Re: Coal Silo Explosion Vent Design
BS EN 14460
VDI 2263
Works fine here. ■
Re: Coal Silo Explosion Vent Design
Originally posted by alex35683
Hello All.
I'm new to engineering, new to bulks material handling and new to the forum 
I have a question:
Are explosion vents for coal silos normal to be implemented? If yes, are there any design standards (preferably AS - Australian Standards) or other documents/journals which detail the design of an explosion vent for a silo, containing coal? (eg: total surface area needed to vent the expanding gasses, etc.)
Calculation procedures, examples and so on would be great!
kind regards
Start with LLoyds of london and in the Unites States national fire underwriters.
If you use a stacking tube you can not go wrong in your design. ■
Coal Silo Explosion Vent
There are various Australian Standards. Start with AS/NZS4745-2004.
Michael Reid. ■
Re: Coal Silo Explosion Vent Design
Hi Alex,
The only Australian standard that specifically refers to plant safety for Explosion of combustible dusts is AS 4745. "Code of Practice for Handling Combustible dusts". Explosion Vent Design and Sizing is covered in VDI 3673 and NFPA 68. Both offer good guidance and design examples.
Could I suggest that if you have a real project then we could provide a design in keeping with the practical and safety needs of the job.
Coal is too broad a description to provide any suggestions - is it pulverised? if so what size? is the silo inside or outside? what sort of volume is it? what is the geometry?is there a need for flame trapped vents?
Happy to help if we can. ■
Re: Coal Silo Explosion Vent Design
Hi all,
thank you all very much for your replies! It's greatly appreciated.
Mr. Vierboom the answers to your inquieries:
The coal is stored in a silo, before it enters a coal mill. The average size of the coal is 40mm and the maximum lump size is 70mm at a moisture contents of 25%. I have received these numbers from one of our engineers, so I am supposing that these dimensions represent the sieve sizes.
The silo is located within a transfer tower structure, approximately 12m off the floor and having a total height of 23.4m. The structure itself is open to the enviroment, but is roofed and houses a conveyor which drops the coal into the silo at the top.
The Silo's geometries, in two parts:
The top half of the silo is a cylinder, 5.6m in (inner) diameter and 11.3m tall.
The bottom half of the silo is a truncated cone, 12.1m tall, upper diameter of 5.6m and lower diameter of 0.610m.
The Silo volume is approximately 389.66m^3.
As an exercise, I have used SHAPA Technical Bulletin No.10 Sizing of Explosion Relif Vents. (http://www.shapa.co.uk/pdf/techdata10.pdf) which gave me a huge ~47m^2 relief area. I followed the example set out on Page 4 of the PDF, since it is close to our design. The values of Kst and Pmax, Pred are 129 bar-m/sec, 9.2barg and 0.38 barg respectively, which I have sourced from another PDF document.
Thanks you very much in advance! ■
Vent Sizing
Alex,
Using the data supplied, I have calculated your vent area at 13.26m2. This is in compliance with NFPA 68, 2002.
The following link is to an area of our website that contains specific details of venting options and data sheets to allow you to choose a specific type of vent.
http://www.fireprotection.com.au/Exp...onVenting.aspx
Please contact us (from the website contact point) and we will be happy to help you with any more information that you require.
Regards
Pat Harrington ■
Re: Coal Silo Explosion Vent Design
Hi Alex,
The data you gave me requires a vent area of 13 square meters according to VDI 3673 and 11 square meters according to NFPA 68. The SHARPA document to which you refered uses the VDI formulae.
Further to the above these formulae refer to a worst case senario where the total volume is filled with a homogenious dust air mixture. This cannot happen in the vessel that you describe. Also the data on the coal is very high for either Brown or bitumonus coal. Please check the data source.
Explosion Relief panels or valves can readily be designed to suit this application.
I would suggest that you contact me directly if you want to get a proper design for the project. Dust explosions involving raw coal bins are not common. Generally explosion protection is applied after the mill as the source of ignition - the mill - and the dust load in the system are at hazardeous levels. The raw coal bin is more likely to have a fire or a smouldering event and thus other protection systems may be more applicable than explosion venting. ■
Re: Coal Silo Explosion Vent Design
Mr. Harrington, thank you so much for your reply.
A question that arises is, do we actually need to have explosion vents installed, even thou we are not storing pulverised coal.
More specifically what is the design point at which we need explosion venting. Is there a certain cut-off point for various material types and sizes?
Also, would it be possible to obtain a copy of the document that you have done the calculations on?
Thanks in advance! ■
Re: Coal Silo Explosion Vent Design
Mr. Vierboom, thank you so much for your reply.
Is there a way to find out why the calculations I have done give me such a huge venting area? One of the fellow engineers double checked my calculations and arrived at the same conclusion.
Could you also please specifiy which data is high? The data was supplied by Tunra Bulk Solids and it is the coal which is falling into the Silo, being stored there.
Thank you very much in advance! ■
Re: Coal Silo Explosion Vent Design
Hi Alex,
If you refer to AS 4745 you will get guidance as to the need or otherwise for explosion protection. A full risk assesment is recommended for any system which handles combustible dusts. The risk assesment will effectively determine the need for protection measures (or the lack thereof) - good engineering will determine the means to the end. The process is too lengthy to attempt here.
As to the data I questioned, the K(st) and P(max) seem high by comparision with other australian coal. ■
Re: Coal Silo Explosion Vent Design
Mr. Vierboom
I obtained the values for K(st) and P(max) from http://www.fike.com/pub/epdocs/stn500.pdf , page 2. Is there any other source for these values, specific to Australian Coal, or could u give me some arbitary figures which seem more applicable.
Thanks in advance! ■
Re: Coal Silo Explosion Vent Design
Sample the coal to be stored and get it's explosion characteristics measured. Relying on data found in a book or on a web site is the last resort, ■
Re: Coal Silo Explosion Vent Design
Dear Sir,
We have supplied in the past in Spain explosion venting using either explosion vents or explosion doors for many coal silo installations.
In order to calculate de venting area you can use VDI 3673 or the more recent EN 14491, in your country maybe the NFPA 68, but all three will give you most likely the same venting area.
In order to implement the best protection strategy, which not only includes explosion protection with venting, but which in your case could include fire protection and explosion isolation, I would recommend you contact CMC Technologies in Australia, www.cmctechnologies.com.au
regards,
Xavier Martino ■
Re: Coal Silo Explosion Vent Design
Dear Sir
Our company has extensive experience for protection of coal silos in event of dust explosions.
Please call to discuss.
My number is +61 2 9669 4000
web site www.cmctechnologies.com.au
Regards
Con Carpis
BE Chem ■
Did You Solve Your Problem
Alex,
Did you resolve your issue. My company, Fire Protection Technologies are a designer and supplier of explosion venting and suppression systems and are the authorised Fike distributors for Australia. I previously posted a link to our website which I have discovered does not work. Please telephone me on 03 9558 0715 to discuss, Also try this link
www.fire-protection.com.au ■
Coal Silo Explosion Vent design
Hello All.
I'm new to engineering, new to bulks material handling and new to the forum
I have a question:
Are explosion vents for coal silos normal to be implemented? If yes, are there any design standards (preferably AS - Australian Standards) or other documents/journals which detail the design of an explosion vent for a silo, containing coal? (eg: total surface area needed to vent the expanding gasses, etc.)
Calculation procedures, examples and so on would be great!
kind regards ■