Technical Article

Understanding Boiler Safety Controls

November 18, 2020 by Muhammad Asim Niazi

This article looks at the safety systems included in boilers to alert malfunctions and prevent damage when issues arise. Learn about the safety systems and the ISO standard used to keep boilers running smoothly.

Boilers are equipped with a safety system to prevent damage in case of any malfunctions. If the problem in a boiler is not addressed in a timely manner, the results can be devastating because a boiler replicates a pressurized vessel’s structure. The complete mechanical, electrical, and electronics structures are tailored to handle pressure from different fluids.


Figure 1. A boiler’s safety system is crucial and requires regular maintenance. Image courtesy of SGS.


Boilers are an essential part of many industries, and how different sectors utilize boilers in their production are many. Making boilers useable is so much more than a simple conversion of water into steam. It involves complex systems made up of many components, including the safety system in the boiler.


Why Worry About Boiler Safety?

The boiler can be dangerous on a considerable scale. Unlike other machinery that only causes danger to products or humans on a relatively small scale, boilers can lead to large-scale destruction. 

Property Damage: The boiler’s unsafe operation can damage the building or the infrastructure of installation. If this occurs, a simple repair is not the solution. At the least, the building will need basic infrastructure repairs or at the worst, a complete rebuild from the foundation.

Loss of Life: Unsafe boiler use or conditions also affect human life due to the boiler’s enormous temperature. The mechanical structure is sturdy, built to withstand high pressure created inside the boiler. In the case of an explosion, the high temperatures and the possibility of shrapnel pose a hazardous situation for anyone on the premises.

Production Loss: Steam is an essential source of heating requirements and it is used in many industries. If there is a problem with the boiler and it completely breaks down, restarting normal operation could take many days or even weeks. Without a functioning boiler, production comes to a standstill. 


Safety Systems for Boilers

Modern-day boiler systems come with a safety system that triggers an alarm, stops the operation or even shuts the system down depending on the issue. These safety systems help avoid dangerous conditions to man, production material, and equipment.

The following types of safety systems are commonly installed in a boiler system:

  • Safety valves
  • Low water level controls 
  • Flame safeguard systems


Safety Valves

Safety valves are the major safety component installed on a boiler. Their basic function is to release the pressure built inside the boiler when it exceeds the boiler’s maximum pressure value. This abnormal pressure occurs when other safety functions do not work due to failure. 


Figure 2. A steam safety valve in action. Image courtesy of Emerson.


The safety valves’ design is according to the pressure that the valve can withstand, often called rated pressure. If the boiler’s pressure becomes greater than the rated value, the safety valve opens, releasing the pressure until it falls back to the safety valve’s rated pressure.

The safety valve requires calibration at regular intervals to test and verify proper operation. This calibration also ensures it is satisfactorily working if an emergency is not necessarily related to the boiler system itself, such as a natural disaster. 


Low Water Level Controls 

Low or no water in the boiler can lead to severe damage. When the water level drops below the minimum level, the boiler’s high temperature affects metallurgy’s strength. If temperature soars to a high enough value, it can even melt the steel.

A control system continuously monitors the water level to avoid problems associated with low water levels. When the system detects low levels, it triggers the safety system, effectively shutting down the boiler. The boiler’s restart condition depends upon the user requirement. Some may opt for an automatic restart, while others may require a manual restart after ensuring the appropriate water level is inside the boiler.


Flame Safeguard System

The flame safeguard system’s purpose is to detect the presence of flame continuously. If a flame is not detected, it shuts off the fuel supply.


Figure 3. Flame safeguard systems detect the absence of a flame. If the flame is not present, the system shuts down the boiler. Image courtesy of Siemens.


If no flame is present, a large quantity of fuel collects in the burner. In large enough quantities, this accumulated fuel could cause the furnace to explode. If the flame reignites after a prolonged period, the boiler could explode due to the large amount of deposited fuel. 


ISO Standards for Boiler System Safety 

The industrial sector benefits from set standards in many ways. Standards provide valuable guidelines to help avoid and overcome dangerous situations for operators and structures. 

In all cases, boiler safety systems are tested and verified. Implementing the standard set forth allows the relevant industry to take advantage of the standardized body’s research and expertise. Additionally, customers have more confidence when buying products that meet or exceed standards.

Different reputable standardization bodies have developed standards for boiler safety systems, but we will look at the International Organization for Standardization or ISO standards. 

The ISO standard for boiler safety is ISO 16528-1:2007, Boiler and Pressure Vessels – Part 1: Performance requirements.

This standard covers the following points:

  • Welding connections in the boiler
  • Threaded joints, flange connections, fittings connection, and safety accessories
  • Feedwater inlet and steam outlet
  • Different interconnecting tubing
  • Safety accessories and connection to the boiler

This standard does not cover:

  • The operation, maintenance, or service procedures required to implement this standard. The ISO, rather than giving methods of implementation, relies on the factory’s methods and procedures. The ISO’s only concern is implementing the specific standard.
  • Nuclear components, railway and marine boilers, gas cylinders, piping systems, or turbine systems.



A boiler’s safety is an essential part of the whole boiler system and should never be neglected. Above all, investment in safety protects a manufacturer’s personnel, money, and time.  Additionally, safety systems must be verified and maintained at regular intervals. The verification process stops the steam production, resulting in a halt of the production. But the cost of this production breakdown is much smaller than the cost of damage caused by a faulty boiler.

Different standards guide boiler systems used in every type of industry. The global footprint of the standard not only provides detailed guidance but also helps in building customer confidence.