Electricity + Control December 2018

HAZARDOUS AREAS + SAFETY

Reducing elevator downtime

variable frequency drive (VFD), the business may benefit from in- creased efficiency and reduced energy costs. However, this does not manage the low-level transient surges that can occur countless times a day, exaggerated by VFD usage. Transient surges can lead to false zero crossings of the sine wave — the instantaneous point at which there is no voltage present. In a sine wave, this normally occurs twice during each cycle. Devices can be falsely triggered because of fast changing signals caused by transients, as they believe the zero point has been crossed, even when it hasn’t. It can cause confusion for all equipment on the grid. Whether it is caused by transients or a freak utility power surge, insufficient power quality is destroying many elevators and their related equipment. For elevator operation, this can cause recurring random failures, lockups and deprogramming of human machine interfaces (HMIs) on each floor. However, this downtime and main- tenance can be eliminated if the right protection is in place. Typical surge protection devices are unable to prevent these is- sues as they are voltage triggered only.This means built in surge pro- tection systems are not a feasible option. The answer to this prob- lem is using a SineTamer ® cascade system.This system offers much more than a standard surge protection device. It is an engineered transient disturbance filter, designed to monitor all 360 degrees of the sine wave. Using 360-degree monitoring, the SineTamer ® can prevent issues caused by false zero crossings of the sine wave. Enquiries: John Mitchell. Email. John.mitchell@cpaltd.net

There are over 900,000 elevators in operation in the US alone, many of which experience mind-boggling lock ups and loss of program- ming. John Mitchell, global sales & marketing

director at supply, installation and repair specialist CP Automation, explains how elevator maintenance managers can prevent these an- noying occurrences. On average, 20,000 people are carried by each of these elevators every year. That equates to 18 billion trips made by elevator annually, just in North America. Elevators play a crucial role in human logistics and thus present a lucrative opportunity to improve the efficiency of buildings worldwide. Modern buildings are being erected to greater heights than ever before. As a result, newly implemented elevators are required to travel higher and faster than their predecessors.With these changes come a new set of problems and maintenance issues for engineers. To manage these new heights, today’s elevator software and hardware are more complex, and therefore more sensitive to fluc- tuations in power surges. This does not only refer to the strong surges from lightning strikes or utility companies, but also the tran- sient surges that can happen thousands of times a day. Transient surges are a change in fundamental frequency of power that can occur multiple times a day on the power supply network. These surges are a result of switching operations of inductive loads, such as air-conditioning units, transformers and lift motors. Surges related to lift motors are most commonly linked with elevator power quality issues. If the lift motor is controlled by a

Electronic instruments in ex-hazardous areas

area and as a direct result, reduce the risk of explosion. Indeed, this method is extensive- ly used in the mining and chemical industry. No trigger Apart from “No Open Flames” signs, pre- caution is taken to prevent electrical equip- ment from being a source of ignition. A simple electrical switch in your home for example, generates a tiny electrical spark every time the switch is thrown. This spark, although harmless in our home environ- ments, can be enough to act as trigger for an explosion in a hazardous area. In a simi- lar fashion, sparks can be created by porta- ble electronic devices. In order for devices to be safe for use in hazardous areas, safety precautions have to be built into the design. Intrinsically safe instruments There are several aspects in the design of in- trinsically safe electronics devices, of which reducing or eliminating switch sparking is but one. Other considerations include, includ- ing fast fuses, controlling component tem- peratures, eliminating too tight component spacing that could lead to a short circuit and reducing circuit current and energy storage.

R&C Instrumentation is geared to sup- ply a considerable range of intrinsically safe instruments: The Raytek MT4-IS handheld non-con- tact thermometer for the temperature range -18°C to 400°C, the Raytek Mi3-IS 4-wire system fixed pyrometer and the Raytek TX-IS 2-wire loop powered system fixed pyrometer. As part of their recently launched range of vibration sensors, there is also a wide range of ATEX IEC and EX certified vibra- tion sensors available. Additionally, due to a special request from a mining client, they now also have in stock the UT390B+IS la- ser distance meter. Enquiries:Tel. +27 (0) 11 608 1551 or email info@randci.co.za

In many industries, there are certain areas that are classified as a Hazardous Area or EX area.This is an area that contains, or may con- tain combustible substances; gas, vapour or dust. Typical industries with hazardous areas include coal mines, grain silos, chemical and petroleum industries, offshore and onshore oil and gas, oil refining, the pharmaceutical industry and paint shops. During the coal mining process, two by-products are pro- duced; coal dust and methane. The build-up of either or both of these substances can be extremely dangerous. Even a tiny spark can set off a disastrous explosion. Similarly, grain silo dust ignited by a spark, have led to nu- merous tragic explosions. Safety measures in hazardous areas In order for ignition to occur, two things are needed, the explosive or combustible atmosphere as described above, and a trig- ger, i.e. a spark or flame. Remove one or both of these conditions and the explosion will not occur. Removing combustible dust and vapour Ventilation equipment can dilute or remove dangerous substances from an enclosed

20 Electricity + Control

DECEMBER 2018