Regulation requires steam boiler to be overhauled once a year. Many owners aim only to get pass the mandatory inspection with the minimum stoppage and at the lowest cost. However, there are many benefits which may be overlooked on a rushed overhaul, and some pitfalls which may cause future harm. This article examines what boiler overhaul is about and the importance of having a detailed and proper overhaul.
Boiler annual overhaul is an annual health check of the boiler. It exposes the interior of the boiler for examination much like a surgery. Certain sign of problems is visible only when open up and should be properly investigated. discover what may be wrong in its operation and what action may be required to preserve and possibly improve its health. These are not observed by the Inspector nor recorded in the certificate issued.
A boiler annual overhaul includes following work:
- Cleaning of pressure vessel, the fireside and water side.
- Cleaning and servicing of first valves and fitting mounted on the pressure vessel. These include the steam nozzle valve, safety valve, feedwater valve, blowdown valve, water level gauges. To ensure that water column reflects accurately the level in the boiler, the crossed fitting must be cleared. This is often missed out.
- Two inspections conducted by the Inspector.
- First a visual inspection of the pressure vessel and the fittings to ensure that there is not cracks, or deformation which may endanger the operation at the approved steam pressure. Any tell tale sign of problems may have been removed by the cleaning.
- A final inspection when the boiler is fired up to check safety features including flame failure and low water cut off.
When a boiler is open up, it is important to examine the following:
- On the fireside, the formation of soot, its location, amount and thickness, any unusual colours each tells a story.
- Fleky ashes settled at base
- unusual formation of soot on third pass but no soot on second pass
- Similarly, on the waterside, the deposit may be in the form of mud, or sandy, or in broken pieces. A study of the deposit reveals effectiveness of the water treatment and any necessary change or adjustment to be made.
- unusual deposit on firetube
- The condition of the furnace reveals the firing of the burner, eg uneven colour, carbon deposit.
- The colour of the diffuser plate and any sign of carbon deposit
- Meet the Inspector. Get a firsthand report of the boiler health from the inspector. Normally early sign of problems are not reported in the certificate.
As can be seen from above, these evidence is lost once cleaned up without examination. The problems are not reviewed and no corrective action can be taken.
Thorough cleaning takes time, normally a minimum of three days are required. An overnight rush job skips over many services and does not realise the full benefits of an annual health check. Some symptoms may need to be brought to the attention of specialists such as the water treatment specialist, and it takes time.