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Miura Boiler Layup Procedures: Wet Layup vs Dry Layup

Boiler maintenance procedures and water treatment chemicals are critical in the fight against the development of scale, corrosion, and pitting inside of your steam boiler. While the boiler is in normal operation, feedwater containing corrosion inhibitors flow throughout the boiler and spread a vital layer of protection over the vessel’s exposed steel metal surfaces. When the boiler is out of operation, or off, the boiler stops the flow of chemically treated water that inhibits corrosion.

Depending on the length of time your boiler is shut down, Miura recommends that you consider performing a proper layup procedure to shield the pressure vessel and boiler tubes from degradation during downtime.

What is a Steam Boiler Layup?

A steam boiler layup is a maintenance procedure that helps to prevent corrosion within the boiler on both the waterside and fireside when you plan to have the boiler out of operation for an extended period of time. There are two (2) types of boiler layup methods — a wet layup and a dry layup.

Wet Layup

A wet layup is defined as filling an idle boiler with chemically treated water so that the boiler can remain in a “flooded” and sealed environment until you’re ready to start up and produce steam again

Dry Layup

A dry layup is defined by emptying the idle boiler of all water and sealing it in a “dry” state; sometimes with chemical, gas or by drying and leaving it empty.

When Should I Lay Up My Miura Steam Boiler?

If you plan to shut down your Miura boiler for an extended period (more than 5 days), then you should perform a boiler layup procedure. There are three (3) different types of boiler layup procedures that vary depending on the amount of expected time of the boiler shutdown. For Miura boilers, we recommend a wet layup procedure for short term and semi-short term shutdowns, and a dry layup procedure for a long term shutdown.

 

  • Short Term Boiler Layup Procedure — If you plan to shut down your boiler for 5 – 10 days, then you should perform the short-term layup. The short-term is a wet layup and consists of leaving the boiler filled with concentrated, chemically treated boiler water; preferably with a pH of 12.4 (or as close as possible).
  • Semi-Short Term Boiler Layup Procedure — If you plan to shut down your boiler from 10 – 30 days, then you should perform the semi-short term layup. The semi-short term is a wet layup and consists of draining the boiler of old boiler water and refilling with fresh feed water and chemical; preferably with a pH of 12.4 (or as close as possible).
  • Long Term Boiler Layup Procedure — If you plan to have your boiler shut down for longer than 30 days, then you should perform the long term layup. The long term is a dry layup. The boiler should first be drained of all water contents within the boiler. After draining the boiler water, the boiler pressure vessel is filled with nitrogen. Nitrogen is an inert gas that is used to avoid unwanted chemical reactions degrading the construction of the boiler. Once the oxygen content level decreases to 3%, continue to fill until the boiler is pressurized to 10 PSI. Once the boiler is pressurized to 10 PSI, close all valves and remove nitrogen assembly.

Schedule a Layup Procedure for Your Miura Boiler System

Need to shut down your steam boiler for more than five days? Want to learn more about Miura’s boiler water treatment programs? Contact a local Miura sales representative near you through our rep locator.