Difference between atmospheric pressure hot water boilers and pressurized hot water boilers
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I used to design pressure-rated boilers, but now some customers are in need of atmospheric-pressure hot water boilers. I have just started working on the design plans and have looked into some issues that need to be taken into account when designing such boilers. However, there are certainly still many aspects that I’m not clear about. I would appreciate any guidance you can provide; the more detailed and clear the explanation, the better. It would also be helpful if comparisons could be made with pressure-rated boilers. Let me first share some information I’ve found: 1. The design, manufacturing, and acceptance processes must comply with JB/T7985-2002 \"Technical Requirements for Small Boilers and Atmospheric Pressure Hot Water Boilers\" as well as the \"Regulations on Safety Supervision of Small and Atmospheric Pressure Hot Water Boilers\". 2. The strength calculation, similar to that of pressure-bearing boilers, must comply with GB/T9222-2008 or JB/T16508-1996. 3. The standard for selecting pipes is GB/T8163-2008 \"Seamless steel tubes for transporting fluids\". 4. The manufacturing of the main components such as header tanks, pipes, and boiler drums is the same as that for pressure boilers. If there is anything incorrect in the above, please point it out. Additionally, I would appreciate your guidance on what differs between atmospheric-pressure boilers and pressure-rated boilers in terms of design, calculations, material selection, standard application, and the layout of pipes and valves.
What are the differences between atmospheric pressure boilers and pressure-rated boilers in terms of design, calculation, material selection, standard application, and piping and valve layout? The difference lies in how much cost the user is willing to bear. In fact, at normal pressure and under pressure, the materials used are theoretically the same, and the standards can also be applied interchangeably.
Upstairs? No way Are pressure boilers and atmospheric boilers the same? To use the simplest analogy, the water pump in a pressure-rated boiler is installed on the water inlet side of the boiler; how can a boiler operating at atmospheric pressure do the same? Pressure-bearing hot water boilers can withstand pressures ranging from a few kilograms to several dozen kilograms; can the manufacturing materials be the same in such cases? Pressure hot water boilers are actually quite similar to steam boilers in terms of structure and material selection. This is my opinion for reference only.
Article 48 of the Regulations on Safety Supervision of Small and Atmospheric Pressure Hot Water Boilers stipulates that the rated power of atmospheric pressure hot water boilers shall be less than or equal to 2.8 megawatts. But many companies’ products achieve 14MW per unit – what’s the reason for this?
For atmospheric-pressure hot water boiler tube sheets and cylinders, Q235 material can be used, while GB8163 material is applicable to the tubes. I’m not quite sure about the specific calculation.
Atmospheric hot water boilers, since they are not under pressure, have lower requirements regarding their design and manufacturing.
However, many sources state that although the design and manufacturing requirements for atmospheric pressure boilers are relatively low, accidents occur frequently. Since many of these boilers are often used under pressure, should we not give more consideration to safety during the design process?
According to the boiler regulations, a capacity of 4 tons is recommended, but higher capacities are not prohibited – they are just not advised. Typically, domestic hot water boilers have a maximum capacity of 6–8 tons; I’ve never heard of any with a capacity of 14 MW. It makes more sense for them to be pressure-rated hot water boilers. Using normal-pressure hot water results in systems that are too large, making their design, manufacture, and use rather complicated.
Using it in accidents is not actually a design issue. When there are problems with these small industrial boilers, it’s usually something like tea makers. For example, many people are unaware of the function of atmospheric vent pipes and block them directly, which of course leads to problems.
For atmospheric-pressure boilers, the wall thickness is just estimated roughly; no one checks it or pays any attention to it.
Are there any reference books dedicated to atmospheric pressure boilers, in addition to standards and regulations? Additionally, what considerations should be taken into account when designing the connection pipes to the atmosphere? The thermal calculations for atmospheric pressure boilers should not differ much from those for pressure-rated boilers, right? This post was last edited by ztsqklmtw on 2009-3-13 at 10:38
Many boiler manufacturers, if they do not have pre-designed atmospheric pressure hot water boilers, simply sell pressure-rated hot water boilers as atmospheric pressure hot water boilers.
Does a atmospheric pressure hot water boiler still need to be equipped with a safety valve? How is then the verification of the safety valve discharge volume calculated?
Is a safety valve still needed at normal pressure? Constant pressure means it should be the same as atmospheric pressure; generally, an expansion tank with an open top is installed above the boiler to ensure constant pressure!
In my opinion, atmospheric pressure boilers should ideally be designed in the same way as pressure-rated boilers. Currently, some organizations, in an attempt to save a small amount of money, purchase atmospheric pressure boilers and then use them as if they were pressure-rated boilers, which is extremely dangerous.
I think what was said upstairs is quite correct; that’s why we leave a larger margin when designing atmospheric pressure boilers. The issue with safety valves isn’t entirely clear to us, so please help us out.
The design and manufacturing of atmospheric pressure boilers are no longer under control at present; **the relevant authorities no longer supervise them, so the method of manufacturing depends on price, requirements, and limitations regarding the service life. Safety valves are not needed and cannot be installed.
Original poster, the most crucial point – and also the one where mistakes are most likely to be made – is to ensure that the pressure in the boiler drum of a atmospheric-pressure boiler remains at 0 at all times. There are no issues with the manufacturing of such boilers; what’s important is the design of the boiler’s valves and instruments, to ensure that the pressure at the top of the boiler drum truly remains zero at all times. I wonder if the original poster has understood
Is it still necessary to install a gas collection tank at the boiler’s water outlet? Where should the outlet temperature measurement point be placed?