls for mining equipment
  

PERFORMANCE RISK FACTORS (for the MINING ENVIRONMENT):

• The presence of metal rich ores, and related dust, may impact the reliability and long term stability of detectors.
• The presence of moving ore with high metal content will desensitize both radio frequency and field disturbance detection devices. To counter this effect higher field levels would be required, further increasing RFI emission levels. (see above)
• The use of a DETECTOR SYSTEM CHECK ELEMENT outside the detector coils would overcome (or at least diagnose) faults caused by these factors.
• There is also the possibility of unwanted system interactions where multiple detectors (some possibly mobile) are operating in a confined RADIO-FREQUENCY environment.
• False triggering, and a single trip event causing multiple detections on different equipment, are examples of operational scenarios that must be reviewed.
• ACTIVE tags with RFID style detectors are a possible technology solution to these kinds of problems.

OPEN CUT MINING - Consideration of OPEN-CUT Problems and Solutions

Mine management raised the following concerns in the areas of MACHINE GUARDING and SAFETY MONITORING:

1. They need a PROXIMITY WARNING DEVICE to control interaction between heavy mining equipment & vehicles (80 to 100 tonne) and light vehicles (1 to 2 tonne) in operational areas and roads around the open-cut. The problem is that very large units tend to miss seeing smaller stationary vehicles, lighting plant, laser equipment etc. as they maneuver on site, leading to very one-sided and costly collisions.
   • The device would need to have a detection range of at least 10 – 20 metres.
   • It would need to generate an AUDIBLE DANGER SIGNAL/CLOSE PROXIMITY WARNING in the larger units.
   • It was felt that an emergency stop would not be required in these circumstances.
     
   • COMMENT: The required 10 – 20 metre detection range is beyond the capability of PASSIVE EAS technology. The RF fields would have to be intolerably high from an EMC viewpoint. This is mainly due to EMC limitations to comply with emissions of frequencies below 20MHz … and at present the RF allocated for a PASSIVE system is below 20MHz. In order to cover the range the power would have to be greatly increased (by at least 18.6 times) … which would place it way above the EMC limit. There are possibly much lower frequencies in the KHz range that could be used as well.
   • This detection range could be addressed by use of ACTIVE or SEMI-ACTIVE tags (battery or vehicle powered). They would cost more, but this would be justified.
   • Which units would carry tags and which would carry detectors? You would expect that smaller plant and vehicles would just be tagged to signal their presence to larger units.
   • Interaction between smaller units would be governed by existing road rules and normal operator alertness. Interaction between large units would be more of a challenge.
2. They need a PROXIMITY WARNING DEVICE+ AUTOMATIC MOTION-ARREST to control interaction between pieces of heavy equipment (such as large wheeled dozers (TIGERS) in speedy reverse mode).
   • Once again a detection range of at least 10 – 20 metres is required.
   • AUTOMATIC MOTION-ARREST could be achieved by automatic de-throttle + brakes applied.
   • Such a collision at New Hope Colliery generated more than $250,000 in repair bills + on-costs such as downtime, lost production, workers compensation etc. There was also the effect on workforce attitudes and morale of seeing a driver being thrown from his cabin and left draped over a guardrail.

   Collision Warning Systems for Surface Mining Dump Trucks
   www.cdc.gov/niosh/pdfs/ri9652.pdf

MAJOR BENEFITS OFFERED BY IndSAFE:

• Greatly increased cost effectiveness and efficiency, in ongoing R&D of radio frequency based MACHINE GUARDING, SAFETY MONITORING and MATERIAL PROCESSING systems … with incorporation of other new technologies as they arise.

• Provision of a CONTROL INTERFACE for:

• WARNING of presence.

• AUTOMATIC STOPPING.

• CONTROLLED START-UP.

  … of potentially dangerous plant and equipment … for the protection of personnel and other pieces of plant and equipment.

• The ability to provide ONGOING SPECIALIST CONSULTATION … to assess and provide solutions for a large number of PRODUCTIVITY ISSUES in the mining field.