A dryback boiler has a rear wall that is lined with refractory, a wetback boiler has a rear wall that is jacketed by water. Because of this fact, wetback boilers typically boast higher efficiency than dryback boilers as the heat from combustion goes directly into heating water instead of refractory. Wetback boilers are also more forgiving with load changes as the reversal chamber of the boiler is totally submerged in water creating an even heat transfer on the intermediate tube sheet to furnace joint.
Boilers with low water volumes require a minimum flow requirement to prevent localized boiling and subsequent heat exchanger damage in a low to zero water flow situation. Minimum flow requirement varies by boiler design. Regardless if a boiler itself has a minimum flow requirement, every hydronic heating system needs to be designed to carry the energy being created away from the boiler to avoid high temperature shut down.
The choice between a steam system or a thermal fluid system is governed by the process requirements. The range or process temperature is a deciding factor. If the system’s required temperature is above the freezing point of water (0°C) and below approximately 160°C, the choice is usually steam. However, if the required temperature is above 160°C, thermal fluid may be a better solution. Thermal oil heater systems can be designed with maximum operating temperatures to 325°C.
A fire tube steam boiler is a boiler where the combustion gases from the burner are channeled through tubes that are surrounded by the fluid to be heated. The boiler body is the pressure vessel and contains the fluid. In most cases, this fluid is water that will circulate for heating purposes or become steam for use in processing.
Each set of tubes through which the combustion gas passes, before making a turn, is considered a "step". Consequently, a three-step boiler will have three sets of pipes with the outlet located at the rear of the boiler.
The primary objective of an industrial boiler is the generation of steam. Steam is generated by heat transfer at a constant pressure. The fluid, which is initially in a liquid state, is heated, produces a variation in its phase and becomes saturated vapour.
This saturated steam can then be used for different applications such as sterilization, fluid heating or electricity generation.
In superheated industrial water boilers, the water is pressurized and boiled to 100°C producing steam. These boilers are pyrotubular, with a high volume of water and a large temperature exchange zone. The designs can adapt to temperatures and pressures according to needs.
1. Hydraulic should be carried out at a defined pressure before the start of a boiler.2. Check if the pump inlets are open at the start of a boiler.3. Install an automatic ash removal system such as rotary valves in a boiler so as to prevent the accumulation of ash in a furnace or other equipment. The accumulation may result in the blockage or excessive heating of boiler parts resulting in its failure.4. Pump priming must be done at the start of the boiler.5. All loose and wrong connections must...
All thermal fluids expand as they are heated. The amount of expansion is based on the operating temperature, system volume and the coefficient of thermal expansion of the fluid. An expansion tank must be provided to accommodate the increased system volume at operating temperature.
NOTE: All fluids expand at a different rate.
