Boilers Big and Small Trivia Quiz

Answer: To prevent steam from the main steam range flowing back into the boiler.

Once boilers are supplying steam to a range it is their steam flow which will fluctuate. This is caused by differing firing rates across the boilers. If a boiler fining rate decreases too much then as the steam flow decreases then also the pressure will drop below that of the range.

When this is achieved the non return will close and prevent any steam flowing back into that particular boiler.

Answer: To warm through and equalize the pressure of the main steam line.

This bypass valve, once open, will allow only a restricted flow of steam into the main steam line and therefore prevent any rapid heat expansion to the steam line. Once equalized pressure is reached, there will be no rapid flow of steam into the main steam line which could cause violent movement in the line.

Answer: Inefficiency.

With too much air, the fire tends to be lifted higher in the furnace and causes the flue gases to carry that heat further into the back end of the boiler. With this extra heat, the super heat temperature increases too high and will need to be cooled to bring it back to normal operating temperature. This requires more fuel as you are cooling steam which has already been heated.

Answer: To prevent a vacuum in the boiler pressure parts.

Boilers are designed to withstand great pressures, but they are not designed to hold a vacuum. As the steam condenses in the boiler the reduced volume of the steam will cause a vacuum. This vacuum is likely to break seals around the man hole doors and could also break the glass of water level indicators.

Answer: The independent test.

In Australia, the common term used is the independent test. This test requires the steam way and waterway passages are clear. At the end of the test, when the blow through cock is shut, it is stated that the water will return smartly to the correct water level in the boiler. If at the end of the test, the water was to return slowly, or raise then lower, these conditions would indicate obstructions in either the steam way or waterway passages which therefore must be cleared. That would be another question.

Answer: To control the high temperature of superheat steam.

Due to the numerous variables associated with boilers and the demands on them, sometimes the condition of over firing is unpreventable. With this condition, generally the superheat temperature will be above the required operating temperature. To help control the temperature, the de-super heater is utilized.

There are several types of de-super heaters used with the varied configuration of boilers on the market.

Answer: To allow for the expansion of the line and to absorb movement.

There are several differing methods of supporting the main steam line, due to the fact that the line comes from a level above the ground. The most common is the suspended type hanger. The ability of the line to expand as it heats is important.

Answer: To blow out sedimentary contaminants from the bottom of the boiler.

Many smaller boilers with limited quality may have a daily short blow down to reduce the effect of sedimentary build up in the lower reaches of the boiler. In high pressure water tube boilers it is not advisable to do this, as opening the blow down from the lower water wall headers will interfere with the water circulation and could cause tube failure.

In these type boilers, the best time to blow down the headers is when the boiler is out of service and at lower pressures.

Answer: To ensure the gas spaces of the boiler have been purged of any combustible gases prior to light off.

The purge takes into account the type of fuel you use, the volume of the boiler gas spaces and the capacity of the draft system. This is then calculated at a given preset air flow to account for the complete change out of air a pre determined amount of times.

Answer: Drum level, steam flow and water flow.

If load is increased, this causes the water level to be momentarily raised as the pressure is released from the surface of the water level in the drum. If this was the only element to be considered, then the level controller would try to reduce water going into the boiler when indeed it will need more, due to the increased demand for steam.

This is where the steam flow increase comes into play. There is now more demand, so the flow controller will open.