Boiler Safety Series | Boiler Water Level Accidents Causes and Preventive Measures

August 10, 2021

Water level accidents are common main accidents in boilers, which are divided into two types: less water accidents and full water accidents. Whether the boiler lacks water or the boiler is full, the damage to the boiler equipment is very serious. Therefore, to understand the situation, cause and solution of the boiler water level accident is very important for the safe and stable operation of the boiler.

Through years of theoretical accumulation and field practice, EPCB has summarized the situation, causes and solution of boiler water level accidents, helping your boiler to operate efficiently and safely, and helping you become a leader in the industry.


Boiler Water Shortage Accident


The lack of water in the boiler refers to the occurrence of accidents that endanger the safe operation of the boiler when the water level in the boiler is lower than the minimum safe water level when the boiler is running.



1. The water level in the water level meter is lower than the limit water level and cannot be seen

2. The two-color water level gauge shows all the vapor phase indication colors

3. The negative value of the low water level indicator increases to exceed the limit

4. The water level alarm sends out a low water level signal, a bell rings, and a light is on

5. The low water level interlock device stops the operation of the drum, induced draft fan and grate motor

6. The steam temperature of the superheater rises and is higher than the normal outlet steam temperature

7. Boiler exhaust gas temperature rises

8. The boiler feed water volume is significantly less than the evaporation volume

9. When the water shortage is serious, the stove top will produce a burnt smell

10. When the water shortage is serious, the red water wall tube can be seen from the furnace door

11. For internal combustion boilers, you can see from the fire door that the deformed furnace bladder protrudes to the fire side and becomes red.

12. When there is severe water shortage, the furnace tube is deformed or even bursts

13. When there are flammable wood and straw ropes near the steam pipeline, smoking and burning may occur




1. Boiler workers do not pay attention to work, leave their posts, and do not monitor the water level

2. Boiler workers can't judge water shortage and fullness, and blindly discharge sewage, which aggravates water shortage

3. When the boiler worker was flushing or repairing the water level gauge, he accidentally turned off the steam and water cock, resulting in a false water level

4. The water level meter is not flushed for a long time, causing the water connecting pipe to be blocked, resulting in the accumulation of scale, rust and slag, resulting in a false water level

5. Water level alarm, low water level interlocking device, automatic water filling device malfunction

6. The water supply system fails, the pipeline or valve is blocked, and the water supply valve is closed

7. The design of water supply pump and water supply pipeline is unreasonable, and the phenomenon of "grabbing water" often occurs

8. The blowdown valve is not tight or the spool is stuck by dirt, or the boiler worker forgets to close the blowdown valve, causing the boiler to lose water too much



1. When there is water shortage in the boiler, the main steam valve and feed water valve should be tightly closed for the boiler whose water connecting pipe of the water level gauge is lower than the highest fire boundary.

2. For boilers with water connecting pipes higher than the highest fire boundary, the "calling water" method can be used to judge the severity of water shortage

3. The status of the boiler water level gauge cock switch during operation is; the water level gauge steam cock is turned on, and the water level gauge water cock is turned on. The "calling water" method is operated as follows; (1) open the drain cock, flush (2) close the steam cock (3) close the water The cock (4) closes the water cock (5) and then turns on the water cock to see if there is water rushing out of the water connecting pipe. If there is water, it is a slight lack of water

4. When it is judged that the water shortage is not serious, you can continue to feed water to the boiler. After the normal water level is restored, the combustion equipment can be started to gradually increase temperature and pressure, and then put into operation.

5. When it is judged that the water shortage is serious, the boiler must be shut down urgently, and it is strictly forbidden to blindly feed water to the boiler, otherwise it will cause an accident


Boiler Full Water Accident


The full water in the boiler refers to the phenomenon that the water level in the boiler is higher than the highest safe water level when the boiler is running, which endangers the safe operation of the boiler. For power station boilers, it will cause deterioration of steam quality and cause serious harm to superheaters or steam turbines.



1. The water level in the water level meter is higher than the upper limit of the water level, and the water level line cannot be seen in severe cases

2. The two-color water level gauge shows all the water phase indication colors

3. The water level alarm sends out a high water level signal, a bell rings, and a light is on

4. The steam temperature at the outlet of the superheater drops

5. The feed water flow is abnormally larger than the steam flow

6. A large amount of water is stored in the sub-cylinder, and the drain pipe vibrates violently

7. When the water is seriously full, water hammer will occur in the steam pipe, steam will be emitted at the flange, and water will be emitted from the safety valve when the pressure is high


1. The boiler worker does not monitor the water level and blindly fills the water.

2. The water level meter discharge cock leaks, causing the water level display in the meter to be lower than the actual water level, forming a false water level.

3. The water level gauge is poorly illuminated and the water level line cannot be clearly seen. The two-color water level gauge is out of order and the color display is wrong.

4. Failure of automatic water supply adjustment.

5. The high and low water level alarm fails and does not send out a signal.

6. The water supply valve leaks, or the boiler worker forgets to close the water supply valve.

7. The feed water pressure increases suddenly, and the water inlet speed increases.




1. When the water level line is not visible, open the water cock of the water level gauge. When the water level line appears, it is slightly full of water, and when the water level is not visible, only rising bubbles are severely full.

2. When there is severe water, you should shutdown emergency.

3. If it is slightly full of water, the combustion should be reduced, the water supply valve should be closed, the drain valve should be opened to drain the water, and the drain should be stopped when the water level reaches the normal level.

4. Open the trap on the main steam pipe for drainage.

5. Check whether all the valves and instruments of the water supply system and the water level display and control system are normal, and they can be put into operation only after they are qualified.


Preventive Measures for Boiler Water Level Accidents

(1) Strengthen the training and education of operating personnel, so that operating personnel can truly feel the dangers of water shortage and full water to the safe operation of units.

(2) Strengthen business learning to understand the principles of the water supply regulation system, working performance, and the number, position and function principle of each valve to ensure the correctness of operation.

(3) Strictly implement the operations specified in the regulations.

(4) Strict and meticulous inspection, and promptly deal with problems found.

(5) Strengthen the ideology of safety first, and improve the skills of surveillance operations.

(6) Strictly implement the regular work system, flush the water level gauge in time, and check the water level gauge.

(7) During the start and stop of the unit, the large swing of steam pressure, and the action of the safety valve, it is necessary to fully understand the changing trend of the drum water level, and do not be confused by the false water level and cause misoperation.

(8) Regularly organize accident learning and necessary accident drills to improve the ability of operators to deal with accidents.

(9) Do in-depth study, analysis and discussion of major accidents of the same type of units, learn from them, and avoid similar accidents.

(10) Make an accident record and hold an accident analysis meeting.




Through the above content, you can have a comprehensive understanding of the boiler water level accident, understand the boiler failure and take corresponding measures to actively prevent it, and your boiler can be used more safely and lastingly.


EPCB, your private boiler system expert!

Further Reading:

Boiler Safety Series | Boiler Tube Burst Causes and Preventive Measures in Boiler Accidents

Boiler Safety Guide | Industrial Boilers'Common Accidents and Solutions

Industrial Steam Boiler Common Malfunctions Reasons and Solutions

  • Send You Inquiry

  • Give You Boiler Solution

  • Place The Order

  • Get Your Boiler

Ask for Boiler Solution Suited Your Condition!

Tell us your need about boiler capacity in your industry, we will recommend the most suitable boiler model for you!

Consult online customer service
Boiler fuel: