Is there a relationship between the steam space of a steam boiler and the water volume of the boiler?

The volume of the steam space should be related to the steam generation rate, with the aim of ensuring good separation between steam and water. Our horizontal boilers are equipped with a steam drum at the top, and the separation of steam from water takes place inside this steam drum.

The steam space is related to the steam flow rate and the specific volume of saturated steam. During design, the volumetric load of the steam space is determined. In other words, a large drum is not economical, while a small one results in poor separation efficiency. It is possible to place the steam space externally, just as the boiler drum can be placed externally. However, there are no relevant standards for the flange connection between the external boiler drum and the main body, which is a borderline case. Welding is recommended. “The steam space of a horizontal steam boiler must be at least 300 mm,” which is likely restricted by a minimum inner diameter of 910 mm for the boiler drum. For a boiler used for heating, the height of the steam space can be set at 0.4–0.6 m.

How is the volume of a steam drum determined? Can a flange be used to connect the boiler and the steam drum?

Steam Drum Sizing: a. The inner diameter shall be not less than 910 mm (36”) to provide space for access and for the internal components of the steam drum. b. The steam space must be sized appropriately to accommodate the steam separation equipment needed to maintain the specified steam purity across the entire operating range. c. The water retention capacity between different water levels – such as NWL (Normal Water Level), LWL (Low Water Level), LLCO (Low Level Cut Off), and HWL (High Water Level) – must be evaluated to determine the impact of evaporation at MCR when there is no feedwater flow. The typical water retention time in the steam drum between the normal water level and the low level cut off is between one and two minutes at MCR with no feedwater flow. d. The LLCO shall be located above the top of the highest downcomer. e. An increase in water level above the NWL, as result of the specified requirements, shall not cause overflow or activation of the HLCO (High Level Cut Off) if such a device is used. f. A decrease in water level below the NWL, due to the specified requirements, shall not trigger the activation of the LLCO. Pipe sizes of 1¼ inch, 5 inch, and 7 inch NPS shall not be used. Manways shall be provided at both ends of the steam and water drums, equipped with hinged covers or lifting devices.

The separation of steam from water requires a certain area (the interface between water and steam), which in turn necessitates some space (this can be explained by the specific volume of steam). When water is heated, its molecules gradually separate from the water. Once the water molecules in the steam space can no longer be separated by further heating at a certain pressure, a saturated steam space is formed, resulting in saturated steam and saturated water.

Can a flange be used to connect the drum and the boiler?

Personal advice: For boiler drum applications, flange connections are not recommended. There are two reasons for this: first, flange connections rely on bolts and gaskets for sealing, and their sealing performance is much worse compared to welding, making leaks more likely； 2: It’s difficult to distinguish the definition of the boiler itself.) ； If it is a functional steam drum, flange connections can be used entirely.

This explanation is reasonable; problems with the gasket can directly affect the operation of the entire system, especially in terms of safety.