PROFESSIONALS AND BUSINESSES PARTICIPATING IN DISCUSSION
Process Industry Consultant / Soft Skill
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V.RaghunathanDear Kailash Bharadwaj,
As per approved safety measures what you have asked is correct.
In confined space only 24 Volts supply is to be taken inside for lighting purpose.
There are approved safe STEP DOWN TRANSFORMERS (240 / 24 volts )
available for this purpose.
These will be located outside.
Only the output lead carrying 24 Volts will be taken to the confined space.
These lamps come with special shades / grill type cover.
Wattage will depend on the the number of lamps you need.
Safety approved vendor will furnish the details.
In closed space you have to be careful about obnoxious vapour / gas also.
Further you have to exercise caution if the inside ambiance is likely to be wet.
We had great discussion on the use of 24V supply inside confined spaces in the past in this forum.
We come to a common conclusion that the supply inside confined space should be so robust with earth leakage protection, instead of keeping it just 24 volts. If your supply to confined space is routed through proper ELCB/RCCB/RCBO, then you can even use 230 V inside confined space.
As said by Raghunathan, people do use Step Down Transformers and its a best practise to adopt. In that case what about your welding machine cables, grinders inside confined space??? Are you going to ensure 24V supply for those too???
If you are interested, read our earlier post and reply of Mr. Kesava Pillai:
Still if you wana learn more about Confined Spaces, please reply to the questions in the below thread asked by Mr. Kesava Pillai. I would love to participate, if someone is interested.
I was thinking, I have a good understanding about the confined spaces. Recently I got this question during one of my training session and failed to answer and learned more further. Why it says to ventilate at the rate of at least four (4) volumes per hour inside confined spaces?
Thanks for your response and active participation. Much appreciated. Do keep up the rhythm.
V.RaghunathanThank you Mr Dipil for your mail.
A 24 Volt light source is the safest way to start any activity in a confined space.
It is just a beginning.
As you rightly pointed out we need to take higher voltages to carry out maintenance work.
This is normally done after ensuring adequate safety. There are instances when you have to build scaffolding. Step by step these activities are to be carried out.
I am also not exactly aware about the four times volume sweep. However the logic is not difficult to understand.It is something like the concept of factor of safety. What is your satisfactory number? Two or Three..? The factor of safety is also fixed by experience.
You can take the thickness of LIFT/ ELEVATOR ropes as example. While higher numbers might give more degree of comfort, often experience emboldens one to go for proven economical designs.
In a confined space you can expect Heat, Dust, Toxins, Odour, Vapours etc. More air is required to mitigate all these effects and ensure that adequate air supply is there for persons to breathe safely. While more than four is welcome, four might have been fixed based on reliable past experiences. Perhaps OHSAS covers this aspect.
Some of the biggest operations I have witnessed include the Under ground Mining of Non Ferrous Metals like Zinc, Silver, Cadmum , Lead etc. Scores of People work several meters below MSL. Very huge machinery driven by diesel / electric power operate
below the ground level.
Adequate ventilation is provided by forcing fresh air from the base at ground level. DGMS
( Director General of Mines and Safety) is a Statutory authority that governs these operations. One can learn about high standards of safety from these operations.
I came across one interesting presentation and a good article from the internet.
Both are attached to this post.
Hope these add some value.