FEATURE HAZARDOUS AREAS & SAFETY HOW TO AVOID A DUST UP WITH DANGER
ABB’s Luciano Santos explains the importance of picking the right motor and variable speed drive package to reduce the risk of flour dust explosion in bakeries
T
he Health and Safety Executive (HSE) recently announced that bakeries are
among the industries targeted in a new crackdown on dust control. Bakeries can expect to be subject to unannounced inspections, as well as enforcement measures if controls are deemed insufficient. Flour dust is a serious occupational
hazard for bakers. Over time it can lead to health problems, notably Baker’s Asthma, which is one of the most frequent occupational respiratory diseases in the Western world. The HSE advises that flour dust exposure must be reduced as far below the Workplace Exposure Limit (WEL) of 10 mg/m3
as reasonably practicable.
Unfortunately, there is no quick fix to eliminating the accumulation of flour dust completely, as it is a key ingredient in bakeries and difficult to control. The most effective ways to reduce airborne dust levels are employee training to prevent spillages, efficient ventilation and extraction systems, and diligent cleaning when build-ups are identified. Flour dust is also explosive. In high
enough concentrations, when combined with an ignition source such as a hot surface or a spark, it can combust. In enclosed areas it can have devastating results. In fact, airborne flour dust is even more explosive than coal dust.
According to the Combustible Dust
Incident Report, in 2018 there were 278 recorded dust incidents (i.e. fires or explosions) around the world, resulting in 113 injuries and 17 fatalities1
. Of these, around 43
percent involved food products. Furthermore, it is widely accepted that many incidents are either inaccurately reported or not reported at all, and so the actual figure is likely to be much higher.
ARE MOTORS A RISK FACTOR? Explosions require three main components: combustible material (in this case flour dust), oxygen, and an ignition source. Since it is not realistic to eliminate flour dust and oxygen from a typical bakery facility, ATEX regulations focus on removing ignition sources. Standard electric motors, used in a range of bakery processes, can potentially create such an ignition source during operation. This can be overcome by using certified dust- ignition-proof motors. These typically use appropriate ingress protection so that no dust can reach any internal hot surfaces, while motors are also designed to have no hot external surfaces in both rated and fault conditions. Variable speed drives (VSDs) can help to achieve considerable productivity and
energy efficiency gains when used with electric
Motors can create an ignition source in dusty environments, but this can be overcome by using dust-ignition-proof motors
motors, but they also present additional challenges for processes in potentially explosive atmospheres. It is vital that an appropriate motor and drive configuration is chosen, as getting this wrong can compromise explosion protection measures. Furthermore, drives cannot be installed within a potentially explosive atmosphere and must be installed away from the motor in a safe area. The right package for a given application
12018 Combustible Dust
Incident Report,
DustSafetyScience.com
MAKING A QUICK CONNECTION IN EXPLOSIVE ATMOSPHERES
As automation continues to expand into diverse industrial sectors, the demand for multi-channel fibre optic cable is following suit. However, there is an increasing need for high-count, high-bandwidth fibre, capable of delivering an increasing amount of data required in a single cable. This requirement is often most pressing in locations where space limitations simply won’t permit installation of extensive runs of low-count fibre, such as offshore platforms. In addition, for sectors like oil and gas, it’s advantageous to install pre-terminated plug-and-play quick
connectors that meet the recently-adopted international standards for explosive atmospheres. In both offshore and land-based natural gas and oil rigs, multi-channel high-speed fibre optic cable is
required to control automation as well as monitor equipment status and communicate predictive notifications when components are in danger of failing. Because the hazards of explosive atmospheres are a global concern, ATEX (Atmosphere Explosibles) and
the IECEx (International Electrotechnical Commission) have issued special “directives” to establish minimum requirements for improving the health and safety of workers. According to Phillip Hoyle, from Optical Cable Corporation (OCC), there is a lack of available certified fibre connector solutions, particularly with high-count multi-channel options that facilitate the bandwidth that is required. To meet this need, OCC recently developed the EZ-Mate Ex line of quick connectors, which provides up
to 24 fibre connections in a single connector and has hazardous location protection for Zones 1 and 2. “Quick” connectors are an ideal solution for applications that require frequent teardown and setup. Hoyle
said: “Each receptacle can be mounted to an increased safety or flame- proof enclosure, allowing for multiple easy connect and disconnect deployments, reducing teardown time.” Hoyle adds that quick disconnect systems such as the EZ-Mate can be beneficial in switching out
frequently relocated and reconfigured applications such as land-based rigs as well as more efficiently servicing high damage areas on offshore platforms. Optical Cable Corporation
22 OCTOBER 2019 | PROCESS & CONTROL
www.occfiber.com
will depend on a range of factors. These include ambient conditions, supply voltage and frequency, load type and overload requirement, as well as zone, dust group, temperature class and required Ex protection type. It is highly recommended that facilities engage their motor manufacturer in ensuring the right package is selected. Manufacturers like ABB can offer
certified dust-ignition-proof motor and drive packages. In such configurations, the motor is tested together with the drive to ensure compliance to Ex t protection, which saves time by eliminating the need for additional testing and certification after purchase. Ingress protection to IP55 or IP65 prevents any dust from entering the motor, and therefore from reaching any internal hot surfaces. Windings can be equipped with temperature sensors to protect the insulation, while thermistors are fitted to limit the surface temperature of the motor. Severe flour dust explosions are
thankfully rare in the UK, but the risk remains omnipresent, particularly in larger bakeries. Dust-ignition-proof motors and drives can help reduce risks, but only when selected, installed and operated correctly.
ABB
www.abb.com
/ PROCESS&CONTROL
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