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• Another ‘first' for Nullifire S707 – Now available for 90 (as well as 30, 60 & 120) minutes fire protection
• The Importance of Volume Solids in Intumescent Fire Rated Coatings
• Guidance for the fire protection of beams with web openings

Another ‘first' for Nullifire S707 – Now available for 90 (as well as 30, 60 & 120) minutes fire protection

This month sees another significant ‘first' for Nullifire S707, the UK's leading on-site, water-based decorative intumescent coating for structural steel. S707 is now available certified for 90 minutes fire protection, making it the only water-based intumescent coating offering the full range of 30, 60, 90 and 120 minutes fire protection currently available on the market.

Thinner film – faster application
Water-based intumescent coatings offer major advantages over traditional solvent-based solutions. First amongst these is that water-based coatings are faster drying. Nullifire S707 combines this with Hi-solids content and Hi-build technology to provide equivalent fire protection with a thinner coat. This further reduces application and drying times, which in turn reduces site costs – and allows faster access for other contractors and site operatives. In fact, Nullifire S707 can cut application times by up to a half compared to traditional solvent-based systems.

The Nullifire S707 basecoat and topcoat system are ideal for both on-site and off-site applications having been fully tested, for semi-exposed environments, in accordance with the new European Technical Approval Guidance Document.

Assured performance
Nullifire S707 has also been independently tested and certified to the most advanced industry standards covering specific tests on Universal, Hollow and Cellular steel sections. Nullifire S707 further complies with the Intumescent Coatings Forum (ICF) Guidance Document and is Certifier Approved. Nullifire S707 is also ASFP (Yellow Book) approved and fully tested and approved to BS476: Part 20/21: 1987 for 30, 60, 90 and 120 minutes fire protection.

Single coat protection and decoration
Up to 60 minutes fire protection can be achieved in a single coat of Nullifire S707. Furthermore, unlike solvent systems, Nullifire S707 dries to a smooth, hard finish. This avoids the need for a top seal in non-decorative areas of C1* buildings, providing even faster and more economical construction times and is the finish of choice for many architects, developers and contractors.

Nullifire S707 Top Seal (where required) is available in a range of RAL or BS 4800 colours. The satin finish is easy to maintain, resistant to damage, and contains no fibres – thus is suitable for clean room and similar applications.

Ready and easy to use
Nullifire S707 is supplied ready for use (requiring no thinning) and easy to spray using conventional or automated spray systems. Nullifire S707 can also be applied by roller or brush.

Contracts support
Nullifire S707 is backed by comprehensive technical literature and expert assistance for every stage of a project, from product selection and specification to installation and verification.

Nullifire operates a unique team of fully qualified contract support engineers. They are available to assist in project management and schedule planning to meet project time scales, and also provide an on-site or off-site inspection service.

For further information call 024 7685 5000 or email protect@nullifire.com.

Is the lack of understanding putting lives at risk?
Concerns have been raised within the Fire Protection Industry as to the distinct lack of understanding of the critical role Volume Solids play in the satisfactory performance of Intumescent Coatings. This lack of understanding is not exclusive to the specifiers (who are remote from such details), but also includes a number of manufacturers, contractors and other ‘specialists’ within the industry.

The ‘Volume Solids’ of a coating is a key fundamental parameter for all coating types. But in the case of intumescent coatings, whose purpose is to provide a specific and reliable period of fire safety, the correct measurement of Volume Solids can mean the difference between safety – and lives placed at risk.

The main concern lies with the critical relationship between the quoted Volume Solids content of Intumescent Coatings and the resulting fire performance. All intumescent coating manufacturers provide a table of material loadings for a product, generally given in the form of DFT (Dry Film Thickness) necessary to achieve the specified period of fire resistance for a given substrate.

Despite its critical role, there is no standard method used by manufacturers to determine Volume Solids. And a significant variation of data is readily apparent in the marketplace. An overestimated Volume Solids figure will lead to applications of lower dry film thickness than expected and, if not corrected on site, will result in A BUILDING WITH FIRE PROTECTION BELOW THAT SPECIFIED OR INTENDED.

Rod Brooks, Technical Director of Nullifire Limited, and Dr Susan Roy, Technology Group Leader, argue that ISO 3233: 1998 should be adopted as an industry-wide standard for the calculation of Volume Solids. This would eliminate the potential risk of under-protected buildings, avoid confusion in the marketplace and help maintain continued market confidence in intumescent systems.

What is ‘Volume Solids’?
The fire performance of an intumescent coating is directly related to the dry film thickness (DFT) of the coating – generally the thicker the coating, the longer the resistance provided. The Volume Solids is the percentage of dry film given from a volume of liquid paint.

The “Volume Solids” of a coating is a key fundamental parameter for all coating types but its importance in the Intumescent Coating business sector is clearly not fully understood or appreciated.

The “Volume Solids” of a coating is best described diagrammatically as below:

Volume Solids may be derived in one of two basic ways;

a. Theoretical Volume Solids: By calculation from the coating formulation using information on all the individual components
b. Practical Volume Solids: By practical measurement most commonly derived from measuring the density of the applied dry coating

What is the Issue?
The main concern lies with the critical relationship between the quoted Volume Solids content of Intumescent Coatings and the resulting fire performance. Intumescent coating manufacturers provide a table of material loadings for a product, generally given in the form of DFT (Dry Film Thickness) necessary to achieve the specified period of fire resistance for a given substrate.

However, it is very clear that these varying loadings lead to a wide range of different values that in many cases do not reflect the dry film thickness that can be achieved from a given volume of coating.

In the diagram above the effects of an incorrectly declared and high Practical Volume Solids or Theoretical Coverage are quickly obvious;

The Volume of coating calculated for a project will be grossly underestimated if the correct dry film thickness is to be achieved during application

1. If the dry film thickness is not corrected during application then the project will have a lower Dft than specified for the degree of Fire Protection and the building will no longer have the Fire Protection originally intended.
2. If the dry film thickness is corrected on site then the applicator will have used more coating than originally expected or costed for the project.

The theoretical Volume Solids can only really be calculated by the owners of the formulation and takes no account of contraction or expansion of resin solutions, packing effects between pigments, fillers and binders or any reactions between volatiles and other components that may render them non volatile. In most cases this results in the lowest Volume Solids figure for a given formulation.

The much more useful “Practical Volume Solids”, if measured correctly, provides the base route to determine the volume of coating needed to coat a known area of substrate with a desired dry film thickness. Consider the following approach:

1. Apply the coating using the application method generally used in the real life situation.
2. Apply the coating towards the upper end of the “Wet Film Thickness” that would normally be applied in a single coat in the real life situation
3. Allow the coating to dry or cure under the typical controlled conditions of use (such as ambient air or higher temperature conditions) to effectively constant weight.
4. Measure the Specific Gravity of this dry coating film.
5. Utilise the simply measured Specific Gravity and Weight Solids of the Wet Coating to calculate the “Practical Volume Solids”

This brief outline essentially describes the methodology used in the ISO and ASTM standards for determining the percentage Volume of non-volatilise or Volume Solids of a coating.

Why is Volume Solids important?
Practical Volume Solids is, either directly or indirectly, the route to determine the theoretical coverage of a supplied coating. It is not too difficult to see from the description of the Volume Solids above that it can be used to calculate the volume of coating needed to coat a known area of substrate with a desired dry film thickness. ie, the number of litres of product needed to coat an area of substrate to a declared dry film thickness. Theoretical coverage typically states the number of square metres of substrate that can be covered with one litre of coating at a declared dry film thickness – it takes no account of any losses in the application.

So where is Volume Solids or theoretical Coverage being used in the Intumescent Coatings business?

1. Intumescent Coating Manufacturers often quote Volume Solids and / or Coverage on their Data Sheets and associated literature
2. Volume Solids is used directly to convert dry film thickness loading tables into wet film thickness loading tables
3. Volume Solids and / or Coverage are used by applicators or end users to calculate the volume of coating needed to complete a project

The Volume Solids figure therefore plays a crucial role, in both the specification and application of Intumescent coatings in order to achieve the required dry film thickness and ultimately the desired fire performance.

See Example 1 below:

Potential for inadequate performance and risk
If the declared Volume Solids of a coating is not correct, this can lead to under-loading of the product - and a building with fire protection below that specified or intended. See Example 2 below:

Nullifire has a clear concern that there is no common specific method for determining Volume Solids used by thin Film Intumescent Coatings Manufacturers. There is also a very strong concern that “Weight Solids” appears to be being confused with “Volume Solids” with even Volume Solids by weight quoted on one data sheet!

In contrast to Volume Solids, the “Weight Solids” of a coating is the ratio of the weight of non-volatile to volatile material in a coating as supplied expressed as a percentage. On a number of product data sheets the Volume Solids either quoted or implied from Loading tables actually exceeds the quoted Weight Solids. Given the high density and the high loadings of the fillers used in conventional Intumescent Coatings it is almost unthinkable that even the practical Volume Solids could possibly exceed the percentage Weight Solids!

Urgent need for an industry standard
To clear up the existing confusion and eliminate risk, there is a very real need for all suppliers of intumescent coatings to use an agreed standard method and protocols to calculate Volume Solids. There is also good justification to suggest this data should be independently verified in the same way as currently assessed Fire Test data.

To meet this key objective, and to ensure that correct and comparable figures for Volume Solids are used throughout the industry, Nullifire Limited recommends that the method laid down in ISO 3233: 1998 (BS3900) be adopted by all manufacturers for the calculation of Volume Solids, provided that the application and drying conditions reflect those used in practice.

As a background to this recommendation, in the last few months Nullifire have completed studies with a wide range of commonly available Intumescent coatings. This programme has confirmed that the method, using sensible protocols, yields Volume Solids data that is very consistent with application experience by way of the wet to dry film thickness ratios seen with each product.

For a safer future
Nullifire believe adopting ISO 3233: 1998 as an industry-wide standard, confusion will be removed in the marketplace, promote continued confidence in intumescent products, and help to ensure that lives are not put needlessly at risk by under-performance of the fire protection system.

Guidance for the fire protection of beams with web openings
Beams with web openings, including traditional castellated beams,cellular beams with circular openings, and beams with multiple openings of varying size and shape have traditionally been fire protected using the guidance given in Fire protection for structural steel in buildings, the "Yellow Book". This gives an empirical rule for calculating the passive fire protection thickness to be applied to castellated and cellular beams, in which the thickness required for the solid parent beam is increased by 20% in recognition of the fact that these beams have been found to heat up at a slightly faster rate than solid beams. Although the Yellow Book states that the rule applies only to passive materials, it has been widely applied to perforated or cellular beams protected using intumescent coatings.

In recent years, fire resistance tests have been carried out on beams with web openings protected using an intumescent coating. These tests showed that the 20% rule could not be safely applied. This is also the view of the ASFP and its members.

The SCI feels that in light of this recent information, new guidance on the protection requirements for the use of intumescent coatings for cellular beams and beams with large discrete openings is required.

SCI published AD269 in November 2003. The guidance is interim and will be updated when more information is available. More detailed guidance is available in RT983, Interim guidance on the use of intumescent coatings for the fire protection of beams with web openings. This report also contains AD269 as an appendix.

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