Alarm on drum water level is required to control level of boiler water in the steam drum in which steam boilers are run with no continuous supervision that involves the vast majority of steam boilers especially for industries. Alarm on drum water level is needed to give signal either on low water level or high water level condition. The steam boiler will be shut down if alarm shows that water level in steam drum is low level. The condition of boiler water level on low can be triggered by:
- Inability to maintain procedure of drum level control system.
- There is leakage in feedwater piping system.
- Boiler feed pump cannot work properly.
The codes, regulations, and standards such as ASME, ABMA, NFPA and the others are made to protect steam boiler and make sure them can being operating securely and safety for many years. Furthermore, the explosion, damage, and life loss related to steam boiler operation can be prevented. However, human error and other possibilities which lead to boiler damage may be occur when the low water level is not avoided.
The impacts of low water level in a steam boiler are as follow:
- The water wall tubes or furnace wall tube will be over heating because these tubes are not anymore cooled by water due to the lack of water in steam drum.
- If the tubes is overheating, the temperature of the tube metal will quickly increases so based on ASME BPV Section II D, the maximum stress will be reduced along with increasing its temperature.
- The final impact is the tubes will be crack, rupture and damage.
The following below is the steps of alarm on drum water level based on international regulations due to low level of boiler water:
- First alarm on low level of boiler water: shut down or turn off the burner when this alarm is sounded, but enables the burner is turn on when the level of boiler water is recovered.
- Second alarm on low level of boiler water (generally known as lockout): this alarm type is same with first alarm, the burner will be shut down when low level is reached but it keep on being 'locked out’ although the level of boiler water is recovered and almost any errors are already rectified. The lockout needs to be by hand reset to enable the burner turn on and working back.
Along with the exclusion of 1 or 2 working standards, the hazards coming from high level of boiler water in steam drum are treated quite without due consideration, otherwise ignored entirely. The hazard of an exceedingly high level of boiler water in a steam drum involves:
- Greater water which is carried over into steam may lead to bad function and also failure of steam process elements, because of dirt.
- Overfilling the steam boiler may result in water hammer within the steam process, risking destruction to the power plant and also harm to workers.
- Unclean and wet steam may contaminate the solution in which it’s employed instantly. Wet steam may maximize the water film depth of the heat transfer area, reduced control temperatures, probably interfering by using appropriate sterilization of the product. Ideally, reduced course of action and generation productivity will enhance course of action time and also unit prices.