Hello jonesliu:

Welcome! Are you speaking of the 'contents' tempurature, or ambiant working temp?

Check out this site for a whole range of stats on heat disipation and MP (Melting Points).

"PN" means "Pressure number"...

It can't be that high as this valve is brass. The site below seems based on water pressure. Hope this helps.

below:
In a working pipeline system, however, the useful working pressure can be limited by the sealing ability of the joints, the pressure rating of the fittings or by the ability to the resist the end-loads that result from pressure.
The maximum system pressure should normally be lower than the maximum pressure rating of the pipe and fittings used. The main exception is that site commissioning tests (leak tests) are often carried out above the rated pressure but this is usually only for a short time and the effects of the excess test pressure should be covered by the safety factor. The recommended test conditions vary for different pipeline materials, and may vary from job to job so it is important to check.
Pressure rating is described in a number of ways – for example by a pressure Class "A", "B", "C", etc or by nominal pressure as PN10, PN16 etc (PN comes from the French for Nominal Pressure, which is the official pressure rating rather than the actual pressure capability of an individual pipe).
Rather than explain them all in detail, the table below shows how the different descriptions of pressure class compare with each other. The conversions aren't exact, but are close enough for everyday purposes.

Approximate conversions between common pressure units.

Until recently, the pressure class of ductile iron pipes (and cast iron pipes before that) was described through the wall thickness K9, K12, K14 etc, which was used to work out the pressure rating. Since 2004, these K classes have been replaced by PN ratings but K classes will be around for a while as old stocks are used up and, of course, older fitting and pipelines with these ratings will remain in service for many years to come.

babybear

Hello again, I forgot to mention the MP of brass. I have pasted a comparison chart, (and I forgot to spell check the first post of mine, sorry).

This chart is from the 'muggyweld' site:

Melting Points of Metals

Hope this helps babybear

Please refer to the following CR4 threads: Pressure Rating , Pound Rating & PN numbers vs. valve class in ASME standard