When steam boilers or water boilers are going to be out of service for an extended length of time, the best practice is with a boiler lay-up procedure. There are two methods, and each offers advantages and disadvantages.
Before either operation can begin, boilers must be tuned to ensure that they start without difficulty after boiler lay-up. It’s also critical to restarting boilers properly following boiler lay-up. You may reach out to Bay City Boiler for all of your boiler service needs, including repair and replacement, or keep reading to learn more to learn more about the boiler lay-up procedure.
Dry Boiler Lay-up
When a water boiler is to be shut down for an extended period of time—typically at least a month, or when restarting it is not necessary—dry boiler lay-up should be utilized. This approach may also be used in areas where idle boilers are exposed to subfreezing weather. This is essential boiler maintenance, but it does not need as much attention as the wet boiler lay-up method.
Boiler service companies can assist you with this process, but after performing a lockout and tagout of the system boiler, the steps for dry boiler lay-up can be fairly straightforward.
1 — Draining the Boiler
It’s critical to do a boiler blow down before and after the shutdown to remove sediment and scale, as well as lower the unit’s pressure and temperature. When the psi level is at zero and the water temperature has fallen below 140°F, open an air vent and drain the boiler.
DO NOT USE THE SAFETY VALVES FOR VENTS. If a vent valve isn’t used, you may need to call a local boiler company to assist you. This allows air to escape as the boiler is refilled, so it’s not something that can be overlooked when it comes to boiler maintenance.
2 — Opening the Fireside
Look for rust (orange) or scale (grayish white) streaks on the pressure boundary wall while cleaning a boiler’s fireside. For further testing of leaks, make notes on those areas.
Examine the refractory and insulation on the fireside as well. Due to repeated expansion and contraction, tiny fractures in the refractory are expected.
However, be aware that discolored or chalky paint might signal overheating. In this situation, it’s critical to contact a local boiler repair business for help. Regularly scheduled boiler maintenance can prevent costly repairs by keeping your equipment in good working order.
3 — Opening the Waterside
Remove all inspection cover closures with the outlet, feed, and make-up valves locked and labeled shut, as well as the air vent valve.
Examine the gasket seating surface for signs of a leak, as well as indications of gasket wear. This might prevent a decent seal. Then check all handhole and manway yoke bolt and nut tightness for deterioration, which may prevent uniform gasket tightening. Examine the waterside (by all relevant confined space entry procedures) using a battery-operated light to evaluate the scale and corrosion state.
Rinse the boiler and try to remove all scale and silt from the washout openings at the bottom. Any scale and silt that isn’t removed will trap moisture and oxygen, which can corrode the boiler. If these operations appear daunting, a boiler service center can safely take care of all of your maintenance needs.
4 — Drying All Surfaces
A fan can be used to dry the waterside when the ambient air temperature is lower. Electric air heaters may also be utilized on the fireside to warm and dry out the waterside. Although, fuel-fired air heaters are not advised. If that’s how you want to go, you may contact a local boiler service company for advice.
5 — Performing an Inspection
Closely examine all surfaces that show potential signs of leakage. Dye-penetrant examination is an inexpensive method to check leaks for potential cracking in commercial boilers. It’s a good idea to take special precautions with an industrial boiler. A pressure test may be required before startup.
6 — Are Any Repairs Required?
In the event that repairs are needed, Bay City Boiler carries an R Stamp for repairs on pressure vessels. If you’re unsure of whether or not your unit requires boiler repair, we’re here to help with all your boiler service needs, and we’re happy to answer any questions you have.
7 — Closing the Dry Boiler
Boilers may be kept open if the ambient air is always dry. However, if humidity and dew points fluctuate or remain high, the boiler should be shut. Place moisture- absorbing material in the waterside and fireside of the boiler, such as desiccant or lime, before closing it. This material is also known as unslaked lime, quick lime, calcium oxide, burnt lime, calx, and caustic lime. To contain absorbent material use a flat tray or pan. Set it inside the boiler and seal all openings. This stuff should be replaced or dried every three months.
The stack should also be covered to prevent moisture from accumulating near the boiler stack connection. A sign or tag can be placed on the boiler power disconnect to warn of the stack cover. A stack damper does not provide a sufficient seal from the main stack. If the main stack cannot be sealed, slip a piece of sheet metal between the boiler exhaust flange and stack flange.
For smaller commercial boilers, incandescent lights have been used to keep the boiler and/or control panel warm in order to prevent the collection of moisture. Electrical safety should be considered before placing light fixtures inside a boiler.
Wet Boiler Lay-up
For brief periods of boiler lay-up, or to keep a boiler ready for easy startup, a wet boiler lay-up is the more appropriate method. The steps to prepare a boiler for wet boiler lay-up are essentially the same as for a dry boiler lay-up. The exception is that the boiler is prepared to be filled with water and water treatment chemicals. First, perform the dry boiler lay-up steps 1-6.
7 — Filling the Boiler with Water and Treatment Chemicals
The alkalinity of the water should be adjusted to a level greater than 400 ppm for this boiler maintenance procedure. This prevents acidic corrosion of the waterside. Tri-sodium phosphate or caustic soda has been used in the past to achieve this (about 3 pounds/1000 gallons). Also, add an oxygen-scavenging chemical, such as sodium sulfite, to a concentration of at least 200 ppm (about 5 pounds/1000 gallons). For further information on corrosion inhibitors, contact a water treatment company.
Fill the boiler to the fullest extent with water that is hotter than 180°F. This temperature aids in the gas removal process. If hot water isn’t accessible, you may heat it similarly as described above after the water level reaches the lowest permitted level on the boiler.
On water boilers, the chemicals should be prepared in advance with the water before being placed inside the boiler so that no gases or vents are required. There are no feed or condensate tanks on water boilers, thus it’s ideal if the chemicals are combined with the water before it’s put inside. Fill the boiler until all of the air has been vented, or until the steam boiler is at its normal operating level and hot water is available.
Be sure to follow the manufacturer’s instructions for your boiler when adding chemicals. Too much chemical can lead to foaming, caustic embrittlement, or other problems. Not enough chemical leaves the boiler unprotected and subject to corrosion.
Add the chemical one bag (or jar) at a time while maintaining a slow, steady water level in the boiler by opening the make-up valve as needed. Maintain circulation through the use of the boiler’s circulating pump(s). The system should be full of water and under pressure before any chemicals are added so that there is no chance for the chemicals to become concentrated in any one area.
After the last bag or jar has been added, continue to circulate the water for at least 30 minutes. This allows the chemicals to fully mix and provides time for the boiler to come up to operating temperature if it was below that when the chemicals were added. If you are unsure of how much chemical is needed for your boiler, please contact your local Bay City Boiler dealer or representative. They will be able to help you determine the correct dosage based on the size of your boiler and other factors.
When Wet Boiler Lay-up is Complete
It’s critical to keep the boiler water circulated on a regular basis to avoid chemical stratification. The burner may be used to heat the water and create a natural circulation. Of course, a system circulator from a water boiler can be utilized, but doing so would lower the concentration of chemicals.
For proper boiler maintenance, routinely monitor the chemical concentrations while the unit is in lay-up. System leaks can cause additional water to be introduced, along with more oxygen and carbon dioxide.
Before starting a wet steam boiler lay-up, first perform a boiler blowoff to reduce the alkalinity. This minimizes the chance of carryover.
For all boilers, ensure tags and locks are removed. Also, remove any lime or desiccant from the fire and water slides, and observe the system for a minimum of three cycles. This will help ensure proper operation of the boiler before leaving it in automatic mode.
Boiler Service and Repair
If you need boiler services, please contact us at Bay City Boiler & Engineering to schedule an appointment today. Our experienced staff is here to help. Call us at (510) 822-8443 for more information.