Is your boiler protected from a dry-fire event?

By Emily Newton, revolutionized.com

Process engineers across sectors, including pharmaceutical and food and beverage, constantly work with boilers and thermal heaters requiring constant attention. Proactive monitoring and preventive maintenance are crucial for mitigating a common hazard — dry fires. Uncover why boiler safety monitoring and dry-fire prevention keep industries operational and workforces safe through careful strategising and oversight.

What Causes a Dry-Fire Event?

A dry-fire event occurs when boilers and fluid heaters continue to receive heat even after the protective water layer has dissipated. Keeping heat-transfer surfaces adequately supplied with water is essential to preventing overheating of the burner. The American Society of Mechanical Engineers (ASME) advises operators to prevent large changes in heat transfer. Since the convective heat transfer coefficient varies, consistent monitoring and preventive maintenance are vital. To maintain systems, process engineers must ensure the heat sink remains stable.

If technicians do this effectively, it keeps the boiler materials, such as carbon steel, at a safe temperature and at an adequate pressure. It also allows the phase changes in the boiler to remain dynamic and uninterrupted, transitioning from liquid to steam. Neglecting the balance could cause the boiler’s materials to overheat, lose tensile strength, bulge or fracture.

The structural collapse will cause thermal shock to the system. The combination of pressure and unexpected cold feedwater entering other parts of the machine will cause the pressure to skyrocket and potentially make the machine explode from flash steam expansion.

Some process industries have standardised and enforced protocols to keep machinery and technicians safe from dry-fire events. However, more comprehensive guidance is needed from a safety perspective.

Detection and Intervention for Boiler Protection

Process engineers across industries can integrate a few strategies into their maintenance and safety plans to reduce dry-fire events. Sensors are the most crucial and several diverse types detect low-water conditions, temperature shifts and differential pressure changes. When teams have a tool, such as a low-water sensor, it could reveal whether conditions are caused by low feed tank levels or boiler component failures.

These insights allow operators to catch disasters before they occur. The sensors should feature corrosion-resistant materials with protected mechanisms to prevent biofilm accumulation and failure.

Physical redundancy and the placement of smart safety mechanisms in the boiler infrastructure will also help. For example, safety trips should exist outside the basic process control system and be certified by a regulatory agency. This separation provides an independent protection layer to prevent human error during operations. Operators can test how well these shutdown features function, ensuring that all valves and airflow purges perform as expected.

Finally, workers must know how to intervene during an emergency event. It may feel intuitive to add water to cool down a hot boiler, but this will exacerbate the situation. Automated shut-off and de-energisation should occur, and engineers should avoid changes to safety features. The mechanisms should prevent reactivation until temperatures return to a safe level. Heat must dissipate naturally, and teams should evaluate the boiler before using it again.

Operational Monitoring and Predictive Maintenance

For operators to know the sign an event is about to occur, they need the skills and training to deescalate the situation.

The most essential steps experts can take to keep facilities safe, include:

• Leverage data analytics and trend analysis to determine the most common triggering environments.
• Monitor critical metrics, such as mass flow rates and steam generation, and note any anomalous behaviour.
• Inspect boilers for fluid loss.
• Observe flue gas temperatures.
• Use tools such as thermal imaging via robotics and acoustic sensors to identify hot spots and maintenance opportunities.
• Keep change management records of the boiler’s maintenance history.
• Clean elements like the boiler tubes and conductivity probes to prevent system stressors like scale buildup.

Process engineers can also collaborate with other team members to develop the ideal water chemistry. Treating water can prevent issues, such as calcium carbonate buildup that can lead to erratic heat-transfer behaviours.

Industry-Specific Risk Mitigation and Compliance

Process engineering is a cross-sector discipline, and every organisation that uses boilers may need specific tactics to care for its machinery. Some industries have unique stressors — food and beverage would not have the same environmental interferences as the chemical processing field.

The Observance of Regulatory Frameworks

ASME has several guidelines for safely maintaining boilers. Its Boiler and Pressure Vessel Code includes information about powering boilers and specific heating applications.

It also incorporates industry-specific guidance, especially if working with hazardous chemicals and other life-safety utilities. European Union equivalents include EN 12952 and 12953, covering water-tube and shell boiler design, inspection and manufacturing for safety.

Manufacturing and safety regulations can vary by country, and framing development around regional specifications is essential. These can dictate everything, from preventing jumping low-water safety circuits to restricting modifications to trim valves.

Other organisations, such as the Occupational Safety and Health Administration (OSHA) and the Control of Major Accident Hazards (COMAH), have guidelines that outline process safety management rules for harmful substances. When boilers are involved in chemical operations, their safety may fall under these auspices.

The Pharmaceutical Industry

The pharmaceutical and medical industries need pure steam from boilers, as it is crucial for sterilisation. Therefore, they should use reverse osmosis systems and closely monitor electrical conductivity levels to ensure reliable performance. These companies may also be required to use different vessel metals, such as stainless steel, because of its hygienic properties.

The Food and Beverage Sector

Boiler safety monitoring in the food industry also requires special attention to sanitisation, but it can also require more extreme temperature variances. Cooking cycles for some products can demand a lot of pressure from boilers. Rapid changes in temperature and pressure can lead to dryout.

Additionally, food and beverage experts must prevent cross-contamination. Condensate from food plants could contain anything from sugars to acids, which can affect the boiler and its safety features, such as by corroding sensors. Teams must regularly monitor water quality to prevent dry-fire events.

Boiler Dry-Fire Prevention and Process Engineering Safety

Worldwide, engineers must follow the advice of regulatory bodies and safety experts to prevent dry-fire events in their boiler systems. These can cause catastrophic damage to infrastructure and harm to employees. Implementing industry guidance and prioritising compliance will keep equipment functioning for years to come, while improving the facility’s safety record.