Bernd Schneider, Author at AUTOMATION INSIGHTS

Certification of Equipment in Hazardous Areas

This post was originally published on Innovating-automation.blog.

Industrial processes often need to be carried out in a hazardous atmosphere or when hazardous materials such as explosive gases, dust or flammable liquids are present. Such substances can be ignited by sufficient energy coming from sources like electrical sparks, open flames, and hot surfaces. The equipment installed in these areas must therefore be planned such that it does not represent an ignition source. In most countries around the world, national and/or local governments enact electrical construction standards intended to prevent accidents and enhance the safety of people and property. To ensure that installed components have been designed and tested according to regulations and offer sufficient protection, testing agencies are used. They certify that a particular device meets the specifications of the special standards for hazardous locations.

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Country Certification

There are many types and categories of possible hazards in explosion hazard areas. How these areas are classified depends on in which country or region the equipment is being installed:

In the USA the NEC (National Electrical Code) uses two methods for classifying hazardous locations: these are based on both the class/division and the zone. Categorization into class/division is a long proven procedure in the USA. Division into zones is a newer alternate concept which is becoming more and more established. As soon as the decision is made as to which method will be used for certification, that method is consistently applied.
Canada is similar to the US but follows the Canadian Standards Association (CSA) electrical codes.
In the European Union a harmonization scheme is used to eliminate technical trade barriers. The ATEX Directive 2014/34/EU is applied to devices and protection systems for proper use in explosion hazard areas. As part of a hazard assessment the operator divides the areas into zones and selects devices for the corresponding category.
For the rest of the world various local regulations and standards apply. But more and more countries are turning to the uniform global standard IECEx (International Electrotechnical Commission Explosive). It is however possible that a country specifies IECEx as the basic standard while requiring additional national certifications to meet country-specific regulations.

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For a comprehensive overview about the protection classes for electrical devices you may refer to following poster and brochure (including Balluff products for hazardous areas) that can be downloaded from the Balluff Homepage – or ask your Balluff sales representative for a printed version.

How to Simplify Wiring in Process-Related Applications

If you have ever been on a process or power plant during commissioning or in case of a fault, you have probably asked yourself how to simplify wiring in process-related applications. In these industrial segments, engineers often encounter complex structures and are confronted with long signal paths. Individual subsystems, equipped with local programmable logic controllers (PLCs) or remote terminal units (RTUs), are usually connected via bus systems to the control room and SCADA system, whereby diagnostic tools are available for this network.

The fun starts with troubleshooting on the subsystem level. The individual sensors and actuators are still very often wired with copper in the traditional manner. This means that there are thick cable bundles in cable ducts, and the individual conductors at the cable ends must be terminated correctly and securely. Special care must be taken with analog signals, as a missing or incorrectly connected shield can also cause signal or measurement errors. Troubleshooting under these conditions can be very nerve-wracking (if all eyes are on you) and expensive (production or power downtime).

There are some markets where there are both strong automotive and process industries. Engineers who change sides are bringing alternative field wiring approaches, such as ASi and IO-Link with them. Since these technicians are familiar with the advantages of commissioning and troubleshooting in the production line, they have no reservations about implementation. So let’s take a look at the other side:

In the past in factory automation, parallel wiring has been used.

As product life-cycles are getting shorter and availability has to be high, there is a greater need for modular systems.

Therefore on the sensor/actor level, they are implementing IO-Link more and more, which some people already call the USB port of automation systems. Some advantages of IO-Link include:

Flexibility in connecting to a wide variety of devices through the same M12 connector. The unshielded cable and robust digital signal effectively conquer issues such as line interference and overcome flexing or bending restrictions
Digitized analog values (from 4-20 mA, 0-10 V, PT100/1000, thermocouple Type J/K) instead of analog signals
Additional diagnostic information directly from hubs and sensors/actuators
Possibility to adapt the host bus system to other countries or customer demands. Only the master module has to be exchanged (most of the wiring diagram will stay the same)

This interesting technical report by Andritz Hydro (Austria) shows how IO-Link was successfully implemented in a hydro power project: “Powering Africa”! (more information about IO-Link solutions).

How to Develop and Qualify Sensors for Arctic Conditions

The climatic conditions in the arctic are characterized by cold winters and short summers. There is a large variability in climate and weather: Some regions face permafrost and are ice covered year-round with temperatures down to -40°C / -40°F (and lower), other land areas face the extremes of solar radiation up to +30°C / +86°F in summer.

As oil and gas exploration, as well as renewable energy (e.g. cold climate versions of wind turbines) move into arctic areas, the need grows for sensors designed to deal with the extreme conditions and to perform reliably over their whole life cycle.

One option is the implementation of a Highly Accelerated Life Test (abbreviation HALT) in the development process. The basic idea of HALT is the accelerated aging of electronic products (including sealing gaskets, potting compound, housing etc.) with the aim of detecting their possible weak spots as early as possible and to correct them at the development stage.

Example of a sensor in the HALT test facility (Balluff magnetostrictive linear position sensor BTL)

The item under test is subjected to higher and higher thermal and mechanical stress in order to cause failures. The limits where the product will fail functionally or be destroyed are determined in order to push these limits as far out as possible, and so achieve a higher reliability for the product.

Product operational specs = data sheet values

The HALT procedure – in brief:

a) Analysis of weaknesses already known, definition of failure criteria, establishing the stress factors

b) Stressing the test specimen beyond the specification to find the “upper and lower operating limits”, and the “upper and lower destruct limit” for temperature, rapid change of temperature, vibration, combined vibration and temperature stress

c) Determination of the causes of failure

d) Devising a solution to eliminate the weaknesses

e) Repeating of steps b) to c)

Example: Temperature step test – cold and hot

Example: Combined vibration test and rapid temperature changes

Example: Cowan Dynamics E2H Electro-Hydraulic valve actuator Photo: Cowan Dynamics (Canada)

In contrast to other environmental tests, HALT is not qualification testing according to specific technical standards (as ISO/IEC etc.), but it applies stimuli to the items under test until they fail, so weak spots will be revealed. A HALT test is not an exam you can pass!

However, if sensors are implemented into more complex automation systems that will be operated in remote areas, this method may help to prevent major faults in the field and is therefore also used in the aircraft and automotive industry.

For more information about Balluff testing methods and the laboratory, please visit www.balluff.com or download our brochure “The Balluff Testing Laboratory”.

Position and Level Measurement for Clean Energy

A few years ago, a new gas station opened in our neighborhood situated at the edge of town. Some new customers started showing up with camouflage painted cars, especially early in the morning or late at night. They always seemed to be a little shy, never leaving the cars alone and sometimes, while grabbing a cup of coffee, they would even cover their cars with a tarp. It became obvious that this gas station was also used as a base for the test fleet of some major car manufacturer, and even after years, it is still exciting to get a glimpse of a new prototype. Working for the international Balluff energy team, it was even more exciting to see that a new hydrogen fuel dispenser had been installed at this gas station a few months ago.

Hydrogen seems to be one of the promising possibilities to store surplus energy from wind or solar power and to realize climate friendly mobility. But the processing and transportation of hydrogen poses new challenges for the equipment with regard to pressure, temperature and material properties.

One of the possibilities for position and level measurement in such a harsh environment is magnetostrictive measurement systems.

This type of transducer comprises current position information transferred via magnetic fields contactless through the housing wall to the internal sensor element. The operation principle enables the installation in hermetically sealed rod/housing against the process medium.

Another point to note is the presence of a possibly hazardous atmosphere that can be ignited by electric sparks or hot surfaces. Therefore the measurement systems installed need to be designed in accordance with applying explosion protection regulations.

Considering the above mentioned framework conditions, specific part testing and verification is necessary within the development process as well as in series production. In addition the necessary approvals and certificates have to be provided on an international scale.

For more information about the future market of Clean Energy, the measurement systems in use and the cooperation during the R&D process, visit the full report from Linde AG Austria (AUTlook 4/2017).