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Why do you need dust testing?

By Kevin Spiess of BS&B Safety Systems

 What is dust testing?

In industries that handle or store organic materials for processing, there is always a risk of dust explosions occurring. A myriad of powdered or ground organic materials ranging from carbon to milk powder are key constituents for ignition and fuelling of ensuing primary explosions within process facilities. Taking every precaution to ensure that such explosions don’t happen is of paramount importance for the protection of personnel, equipment and facilities.

Before installing any explosion protection equipment, it is imperative to understand what kind of dust you are protecting against; they all have different flammable properties.

Laboratory testing a sample of the particular type of dust generated in a factory, will reveal the dust’s performance under specific equipment operations and processes.

How does it work?

Dust testing is designed to identify two key performance characteristics of dust, which in turn influence explosion protection equipment design and their application.

  • The first measures maximum pressure of a dust explosion (Pmax in bar)
  • The second identifies the speed of the rise in explosive pressure (KSt in m/sec)

Different types of dust have different particle sizes, properties, ignition temperatures, and ignition sources, from each other. Dusts are given explosion severity classifications; St1 to St3. ‘Not specified’, means the material is non-explosive and St3 is the most explosive type of material.

Testing under laboratory conditions will tell you what St class your dust is, based on its KSt value. It also discloses the dust’s performance when subjected to certain processes; for example, is it being milled, ground, poured or dried? While being subjected to these processes, what is its Minimum Ignition Temperature (MIT)? In other words, what temperature will the dust withstand before it becomes an ignition risk?

Why would you use it?

In the UK and Europe, there is a requirement to identify any potentially explosive substances in the workplace. In the UK, this requirement is governed by the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR). DSEAR classifies dangerous substances as those used or present at work that could, without adequate controls, cause harm as a result of a fire or explosion.

In Europe, ATEX is the common name given to two European directives that specify what controls employers should use to prevent explosion risks, which are divided into danger ‘zones’.

Both DSEAR and ATEX recognise dusts as explosive risks.

Dust testing determines which kind of explosion protection you should use for optimum performance. For example, do you need spark detection, chemical suppression and isolation or relief venting? It’s important to know for sure what kind of protective measure counteracts the type of dust your factory generates. Because dusts have different explosive properties, they are often handled and stored in different ways and locations. The protective measures in each location will be tailored to meet the associated risk.

(Always engage an explosion protection consultant to advise on the best protective solutions for your factory.)

How advanced is it?

Laboratory dust testing can be extremely thorough, sometimes demanding hundreds of process test methods to ascertain the full spectrum of performance characteristics of different dusts. This includes the careful testing of toxic dusts, which pose a high health and safety risk in some industries. The direct exposure of personnel to toxic dusts is almost as dangerous as the threat of a dust explosion itself.

Is it safer than other methods of explosion protection?

Dust testing isn’t strictly a method of explosion protection; however, its benefit is found in the ability to make explosion protection methods perform at their best. By matching the type of dust generated with the most appropriate protection method to withstand its effects, optimal protection is achieved. This only succeeds if dust testing and identification under laboratory conditions is carried out.

How does it enhance solids and bulk handling and production?

Apart from the obvious safety benefits, dust testing offers a significant cost benefit to factory owners. If you decide to invest in advanced explosion protection equipment without conducting a factory survey and dust testing service, there’s a risk that your equipment won’t work properly. In the worst case, it won’t protect your staff and equipment from an explosion. Understanding the nature of your dust is key to getting the best performance out of your equipment.

To find out more: www.bsbipd.com.

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