Transcript Introduction To Fire Proetction

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