7 replies to this topic

[vnpetroleum]

Hi All,

I am working on reviewing the insulation requirement for all pipings flowing IN/OOUT some vessels on platform. The current status shows that outside surface of all pipings which are insulated by Calcium Silicate (Heat Conservation) are corroded. We would replace all HC(Heat Conservation) insulation by other methods (metal wire mesh) to visual check and inspection.

I had a draft calculation to check the processing conditions of fluid without insulation for these pipings - confirmed operating temperature is higher than WAT (wax appearance temp).

My question is that which other scenarios/cases/factors I need to concern when removing their insulation.

looking forward to hearing from you soon.

Thanks - vnpetroleum

[ankur2061]

vnpetroleum,

If the original intention for the insulation was to have heat conservation for reasons of wax formation at low ambient temperature conditions then you are taking a big risk in removing insulation permanently.

One of the best methods to avoid corrosion on piping due to wet insulation is to have a suitable coating (e.g. fusion bonded expoxy) on the bare pipe surface and then apply insulation. This would ensure suitably insulated pipe with minimized risk of corrosion.

For subsea pipelines a multicoated / multilayered pipe-in-pipe insulation strategy is adopted for mitigating insulated pipeline corrosion.

Hoe this helps.

Regards,
Ankur.

Edited by ankur2061, 26 May 2011 - 03:18 AM.

[vnpetroleum]

Thanks Ankur for your reply,

I got your idea and had a draft calculation to estimate the fluid condition during process shutdown in at least 2 hours. Consequently, we cannot remove insulation because fluid temp is too lower than WAT.

Other question, what is the minimum temperature required to install Personel Protection? What is the standard? 70oC - I remembered - Is that correct?

Regards,

vnpetroleum

[ankur2061]

vnpetroleum,

I think 70 deg C is a wee bit too hot. I would go with 60 deg C or even 55 deg C. Most company standards recommend PP insulation to be provided if the surface temperature is expected to be more than 60 deg C.

Regards,
Ankur.

[Himanshu Sharma]

Interestingly this topic relates to hot touch temperature limit and the degree of burns associated with it.The thresh hold values for a particular time and temp limit is determined by experimentation dealing with lots of heat transfer variables applied to human skin followed by finite element analysis.

One such study establishes that threshold of burn for human finger is 65.6 deg c temp with exposure of over 1.6 seconds.

This can be related to Personnel protection or safety insulation being specified typically over 60 deg c.( I am yet to see a safety insulation specified below this value)

[Art Montemayor]

Himanshu’s point is pertinent to the discussion of what is the correct or logical maximum temperature that should be allowed for personnel protection.

I fully agree with ankur regarding the excessiveness of 70 ^oC. I believe the scope (or intent) of the recommmended practice for personnel protection is not being applied or is being misunderstood. I have always designed processes to incorporate personnel protection that is judeged by applying 130 ^oF (54 ^oC) because the scope of design used has been one where I have taken the position that the hot surface should always be a safe, potential means for human support – i.e., an operator should have the facility of grabbing and holding onto the hot surface in order to stop a fall or gain safe support from a hazardous fall. I have taken this scenario as my design basis because of my belief that an operator should have as complete a freedom to save his health and well-being as is possible. We can never pay or compensate anyone enough for risking his life and well-being.

As Himanshu indicates, it is not to be expected that an operator could hold onto a surface at 65 ^oC without risking having to let go. And if that hot surface was the difference between his being able to recover or suffer a dangerous fall from a platform or ladder, it is a serious subject to come to terms with.

In the past, I frankly have not understood the economics or logic that places costs above operator well being and protection. I continue to have a lot of problems with logic that restrict me from applying as safe an environment as I can for the people who put their safety on the line in order to follow our rules and instructions in producing product that will generate the revenue that pays all our salaries. It just doesn’t seem fair to me to quibble over an inch of insulation or a protection screen that could save a human life or prevent a serious burn.

I don’t believe that just the act of “touching” a hot surface is the main point here. Many top, world-wide processing companies agree with the concept of furnishing a processing system that allows an operator to safely touch AND HOLD ONTO any surface or object made available to their reach. And the time that he/she should be able to hold onto that object should not be measured in seconds. It could conceivably be much, much more than that. The time required to hold onto a hot surface may vary depending on the installation, but I have always used a minimum of 10 minutes as an arbitrary value to allow the operator to mitigate any potential hazardous circumstances.

I don’t intend to impose my beliefs or ideas on anyone; rather, my intent here is to focus the topic on the basic premise of safety and good practice for all process plant operations. Hopefully, this will generate more comments on a recommended method of designing for safe hot surface exposure to operators. Selecting the best pipe insulation, in my opinion, should also take into consideration operator exposure.

The subject of process operator safety is, in my opinion, the most important topic we can discuss in our Forums.

[vnpetroleum]

Thanks Art for your description. It is very useful for us.
Regards,
Vnpetroleum

[breizh]

Hi ,
May be a bit late , please consider this resource :

http://www.insulatio.../iibrochure.pdf

Breizh