In the zone

The Dangerous Substances and Explosive Atmosphere Regulations 2002 (DSEAR), defines a hazardous area as “any place in which an explosive atmosphere may occur in quantities such as to require special precautions to protect the safety of workers”. As Paul Mannion, project engineer at engineering solutions provider Boulting explains, it is vital that precautions are taken when constructing, installing and using apparatus in areas that have been defined as hazardous.

In the UK, the regulation BS EN 60079 part 10-1 and part 10-2 are used to determine the area classification, a method of analysing the environment where explosive gas and or dust atmospheres may occur.

The DSEAR scope is extended with BS EN 60079 part 14 detailing the design, selection and erection of electrical installations within a hazardous area and BS EN ISO 80079-36 to incorporate non-electrical sources of ignition and mobile equipment that could also pose an ignition risk.

Hazardous areas are classified under six zones. Three zones associated with gas are classified under Zone 0 and are areas where an explosive gas atmosphere is present continuously or for long periods of time. Zone 1 is an area where an explosive gas atmosphere is likely to occur in normal operation, while Zone 2 covers areas where an explosive gas atmosphere is not likely to occur in normal operation and if it occurs, will only exist for a short time. The other three zones are associated with dusts, which are either flying and explosive, conductive or non-conductive.

It’s worth noting that 80 per cent of dusts are combustible, asserts Mannion. The associated three zones are Zone 20, an area where ignitable concentrations of combustible dust or ignitable fibers/flyings are present continuously or for long periods of time under normal operating conditions; Zone 21 an area where ignitable concentrations of combustible dust or ignitable fibers/flyings are likely to exist under normal operating conditions and; Zone 22, an area where ignitable concentrations of combustible dust or ignitable fibers/flyings are not likely to exist under normal operating conditions.

Any facility that processes, uses or manufacturee materials that may give rise to a flammable atmosphere, such as gas, mist, liquid and small fibres (dusts), may have a potentially explosive atmosphere and therefore fall into one of these six zones. Industries that may have an explosive atmosphere include food manufacturing, power generation, water treatment, oil and gas, chemical manufacturing and pharmaceutical.

While areas classified as Zone 0 or Zone 20 continuously face the potential for the creation of an explosive gas or dust atmosphere, work still needs to be conducted in these areas. To continue this work safely, the equipment used needs to be weighted so that there is no chance of creating explosions. Equipment should be designed in such a way that it is stringently safe and includes current limiting devices to stop sparks. The equipment that will be used should be chosen and tested as early in the design process as possible.

Before equipment can be used in any hazardous area, it must undergo a programme of rigorous checks and testing by a registered ATEX test house. ATEX is the name given to two European directives that aid in controlling explosive atmospheres. The first, Directive 99/92/EC (ATEX 137) assess the minimum requirements for improving health and safety protection for workers in potentially explosive environments. Directive 94/9/EC (ATEX 95) looks at the laws concerning equipment and protective systems intended for use in potentially explosive environments.

When constructing a new facility or working in an existing environment, it is important that the installation of new components is done using the most efficient techniques to reduce the risk of incidents. Modularisation is a technique often used by Boulting. This method sees equipment or parts of a facility built offsite and installed at a later date, taking the risk out of working on a hazardous site. In addition to constructing in a safer environment, modular builds reduce site disturbance, minimise waste, are more cost effective and allow for far greater design flexibility. Construction of the overall build can also take place much quicker as modular builds occur simultaneously to the main build.  

While ATEX testing is vital to identify and resolve potential risks at the start of a project, it is important that inspections continue to take place on a regular basis throughout the equipment’s lifespan. With the development of new software these inspections have started to incorporate risk based elements which are identified by HSE. This method of inspection looks at the type of protection used, the installation factors i.e. vibration, corrosive, outdoors etc in addition to common manufacturer/model failures

Engineers should factor in the production of a schedule for periodic inspections at the design stage. Boulting provides clients with a digital cloud based system where they can upload inspection schedules and what exactly needs to be checked.

Solendoid valves

Designing process control systems that meet DSEAR, ATEX and other similar standards requires considerable levels of expertise and competence to deliver a suitably compliant process that meets the demands of the application. When it comes to creating a new, fully certified installation, Paul Hobden, Bürkert UK ATEX solenoid valve champion stresses that it is important to select partners that understand process control design with the ability to deliver bespoke solutions using the latest technology that is certified to the standards in force locally.

This allows design features such as vibration-proof, bolted coil systems, and increased leak-tightness to be included in a potential system. Just because the application requires a component that is certified for operation in potentially explosive atmospheres, it shouldn't mean that the choice of control valves is reduced.
As part of its development of ATEX and IEC-Ex certified versions of its components and systems, Bürkert has established a centre of competence in Menden, Germany.

Bürkert not only designs a comprehensive range of solenoid valves to cover both standard and specialist applications, it also manufactures every component which includes the machining of the valve body, the injection moulding of the coil body and the manufacture of the coil itself.

The testing of individual components and complete valves is a continuous process, partly to ensure continued compliance with a wide range of certifications, but also to ensure that the high-quality standards are being maintained. In this way, the customer can be sure of reliable operation, especially in tough operating conditions.
In situations where an existing component will not satisfy the demands of an application, it is possible to work with development engineers to create a bespoke solution that can also be tested and certified in-house. Having this facility within the company also reduces lead times and helps to deliver projects on time.

Efficient connections for the Ex zone

Operators of oil and gas platforms need to continuously monitor their sites’ ambient condition status through parameters such as gas concentration levels, differential pressures and temperatures. Mobile explosion-proof detectors and transmitters allow such measurements to be made at various different key locations on the platform and then be re-positioned as required. The readings from these instruments are switched and recorded via an explosion-proof central controller. These pre-existing detectors and central controller enclosures will typically already have glanded conduit access points. Because of the stringent requirements of explosion-proof equipment, users need to avoid making any modifications to such certified equipment.

In order to save valuable installation time and to maximise location flexibility of such a mobile detection system onto an oil or gas platform installation, Harting offers an explosion-proof connection solution with Harting's compact Han Ex 4A cable-to-cable connector system, a product that can be retrofitted without compromising the equipment’s Ex certification compliance. Because all detectors are provided with pre-fitted connector cable ends, they are supplied to site fully pre-tested, which ensures fast pluggable installation.

Hazardous location-ready microstepping drive

Applied Motion Products (AMP) has released a variant of its STAC6 series microstepping drive for high performance motion control that has international certification for hazardous area use. Available with full support from Mclennan, the drive is aimed at machine automation applications in oil & gas, mining, printing and other industries where ATEX, IEC-Ex or UL certification is required. The drive, designated STAC6-Q-H, specifically covers ATEX and IEC-Ex certification for Class I, Zone 2 locations and UL certification for Class 1, Div 2, Group C & D locations. These hazardous areas are characterised such that flammable gases, vapours or liquids are not likely to occur in normal operation but, if they do occur, will only persist for a short period of time.

The panel mounted STAC6-Q-H includes an integrated intelligent drive with RS-232 and RS-485 communication and offers motion control configuration options that include step and direction, analogue voltage, PC or PLC host control, as well as standalone multitasking programmable control. With its direct-on-line AC power and programmable output current, from 0.5 to 6.0 A/phase, the drive will suit medium-to-large sized hazardous area compatible stepper motors producing a high holding torque and a wide speed range (contact Mclennan for suitable ATEX and UL approved motors).

Stackable multi-turn encoder

Sensata Technologies has launched what is reported to be the first explosion proof stackable multi-turn encoder for use in oil and gas applications.

The new encoder, BEI Sensors’ model MAAX, is ATEX and IECEx certified to operate in explosive environments and features a Profibus output in a bespoke, stackable package.  CANopen and SSI outputs are also available. The MAAX provides up to 16 bits of resolution as well as up to 16 bits of turns by mechanical counting. The product operates directly in Zone 1 environments without the need for an accompanying Intrinsic Safety barrier.

The stackable and explosion proof design makes for a simple installation wherever encoders are mounted in tandem to provide multiple signals for redundancy or when data sharing is desired. The Profibus interface simplifies system set up as it allows for daisy chaining products together without the need for running a control cable from the panel to each individual component. 

All exposed parts are either stainless steel or hard anodized to resist corrosion.  This rugged encoder is shock and vibration resistant and can operate in field temperatures from -30°C to +65°C.  Fitted with a unique 20 mm diameter integrated coupling, the MAAX housing can be rigidly mounted, reducing stress to the encoder’s bearings and providing a secure attachment for the hazardous area conduit fittings.  A through hollow shaft design with up to a 30mm flexible shaft bore is also available to fit a wide range of installation requirements.

Worker protection

For those staff faced with the challenge of working within hazardous environments, technology can play a key role monitoring and improving safety. As Glyn Jones, Group CEO, Trolex points out improvements in wireless tech and connectivity mean it is now easier for operations managers to track the locations, movement and environment of workers in real-time. These real-time insights allow operations managers to be far more proactive in managing the working environment, using data collected from connected devices and equipment to ensure operatives are both safe and working in an efficient environment at all times.

Dust monitor units located in tunnels and mine shafts that track dust within the environment, for example, can be directly linked into the supervisory control and data acquisition (SCADA) system to provide real time monitoring information, enabling operations managers to automatically manage air conditioning and dust suppression to optimise the environment.
 
By monitoring worker activity and location alongside environment condition monitoring, integration with the communications systems means workers can be warned if they are working in an area that is becoming unsafe. This can range from complete evacuation to a request to put on a mask in an area where masks are not always required or by employees who are not always required to wear masks as part of their day to day activity.

Tablet for hazardous areas

Part of Pepperl+Fuchs brand ecom ́s wirelessly interlinked, explosion-proof Mobile Worker Ecosystem that includes smartphones, tablets, peripherals as well as software applications, the Tab-Ex 02 industrial tablet is reported to combines top performance with innovative applications such as augmented reality. It is suited to IoT-capable applications and simplifies data exchange with SCADA / DCS systems, enterprise resource planning systems (SAP, IBM Maximo), project management systems and computer-aided system planning. As a compact lightweight tablet, the Tab-Ex 02 is aimed at a wide range of tasks such as inventory, material tracking, maintenance, and supply chain or asset management.

Based on the latest Samsung Galaxy Tab Active2, the Tab-Ex 02 uses the high-performance Android 7.1 Nougat operating system and features a powerful Octa Core processor with 1.6 GHz and 3 Gigabyte RAM.