Australian hazardous area standard classification of diesel storage

[goldyvb]

Hi all,

We are completing a project for a client of ours for 2 x 3.4 million litre storage tanks and have to classify the zone in the tank. As diesel is a combustible and not flammable this normally would negate the need for classification, but there are a lot of differring opinions on forums on diesel tanks. The main point of contention seems to be that the tank inside is Zone 0 and the rest of the installation (pumps, pipe work, etc) are not zoned. If we zone the tank 0 our client will no doubt want verification from the standards. Can anyone shed some light on this issue?

Thanks

Michael

 

[Mass44]

Hi there,

To determine where you need to do IS protection, you first need to look at the Zone classification of your plant. Where is Zone 0 areas in the plant.

Only IS protection may be done in Zone 0 . IS protection may also be done in Zone 1 and 2 but Explosion proof (Ex d) and Increased safety protection (Ex e) may only be done in Zones 1 and 2.

Ex d protection combined with IS protection is normally done in Zone 0 but IS is minimum for Zone 0. You can combine IS with Ex d or Ex e for Zone 1 and 2 as well where needed. The important thing is to know what is the minimum protection required for a Zone.

So to recap on the minimum required protection for Zone 0,1 and 2.
Ex ia = 0, 1, 2
Ex d = 1, 2
Ex e = 1, 2

Zone 0 = Most hazardous environment where explosive gas will be present all the time or long periods of time.

Zone 1 = Areas where explosive gasses may be present for short period during normal operations.

Zone 2 = Areas where explosive gasses are unlikely to be present and if they are present will be present for short periods due to abnormal operations.

You cannot make the tank alone a Zone 0 and the piping Zone 1. You need cassify the plant areas as Zone 0 or Zone 1 or 2.
Look above how Zone 0,1 and 2 are being classified and you will see they talk about a area and environment and not about a specific piece of equipment.


the European way:

http://www.engineeringtoolbox.com/hazardous-areas-classification-d_395.html

North America have their own way of doing things but the rest of the world work on the European standard as the international standard.

The NA way:

http://www.engineeringtoolbox.com/hazardous-areas-classification-d_345.html

 

[goldyvb]

Hi,

Thanks for your response. I am pretty well versed in area classifications, but have come across articles where even though diesel is classed combustible and not flammable (ie. Non hazardous), there is the potential for an explosive atmosphere to form in a storage tank. Any other comments and this would be appreciated?

Thanks

Michael

 

[ilan7]

as mensioned, the liquid is no classifide as flammable so no EX protection is needed for the electrical instruments involved. See what is done at a regular gasolin station - pumps are not EX and all other instruments.
We build systems that uses thermal oil in compressed natural gas stations. Everything at the gas area is EX (or IS) and whatever is at the thermal oil area is not classified.

 

[sow]

Its covered in the EN regs by the nature of the gas -Ive done zoning before a good while ago and Im pretty sure it specifically covers stuff like diesel, no justification is needed, it is or it isnt.

 

[ICLL]

I'm not sure which jurisdiction the OP is in, but in Australia the area classification standard AS2430.3 for flammable liquids (Section 3.3) requires you to regard a combustible liquid as a flammable one if it is being handled or stored within 6 degrees C of its flashpoint. In such a case the normal flammable liquid classification boundaries would apply.

Diesel does not have a fixed chemical composition and its flashpoint can vary widely, being as low as 60deg C from some refineries. It is completely credible that diesel sitting stagnant in pipes exposed to the sun e.g. around a pumping station would reach such temperatures. As a result in Australia (WA in particular) regulators are starting to express opinions that diesel pumping facilities to be classified as hazardous. However, this is contentious.

Obviously this would not apply to the OP's tank example (there's no way that an entire tank would get hot enough to be regarded as flammable).

 

[dpc]

Can't speak to Australia, but in the US, no special provisions are required for diesel. Been through this many times with engine-generator suppliers. Diesel fuel tanks are not considered hazardous locations.

David Castor

http://www.cvoes.com