External Insulation Temperature Specification 2

[jproj]

Are there any specifications that deal with the maximum external surface temperature of an insulated pressure vessel? I thought that OSHA would have specified a maximum temperature for personal protection, but I haven't been able to locate anything. I think I've seen 140ºF listed somewhere, but I'm not for sure. Any help is greatly appreciated!

jproj

 

[Montemayor]

jproj (Chemical):

With regards to PP (Personnel Protection), a vessel does not have to be insulated to qualify - as your opening statement implies. A non-insulated vessel is also subject to the ruling of PP (and this is the usual case).

The maximum surface temperature allowed is dependent on the company in question, in my opinion. I have been mandated to use 120 oF on DuPont projects while Oxy Petroleum has been satisfied with 140 oF. I have personal preference for the DuPont limit. If you want to know why, evaluate my logic: knowing that 120 oF is the max. temperature that an average human being can tolerate by touch with his hands, try to wrap your right hand around a 1-1/2" pipe that is at 140 oF and see how long you can tolerate the heat pain. The result will tell you why I tend to be conservative.

Let's face engineering reality: this is an important safety subject because the majority of times a human being touches or grabs a hot surface is due to the fact that he/she is in dire need of a physical support for balance and stability while doing his/her job. If you are working at an elevated platform and have to rely on a hot pipe for support, you would want to know which pipe you can safely rely on, wouldn't you??

Your interest and concern in this subject is, in my opinion, a very important point and item for everyone involved in process plant work and projects. I would hope your question inspires other experienced engineers' comments and opinions on the subject.

Art Montemayor

 

[quark]

Montemayor has very good points to say. I will just give some facts (though I don't know whether they are relevant to the original post or not)

1. As far as fatality is concerned, the temperature in wet condition should be 121⁰C for min. 15 minutes and in total dry conditions it is about 270 ⁰C for morethan 30 minutes. (that is why some living organism is found in the craters of volcanoes)

2. I read one article recently (couldn't get the link now) which describes about a person's capability to withstand heat. Two persons sat inside an oven at 150 ⁰F for one hour without any trouble and considered that as a benchmark of maximum temperature.(infact they did it at various temperatures)

3. When water temperature is maintained at minimum 75 ⁰C no bacteria or any living organism can grow.

But when exposed to indirect heat, perspiration will reduce effect.

Wrapping around a heated object is a different issue. Going for extra insulation because we have to touch it occassionally (and not using personal protective equipment) is not fitting into my thoughts. (and I was not new to burns, thanks to the distillation columns) So I stick to 140⁰F.

The following link can give you some insight on insulation and skin temperatures of cladding (which I have already given in your other thread).

http://www.cheresources.com/insulationzz.shtml

You might have known it already but here is the link for economic insulation thickness program by DOE.

http://www.pipeinsulation.org/pages/home.html

Note: I am still an engineer very much and never took a management course.

 

[hacksaw]

PP at 120 F is not for the pain but rather for the fact that at and above this temperature, the heat kills the nerve and continued exposure is capable of higher order tissue damage without the individuals knowledge.

Insulation is not the only accepted means for personnel protection. The actual rating is likely contained in the OSHA standards.

For safety issues relating to vapor ignition, etc. the surface temperatures are increasingly covered by the respected safety code. Insulation does not solve this problem.

Heat conservation is the obvious issue and already discussed.

 

[25362]

Thermal insulation -in particular that installed for personnel protection- should be periodically inspected, upgraded and maintained just as with any other potentially hazardous uses. Changes in plant operations and in weather "worst" conditions may affect the temperature inside the insulated pipes or equipment as well as external surface temperatures, and thus affect overall insulation performance and safety.