Pressure

Welcome to a world’s first in contents monitoring for inert gases, such as Inergen™. Either monitoring pressure directly, using acoustics and sophisticated signal processing, or by monitoring mass loss and automatically converting this into pressure, you can now detect changes in pressure and losses of contents quickly, easily, and completely non-invasively.

At Coltraco Ultrasonics, we pride ourselves on the quality, reliability, and accuracy of our instruments – all made in the UK. With the arrival of this new technology, we now provide portable and fixed solutions to non-invasively monitor the contents of inert gas, CO2, and other clean agent fire systems

Portagas® is a world’s first technology for non-invasive, non-destructive monitoring of pressurised, inert gas systems.

P/N: 3107505-GAS

The most accurate and fast acting constants loss monitoring system of its kind. Capable of detecting a loss of agent mass to within 1% in Inert gas, CO2 and Clean Agent systems, and in addition to weigh loss, will provide accurate percentage pressure loss of Inert gas systems associated with agent contents leakage.

P/N: 2594650-FW

Why is Monitoring Pressure Important?

Inert gas fire systems, such as Inergen™, are used to protect high value assets and critical infrastructure in occupied spaces, where CO2 systems are not suitable, due to risk to life. Any fire extinguishing system is designed to a produce and maintain a certain concentration of the extinguishing agent. In the event of a fire, if this concentration is not met, or is met for an insufficient length of time, there is no guarantee that the fire will be successfully extinguished, potentially leading to catastrophic damage. It is vital, therefore, to accurately monitor the contents of fire extinguishing cylinders, to ensure that there is no leakage of agent that could lead to an area being unsafe without you even knowing about it.

For inert gas fire systems, in accordance with standards such as ISO 14520 and NFPA 2001, temperature-adjusted pressure is a direct indication of cylinder contents. For such systems, true loss of pressure of greater than 5% will require that the cylinder be refilled or replaced.

For this reason, precise measurement of pressure, as well as accurate and reliable adjustments for temperature, are vital for properly monitoring an inert gas fire system. Regular, reliable measurements will allow you to detect a leaking cylinder long before it passes the 5% threshold and thus ensure a higher level of safety and security for whatever assets your fire system is designed to protect.

 

Acoustic Pressure Monitoring

Acoustic pressure monitoring is exactly what it sounds like. It is utilising acoustics – specifically resonant frequencies – to monitor and detect changes in the pressure of a sealed container with a fixed volume. It is a completely non-invasive technique that can quickly and easily detect even small changes in pressure.

 

How does Acoustic Pressure Monitoring Work?

Acoustic pressure monitoring utilises the resonant frequency of a container to monitor its internal pressure completely non-invasively. In simple terms, the resonant frequency of an object or container is the frequency at which it will vibrate or “ring” after some excitation.

Many of an object’s intrinsic properties will affect this frequency, such as shape, size, thickness, and material. However, in the case of a sealed, pressurised container, such as a fire cylinder, the tension in the material will also have a key effect. It is well understood how the tension in a string or wire will affect its resonance, and these same physical principals can be extended to more complex systems.

For a fire cylinder, this means simply that the greater the tension within the cylinder walls, the higher frequency of any resonant mode will be. This is the key to acoustic pressure monitoring; the tension in the walls of a pressurised cylinder is generated primarily by the cylinder’s internal pressure, such that there is a direct, quantifiable relationship between pressure and resonant frequency. This pressure, in turn, is directly related to the amount of gas contained within the cylinder and its temperature. Thus, adjusting for changes in temperature, pressure can be used to predict exactly how much gas a cylinder contains.

Therefore, if one can safely excite resonant vibrations in a cylinder, analyse these vibrations and carefully calibrate the system, it is possible to detect even minor changes in the internal pressure of a cylinder. Combining this with temperature measurements, and using the most accurate mathematical models available, allows changes in contents (i.e., a leak) to be clearly distinguished from fluctuations in pressure caused by temperature.

 

Continuous Monitoring of Pressure using Mass

Another option to non-invasively monitor the contents of fire cylinders is to monitor their mass. Agent mass is the most fundamental metric for monitoring contents, as it will only change if the physical quantity of the agent changes. This eliminates factors such as temperature, making the measurement simple and effective.

Monitoring the mass of a cylinder also allows other types of agents to be monitored, including  liquefied gaseous systems, with some propellant gas and a liquefied extinguishing agent. Whilst mass measurements will not differentiate between a loss of agent or a loss of propellant gas, a leak of any kind could still be rapidly detected and acted on.

For non-gaseous systems, as the regulations reference pressure loss, it is imperative that mass loss must be reported as an equivalent loss in temperature-adjusted pressure. Our digital, fixed weight monitoring system, PermaMass® FEATHERWEIGHT, addresses this by utilising the fact that, for pressurised gases, mass and pressure are intrinsically linked. When connected to inert gas cylinders, PermaMass® FEATHERWEIGHT will automatically convert any measured mass loss into an equivalent loss of pressure (adjusted to the original fill temperature and compared to the fill pressure), allowing you to fully understand how your systems are performing compared to the regulations.