Boiler Blog | Nationwide Boiler Inc.

Boilers are important components in many industrial settings and ensuring their longevity and efficiency requires proper maintenance, even during out-of-service periods. To prevent corrosion and other forms of damage when a boiler is offline, it is important to protect both the fireside and waterside of the boiler. There are two methods in achieving this – the dry method and the wet method.

Dry Storage

When a boiler is expected to be out of operation for an extended period of time and needs to be ready for service quickly, dry storage is advised. The dry storage method for industrial boilers involves draining, thoroughly cleaning, drying, and sealing the boiler to prevent moisture and air entry during extended periods of inactivity.

NOTE: If you are placing your boiler in storage for less than one month, follow steps 1 and 2 only. Be sure to follow your company guidelines and, at a minimum, label it as an oxygen-free atmosphere.

The following general procedure is advised for placing a unit into dry storage:

1. Shut down and secure the boiler. Once the pressure decreases to 20 psig, drain the boiler and header valves under air. Once the pressure is reduced to 0, open the drums to allow air to circulate and facilitate the drying of all internal surfaces.

2. If the unit is cold and filled with water, drain it under air, blow out non-drainable tubes with compressed air, and use external heat sources to aid in drying internal surfaces. Install non-porous trays with moisture absorbent (preferably silica gel) into the drums, ensuring they don't touch the drum's metal surface. Use at least one pound of absorbent per 1,000 pounds per hour of steam capacity.

3. Attach nitrogen to the steam drum vent, close all other vents, and pressurize the boiler to reach 10-15 psig with nitrogen, adjusting the amount based on the unit's volume.

4. With the boiler and superheater pressurized, alternately open all drains to purge air until the pressure drops to zero, repeating as needed to minimize oxygen levels.

5. The unit should now be stored with a nitrogen pressure of 5-10 psig in the steam drum. To maintain this pressure, ensure all connections and valves are sealed or tightly closed, and check the gas pressure daily for proper protection.

6. Boiler inspections are recommended every 3 months to ensure no corrosion is occurring and to replenish the absorbent as needed. During these inspections, air will enter the unit so you will need to repeat steps 3 and 4 to expel the air.

Wet Method

Wet storage prevents corrosion by keeping the boiler fully submerged with the right chemicals. Volatile chemicals are recommended to avoid increasing dissolved solids in the water.

The following general procedure is advised for placing a unit into wet storage:

1. Fill the boiler with deaerated, demineralized water treated with 200 ppm hydrazine and enough ammonia to reach a pH of 10.

2. Pre-mixing chemicals with water is recommended, using the blend-fill method to ensure uniform distribution in the boiler. Simply adding chemicals through the drum manhead may not adequately disperse them unless the boiler is heated to induce circulation.

3. Fill the unit with treated, demineralized water up to the normal centerline of the steam drum, then stop the filling process.

4. Refill the superheater with treated demineralized water until the steam drum level rises. Keep filling until water starts to flow from the steam drum vents. Once the filling is complete, make sure all connections are securely sealed.

5. Attach a low-pressure nitrogen source to the steam drum to maintain 5 to 10 psig and prevent air from entering the unit during storage.

6. When the boiler is ready for use, drain the superheater and the boiler drum to the normal start-up water level and resume operation.

7. Analyze the treated demineralized water weekly and add chemicals as needed through the chemical feed line to maintain recommended levels. Water samples can be collected from the continuous blowdown line or a suitable drain.

8. A boiler should not be stored wet if there is any risk of temperatures dropping to freezing, unless adequate heating is provided. Adequate heating will prevent water from freezing and avoid damage to the pressure parts.

Protection of External Surfaces:

Protection of external surfaces is also necessary during periods of extended downtime. Fireside corrosion in idle boilers can cause damage to components due to sulfuric acid from flue dust and ash. To mitigate this, remove deposits using air blasting, washing, scraping, or brushing, and neutralize any residual acid with alkaline water until the water is fully neutralized. Once flushing is complete, fill the boiler with treated water and fire it with low sulfur fuel to ensure complete drying.

Auxiliary heaters and blowers may be needed during storage to keep the metal temperature above the dew point and prevent freezing, especially with wet storage in cold conditions. Additionally, protect machined surfaces with preservative coatings and ensure there are no fuel leaks by disconnecting all oil and gas connections.

The choice between dry and wet storage depends on different factors. Although wet storage is often preferred, factors such as water quality, weather conditions, storage duration, and heat availability may make dry storage a more practical option. Be sensible when considering the conditions and needs of your boiler and choose the best storage method to ensure your equipment remains in excellent condition and is ready for use when needed.

Learning and performing proper water treatment will protect your boiler system from tube damage and corrosion, and can also contribute to maximizing boiler efficiency. In this edition of Boiler Basics 101, we will discuss the consequences of improper water treatment and how to implement a proper water treatment plan.

If feedwater is not treated properly before entering the boiler, a chemical imbalance can initiate the formation of scale. Scale is the accumulation of mineral deposits, primarily calcium and magnesium, on the internal surfaces of the boiler.  These minerals have the potential to precipitate from the water and bond to surfaces, creating a layer that may result in harm to boiler tubes, reduced boiler efficiency, and potential for ruptures. Proper water treatment methods, such as the use of water softeners and deaerators, reverse osmosis, and chemical additives to condition the water, must be employed to prevent scale formation.

1. A water softener will remove the calcium and magnesium content in the boiler’s water supply. This effectively “softens” the water before it enters a boiler and removes the minerals that are often the cause of scale in a boiler.
2. A deaerator should be utilized to mechanically remove oxygen from the water before it enters the boiler. This will prevent boiler tube failure.
3. Reverse osmosis can also be used to aid your boiler. Reverse osmosis is a process that can be used in boiler water treatment to purify and condition the water by using pressure to filter out any hardness and impurities.
4. Chemical treatment is also necessary to ensure proper water conditioning alongside the mechanical treatments listed above. Typically, the chemicals used for treatment purposes are an oxygen scavenger, scale inhibitor, and an amine to treat the steam system piping.

It is important to note that from a rental perspective, it is the customer’s responsibility to maintain the water treatment conditions of their rental boiler to avoid equipment damage and additional repair charges that can result from improper water treatment procedures. It is recommended that the services of a reputable boiler chemical consultant are retained in order to supervise the water treatment conditions on a regular basis. Weekly tasks should include maintaining daily boiler logs, conducting chemical treatment tests, providing a report from the chemical treatment consultant, and sharing maintenance records with your rental boiler supplier.

All boilers are subject to damage if proper water treatment procedures are not followed. This is an important consideration both during operation and when the boiler is idle. Maintaining a water treatment plan will not just extend your boiler’s lifespan and the durability of its components, but it will also facilitate long-term cost savings. It is an investment that pays off in the form of lower energy costs, fewer repairs, reduction of costly down time, and compliance with regulations; all contributing to long-term cost savings.

Make sure to explore our earlier Boiler Basics 101 articles and keep an eye out for the upcoming edition!

Maintenance budgets are among the first to be cut when companies need to decrease costs. Unfortunately, this means that critical equipment, such as the safety of combustion equipment, may be overlooked, specifically the testing of fuel trains.

Gas trains regulate the amount and the pressure of gas to the boiler's burners and are used to eliminate gas from entering the combustion chamber. This is achieved through a series of shut-off valves that are specifically designed to close when the combustion process occurs (through safety shutoff and blocking valves). Gas trains also include a series of pressure switches that prevent gas under pressure from entering the burner. If anything should go wrong, shutdown would occur immediately.

As crucial as gas trains are for the safety of the boiler, many facilities are unable to perform the preventive maintenance and testing work on the equipment as should be necessary to help decrease combustion incidents from occurring. John Puskar (Combustion Safety Inc.) has developed the following strategies that can help any facility to be proactive in the maintenance of fuel trains and combustion equipment. Overall, the goal of any safety program is to improve the reliability and life of boiler related equipment. These guidelines not only help to achieve those goals, but more importantly they help lead to fewer unplanned outages and improve the overall safety of plant personnel.

1. Most of the explosions and fire incidents, by far, have historically been due to human error. All of the safeties and interlock equipment in the world won't help if you attempt to bypass or jumper-out safety controls. There is no possible substitute for proper training. Training has to include mock upset and hazard recognition drills. Your site needs training even if you will have contractors doing preventive maintenance work.

2. Start-up and shutdown are your biggest risks. You need clearly written procedures that everyone understands and agrees with so that consistent, safe practices are in place with every shift and every employee.

3. Make sure that you do regular and complete interlock and fuel train valve tightness testing. Jurisdictional inspectors, even where they are mandated to be around, cannot be at your facility every day. Combustion equipment safety testing needs to be part of your organization's culture regardless of what it costs and what the perceived hurdles are. You should comply with code requirements for testing even if they are not enforceable in your area.

4. Create corporate guidelines for third party combustion equipment reviews and commissioning for newly acquired equipment or for major upgrades. Now that you see how little review and attention combustion equipment may receive from the time it's specified to when its really operating, you may want a dedicated professional review of the process.

5. Upgrade equipment for safety's sake. Do not wait for a problem and let attorneys dictate when this happens.

The winter season is here and for many users affected by freezing temperatures it is critical that the boiler unit is properly protected. Nationwide Boiler recommends the following in order to ensure that your unit continues to operate while facing freezing conditions.

1. Enclose both the front and rear of the boiler area and use an external heat source to minimize freezing conditions.


2. Install heat tracing with insulation to protect exposed stagnant water lines.


3. Utilize an appropriate heat tracing method (electric or steam tracing) to all of your main lines and piping components. This includes the following lines which should be heat traced regardless if the boiler is in operation or not (in freezing conditions): sensing lines (steam drum to CMR, high steam and steam gauge), auxiliary low-water-cut-off, water column and level control blowdown. Depending on the length of piping runs, the main and continuous blowdown should also be heat traced.


4. In addition to heat tracing on stagnant sensing lines, drain the lines and fill them with a 50/50 (water/glycol) solution, making sure to re-connect the line.


5. When an extended boiler down time is expected, completely drain the boiler and stagnant water lines.

The above are recommendations, however, use sound engineering judgment calls when there are concerns of possible freeze damage to the equipment. Call us if you have any further questions at 1-800-227-1966.