Boiler emergencies and their control methods

Emergency Response Plan

Since few people can think clearly and logically during a crisis, it is very important to be prepared to respond to such situations. Emergencies can be natural or man-made, such as floods, storms, fires, releases of toxic gases, and chemical spills.

The activities that are carried out to deal with an incident or crisis and minimize its effects and to save lives, reduce physical or mental injuries, and prevent future injuries are called emergency response, and the set of actions that ensure the safety of the employer and employees in emergency situations is called an emergency response plan. In other words, this plan includes the process of preparation, risk reduction, and normalization of the emergency. In industrial power plants, boilers are sometimes placed in emergency situations, which we will examine in this study.

Definition of Emergency:

Emergency refers to any fire, explosion, release of toxic and hazardous gases, release of liquids and chemicals, etc. that can have severe effects on the environment or pose risks to employees and facilities.

Status and degree of emergency:

a) Emergency number one (yellow): The safety of the unit is not threatened and no serious harm is caused to individuals. This situation can be handled by the unit's staff without requesting assistance from outside the unit.

b) Emergency number two (orange): External assistance may be required and there is a possibility that it will attract the attention of local, provincial and national media.

c) Emergency number three (red): The facility is under serious threat and there is a possibility that the danger will spread to areas beyond the facility or that it will cause multiple injuries or deaths.

Emergency announcement:

Emergency is announced with four 15-second whistles (sirens) at 10-second intervals.

Announcement of normal conditions:

The end of the emergency condition is a continuous two-minute whistle.

Boiler emergency conditions:

Sometimes, conditions may arise in boilers that are not considered shutdown factors, but they can cause a problem in the boiler and cause one of the shutdown factors to be activated, which will then activate the interlock systems and take the boiler out of service through Emergency Shut Down. In this situation, the operator tries to solve the problem in a short time before the interlocks are activated, and if this is unsuccessful, the boiler is taken out of service normally.

The following are some of these emergency conditions:

1- Fuel and water supply to the boiler cut off:

If the boiler water level is not controlled accurately, very dangerous consequences are possible. If the water level drops too low and the boiler tubes dry out, the tubes may overheat, crack, or even explode. If the water level rises too high, water may enter the steam distribution system and cause subsequent problems.

For this reason, level controllers are used in steam boilers that are equipped with an alarm system to warn or completely shut down the burner in the event of a problem.

The modern method of level control is to use water level sensor rods inside steam boilers. If the boiler water level drops below an acceptable level, the controller sends a signal to the pump, which turns it on and supplies water. And after reaching the high level, the off command is issued again. The sensor rod senses the levels related to the pump turning on and off and the high and low alarm levels and issues the necessary command. Other alternative systems use float level controllers.

* How to be informed of emergency conditions: by the operator of fuel discharge, occurrence of faults and disruption of normal operation of the equipment - daily inspections and observations of the operation and safety operators.

* How to prevent emergency conditions: conducting scheduled daily and monthly inspections - normal operation and timely servicing. Checking the fuel transfer pipes from the tank to the burner.

2- Complex Blackout:

The occurrence of this problem causes many steam consuming units to be taken out of service. As a result, the steam produced by the boilers is not consumed and the pressure in the steam header will increase. If the power outage is limited to a short time, the steam produced is discharged to the atmosphere through safety valves on which silencers are installed, but if the power outage is prolonged, the operator has no choice but to take the boiler out of service.

* How to be informed of emergency conditions: by the operation operators. Mobile unit (unit trip).

* Methods of preventing emergencies: Complete coordination between national dispatching and power plants - preparing power plants with maximum production capacity and preventing emergency outputs and trips of power plant units in the country.

* How to control emergencies: Ready to use emergency equipment such as diesel generators and batteries - timely start of necessary equipment and use of auxiliary electrical power supply - readiness of power plants and dispatching in response to unexpected network incidents.

* How many personnel are required to control emergencies? Operation personnel, electrical repairs and safety personnel.

* How long is the allowed time to control emergencies? In the shortest possible time, maximum ten minutes

*How to clean the environment after the accident? Does not cause any particular pollution.

3- Cooling water cut-off:

In this situation, the temperature of equipment such as blowers and pumps will increase and there will be problems in their operation. In this situation, the boiler must be taken out of service. Sometimes the cooling water flow rate is reduced, which may cause the operator to reduce the boiler capacity to prevent the boiler from shutting down.

* How to be informed of emergency conditions: By operating operators.

* Ways to prevent emergency conditions: Conducting scheduled inspections, using the boiler shutdown system in case of shortage and water cut-off.

4- Severe leakage:

Sometimes, problems such as severe leakage from boiler pipes, upper and lower headers are also considered emergencies. Leaks can be steam, fuel leaks or leaks in water transfer facilities.

* How to be informed of emergency conditions: By operating operators - observations and informing other personnel.

* Ways to prevent emergency conditions: Continuous inspections of equipment and facilities - normal operation of equipment and maintaining normal fuel pipes and tanks.

* How to control emergency situations? Keep other people away from the scene of the accident - use appropriate safety and protective equipment (such as a leak detector)

* How many personnel are required to control emergency situations? Firefighters and trained shift boiler operators

* What is the allowed time to control emergency situations? As soon as possible (one hour)

* Boiler pipe leak detection system: which includes sensors located in different parts of the boiler and receives and records the vibration caused by leaks as signals.

5- Boiler fire and explosion:

Explosions in boilers are due to non-standard boiler body and internal equipment, or due to lack of service of the boiler internal pipes, or fuel accumulation in the furnace. Also, increasing pressure inside boilers and pressure vessels causes them to explode.

One of the causes of perforation and eventual explosion in steam boilers is the presence of scale inside the boiler. Over time, due to scale and lack of timely service, the walls of the pipes thicken, and in order to reach the required temperature, more fuel and heat are needed. This high temperature causes the hardened salts to crack, enter the boiler, and the fire reaches the body of the pipes, causing perforation of the internal pipes of the boiler and ultimately an explosion. Therefore, regular service inside the boiler, according to the manufacturer's instructions, is essential.

Opening doors during a fire is a provoking factor for the continuation and intensification of the fire. Opening a safety valve when the temperature of a boiler rises is a preventive or limiting factor.

* How to be informed of emergency conditions: By the fire alarm system by the operation operator or safety personnel.

* What are the ways to prevent emergency conditions: Testing the boiler safety valves and ensuring their proper functioning - Normal operation of the boiler according to the manufacturer's instructions - Timely control of temperature and pressure according to daily schedules to prevent sudden increases in boiler water vapor pressure.

* How to control emergency conditions: Removing units and other electrical and mechanical equipment from the circuit - Preventing unauthorized persons from entering the accident site - Using all available fire and rescue facilities.

* How many personnel are required to control emergency conditions: Fire, safety and operation personnel.

* What is the allowed time to control emergency conditions: Two hours

*How to clean the environment after the accident: Collecting damaged equipment and waste from the site - Washing the area