Permalevel FEATHERWEIGHT is the remote constant monitoring system for CO2, inert  and clean agent gaseous fixed fire suppression systems with real-time diagnostics. It is the world’s first such system with 3 gas-group capability.

Gas Weight Constant Monitoring System
P/N: 3542055-PML-FW

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Improve your fire safety by constantly monitoring the fixed fire suppression systems cylinder contents required to extinguish a fire event, with this brand new system from Coltraco Ultrasonics.

  • More than just CO2; also high pressure inert gas systems and clean agents in high pressure seamless cylinders
  • Innovative software showing real-time diagnostic information
  • Unique mechanical device removes the need for downtime
  • 80% lighter than existing load weigh devices

We have designed Permalevel® Featherweight (PML® FW), a constant monitoring system for CO2, Inert Gases and the combined weights of Clean Agents and Nitrogen, all in one lightweight system.

The Permalevel® FEATHERWEIGHT from Coltraco

Core Features

Innovative New Design

A low cost simple method of constant monitoring for fire suppression cylinders, Permalevel® Featherweight builds on the first generation of Load Weigh, now with live diagnostic features.

12 Cylinder Input

Each unit can connect to up to 12 cylinders identically, and multiple units can be chained together.

Real-Time Diagnostics & Remote Alert

As the agent is discharged, the weight of the cylinder reduces setting off an alert system which will be displayed on the device. If using the communication feature, an alert will be sent to the Fire Panel.

Core Benefits of the Permalevel® FEATHERWEIGHT


The system can be calibrated without disconnecting the cylinder while the rest of the system is still being monitored meaning no disruption to your fire protection


All new multi-cylinder system meaning one device covers up to 12 CO2 cylinders all being monitored simultaneously. Multiple devices can be connected together to cover the entire cylinder installation, creating one fully integrated monitoring system


Competitive pricing. Highly configurable to suit customer needs.


Installation is quick and easy, with customisation available to suit your fire suppression installation requirements

4 Advantages compared to existing Mechanical Load Weigh Devices:

  1. An integrated continuous monitoring system.
    Twelve cylinders are connected through one device. Each device connects together joining sets of 12 cylinders or as many as your system requires. All connected to the fire panel via the monitored input allowing for a fully integrated monitoring system with alerts available on your centralised system.
  2. Real-time cylinder diagnostic information
    Each device will display the respective 12 cylinders information in real-time. You can view the current weight and percentage loss if applicable. Preventative maintenance; it allows you to track cylinder leakage. For example, the device will tell you if the cylinder continues to leak at that current rate when it will reach the predetermined threshold of 5 or 10%. It will only set off an alarm if it reached a predetermined value, i.e. 10%. (5% for FM-200). Currently devices only alert when the cylinder has leaked past a pre-defined amount (5%, 10%) usually with a visual alarm, LED or fire alarm, not with an actual value given no indication of severity.
  3. A shared power relay system
    Each device is powered in series sharing the same power source and reducing wire congestion and reducing the number of mains power outlets needed.
  4. Most accurate constant leak monitoring system on the market.
    Accurate to 0.03% of max load.



Non-liquefied, pressurised inert gas systems currently rely on pressure gauges to determine their contents, as it is known that the pressure (adjusted for temperature) of a gas is directly related to the quantity of the gas. In fact, the ISO regulations for non-liquefied gases are as follows:

ISO 14520-1 Gaseous fire-extinguishing systems – Physical properties and system design – Part 1: General Requirements

  1. Inspection, maintenance, testing and training
    9.2 Inspection
    9.2.1 General The storage container contents shall be checked at least every six months as follows:  Non liquefied gases: for inert gas agents, pressure is an indication of agent quantity. If a container shows a loss of agent quantity or a loss of pressure (adjusted for temperature) of more than 5%, it shall be refilled or replaced.

Permalevel™ Featherweight directly relates a change in pressure of a cylinder at a known temperature to a change in its mass. The well-known ‘ideal gas’ equation predicts a 1:1 relationship between fractional changes in pressure and mass. The truth is that there is an intrinsic relationship between the two, however, it is more complicated than this and depends on the specific contents of the cylinder. At Coltraco, we are able to account for this in specific cylinders and inert gas agents, allowing us to accurately and reliably convert a change in mass to a change in pressure.


Key Advantages Explained

  • The mass of agent is completely independent of temperature. A change in mass will always correspond to a change in the cylinder contents. This is not the case for pressure, as the internal pressure of a cylinder depends on its temperature. Pressure values must, therefore, take temperature into account, adding another potential source of error. In addition, service personnel often fail to take temperature into account at all.
  • Accuracy: The PML® FW can detect a change in mass of <1% in high pressure Inergen systems. Pressure gauges are not only unreliable, they are limited in their accuracy as they use an analogue scale. Pictured is a typical pressure gauge that would be used on a high-pressure inert gas cylinder. For a 20MPa (200 bar) cylinder, the accuracy of this gauge is limited to 2.5% of the fill pressure. This is compounded by the potential for human error in reading any analogue scale; two people reading the same analogue scale could report slightly different values. In contrast, a digital scale will give the numerical value as accurately & precisely as it is capable of doing.
  • This accuracy can be achieved for all high-pressure Inergen/inert gas systems. Inergen is one of the most common inert gas fire extinguishing agents, and itself comes in 3 common blends, IG541, IG-55 and IG-01. The vast majority of Inergen systems use one of eight types of cylinder. <1% accuracy can be achieved for all of these blends in any of the common cylinders, (in many cases, even <0.5%).
  • If a fast leak forms, far more than a 5% decrease in pressure could occur between measurements. The ISO regulations shown above only require pressure to be tested once every six months. A fast leak, or indeed a slower leak occurring shortly after a check, could lead to an incredibly unsafe environment, where any fire would almost certainly fail to be extinguished. This could potentially go unaddressed for months.
  • Constant, automated monitoring. The PML® FW addresses this issue, as once a cylinder is mounted, it is continuously monitored. If the agent mass drops by more than 1%, the cylinder is marked as ‘LEAKING’. If mass loss exceeds 5%, the system will initiate an alarm and note a ‘CRITICAL LEAK’ on the cylinder.


How do we achieve this accuracy?

The PML® FW is fundamentally simple: the cylinder is threaded onto a high-precision load cell, which, once calibrated, will return the weight of the cylinder, accurate to approximately ±100g. Therefore, any cylinder with an agent mass greater than 10kg can be measured with precision greater than 1%. However, simply monitoring the weight of a cylinder is not sufficient to deduce fractional changes in the agent mass.

The output of the load cell is the total mass of the cylinder and its contents. To determine percentage change in agent mass, therefore, we have developed unique algorithms to allow us to accurately and reliably calculate the initial mass of the agent based off the cylinder volume, its fill pressure and temperature and molecular makeup of the agent.

  • The most common method to determine the mass of a pressurised gas is to use the well-known ‘ideal gas’ equation, which is an approximation that ignores some physical properties of the gas molecules.


  • At Coltraco, however, we believe that this equation does not deliver sufficient accuracy, so we use more complicated and more accurate equations, to develop the unit’s algorithms which takes into account the physical size of molecules and the interactive forces between them.


  • This allows us to calculate the initial agent mass to a high degree of accuracy, as well as converting changes in mass to changes in pressure at constant temperature.

Authors Details

Carl Stephen Patrick Hunter OBE is Chairman of Coltraco Ultrasonics, a high-exporting manufacturer of monitoring systems of gaseous extinguishing systems for the global fire sector. Their flagship instrument is Portalevel™ MAX and Portasteele™ Calculator which pioneered the ability of fire technicians to converts contents readings to ones of agent mass.


For the Permalevel® FEATHERWEIGHT, Contact Coltraco Today

For more information on the Permalevel® FEATHERWEIGHT, get in touch with the Coltraco team today, we can always be on hand to help and answer any questions that you may have.

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