The SUREFIRE™ Automatic Snow Detector provides dependable, efficient sensing of falling and blowing snow and other icing conditions. It can be used to automatically control snow melting equipment at railroad track switches. It is a complete system, including a weather tight enclosure, power supply, relay with timer, temperature control, and sensing heads. Individual sensing heads may also be used with MAGNUM™ gas and electric track switch heater control systems from Railway Equipment Company.
The snow detector sensing head contains a self-regulating heater, which maintains a constant temperature in the head. A snowflake or ice crystal coming in contact with the sensing head will melt, forming a water droplet. This water droplet will bridge the gap, making an electrical circuit. The moisture sensing circuit in the relay module senses the resulting electrical circuit and the output relay is energized. An adjustable timer maintains the contact closure for a time period after the moisture has vaporized.
The plug-in relay module includes indicating lights to show the detection of moisture and to show that the timer is maintaining the relay contact closure. The temperature control is normally set at 36�-38� F, thus determining whether freezing conditions actually exist. Either one or two sensing heads may be used. A common installation will have a sensing head mounted in proximity to the switch point and another mounted on a pole in the vicinity of the switch heater.
A relay contact closure can be used in conjunction with a dispatcher’s relay, either in a series or parallel configuration to control track switch snow melter systems. The S UREFIRE™ Snow Detector can also be used to provide an indication to personnel of snow or icing conditions at remote locations.
Railway Equipment Company manufactures several different types of track switch snow melter systems that incorporate both snow detector control and temperature control. Two such systems are:
Model 922 Electric Track Switch Heater Control System for tubular heaters includes temperature control and the power supply as standard. Snow detector operation can be included by adding the No. 9258-0002 snow detector plug-in module and the No. 9258-0020 sensing head.
Model 933 Gas and Model 934 Electric Hot Air Blower snow melter systems include the temperature and snow detector controls as standard. Snow detector operation can be included by adding the No. 9258-0020 sensing head.
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