Switches Indicators & Gauges

Powerlines

Powerlines are one part of a power transmission network transferring electrical energy from power plants to multiple substations, eventually powering homes and businesses.  The use of powerlines allows bulk transfer of electricity generated from distant sources (whether hydroelectric or coal-powered) to the consumer in populated, urban areas. This means that fuel resources do not have to be transported to city centres in order to fuel generating facilities. Power is usually transmitted as alternating current (AC) through overhead powerlines, which are usually composed of an aluminium alloy made into several strands and reinforced with steel strands. These are uninsulated, which means that they have to be designed to be higher that a certain clearance level to ensure safety. These can particularly be dangerous for maintenance crews, who might need to use an overhead voltage detector.

Powerlines can also be placed underground, with several advantages over overhead powerlines including not being subjected to adverse weather conditions, reduced emission of electromagnetic fields into the surrounding area, less clearance area (overhead lines require 20-200m clearance for safety), and less of a hazard to low flying aircraft and wildlife. However there are also disadvantages, including a much greater establishment and maintenance cost. For example, repairs to underground lines can take days or weeks which means that extra lines must be laid just in case.

Overhead Voltage Detectors

Overhead voltage detectors are used to test the presence or absence of a voltage on a powerline in order to carry out maintenance and repairs on the powerlines themselves, to prevent injury when operating crames, cherry pickers or outdoor TV broadcasts.

When a voltage is detected it emits an alarm, which can consist of a visual alarm (such as a flashing red light) and/or an audible alarm (both an internal buzzer and an external horn), that repeats proportional to the electric field intensity. Both the sensitivity of the alarm and the range of effectiveness, depending on the proximity of the overhead voltage line.

Cranes

A crane is a machine that can be used to lift, lower and move materials horizontally. It is composed of simple machines, as thus has been used since ancient times in varying size and complexity. A crane is useful because its use of simple machines enables it to move loads beyond human capability, and as such is employed extensively in the construction, manufacturing and transport industries.

It is used in construction to lift large tools and machinery and put concrete or steel walls into place in buildings. Cranes can be used in the manufacturing industry to assemble large machines (such as cars), and is useful in the transport industry for loading and unloading freight off ships.

There are two main types of cranes: mobile and fixed. Examples of mobile cranes are truck-mounted cranes, sidelift cranes, rough terrain cranes, all terrain cranes, floating crane, aerial cranes and crawler cranes. Fized cranes  are able to reach greater heights and carry larger loads because of better stability, and can take the form of tower cranes (the most common), telescopic cranes, overhead cranes, bulk-handling cranes, stacker cranes and hammerhead cranes.

Crane Safety Systems

Due to the height of cranes and the size of the loads that they carry, mistakes can be potentially deadly. As a result all operators must be trained and certified to reduce the risk of injury on construction sites. Additionally, there are safety systems that can be installed to ensure that the crane operates as it should and that the operator is given warning if there are any faults.

Examples of crane safety systems are load monitors, load moment indicators, wind speed indicators, overhead voltage indicators, boom angle indicator systems, and anti-2-block systems. Other instruments that could be used include tension load cells, load measuring shackles, handheld indicators, linear displacement transducers, pressure transmitters and load measuring pins.