Boilers Steaming Along Trivia Quiz

Answer: Poor heat transfer.

As scale builds up on the internal, water side of a boiler the transfer of heat is reduced. As the scale gets thicker it reduces the amount of heat transferred to the water and begins to cause the over heating of the fire side of the metal surface. This will then cause the metal to overheat and begin to blister and eventually fail.

Answer: Together, all answers are correct.

In most cases, depending on how severe the tube failure is, it will be heard as you would expect to hear any high pressure leak. Your feed water control system will try and make up for the water losses from the failed tube leak. The firing will increase in much the same way as it will try and compensate for the loss of pressure the tube failure will cause.

Answer: There is insufficient air to complete combustion.

Black smoke can be a symptom of many problems like loss of atomizing steam, dirty burners, cold oil, poor performance of a coal mill or other such problems. The fundamental cause of black smoke is the inability to provide enough air to complete the cycle of complete combustion.

Answer: Reduce flow manually to control drum level.

With the right type of plant and with enough experience, this scenario is one which can be easily controlled if you have enough people and are able to act quickly enough. If you are unable to control the situation, the best thing to do would be to prevent water getting into your super heaters and then into the main steam line where major damage can be the result.

In this case, tripping the turbine or closing the main steam sop valve would be prudent.

Answer: Do not continue with the operation of the boiler.

Due to the dangers associated with boilers, their design, construction and operation are very heavily regulated and in most countries they would be considered as classified equipment. With this classification there are certain rules which must be followed.

A safety valve, low water mechanical trip and other such equipment are considered as essential fittings and must be well maintained and tested and function correctly. If any of these essential boiler fittings fail to function correctly, the boiler must not be operated until they are repaired and proven to function correctly. Most areas would require the failure of any such equipment be reported to the local machinery inspection government body.

Answer: Reduce the load and attempt another purge then re fire the boiler.

Again, with experience an operator can be fully aware of the fault and confident that the boiler firing trip was a simple spike in the electrical system. He could recover the boiler without the need to shut down the turbine. He must be aware of the superheated steam temperature lower limits while attempting to recover. Under no circumstances are purge timers to be tampered with to hasten the process.

This could lead to a boiler explosion with the outcome likely to be serious injury or death.

Answer: Trip the turbine immediately to protect internal moving parts.

When a boiler is supplying steam to a process, high pressure and temperature steam is being demanded from the process in the form of steam flow. As the demand increases so does the velocity of the steam to the process. If water was to find its way into the main steam line and then into the process, perhaps a turbine rotating at 3000 rpm, the introduction of water would cause catastrophic failure of the moving parts and again could cause serious injury or death. Also, any bends in the main steam line would be subject to serious water hammer with the potential of destroying the main line.

Answer: The high furnace pressure trip will shut down the forced draft fan and the firing.

With a balanced draft system there could be an electrical interlock between the induced draft fan and the forced draft fan. In this case the forced draft fan would trip instantly. Otherwise the furnace pressure trip will initiate to prevent increased furnace pressure. Particularly large boilers with a high percentage of refractory are subject to greater levels of damage due to the larger surface areas of the furnace walls.

Answer: Your air heater has developed a leak from the air side to the flue gas side.

Air heaters are generally of two types, rotating or stationary. Both are sealed from the air side to the flue gas side. When a hole develops between the two, there will be an increase of pressure from the air side given to the flue gas side. This is a reason why operators need to take logs and compare readings to highlight even minor changes in their plant conditions.

Answer: Shut down the boiler in a controlled manner as the super heater safety valve should have lifted first.

The final safety valve in the process flow in this case is where the steam leaves the boiler. This is also the lowest pressure; therefore the super heater safety valve should be set the lowest pressure and should lift first. The reason for this is to ensure there is a flow of steam maintained through the super heaters.

This protects the super heater elements from overheating and failing. If the drum safety valve was to lift first, this would also interrupt the flow of steam through the super heaters.

This scenario would need to be acted on very quickly and if not, then the boiler firing should be tripped.