Spray Applied Fire Resistant Materials (SFRM) – The Efficient Way of Protecting Steel Against Fire

Promat 12/09/2018

structural steel protection
SFRM
the opus dubai spray steel structure protection
the opus dubai spray steel structure protection

A non-reactive coating is one of the easiest and most efficient ways to protect load bearing steel elements against fire in a building. It is a technical fire protective product, which delays the collapse of the steel structure through insulating the structural elements (columns, beams, floors and roofs) that support the building, achieving specified fire resistance in terms of time. Therefore it fulfils with the highest priority of passive fire protection, which is to increase fire safety, to prevent building collapse allowing time for safe evacuation of people from the building and make the building safer for the emergency services (fire brigade) and rescue teams.

Spray applied fire resistant spray materials (SFRM) represent a proven and well known used way to provide passive fire protection to the load-bearing structures, especially structural steel that is more and more used in modern architectural design in industrial and commercial buildings. It presents several advantages: it does not modify the intrinsic properties of the materials, like for example the mechanical properties; it is easily processed, and different version of sprays can be used on a variety of materials such as steel, composite elements and concrete.

The family of Spray Applied Fire Resistant Spray Materials knows 2 different families:

  • Gypsum based spray material
  • Cement based spray material

Depending on the intended field of application the different material can be applied. The biggest influencer is the climate conditions.

Gypsum based product are used internally, cement based products are use semi-exposed or externally.

How non-reactive coatings work?

Spray applied fire resistant material is a non-reactive coating. The applied material acts as an insulation layer when exposed to extreme temperatures during a fire. In this case it keeps the steel “cold” and the steel keeps his original strength so it can withstand the loads as designed even during fire.

The scope of the SFRM product is the prevention of the structural collapse of the building, which can occur if load bearing steel elements reach a critical state. For steel, this is linked to the critical temperature, defined as the temperature for which, the load bearing capacity becomes equal to the effect of the applied loads (so the steel element is very close to the collapse). Critical temperature of steel can vary from 350°C to 750°C, depending mainly for the loading scheme, but in most of the cases is between 550°C (columns) and 620°C (beams). For concrete the critical state is linked to the critical temperature of the reinforcing bars (normally from 350°C to 500°C) and the reach of a temperature of 500°C inside the concrete element.

How to correctly apply sprayed non-reactive coatings on steel materials?

Preparation tips: 

Spray applied fire resistant spray materials (SFRM) are always part of a full system. For steelworks, the system can include an anticorrosive primer.

  • The scope of the primer is assuring adhesion to substrate in cold state, anticorrosion protection and stickability of the applied fire resistant spray.
  • Steelwork must be prepared to International Standards before being coated with a compatible primer or, if already painted with a compatible primer, must be cleaned (free from grease, oil, rust, dirt or any other contaminant that may inhibit the bonding).

The compatible primers tested with the main Promat products are:

Gypsum based Spray materials:

  • Short/medium long oil alkyd primers
  • Two component epoxy primers
  • Epoxy rich zinc
  • Zinc silicate

Cement based Spray Materials need to be checked in the application manual.

For any other primers, please contact your Promat Technical Local office.

Bare steel (unpainted/unprimed) structural members free of loose rust, loose mill scale or dirt can receive direct application of PROMASPRAY®-P300, according to the existing tests reports. These conditions are typically corrected by wire brushing or sandblasting.

For concrete, the preparation depends on the physical state of the support. For more information contact our technical support.

photo of structural steel protection using PROMASPRAY P300

Spray Solution

photo of structural steel protection using PROMASPRAY P300
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What is thickness?

The thickness and quantity of material required for a certain fire resistance time (R30, 60, 90, 120 minutes or more),is dependent upon various factors.

Regarding structural steel, the mains are:

Dry film thickness is determined by:

  • Mass factor (called also massivity, section factor or W/D, HP/A or A/V). The mass factor is a ration between the area of the steel exposed to the fire and the volume of the steel section. The higher the mass factor (For HP/A and A/V, for W/D it is the opposite), the faster the steel section heats up, and so the greater the thickness of fire protection material required.
  • Exposure: that is number of faces exposed to fire, is it a column or beam, composite elements, hollow section, etc.
  • Critical temperature: limiting temperature a s a function of the degree of utilization. The lower the critical temperature, the faster the steel section will reach it, and so the greater the thickness of fire protection material required.
  • Duration or fire rating: the level of protection required (R60, R120, etc.).
  • Test Standards and Approvals: different standard and assessment can give different thickness for the same protection.

When to measure thickness?

During the application it’s necessary to measure thickness frequently, with a thickness gauge.

To determine dry film thickness (DFT) for non-reactive coatings is the same as the wet film thickness (WTF), 

contact Promat technical support

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