A penetration seal must do more than achieve a fire rating under test conditions. It has to remain effective while the building and pipework continues to move.
Recent discussions shared by the Passive Fire Knowledge Group, have encouraged greater scrutiny of the movement capacity of penetration sealing systems and in particular, the evidence used to support manufacturers’ performance claims.
The article highlights that the current BS EN 1366 fire-resistance test standards do not provide a mechanism for demonstrating the compression or extension capacity of penetration sealing products.
In practical terms, a fire classification should not automatically be taken as evidence that a seal can withstand movement. Neither should a general description such as ‘flexible’ be accepted without understanding exactly what has been tested.
Movement is part of normal building operation
Once a building becomes operational, service penetrations are subjected to continual movement caused by thermal expansion and contraction, vibration from mechanical services and the natural settlement of the structure itself. A single movement can be insignificant, but these forces can be repeated thousands of times over the life of a building or asset. Where a penetration seal cannot accommodate them, stress can build up.
Over time, that can lead to cracking, separation or a loss of tightness – potentially compromising the compartmentation the seal was installed to protect.
Understanding how a sealing system responds to those conditions and whether that performance has been independently verified, is becoming an important part of the specification process.
What should movement evidence tell you?
An evidenced movement claim should make clear:
- Whether the movement is axial, radial or both
- How much displacement was applied
- The annular clearance around the pipe
- Whether the test involved a single movement or repeated cycling
- How many cycles were completed
- The speed at which the movement occurred
- Whether the seal remained intact and tight afterwards
The figures also need to relate to the proposed installation. A product may have demonstrated movement in one particular pipe, opening and seal configuration, but that does not mean the same capacity automatically applies to every penetration detail. Pipe supports, fixings, opening dimensions and the supporting construction must all be considered as part of the design.
NOFIRNO® : designed for movement
NOFIRNO® is designed to address the practical demands placed on service penetrations throughout their working life, maintaining fire, water and gas tightness while allowing the movement that naturally occurs within operational buildings.
The NOFIRNO® Flexible Pipe Penetration System uses a combination of flexible rubber sleeves and NOFIRNO® sealant to form a seal.
Movement capability is not an additional feature of the system, it was considered as part of its development, with the aim of absorbing mechanical loads and reducing the transfer of stress into the surrounding construction.
A dedicated mechanical test programme was carried out to examine how the system responded to both axial and radial pipe movement. The resulting data provides measurable performance information rather than relying on a broad claim of flexibility.
Axial movement: 50 mm
Axial movement occurs along the length of the pipe and is commonly associated with thermal expansion, contraction or longitudinal displacement.
In the largest axial configuration recorded in the test programme, the installation comprised:
- a 102 mm internal-diameter conduit sleeve;
- a 42 mm outside-diameter pipe;
- a 30 mm annular clearance;
- and a 100 mm-long conduit sleeve.
The seal accommodated:
- 50 mm axial displacement
- 195% stretch
- 100 movement cycles
- movement speeds of up to 750 mm per minute
During the test, the rubber sleeve and sealant deformed around the moving pipe while remaining contained within the penetration.
This gives contractors and designers a defined movement result linked to a specific pipe and opening configuration.
Radial movement: tested over 22,845 cycles
Radial movement takes place laterally across the opening. It may result from vibration, pipe-support movement, structural displacement or other operational forces.
This can be particularly demanding on a penetration seal because the material is repeatedly stretched on one side of the pipe and compressed on the other.
During the NOFIRNO® radial test programme, the seal completed:
- 22,845 movement cycles
- approximately 76 hours of cycling
- and 456.9 metres of cumulative movement
The report recorded no damage or loss of sealing to the sealing system during this programme, with the compression and stretch forces remaining similar throughout the test duration.
Accommodating one movement event is not the same as tolerating repeated movement over an extended period. Cyclic testing gives a more useful indication of how a seal may respond to the conditions experienced in an operational building.
Designing for long-term radial movement
Testing to an extreme does not mean that the maximum tested displacement should automatically become the routine design allowance.
The NOFIRNO® report identifies movement of approximately one-third of the annular clearance as the optimum value for long-term radial performance, based on a maximum movement speed of 100 mm per minute.
| Annular clearance | recommended radial movement |
| 15 mm | 5 mm |
| 25 mm | 8 mm |
| 30 mm | 10 mm |
This relationship between movement and available clearance gives the design team a practical basis for coordinating the pipe, builders work opening and penetration seal.
It also reinforces the importance of addressing movement early. If the required movement allowance is not considered until the opening has already been formed, there may be insufficient clearance to create the correct detail.
Watertightness after movement
A penetration may appear undamaged while no longer providing an effective seal against water or pressure.
For that reason, visual inspection alone is not enough. In one radial test configuration, a system with a 25 mm annular clearance was subjected to 345 cycles at different displacement amplitudes and speeds. A post-movement watertightness test was then carried out at 2.5 bar.
This is particularly relevant in applications where penetrations may be exposed to groundwater, weather, washdown, moisture or pressure differentials.
It demonstrates the importance of assessing what happens after the movement, not just whether the sealing material can visibly deform.
Fire performance and movement performance are different questions
Movement testing does not replace fire testing. Equally, a fire classification does not, by itself, demonstrate movement capacity. Both forms of evidence need to be considered.
For any project, the proposed penetration should be checked against the current fire-classification and certification documents for the exact:
- service type and material;
- pipe diameter;
- supporting construction;
- opening size;
- seal depth and configuration;
- and required period of fire resistance.
The strength of the NOFIRNO® approach is that its fire-sealing function is supported by separate, quantified mechanical evidence addressing the movement that can occur once the building or asset is in use.
Better evidence supports better decisions
The Passive Fire Knowledge Group’s guidance is a timely reminder that manufacturer movement claims should be examined carefully at the specification and design stages.
For contractors, that means looking beyond headline claims and asking for the detail behind them.
NOFIRNO® provides clearly defined test information covering:
- axial and radial movement;
- repeated cyclic loading;
- movement in relation to annular clearance;
- test speeds and cycle numbers;
- cumulative movement;
- and post-movement watertightness.
Movement requirements are best resolved early. We can review the proposed pipe type and diameter, supporting construction, annular clearance, expected movement, fire-resistance requirement and any water or gas tightness criteria to help identify an appropriate NOFIRNO® solution.