# How are pressure vessels heated?

I'm working on a project in which I'll be dealing with pressure vessels. As of now I've drawn/conceptualized everything on theory basis. The diagrams are made on the basis of theory, but then I came through a situation where I'll require to heat water under high pressure at around 300-350 Celsius. So then I decided to use pressure vessels and to use LPG gas for heating it (LPG has flame temperature of around 1100 Celsius, but please note that I want to heat the water kept in vessel at just 300-350 Celsius)

Now, I'm stuck in thinking that how do you heat pressure vessels? Are there any special port/connections provided to heat them/the content inside them? Or are any special type of heaters used to heat them? Would be great if you can tell everything you know about heating it

Optional to read(this could be wrong): Are we supposed to directly heat them on flame? Just like cooking your food on the gas-stove running using LPG? If this is so, then won't it take too much time because the walls of vessels would be very thick?

• Sounds extremely dangerous. At 350 C, pressure will be about 200 atmospheres. How do you know that the material of the container will be strong enough to hold that kind of pressure, when heated to 1100 C? – DavePhD Feb 19 '15 at 17:15
• No, I don't want to heat it up to 1100C, that's just the flame temperature. I just want to heat the water at around 300-350 (so that it's superheated). And the PSI would be around 1900-2500. I've checked few sites and there are companies that make pressure vessels which can hold that much PSI along with temperature. ;) – george mik Feb 19 '15 at 17:17
• I understand the contents will not be 1100C, but the outer surface of the container may be. Also you are underestimating the flame temperature of LPG which is 1980C elgas.com.au/blog/453-the-science-a-properties-of-lpg – DavePhD Feb 19 '15 at 17:46
• Yes, it will have to adhere to ASME Pressure Vessel standards (or equivalent outside the US). However, for inspiration on how to heat water to those temperatures and pressures, you should look at steam locomotive boiler designs. Combustion takes place in the firebox, and the hot gases are directed down a number of flue tubes that all go through the tank of water, offering large surface area for transfer of the heat to the water. – Jon Custer Feb 19 '15 at 20:36
• @DavePhD If that is the case, then think about our normal cooking fry pans. The LPG/flame is same in both the case, so don't you think that if our fry pans can handle 1980C then why can't a specially built vessel won't? – george mik Feb 22 '15 at 5:28