calculation of pfp thickness friday, 28 august 2015
TRANSCRIPT
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Calculation of PFP ThicknessWednesday, April 19, 2023
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The thickness of fire protection required is determined by:
1. Duration
2. Critical Steel Temperature
3. Steel section size and type
Hp/A ratio
4. Thickness stated in the local or international approval
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SI Units:
Hp/A =
M/D =
A/V =
Imperial (US) Units:
W/D =
A/P =
Heated Perimeter
Cross Section Area=
metres
metres²= m-1 or /m
Heated Perimeter
Weight of section= inches
Pounds/foot= lb/ft/in
Heated Perimeter =Square inches =Cross Section Area
in2/ininches
All express the relationship between the amount of steel capable of absorbing heat to the area of steel surface exposed to the fire.
Heated Surface Area=
metres²
metres³= m-1 or /m
Volume of Steel
Mass of Section
Heated Perimeter=
Kilograms / metre
metres= kg/m²
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How much PFP do I need?
Hp/A - Section Factors
Cross Sectional
Area (A = m²)
Heated Perimeter (Hp = m)
Low Hp/A = Thinner PFP305 x 305 x 240 kg/m
Hp/A = 1.905m / 0.0305m²Hp/A = 62 m-1
For H120 (400°C): Chartek 7 = 11 mm
High Hp/A = Thicker PFP305 x 305 x 97 kg/m
Hp/A = 1.789m / 0.0123m²Hp/A = 145 m-1
For H120 (400°C): Chartek 7 = 16 mm
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How much PFP do I need?
How Hp/A changes with sides exposed to fire.(Example 305 x 305 x240 Kg/m UC)
Note: Cross Sectional Area Remains the same in all cases!
Wall, Floor or Deck Wall, Floor or Deck
4 Sides exposed
Hp/A=
Hp/A = 62 m-1
0.0305 m²
1.905 m
3 Sides exposed
Hp/A=
Hp/A = 52 m-1
0.0305 m²
1.587 m
Flange only exposed
Hp/A=
Hp/A = 13 m-1
0.0305 m²
0.393 m
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How to calculate an Hp/A?
www.asfp.org.uk
TheYellowBook!
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How to calculate an Hp/A?
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What do I do with my Hp/A?
Example of Certificate of Fire Approval with table of Hp/A v required PFP thickness
Chartek 7 Certificate Interchar 963 loadings
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What do I do with my Hp/A?
Interchar 963 loadings
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What about other section shapes?
Wall, Floor or Deck Wall, Floor or Deck
Decreasing Hp/A = Lower PFP thickness required