Maintaining fire suppression systems is crucial for ensuring the safety of people and property. Traditionally, measuring the contents in these systems has involved labor-intensive and time-consuming methods. However, with advancements in technology, ultrasonic level indicators have emerged as a cost-effective solution. In this blog post, we will explore the drawbacks of traditional methods, introduce ultrasonic testing, and highlight the cost-saving benefits of using Coltraco Products’ Portalevel® MAX PLUS and Portasteele® CALCULATOR.
Gaseous suppression systems play a critical role in protecting lives and valuable assets by quickly extinguishing fires in enclosed spaces. These systems rely on the proper functioning of fire suppression cylinders, which are pressurised containers filled with liquefied clean agents or inert gases like Nitrogen. To ensure the effectiveness of these systems, it is crucial to detect any leaks that may compromise the contents of the cylinders. While pressure gauges are commonly used to monitor the internal pressure, they alone are insufficient for detecting leaks in liquefied gaseous suppression systems.
One of the primary limitations of pressure gauges is their inability to differentiate between leaks in the liquefied agent and leaks in the pressurising gas. When a leak occurs, the internal pressure inside the cylinder decreases, but it does not provide information about the specific substance being leaked. This ambiguity can be dangerous, as the true contents of the cylinder may not be known, putting the safety of individuals in the vicinity at risk. To ensure the proper functioning of suppression systems, it is necessary to perform additional tests, such as liquid level indication, to accurately determine the cylinder’s contents.
In pic: A bank row of cylinders with individual Pressure Gauges
In pic: A closer look at Pressure gauge attached to a fire suppression cylinder
Cylinder Internal Pressure and How It Is Affected By Leakages
When a portion of the contents of a super-pressurised fire suppression cylinder leak, the internal pressure inside the cylinder will decrease. However, it is generally not known if the leak is from the liquefied agent (such as FM-200® or Novec™ 1230) or the Nitrogen gas used to pressurise the cylinder. Adding to this is the dependence of the internal pressure on the temperature of the cylinder and the difficulties involved in accounting for this, thereby endangering the lives of those in the vicinity if the true cylinder contents is not known. Liquid level indication is therefore a necessary additional test required to ensure that suppression systems are safe and functioning correctly.
When a cylinder is filled with liquefied agent and Nitrogen gas at the required fill temperature, the pressure in the cylinder starts to increase until the required fill pressure of the cylinder is reached. The temperature of the cylinder is closely monitored and the indicator of the pressure gauge will be in the “GREEN” zone when the cylinder is considered full.
Liquefied clean agent systems (such as FM-200® or Novec™ 1230) are stored in liquid form in the fire suppression cylinder and are being pressurised by Nitrogen, often referred to as the “Nitrogen head” as the Nitrogen is added after the liquefied contents are filled in the cylinder. The pressure gauge on the cylinder reads the internal pressure inside the cylinder, however, it does not show the individual quantities of the liquefied clean agent or Nitrogen gas.
As a result, a fire suppression cylinder can be underfilled with liquefied clean agent, but overfilled with Nitrogen gas, yet the pressure gauge continues to read in the “GREEN” zone. This can often happen when the “leaked” cylinder is refilled with Nitrogen gas, rather than the liquefied agent itself, as it is the cheaper option to pressurise the cylinder and the pressure gauge to the “GREEN” zone.
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Variation in Pressure Over Modest Temperature Fluctuations
A change in temperature of just 5°C, for example from 17°C to 22°C can lead to significant changes in pressure in cylinders, while the liquid level remains comparatively constant. The below data demonstrates this for three typical super-pressurised cylinders.
| Agent Type | Fill Pressure (bar) | Printed Agent Mass (kg) | Pressure Change | Liquid Level Change |
| FM-200® | 25.8 | 96.8 | 4.85% | 1.39% |
| FM-200® | 42.4 | 104 | 3.11% | 0.27% |
| Novec™ 1230 | 25 | 10 | 2.70% | 0.70% |
Official ISO 14520 and NFPA 2001 regulations state that if the pressure in a cylinder for liquefied agents were to drop by greater than 10% of its initial value, it should be refilled or replaced, however, if the temperature of the contents increases, the base pressure may increase by up to 5% (or more for greater temperature changes). This means that the equivalent isothermal pressure would have to drop by close to 15% before a leak is recognised.
Technically, one should account for the effect of temperature when checking a pressure gauge, however, many servicing personnel do not know how to do this and it is often difficult to determine an exact pressure value from a gauge (for example gauges frequently consist simply of a green section and a red section with widely-spaced tick marks). In addition to this, sometimes the internal temperature of the cylinder varies with respect to the ambient temperature.
Given that the liquid level in a cylinder tends to vary far less with temperature, liquid level indication is a reliable method of detecting leaks in cylinders even when pressure gauges fail to do so. Indeed, using the Portalevel® MAX PLUS in combination with the Portasteele® CALCULATOR enables the recorded liquid level to be converted into a record of the agent mass which accounts for the change in ambient temperature. Thus, the recorded agent mass is negligibly affected by changes in temperature and one can be sure that, if the agent mass remains within 5% of the original value and the pressure within 10%, the cylinder in question need not be refilled or replaced.
In pic: Portalevel® MAX PLUS
in pic: Portasteele® CALCULATOR
Key Benefits of the Portalevel® MAX PLUS and Portasteele® CALCULATOR:
- Accurate liquid level indication with ±1.5 mm tolerance
- Versatile calibration modes for testing different fire suppression agents
- User-friendly display for easy reading and interpretation of measurements
- Enhanced safety by ensuring proper functioning of gaseous suppression systems
- Accurate agent weight calculation by converting liquid level measurements
- Traceability and comparison to ensure intended fill level of fire suppression cylinders
- Temperature compensation for precise calculations in varying ambient conditions
- Easy integration with the Portalevel® MAX PLUS for comprehensive testing and monitoring of gaseous suppression systems.
Conclusion:
Pressure gauges alone are insufficient for detecting leaks and accurately determining the contents of fire suppression cylinders. Ultrasonic technology, such as Coltraco’s Portalevel® MAX PLUS and Portasteele® CALCULATOR, offers a reliable and non-invasive solution for testing and monitoring gaseous suppression systems. These tools provide precise measurements and calculations, ensuring the proper functioning of fire suppression systems and enhancing safety in enclosed spaces. For reliable and efficient fire safety solutions, Coltraco Ultrasonics is a trusted global leader in ultrasonic technology.
