Guidelines for Inspecting a Boiler-Boiler Inspection

Boiler Inspection

The purpose of a boiler inspection is to provide assurance of equipment integrity to minimize safety issues with operating a pressure vessel. A minimal frequency is established by law and the Insurance Company that is covering customer liability in case of any operational failures. It has a useful secondary function of acting as an early warning of potential problems and determine the water treatment program’s effectiveness.

An internal boiler waterside inspection consists of all waterside areas of the vessel (e.g., steam and water areas, blowdown lines, feedwater connections, and low water safety devises) as well as dearators, superheaters, economizers, and blowdown heat exchangers. If possible, this inspection should occur with the owner/operator present.

Inspection Frequency

Steam boilers typically have an internal inspection once per year, at a minimum. Where water quality and/or program control is poor, more frequent inspection may be necessary. 

General Guidelines

All manhole and handhole covers should be removed to provide a thorough inspection. Have a working flashlight, camera, and a scraping tool, such as a knife or screwdriver, with you. Great care must be taken to insure that any items used during the inspection are not left in the boiler. Prior to an inspection, boiler internals such as baffles, feedwater lines/troughs, and any steam drying devices should be removed where needed to fully inspect the waterside internals.

Safety Guidelines

1. Follow all plant safety rules regarding confined space entry and lock out/tag out. Use proper engineering controls and personal protective equipment.
2. Make sure all online valves that could allow steam, chemicals, and water to enter the boiler are locked and tagged out in a safe position.
3. Notify all operators and anyone that is working on the boiler before entering. 
4. If other boilers are present, lock out their blowdown to prevent any steam from entering the boiler you are inspecting.
5. Test the boiler for sufficient oxygen levels before entering.
   1. If required, ensure the boiler has a safe air supply. Ensure that any traces of nitrogen, amines, or any toxic fumes are evacuated. Some moisture absorbents used for dry storage may generate toxic fumes. The presence of nitrogen would only be likely if the boiler had been stored with a nitrogen blanket.
6. Never enter a boiler with a high voltage (110 Volts) light or extension cord.
7. NEVER inspect a boiler alone. Always have a qualified attendant outside the entrance who can be signaled for help.

What to Observe

 

Note: Take pictures and make notes on the current inspection. All observations should be compared to notes and photos of the previous inspection.

1. Point of Chemical Feed:  Is the chemical fed to ensure good distribution through the boiler before it comes in contact with the blowdown pipe?
2. Continuous Blowdown Piping:  Look for corrosion or plugging of the blowdown pipe.
3. Point Where the Feedwater Enters the Boiler:  If a scaling problem exists, it will probably be more noticeable where the feedwater enters the boiler. If the feedwater line has been removed or has an inspection port, look for corrosion and/or scale deposits in the line.
4. Water Line:  Is the water line a broad band indicating an unstable water level? Does the position of the water line vary along the length of the drum indicating surging? Is the water line at a safe level above the tubes? Is the water level high, decreasing the available steam space and possibly causing carryover?
5. Baffles and Screens:  Check the condition of baffles and screens.   
6. Oxygen Corrosion:  If oxygen corrosion is present, is it active? Oxygen corrosion is identified by well-defined pits or a very pockmarked surface. Active pits are identified by a reddish brown oxide cap (tubercle). If the pit is active, removal of the cap exposes within the pit black iron oxide or shiny metal.
7. Scale:  Location? Thickness? Is it loose or hard? Composition? Color? If the amount of the deposit is considered a problem, send a sample to a lab for analysis.
8. Sludge:  Excessive sludge deposits could indicate hard water intrusion or insufficient bottom blowdown. Sludge baked on the top portion of tubes (firetube boiler) could indicate insufficient cooling prior to draining the boiler.

Exit Interview

Upon conclusion of the inspection, discussions between the boiler inspector, owner/operator, and water management professional should be done to compare and contrast the conditions observed with that of prior inspections.  Any concerns noted should be documented with a constructive action plan that can be taken to avoid recurrence.