An introduction to Hazardous Areas in a distillery
I am writing this to give distillers some guidance on hazardous areas and how to deal with them. I will declare that I am not a “competent person” by the legal definition and cannot do any hazardous area assessment, but I have read and learnt and I need to give you guys some pointers so that you understand that there are options and you may not need explosion proof everything. This a long essay, but it is useful and may save you a lot of money, so be patient and read on.
The first thing you need to know is that a distillery will be classified as a hazardous area and this means there are some safety issues that need to be dealt with. What is a hazardous area you ask? Great question. It is an area where gasses, vapours or dust are present in sufficient quantities that, under the right circumstances, may explode. We are dealing with alcohol (ethyl alcohol or ethanol) which is flammable as we all know. What a lot of us don’t know, is that it is as dangerous as petrol.
In order for an explosion to take place you need 3 conditions to be met: there must exist fuel (alcohol), oxygen (air) and a spark (caused by electrical fault, static, mechanical implement, match, etc). The fuel needs to exist in sufficient quantity to ignite and this is called the Lower Explosion Limit (LEL) which is 3.3% alcohol by volume (ABV) in air. Less than this and the mixture is too lean. Alcohol also needs to be above its flash point, the temperature at which alcohol gives off enough vapour to ignite. This depends on the ABV of the liquid but let’s just say that around ambient temperature we have a potential problem with alcohol. And when you boil it you have more of a potential problem. There is another term: lower flammable limit (LFL) which is lower than the LEL and this is 3.1% ABV and is the number used in IEC Ex codes (we will get to them later) since some time after 2015.
Now, remember that we need fuel, air and ignition for an explosion, so if we can eliminate fuel we are ok. So, if you can keep the alcohol away from any source of ignition, you will be ok. This possible but very difficult and the idea with hazardous area codes is to deal with risk mitigation: how do we limit the alcohol vapours and limit the potential for ignition?
The first process is to determine the hazardous zone classification. This is the point where you need a “competent person”, someone qualified to do the assessment, to look at your distillery and your equipment and make the assessment. This is also the point where these competent persons may give a different assessment depending on their training and experience. The reason for my missive to help ensure that the correct competent person is identified.
Here is what the zone classifications are:
- Zone 0 – An area in which an explosive atmosphere (above 3.1% ABV) is present continuously, or for long periods.
- Zone 1 – An area in which an explosive atmosphere (above 3.1% ABV) is expected to occur occasionally during normal plant operation.
- Zone 2 – An area in which an explosive atmosphere (above 3.1% ABV) is not expected to occur in normal operation, and if it does occur, will exist for a short duration only.
- Non hazardous – no explosive atmosphere.
These zones are important because they will determine what action you need to take and Zone 0 needs more actions than Zone 2. More action means more cost and it is necessary to get the zone right to avoid unnecessary cost. We don’t really get Zone 0 so we will be expecting Zones 1 and 2.
Ok, so where do these Zones come from? It is now time to talk about the IEC Ex codes. The IEC is the International Electrotechnical Commission and these guys have a code for everything to do with electrical and I think communications stuff. They take experts from around the world and together they formulate best practise and write it down. It is pretty much the same as our AS/NZ standards here in Australia. If we have our own standards, why do we need something from the IEC? Well, here is Australia we have a wiring code – AS 3000. This wiring code is legislated or written in regulations of every state and territory and everyone has to comply with AS 3000. I won’t quote all the legislation, but I will quote AS 3000: in Section 7, which is titled Special Electrical Installations and deals with things like Safety Systems, Generation, High Voltage and at 7.7, Hazardous Areas.
At 7.7.2.1 it says, “The responsibility for classification of a hazardous area (see Clause 1.4.15) rests with the persons or parties in control of the installation. The requirements are contained in AS/NZS 60079.10.1 for gas or vapour and AS/NZS 60079.10.2 for combustible dust.” Fast fly to AS 60079.10.1 and at 4.6 it says: “The hazardous area classification should be carried out by persons who understand the nature of flammable substances, gas dispersion and ventilation and are familiar with the process aspects for the plant under consideration. It may be beneficial for other engineering disciplines , eg electrical and mechanical engineers, and personnel with specific responsibility for safety..…to have input”.
You will find a lot of electrical people involved in the Zone classification and I guess that if they have relevant training on process calculations they would be considered competent. So when you look for a competent person you need to make sure they comply with AS 60079.10.1 clause 4.6. This is particularly important when you looking to get the right classification to keep the costs at an appropriate level and still maintain a safe and compliant distillery. It definitely is possible to do this with the right help.
Here is a real life example that I have seen in practice. Let’s look at a safety valve on a still…in my real life example, it was classified as Zone 1 by a competent person. In IEC 60079-10-1 there are some examples in Annex E and under E2, Example 1 they discuss a pump with a mechanical seal. Mechanical seals can leak, but not in normal operation. The grade of release is classified as “secondary” because any leakage would be due to “seal rupture”, an event that does not occur in normal operation. A secondary grade release is associated with Zone 2 classification. Apply this reasoning to the safety valve which will only release vapours in the case of a blockage in the column or condenser and the grade of release would be secondary and Zone 2 applies, not Zone 1.
Your choice of competent person will affect your Zone classification! It is not supposed to be this way, but it is.
Let’s go back to this Zone 1 vs Zone 2 classification and see what the effect might be, because in a distillery there is not a lot different in the actions or equipment that are necessary, but the little differences could have a cost impact….here goes:
It is a lesser used technique in distilling to provide protection by ventilation and therefore derate the electrical equipment. I know a distiller who had a consultant do an assessment and came up with a design that included lots of explosion proof electrical equipment. So he appointed another consultant who was more knowledgeable and the system used was called Ex vc – protection by ventilation, and there is a whole standard dedicated to it called AS 60079.13. What this means is that while distilling there is an extractor fan taking air out the space and diluting any releases of vapour to the point that the concentration of alcohol in air is less than 25% of the LFL. And what this means is that you don’t need explosion proof electrical equipment.
Except the fan. And any safety equipment (alcohol vapour detector, level switch, temperature probes used for safety control). But no explosion proof heating elements or lighting.
Now for the Zone 1 vs Zone 2. The scope of AS 60079.13 says that protection by ventilation applies to equipment:
- located in a Zone 2 explosive atmosphere (an area normally requiring EPL Gc) with or without an internal source of gas/vapour release and protected by artificial ventilation;
- located in a Zone 1 or Zone 2 or Zone 21 or Zone 22 explosive atmosphere (an area normally requiring EPL Gb, Gc, Db or Dc), containing an internal source of gas/vapour release and protected by both pressurization and artificial ventilation.
If your space is Zone 1 you need pressurisation and ventilation, a fan blowing and a fan sucking. Two fans that are explosion proof cost $3,500 each at least. For a Zone 2 classification you need just the fan that sucks. So the base cost is $3,500 vs $7,000. Are you starting to get the idea?
There is a tendency of regulators and consultants to specify a ventilation system with a specific flow rate of about 20 space changes per hour. So if your space (room) is 6m x 9m x 3.5m you would need a fan with 20 x 189m3 = 3,780 m3/hr. However, AS 60079.14 has a series of calculations so that you can more accurately achieve the appropriate flow. I have done these calculations for a scenario of a spill that fills a 25m2 bund for a 900L still and the required flow rate is less than 1000 m3/hr. I have considered the case of a loss of water to the condenser leading to a release of vapour from the parrot and its vent. I worked on 25kW of power to the still and 25% heat losses from the surface of the still which yielded a release rate of 46 m3/hr of alcohol. That is quite a release rate and it would need 6000m3/hr of ventilation. The ventilation is best calculated to match the release rate.
If the parrot was design to vent outside the building this release would not need to be considered. The same goes for the safety valve.
Do you see how it all works? There are ways to engineer less risk and therefore reduce costs. A more experienced assessment of the zone classification can also save costs. There are more ways to reduce risk that I have not learnt about yet, but a quick chat with WA company gave me a hint of what can be done with operating procedures and I hope to learn more about this at some stage.
Ultimately, the most important point I am trying to make is that there is value in getting a competent and experienced consultant to help you work out what you can do to get a compliant, safe and economical design.
In the meanwhile I have been searching the world for IEC Ex certified equipment and can happily tell you that I have sourced the following:
Wiring inside Ex d heating element
- Ex d heating elements,
- Ex d level switch
- Ex d alcohol vapour detector
I am getting close to finding Ex d axial fans and Ex ia (intrinsically safe) temperature probes. So, if you are looking for any of these items send me an email to hilton@hhhdistill.com.
