5 replies to this topic

[AndyChemEng]

Quick query. We have suffered from the issue of corrosion under lagging over the years and there is a proposal to remove the top lagging of certain vessels that don't require insulation from a heat loss perspective. To is to mitigate against the main cause of lagging damage to the top of vessels. The sides will be subsequently sealed. 

 

From a fire safety perspective, is this acceptable? Does the top of vessels have to be lagged from a fire relief perspective?

 

 Bleve potential?

 

The top isn't wetted so is vulnerable from that perspective but then again being the top it is unlikely to see high heat loads from a pool fire?

A top located jet fire?

 

The materials involved are a range of flammable liquids solvents (boiling points ranging from 40 to 130 degrees)

 

Any guidance much appreciated.

 

[breizh]

Hi,

Coming to my mind are:

*  The personnel protection and the risk for operators to be burned if you remove the insulation.

** the vapor pressure increases due to temperature increase on the sky of the tank with the release of material from the safety devices (PSV) (loss of material, risk of ignition).

 

 

My 2 cents

Breizh

[latexman]

Breizh has given good guidance based on the OP, but there's not much in the OP to go on, Andy.  I find I want to hear more detail before giving more specific guidance.  A physical and process description of each vessel would be needed.  Is the top of vessel included in the area of fire exposure, or is it above the fire height limit?  Is the fire scenario direct or indirect fire?  Are there other fire protection measures?  What are the other credible scenarios?  Has a management of change analysis been done, or is this the start of that?

[AndyChemEng]

Thank you for the info. 

 

You raise good points latexman. An argument could made that the vessel height themselves means the tops of the vessels are inherently out-with a credible fire scenario i.e. above the fire height. I remember reading in some guidance a specific height above which you discount fire scenarios for vessels e.g. a vessel located 8m above the ground wouldn't be subject to significant heat from a pool fire. I will compare this to the physical height of the top tan line of the vessels vs the ground level.

 

In answer to your questions:

The vessels are standard storage vessels, typically 60m3-100m3 located in bunded tank farms. Top filled and bottom emptied.

Other active protective systems are present (foam systems etc) but I will need to review its coverage vs the vessels concerned.

Pool fires is the most credible scenario but I suppose jet fires are feasible.

This is the start of the management of change assessment.

[latexman]

Okay, not sure about your location, but some chemicals in U.S. are regulated to use 100% of the talk area, like LPG in OSHA 1910.110. Check that too.

[AndyChemEng]

Thanks all for your replies, much appreciated.