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September 14, 2017

15/09/2017: Explosion safety for mills

by Catherine Tyrra, REMBE® GmbH Safety + Control, Germany

It is in the nature of a mill to have metallic parts that collide with one another at high speed, so that ignition sources are highly probable

Again, this is a closed container with a high concentration of dust, which may include oxygen, making an explosion extremely likely. Many mill manufacturers therefore offer their machinery in a design that is resistant to explosion pressure (up to 10 bar).
 


Depending on the size of the mill, this may be very expensive for the operator. Alternatives would be flameless venting solution. In either case a decoupler should be attached both above and below the mill.

One particularly smart solution for the air intake of the mill is to install a Q-Rohr LF. This is a modified version of the Q-Rohr, well known in flameless venting, which does not contain the explosion vent that is normally included.

As a result, it is possible to aspirate air under normal operation, and the air can then be fed through the stainless steel mesh filter without any trouble. If an explosion occurs, this filter removes the resulting heat and protects the environment from the flames and the explosion pressure.

Explosion isolation

In a production facility, pipelines always connect the individual parts of the plant. The purpose of explosion isolation is to ensure that the pressure and the flames cannot propagate and so that any adjoining parts of the plant are protected.

A distinction is made between active and passive isolation systems. An active system is alerted to an explosion at an early stage, when an explosion begins to develop.

This is done through sensors or detectors that register the rise in pressure or the formation of flames and respond by activating the relevant isolator, e.g. a quench valve.

Passive isolation, on the other hand, responds purely mechanically to the spreading or loss of pressure, on account of its structural characteristics. This also applies to explosion valves. Under normal operation, an explosion valve in a pipeline is kept open by the available flow.

When an explosion occurs, the valve is closed by the spreading of the pressure front, thus effectively prevents the pressure and the flames from propagating any further.

Read the full Milling and Grain article, HERE.

Visit the REMBE GmbH website, HERE.
 

The Global Miller
This blog is maintained by The Global Miller staff and is supported by the magazine Milling and Grain
which is published by Perendale Publishers Limited.


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