Wet Storage of Boilers (Low Pressure)

Wet storage of a boiler is the preferred method when the boiler is going to be off line for short periods of time, and when boiler availability on short notice is important. Whenever possible, wet storage of a boiler should not last more than six months. The boiler manufacturer’s recommendations covering specific procedures to follow while removing a boiler from service should be followed. These procedures usually involve lowering the firing rate and gradual cooling, followed by complete draining and washout.

For any lay-up procedure, it is advisable to drain the boiler, washing down all internal surfaces as the boiler drains. This removes loosely adhering sludge and scale. The heating surfaces should be inspected and chemically cleaned if necessary. Next, the boiler should be refilled with feedwater, and sufficient oxygen scavenging and alkalinity building chemicals to provide corrosion protection. it is desirable to start a light fire to provide adequate circulation of chemicals.

During the storage period of the boiler it should be fired twice per month, to bring the water temperature to 160 F and allowed to cool. The water chemicals residual and pH should be tested at this time, with additional chemicals added if necessary. Wet storage of boilers can also be accomplished by cascading blowdown from a fired boiler. This method will be discussed in subsequent technical tips.