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Minimum size for an access 'hole' in the side of a storage tank?
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#1 Posted : 23 February 2006 16:38:00(UTC)
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Posted By Andrew Beveridge
Dear All,

We are having some new storage tanks (30 ton capacity) built to our specifications, and I have the opportunity to have low level access hatches built into the side of these tanks.
The tanks are to store liquid chocolate, and during shutdown, we need to clean and sanitise them. I am familiar with the confined space requirements but was wondering if there is a British/European standard, or any guidance available that you could point me to?

I figure ~ as big as possible, but there are product control and quality/food safety issues as well.

Any help/guidance will be gratefully received.
Regards
Andy
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#2 Posted : 23 February 2006 17:06:00(UTC)
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Posted By peter gotch
Andrew, from Appendix to Confined Spaces ACOP...

Standards relevant to manholes and other access
to confined spaces
The following Standards are relevant:
• BS 8007:1987 Design of concrete structures for retaining aqueous fluids. Code
of practice. Minimum openings specified as 600 mm x 900 mm;
• Silos UK: Draft design code for silos, bins, bunkers and hoppers, published by
BSI in association with the British Materials Handling Board, gives the
minimum as 600 mm x 600 mm;
• BS 5502: Part 50 1993: Code of practice for design, construction and use of
storage tanks and reception pits for livestock slurry gives access hatches etc as
not less than 600 mm x 600 mm;
• BS 8005: Sewerage Part 1 1987 Guide to new sewerage construction gives the
minimum clear opening dimension for manholes for drainage purposes as
600 mm x 600 mm for sewers less than 1 m diameter, except for very
shallow manholes where this dimension may be 550 mm;
• BS ISO 9669:1990 Series 1 freight containers. Interface connections for tank
containers.

Regards, Peter
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#3 Posted : 24 February 2006 11:09:00(UTC)
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Posted By TBC
Good answer Peter, but I've got a better one. Andrew just make the hole big enough for me to get my head in and I'll come and lick the tank out for you.
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#4 Posted : 24 February 2006 11:21:00(UTC)
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Posted By Frank Hallett
Andrew

Please note that the sizes quoted by Peter are minimum recommended sizes.

Ideally, you should ensure that the dimensions are suitable for access by the fully kitted out operative ready to do whatever they have to do - which may well require greater dimensions once you've taken any CS Emergency Resonse issues into account.

Also, the less bending &/or climbing that has to be done to negotiate the access/egress point the better.

Frank Hallett
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#5 Posted : 27 February 2006 10:33:00(UTC)
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Posted By David Tilsley-Curtis
Andrew

The posting so far offer a great insight into your requirements, however they do seem to miss one very important item. What is the reason you need to get into the tank? It's either inspection, cleaning, servicing or repair. All of these items will require you to get to the higher internal areas of the tank, therefore one of the most important issues is what will you get in there through the hatch to enable you to do this.

There are a couple of specific platforms available, I could send you details if you require them.

David
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#6 Posted : 27 February 2006 21:09:00(UTC)
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Posted By Helen C
Don't know how relevant this is.....but consider the possibilty that you may have to evacuate a casualty on a stretcher, i.e. width of stretcher, proximity of access hatch to invert of tank.
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#7 Posted : 29 March 2006 15:13:00(UTC)
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Posted By garyh
If at all posible go for a hole that is doorway sized - like 1 m x 2m - then access etc is easy. And of course, your rescue plan becomes simple (and we all have credible rescue plans for confined space entries, as per the ACOP, don't we?)

If the engineers etc argue, just ask them if they fell whilst inside the tank, and had a broken hip, would they rather be shoehorned out through a porthole or carried out by stretcher?
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#8 Posted : 29 March 2006 15:50:00(UTC)
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Posted By Glyn Atkinson
Don't make the hole too big, and hide all of the spoons in your canteen or site restaurant !!

Can't you just see the works notice ? - "Volunteers required to clean out chocolate tank - large appetite but no previous experience necessary"

Bring your own spade and bucket !! Take away service available !!
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