FIRE PROOFING

F-I-R-E P-R-O-O-F-I-N-G





Example of spray fireproofing, using a gypsum based plaster in a low-rise industrial building in Vancouver, British Columbia. The plaster provides a layer of insulation to retard heat flow into structural steel to prevent collapse.

Delaminated spray fireproofing at Cambrian College, Greater Sudbury, Ontario, Canada, August 2000.

Pre-mixed fireproofing Plaster stored on construction site, ready to spray onto structural steel.

Applications of FIRE PROOFING

• Structural steel to keep below critical temperature ca. 540 °C
• Electrical circuits to keep critical electrical circuits below 140 °C so they stay operational
• Liquefied petroleum gas containers to prevent a BLEVE (boiling liquid expanding vapour explosion)
• Vessel skirts and pipe bridges in an oil refinery or chemical plant to keep below critical temperature ca. 540°
• Concrete linings of traffic tunnels

HISTORY

Asbestos is one material historically used for fireproofing, either on its own, or together with binders such as cement, either in sprayed form or in pressed sheets, or as additives to a variety of materials and products, including fabrics for protective clothing and building materials. Because the material has proven to be causing cancer in the long run, a large removal and replacement business has been established.

Endothermic materials have also been used to a large extent and are still in use today, such as gypsum, concrete and other cementitious products. More highly evolved versions of these are even used in aerodynamics, intercontinental ballistic missiles (ICBMs) and re-entry vehicles, such as the space shuttles.

The use of these older materials has been standardised in "old" systems, such as those listed in BS4

76, DIN4102 and the National Building Code of Canada.

Alternative fireproofing methods

Among the conventional materials, purpose-designed spray fireproofing plasters have become abundantly available the world over. The inorganic methods include:

• Gypsum plasters
• Cementitious plasters
• Fibrous plasters

Manufacturers for these inorganic are in a constant, competitive struggle for commercial success against one another. The competition focuses simply on managing to obtain fire-resistance ratings at the lowest possible cost. Simply, the idea is to become faster and cheaper than the competition.

The industry considers gypsum-based plasters to be "cementitious", even though these contain no

portland cement, let alone calcium alumina cement. Cementitious plasters that actually contain portland cement have been traditionally lightened by the use of inorganic lightweight aggregates, such as vermiculite and perlite.

Gypsum plasters have been lightened by using chemical additives to create bubbles that displace solids, thus reducing the bulk density. Also, lightweight polystyrene beads have been mixed into the plasters at the factory, again, in an effort to reduce the density, which generally makes for a more effective insulation as well as a lower cost. The resulting plaster has still qualified to the A2 combustibility rating as per DIN4102. Fibrous plasters, containing either mineral wool or ceramic fibres tend to simply entrain more air, thus displacing the heavy fibres. On-site cost reduction efforts, at times purposely contr

avening bounding can, at times further enhance such displacement of solids, which has led many architects to insist on the use of on-site testing of proper densities to ensure that they are getting what they're paying for, as excessively light inorganic fireproofing does not provide adequate protection.

Pipes covered with a thin-film intumescent spray fireproofing product called Unitherm. As the flame from the blow-torch hits it, the intumescent expands, forming a layer of insulation, which slows down heat transfer to the pipe below. Hydrates within the coating give up their water content, maintaining a temperature near the boiling point of 100 °C.

In this picture, the flame has been removed after the thin-film intumescent spray fireproofing product has been completely expanded. Some intumescents can undergo shrinkage shortly after full expansion has taken place.

New materials based on organic chemistry are gaining in popularity for a variety of reasons. In land-based construction, thin-film intumescents have become more widely used. Unlike their inorganic competitors, thin-film intumescents go on like paint and do not require the concealment of structural steel elements such as I-beams and columns. Care must be taken to ensure that such products are protected from atmospheric moisture and operational heat, which can adversely affect these organic, covalently bound products. The use of DIBt approved products, which mandates testing of the effects of ageing, is prudent.

Thicker intumescent and endothermic resin systems tend to use an oil basis (usually epoxy), which, when exposed to fire, creates so much smoke, that even though these products work well, they tend to be banned from use inside of buildings and are thus used mainly in exterior construction, such as LPG vessels, vessel skirts and pipe bridges in oil refineries, chemical plants and offshore oil and gas platforms.

Proprietary boards and sheets, made of gypsum, calcium silicate, vermiculite, perlite, mechanically bonded composite boards made of punched sheet-metal and cellulose reinforced concrete (DuraSteel) have all been used to clad items for increased fire-resistance. Cladding is traditionally much more popular and organised in Europe than in North America. Fringe methods have also included intumescent tapes and sheets, as well as endothermically treated ceramic fibre sheets and roll materials. The latter work well but are not particularly popular due to cost reasons. Ordinary ceramic fibre, typically encased in thin aluminium foil is often used to protect pressurisation ductwork and grease ducts in North America. Such mineral wool (rock wool) wraps have been used in Europe for decades more than in North America. Europeans tend to use much less expensive mineral wool wraps for duct fireproofing. All are qualified to the same test regime: ISO6944, with the exception that systems qualified for the North America market also undergo a hose-stream test immediately following the fire exposure in order to validate the firestop portion of the system.

Common errors in inorganic spray fireproofing

• Portland cement bound sprays display a high pH level at first. This has, at times been presumed to last indefinitely, particularly for exterior spray fireproofing of large liquified petroleum gas containers, vessel skirts and pipe bridges. One must use proper primer. The high pH of cement-borne plasters does not safeguard unprotected common steel substrata. Ignorance of this fact, particularly in coastal regions with high salt exposures has led to obscene rusting and delaminations of spray fireproofing on large LPG spheres and more. Proper epoxies must be used for water-resistance to prevent "soaping" when in contact with the plaster.

• Fibrous spray fireproofing on LPG spheres have, at times ignored the necessary dew point calculations, resulting in having ceramic fibre based sprays become totally saturated with water, which has led to other problems.

• Spray fireproofers unfamiliar with and perhaps apathetic about the basic chemistry that governs the forming of cement stone, have been known to go on break, while bags of spray fireproofing mixtures were turning, with water, in mixing drums, ready to be sprayed when workers returned from lunch breaks. Of course, excessive mixing leaves the cement perfectly spent, no longer able to form any more cement stone once placed, resulting in a "spider-web" appearance of the finished plaster, as its setting ability has been largely diminished, the plaster reduced to "sand-castle" quality.

• Spray fireproofers have been known in industrial settings to spray onto vibrating substrata, which can dislodge and weaken plasters.

• Spray fireproofers unfamiliar with basic cement chemistry have been known to have their plasters weakened by common cement poisons, such as high wind and heat exposures to fresh plasters, which should have been suitably covered to reduce premature escape of water, that is needed to form cement stone inside of the plaster. This has resulted in lesser quality fireproofing plasters.

Traffic tunnel fireproofing

Traffic tunnels may be traversed by vehicles carrying flammable goods, such as petrol, liquified petroleum gas and other hydrocarbons, which are known to cause a very rapid heat rise and high heat (see the hydrocarbon curves in fire-resistance rating). It is a known fact in tunnel construction and operations, that where hydrocarbon transports are permitted, accidental fires may occur, causing spilled loads amidst sparks. It is, therefore, prudent to fireproof concrete linings of traffic tunnels. Traffic tunnels are not ordinarily equipped with fire suppression means. It is very difficult to overcome hydrocarbon fires by active fire protection means or to so equip an entire tunnel along its whole length for the eventuality of a hydrocarbon fire or a BLEVE, which then destroys everything in its path, until the fuel is spent.

• What happens to concrete in hydrocarbon fires?

Concrete, by itself, cannot withstand hydrocarbon fires. In the Channel tunnel that connects England and France, an intense fire broke out and reduced the concrete lining in the undersea tunnel down to about 50 mm. In ordinary building fires, concrete typically achieves excellent fire-resistance ratings, unless it is too wet, which can cause it to crack and explode. For unprotected concrete, the sudden endothermic reaction of the hydrates and unbound humidity inside the concrete causes such pressure as to spall off the concrete, which then winds up in small pieces on the floor of the tunnel. This is the reason why laboratories, which conduct fire-resistance testing, such as ULC, iBMB TU Braunschweig, which headed the "Eureka" project, or Underwriters Laboratories insert humidity probes into all concrete slabs that undergo fire testing even in accordance with the less severe building elements curve (DIN4102, or BS476, or ULC-S101). Only once the humidity is low enough, will a fire test be conducted because otherwise explosions would result. The culprit is the hydrates and unbound humidity in the concrete and this is not new. Another prime example of this is the fact that walls constructed of lost plastic forms, which are filled on site with concrete cannot withstand the testing required of a loadbearing Firewall (construction). During the fire test, these walls are subjected to a load, which then leads to such a forceful explosion as to shear the wall with thunderous noise. A hydrocarbon fire is much more rapid and severe than a typical building fire. Consequently, concrete is much more vulnerable and must be protected in order to remain operable during a hydrocarbon fire. The need for fireproofing was demonstrated, among other fire protection measures, in the European "Eureka" Fire Tunnel Research Project, which resulted in building codes for the trade to avoid the effects of such fires upon traffic tunnels. Cementitious spray fireproofing, each of which must be able to prove bounding in accordance with the hydrocarbon fire test curve, such as the one that is also used in UL1709.

• Fireproofing concrete tunnel linings

In essence, this is really not much different from protecting structural steel or electrical circuits or valves. The most important item is to maintain strict bounding. Next, one must slow down the heat transfer into the item to be protected. This is accomplished by the use of firm fireproofing products, such as higher density fireproofing plasters or fireproofing boards, such as those made of calcium silicate or vermiculite. Examples of purpose-made tunnel fireproofing can be seen here. Other things to be kept in mind are as follows:

• If one is fireproofing existing traffic tunnels, one must ensure proper cleaning of the concrete to remove any substances that may impair proper bonding.
• Lighting concerns must be kept in mind. Traffic darkens new fireproofing products. One must, therefore, investigate proper, light-coloured coatings, which reflect light, are easy to clean, are compatible with the substrate and that the combination of the two are also to absorb the kinetic energy of spray cleaning.
• In mountain tunnels, one must ensure that a space is created between the fireproofing and the stone, for water traveling downwards through the mountain to be drained off, to avoid the formation of dangerous icicles and damage to the fireproofing system.

FIRE PROOFING

PERFECT EXAMPLE FOR A POST AND LINTEL

-- G L O S S A R Y --

BEARING:
In a bolted connection, limit state of shear forces transmitted by the bolt to the connection elements.

BEARING TYPE CONNECTION:
Bolted connections where shear forces are transmitted by the bolt bearing against the connection element.

BRACED FRAMES:
An essential vertical truss system that provides resistance to lateral forces and provides stability to the structural system

BUCKLING:
Limit state of sudden change in the geometry of the structure or any of its elements under a critical loading condition.

BUCKLING STRENGTH:
Nominal strength for buckling or instability limit states

CAMBER:
Curvature fabricated into a beam or truss so as to compensate to deflection included by loads.

CLADDING:
Exterior cover of structure

COLD FORMED STEEL STRUCTURAL MEMBER:
Shape manufactured by press-braking blanks sheared from sheets, cut lengths of coils or plates, or by roll forming cold- or hot-rolled coils or sheets; both forming operations being performed at ambient room temperature, that is, without manifest addition of heat such as would be required for hot forming.

COMPLETE JOINT PENETRATION GROOVE WELD (CJP):
Groove weld in which weld metal extends through the joint thickness, except as permitted for HSS connections

COPE:
Cutout made in a structural member to remove a flange and conform to the shape of the intersecting member.

DOUBLER:
Plate added to, and parallel with, a beam or column web to increase resistance to concentrated forces.

DRIFT:
Lateral Deflection of Structures

END RETURN:
Length of the fillet weld that continues around a corner in the same plane

FASTENER:
Generic term for bolts, rivets or other connecting devices

FATIQUE:
Limit state of crack initiation and growth resulting from repeated application of live loads.

FAYING SURFACE:
Contact surface of connection elements transmitting a shear force.

FILLER METAL:
Metal or allow to be added in making a welded joint.

FILLER:
Plate used to build up the thickness of one component.

FLEXURAL BUCKLING:
Buckling mode in which a compression member deflects laterally without twist or change in cross-section shape.

FLEXURAL – TORTIONAL BUCKLING:
Buckling mode in which a compression member bends and twists simultaneously without change in cross sectional shape.

FORCE:
Resultant of distribution of stress over a prescribed area

FULLY RESTRAINED MOMENT CONNECTION:
Connection capable of transferring moment with negligible rotation between connection members

GIRDER FILLER:
Narrow piece of sheet steel used as a fill between the edge of a deck sheet and the flange of a girder in a composite floor system constructed using a formed steel deck.

GIRT:
Horizontal structural member that supports wall panels and is primarily subjected to bending under horizontal loads, such as wind load

GOUGE:
Relatively smooth surface groove or cavity resulting from plastic deformation or removal of material.

GRIP:
Thickness of material through which a bolt passes

LACING:
Plate, Angle or other steel shape in a lattice configuration, that connects two steel shapes together

LOCAL BENDING:
Limit state of large deformation of a flange under a concentrated tensile force.

LOCAL BUCKLING:
Limit state of buckling of a compression element within a cross section.

LOCAL CRIPPLING:
Limit state of local failure of web plate in the immediate vicinity of a concentrated load or reaction.

LOCAL YIELDING:
Yielding that occurs in a local area of an element.

MILL SCALE:
Oxide surface coating on steel formed by the hot rolling process

MILLED SURFACE:
Surface that has been machined flat by a mechanically guided tool to a flat, smooth condition.

MOMENT CONNECTION:
Connection that transmits bending moment between connected members.

MOMENT FRAME:
Framing system that provides resistance to lateral loads and provides stability to the structural system, primarily by shear and flexure of the framing members and their connection

NOMINAL DIMENSIONS:
Designated or Theoretical dimension, as in the tables of section properties

NONDESTRUCTIVE TESTING:
Inspection procedure wherein no material is destroyed and integrity of the material or component is not affected

OUT OF PLANE BUCKLING:
Limit state of a beam-column bent about its major axis while lateral buckling or lateral Torsional buckling is not prevented by lateral bracing.

PARTIALLY RESTRAINED MOMENT CONNECTION:
Connection Capable Of Transferring Moment With Rotation Between Connected Members That Is Not Negligible.

PERMANENT LOAD:
Loads in which variations over time are rare or of small magnitude are permanent load. All other loads are variable loads.

POST-BUCKLING STRENGTH:
Load or force that can be carried by an element, member or frame after intial buckling has occurred.

PRE-TENSIONED JOINT:
Joint with high-strength bolts tightened to a specified minimum pretension.

REENTRANT:
In a cope or weld access hole, a cut at an abrupt change in direction in which the exposed surface is concave.

ROOT OF JOINT:
Portion of a joint t be welded where the members are closest to each other.

SAFETY FACTOR:
Factors that accounts for deviations of the actual strength from the nominal strength, deviations of the actual load from the nominal load, uncertainties in the analysis that transforms the load into a load effect, and for the manner and consequences of failure.

SHEAR BUCKLING:
Buckling mode in which a plate element, such as the web of a beam, deforms under pure shear applied in the plane of the plate.

SHIM:
Thin layer of material used to fill a space between faying or bearing surfaces.

SIMPLE CONNECTION:
Connection that transmits negligible bending moment between connected members.

SLIP:
In a bolted connection, limit state of relative motion of connected parts prior to the attainment of the available strength of the connection.

SLIP CRITICAL CONNECTION:
Bolted connection designed to resist movement by friction on the faying surface of the connection under the clamping forces of the bolts.

SNUG TIGHTENED JOINT:
Joint with the connected plies in firm contact

SPLICE:
Connection between two structural elements joined at their ends to form a single longer element.

STABILITY:
Condition reached in the loading of a structural component, frame or structure in which a slight disturbance in the loads or geometry does not produce large displacement.

STIFFENER:
Structural element, usually an angle or plate, attached to a member to distribute load, transfer shear or prevent buckling.

STRESS:
Force per unit area caused by axial force, moment, shear or torsion.

THERMALLY CUT:
Cut With Gas, Plasma or LASER

TRANSVERSE STIFFENER:
Web stiffener oriented perpendicular to the flanges, attached to the web.

TURN OF NUT MEATHOD:
Procedure whereby the specified pretension in high strength bolts is controlled by rotating the fastener component a predetermined amount after the bolt has been snug tightened.

UNFRAMED END:
The end of a member not restrained against rotation by stiffener or connection elements.

WEATHERING STEEL:
High strength, low-alloy steel that, with suitable precautions, can be used in normal atmospheric exposures (not marine) without protective paint coating

WEB BUCKLING:
Limit state of lateral instability of a web.

WEB COMPRESSION BUCKLING:
Limit state of out-of-plane compression buckling of the web due to a concentrated compression force.

WEB SIDEWAY BUCKLING:
Limit state of lateral buckling of the tension flange opposite to the location of a concentrated compression force.

WELD METAL:
Portion of a fusion weld that has been completely melted during welding, Weld metal has elements of filler and base metal melted in the weld thermal cycle.

YIELDING:
Limit state of inelastic deformation that occurs after the yield stress is reached.

BIAXIAL BENDING:
Simultaneous bending of a member about two perpendicular axes

BRITTLE FRACTURE:
Abrupt cleavage with little or no prior ductile deformation

CYCLIC LOAD:
Repeatedly applied external load that may subject the structure to fatigue

FATIGUE THRESHOLD:
Stress range at which fatigue cracking will not initiate regardless of the number of cycles of loading.

FLEXIBLE CONNECTION:
Connection permitting a portion, but not all, of the simple beam rotation of a member end

UNDERCUT:
Notch resulting from the melting and removal of base metal at the edge of a weld

COATED FAYING SURFACE:
A faying surface that has been primed and painted or protected against corrosion, except by hot-dip galvanizing

ENGNEER OF RECORD:
The party responsible for the design of the structure and for the approvals that are required in this specification

FAYING SURFACE:
The plane of contact between two plies of a joint

SNUG TIGHTENED JOINT:
A joint in which the bolts have been installed in accordance with section 8.1.. The snug tightened condition is the tightness that is attained with a few impacts of an impact wrench or the full effort of an iron worker using an ordinary spud wrench to bring the plies into firm contact.

BENDING MOMENT:
The internal load generated within a bending element whenever a pure moment is reacted, or a shear load is transferred by beam action from the point of application to distant points of reaction (or) The algebraic sum of all the moments of forces acting on one side of a section through a beam

AXIAL FORCE:
A system of internal forces whose resultant is a force acting along the longitudinal axis of a structural member or assembly.

LOADS

DEAD LOADS:
Dead loads are weights of material, equipment or components that are relatively constant throughout the structure's life. Permanent loads are a wider category which includes dead loads but also includes forces set up by irreversible changes in a structure's constraints - for example, loads due to settlement, the secondary effects of prestress due to shrinkage and creep in concrete.

LIVE LOADS:
Live loads are temporary, of short duration, or moving. Examples include snow, wind, earthquake, traffic, movements, water pressures in tanks, and occupancy loads. For certain specialized structures, vibro-acoustic loads may be considered.

STATIC LOAD:
These are loads that build up gradually over time, or with negligible dynamic effects. Since structural analysis for static loads is much simpler than for dynamic loads, design codes usually specify statically-equivalent loads for dynamic loads caused by wind, traffic or earthquake.

DYNAMIC LOAD:
These are loads that display significant dynamic effects. Examples include impact loads, waves, wind gusts and strong earthquakes. Because of the complexity of analysis, dynamic loads are normally treated using statically equivalent loads for routine design of common structures.

GLOSSARY

STRUCTURAL SYSTEM:
An assemblage of load carrying components that are joined together to provide interaction or interdependence

BEAM:
Structural member that has a primary function of resisting bending moments

BEAM-COLUMN:
Structural member that resists both axial force and bending moments

COLUMN:
Structural member that has a primary function of resisting AXIAL FORCE.

DIAGONAL BRACING:
Inclined structural member carrying primarily axial force in a braced frame

PLATE GIRDER:
Built up beam

PURLIN:
Horizontal structural member that supports roof deck and is primarily subjected to bending under vertical loads such as snow, wind or dead loads

VERTICAL BRACING FRAME:
System of shear walls, braced frames or both, extending through one or more floor of a building

PLATE

BATTEN PLATE:

Plate rigidly connected to two parallel components of a built-up column or beam designed to transmit shear between the components.

TIE PLATE:
Plate element used to join two parallel components of a built up columns, girder or strut rigidly connected to the parallel components and designed to transmit shear between them.