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aiden  
#1 Posted : 09 July 2019 19:20:37(UTC)
Rank: Forum user
aiden

I was asked whilst in a client company carrying out training on a separate matter re a potential Confined Space classification.

The equipment concerned is a large cooling cube structure, 4m square by 3m height within which a circular conveyor carries warm food entering at the bottom and exiting at the top, cooling the food items as they spend time within this cube. This equipment is often called a spiral cooler. The refrigerant used is ammonia. The evaporator is situated within the interior of this cube.

The issue is there is a small motor located at the top exit, but within this cube, (tensioning the conveyor). This small motor is assessed internally via a full size door opening into the cube, a fixed ladder and then a walkway on the circumference of the chain conveyor. The client wanted this area not to be classified as a confined space. This equipment has been in this location for approx. 14 years however it is approx. 25 years old. In its 14 years of operation there has never been an ammonia leak. After looking at this item etc. I explained it should be classified as a confined space location, low risk. My rationale is that such evaporators can leak, there is no facility to isolate the ammonia gas and due to the restricted access it would be very difficult to exit within such a hazardous atmosphere. I showed HSE requirements re confined spaces etc.  This caused an issue, it’s never leaked etc. There is more, but this is the gist. I would be Interested in hearing anyone’s thoughts of this scenario and my opinion of a confined space.

Ian Bell2  
#2 Posted : 09 July 2019 20:10:33(UTC)
Rank: Super forum user
Ian Bell2

I think you know the answer.

If you have identified a defined 'specified' risk as listed in the Confined Spaces ACOP - Reg 1(2)a-d then you have your answer.

I have seen a spiral cooler so roughly know what you are talking about - I would say 'b' applies, from the list.

thanks 1 user thanked Ian Bell2 for this useful post.
CptBeaky on 10/07/2019(UTC)
Roundtuit  
#3 Posted : 09 July 2019 20:21:13(UTC)
Rank: Super forum user
Roundtuit

Its never because it is about to. There is a poisonous gas under pressure so controls need to be in place to ensure the gas and employees do not come in to direct contact with each other.
aiden  
#4 Posted : 09 July 2019 21:53:16(UTC)
Rank: Forum user
aiden

Thanks you guys, appreciate the responses.

Ian Bell2  
#5 Posted : 10 July 2019 07:28:01(UTC)
Rank: Super forum user
Ian Bell2

To add a littler further comment, there probably hasn't been an ammonia leak because the pipework is most likely seamless/continuoulsy welded pipework and connections.

I would also expect somewhere in the factory to be an ammonia compressor building and control valves and heat exchangers. In these plant area will be ammonia gas detectors to shut the system down in the even of a leak.

Ian Bell2  
#6 Posted : 10 July 2019 07:41:20(UTC)
Rank: Super forum user
Ian Bell2

Also forgot to say. If your client hasn't yet done so, your client also might need also undertake an occupied building risk assessment.

How much ammonia is in the overall chiller/refrigeration system? At the plant room if an 'industrial' size ammonia system is installed, there will be compressors, heat exchangers, vapour and liquid vessels.

If there were a major leak you would have a toxic gas cloud which could be lethal to hundreds of meters distance.

A building(s) on site should be designated as a toxic refuge - which means it will need certain design features to prevent toxic gases entering - tight fitting doors/windows. Gas detectors in air conditioning intakes that shut down on detection of ammonia.

I have previously done such assessments on food industry ammonia refigeration system.

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