Rexline’s Rip Detection Systems represent the latest in acoustic-based longitudinal conveyor belt rip detection systems. Longitudinal rips are one of the most disruptive problems faced by operators of steel cord conveyor belting and Rexline’s acoustic-based systems have been providing reliable protection against these issues for many years.
It is unique in that it can be fitted to most steel cord conveyor belting without modifying the belting. No sensor loops or antennae are required.
PRINCIPLE OF OPERATION
The Rip Detection System injects acoustic energy into the target belting, at the sensing location and this energy propagates across the belt using the rubber and steel matrix as the transmission medium.
The energy is injected by a transmitter transducer and sensed by a number of receiver transducers, located at various positions across the belt. When a longitudinal rip occurs between the transducers, the level of acoustic energy arriving at a receiver is either reduced or lost completely. This reduction of energy level is used to detect the rip.
HARDWARE
The ‘front end’ of the device consists of a number of transducers (maximum of nine), installed equidistant laterally across the belt. These transducers contact the underside of the belting and are biased against the surface using spring loaded mounts.
These mounts are fitted to a main transverse support, which is purpose-built for each conveyor structure. Once a mount’s lateral location is established it is adjusted for height. The mounts are designed to minimise product build-up and embody ‘parking’ pins so that a transducer can be locked away from the belt surface, to facilitate maintenance. The lateral separation of the transmitter and receiver transducers (transducers are interchangeable), depends on the construction of the belt.
Different types of belting provide different characteristics, as far as acoustic transmission is concerned, however, most common steel cord belting, including M and N grade, B grade, SAR and LRR compounded belts are good hosts. Typical lateral transmitter-to-receiver separation on the above compounded belts is in the range 300mm – 700mm. This separation, together with the belt width, will dictate how many transducers are required to span the active portion of the belting. The number of transducers required to span the belting will determine the cost of each system.
The transducers are replacement items as they are contact components. Transducers can be replaced easily via one M12 mounting bolt and two plugs and sockets and a re-build service is available to minimise cost of transducer replacement. Typical transducer life is in the range nine months – five years.
Each transducer incorporates sophisticated onboard electronics which monitor and log all ‘vital’ life signs and relay this information back to the Main Electrical Enclosure (MEE).
Transmitter and receiver electronic modules are sited close to the sensing location and a single multi-function cable is run to the MEE. These modules are housed in IP 68 rated 316 stainless steel enclosures and a tacho generator is
also fitted to a local idler roller.
The MEE is a stainless steel IP 69K rated enclosure and contains the power supply, motherboard, memory and communication modules. A dedicated single phase electric mains supply of 110VAC / 15amp or 240VAC 10amp is required for the MEE.
SOFTWARE
The Rip Detection System is software controlled. All machine parameters are adjusted and monitored in software. Important machine operational parameters are given ‘windows’ during commissioning. Any violation of a window is logged, established as an “Alarm”, and passed on to appropriate personnel via e-mail or SMS, as provided for during set-up. There are various levels of Alarms, so the nature of an Alarm can be assessed and sent only to the appropriate destination, minimising inconvenience. All receiver data and events of interest are logged and may be downloaded for analysis.
Software updates can be downloaded ‘live’, no technician site visit is necessary. To achieve this, the device MUST be connected to the Internet. This can be done via Third Generation (or later) mobile phone networks or a site LAN/WAN using an Ethernet connection.
DEVICE LOCATION
The transducers and mounts are normally located just downstream from the last load point. This site is chosen as the primary location because experience suggests that most longitudinal rips occur at a load point. It should be noted that this is not always the case, so consideration should be given to multiple locations, including horizontal curves and inside transfer buildings. The MEE is usually located in an electrical sub-station or similar, away from direct sunlight and severe hose down.
MAINTENANCE
Maintenance is usually limited to transducer replacement and this has been covered under HARDWARE. With this in mind, transducer change-out has been designed to be as simple as possible. No unusual tools are required and no special skill set needed.
The mounts are extremely reliable and durable, but again, can be easily replaced if necessary.
All enclosures are IP 68 rated, or better, and are fabricated from 316 stainless steel.
All electronics have been designed and built with their intended use in mind.
Short circuit and over voltage protection is standard.
TROUBLESHOOTING
The device is a mature product. It has been rigorously tested over many years and is very robust and reliable.
A video surveillance camera is usually fitted at the sensing location as part of the installation so that events, such as false trips, can be observed and/or recorded and then correlated with machine data to facilitate troubleshooting.
Occasionally mobile phone networks suffer outages. This will not effect the operation of the machine, if this is the primary method of Internet connectivity, but will prevent alarms and diagnostic data from being sent and downloaded for analysis.
Because the device does not need a full-through rip to operate, aggressive setting of the Trip Threshold can see the device trip on partial depth rips.
