PWR boiler lay up procedure for summer

Boiler lay up procedure for summer

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As warmer months approach, boiler operators should begin preparations for extended periods of shutdown. Boilers that are not in use are still at risk to accumulate rust and other forms of deterioration if not closed properly.

The procedure of shutting down boilers for this purpose is known as “laying up” the boiler. Boiler lay-ups are important for the longevity of your boiler as they prevent internal corrosion. Lay-ups are also an ideal opportunity to perform potentially cost-saving inspections of the condition and efficiency of your boiler.

There are two specific types of lay-up procedures for operators: dry lay-ups and wet lay-ups. A dry lay-up is intended for a long term shutdown, while a wet lay-up allows operators to quickly put a boiler back into service if the need arises. The exact steps involved in both of these lay-up procedures differ between boiler sizes and models, but in general, these are the appropriate steps technicians should follow when shutting down their boiler. If your company does not have an experienced operator capable of performing a boiler lay-up, contact Powerhouse today.

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Step 1 - Drain Your Boiler

Both dry and wet lay-ups require the boiler to be drained. This part of the process begins by clearing the system of sediment using the bottom blowdown valve both before and after the boiler is shut down. Opening the blowdown valve will also drop the internal pressure of the boiler. Once the pressure reaches 0 psi, the air vent and boiler drain can be opened to empty the system.

Step 2 - Fireside Treatment and Drying

The fireside portion of the boiler should receive attention first so that soot can be removed before it dries. While cleaning out soot from the fireside portion of the boiler, operators should look for any areas where rust, cracks, overheating, corrosion, or short-circuiting is occurring. Any areas where this type of wear is found should be marked for further inspection by an experienced technician. Following cleaning and inspection, the fireside should be dried using either fans or electric heaters.

Step 3 - Waterside Treatment and Drying

Open the waterside inspection closures after making sure the air vent valve is securely closed. Thoroughly inspect all surfaces and seals for any signs of deterioration, corrosion, or leakage. Clean out all scaling and sediment through the bottom openings so as to prevent corrosion during the shutdown period. Similar to the fireside, the waterside should then be dried using either fans or electric heaters.

Check out our guide for more information on Water Treatment for Industrial Boilers.

Step 4 - Internal Examination

An internal, certified boiler inspector should perform an examination of the exterior of the boiler, looking specifically for signs of leakage. A great non-destructive way to approach this step of the lay-up procedure is a liquid penetrant examination.

Step 5 - External Inspection

An outside, R stamp certified organization can then be brought in to make repairs as required by the condition. Specific repairs may also be necessary depending on environmental and safety regulations in your jurisdiction, so be sure to consult a professional, experienced team such as Powerhouse.

Step 6 - Close Up the System

For a dry lay-up, begin the close-up procedure by coating the fireside with mineral oil and allowing the oil to dry. A moisture-absorbing material should then be placed inside and replaced every three months during the shutdown. Once this material is inside the system, all openings, including the stack, should be closed to complete the lay-up.

In the case of a wet lay-up, water at around 180oF needs to be premixed with appropriate treatment chemicals to prevent corrosion during the shutdown period. A water treatment company should be consulted to accomplish this. Once the desired alkaline and oxygen levels are reached, the boiler can be refilled with the treated water. Allow the steam to vent until the system is at its regular operational water level.

Step 7 - Post Closing Maintenance for Wet Lay Up

Periodically circulate the water in a wet closed boiler system using the burner to ensure the treatment chemicals are reaching all parts of the boiler. Doing so will prevent acidic corrosion and allow you to start the boiler back up more easily when necessary. Water chemical levels should also be monitored regularly in the event more water needs to be introduced.

Following these steps will ensure that your boiler is still operational when needed next, preventing costly repairs and downtime. Still have questions? Contact Powerhouse today!

Frequently Asked Questions

What are the different types of boiler lay ups?

Dry Lay-Up

A dry lay-up is intended for a long term shutdown or where the possibility of freezing is present. It is achieved by draining the idle boiler of all water and sealing it in a dry state. This process does not require constant monitoring of the water.

Wet Lay-Up

A wet lay-up is intended for short term dormancy when there is no risk of experiencing freezing temperatures.

Nitrogen Lay-Up

A nitrogen lay-up is an additional step that can be implemented in either a wet or dry lay-up to add a nitrogen blanket to prevent oxygen from entering the boiler.

When should you lay up your boiler?

Short Term Boiler Layup Procedure

Typically, a short term boiler layup is considered any duration less than 30 days. This covers a lot of the short term plant shutdowns for various repair, maintenance, or other associated tasks. Short term layups can also be due to external reasons, separate from the boiler room, which result in the elimination of any boiler operation for a limited time. A wet boiler layup is often used for short term shutdowns to minimize water waste but a dry boiler layup would be required if freezing temperatures are expected.

Semi-Short Term Boiler Layup Procedure

Semi-short term boiler layups are a category where the length of the layup is unknown but may last beyond the short term layup timeframe and up to 60 days. While a dry boiler layup is preferred, a wet boiler layup may be used depending on the exact circumstances.

Long Term Boiler Layup Procedure

Long term boiler layups are the layups that last more than 30 days and are often associated with yearly seasonal shutdowns or indefinite plant shutdowns. A dry boiler lay-up is the best plan for these longer shutdowns to ensure the boiler does not experience any corrosion.

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