A 30 storey storey office building building with 2 staircases constructed constructed from ground ground floor floor up to roof level. Both staircases are connected to fire fighting lift lobbies, which in turn are connected to accommodation areas. There is only one single leaf door per floor for staircase. As for fire fighting lift lobby, there is only one single leaf door separating each lift lobby and the accommodation areas. There is one door connecting the lift lobby to a service shaft. However, this is not to be taken into account as it is opened into an enclosed area. Therefore, there are 30 doors in total for both staircase and fire fighting lift lobbies. Refer to Figure 14.1
(i) The staircase and lift lobbies will be independently pressurised. (ii) All pressurisation shafts shafts are not provided provided with sheet metal ductwork. ductwork. (iii) According to UBBL, the no. of opened doors shall be minimum 2 nos. or no. of doors at 10% of the total floors (worst condition), whichever is higher. Hence, for this case study, there will be 3 floors where all staircase and lift lobby doors are assumed to be opened. (iv) The design of pressurisation pressurisation system shall be based on constant speed fan with pressure pressure relief system.
(i) Design criteria based on MS1472 (ii) Leakage Area Calculation: Calculation: Based on 50 Pa pressure differential and interpolation of data from Table 3 and 4 (MS1472). Size Type Of Door
Leakage
Height
Width
(mm)
(mm)
Per Door (CMH)
Case A
Single leaf opening into a pressurised space
2
0.8
210
Case B
Single leaf opening outwards from a
2
0.8
420
2
1.6
630
pressurised space Case C
Double leaf opening into pressurised space
No. of single leaf doors opening into pressurised area
=
No. of single leaf doors opening outwards from an pressurised area
=
No. of double leaf opening into pressurised space
= 28
No. of opened single leaf doors (10% of Doors, minimum 2)
=
(i)
(Case A) Air leakage for 27 no. of door = 210 CMH x 27
(ii)
5670 CMH
=
420 CMH
=
0 CMH
=
6090 CMH
(Case B) Air leakage for 1 no. of door = 420 CMH x 1
(iii)
=
(Case C) Air leakage for 0 no. of door = 630 CMH x 0
14.8.2.3 Calculation of Total Air Leakage Total Air leakage = 5670 + 420 + 0
(A)
14.8.2.4 Estimation of Air Flow Past 3 Opened Doors (i)
The size of each door is
m (H)
m (W)
(ii)
Therefore, area of door is
(iii)
Based on design criteria of 1 m/s air flow through door when the door is opened, air flowrate
1.6 m²
1.6m² x 1.0 m/s x 60 sec x 60 mm =
5,760 CMH
(iv) For 3 opened doors, the air quantity = 5760 CMH x3 =
17,280 CMH
14.8.2.5 Selection of Capacity for Pressurisation Fan (i)
The minimum air required = (A) + (B) = 6090 + 17280 CMH = 23,370 CMH
(ii)
Add
leakage factor (masonry shaft) = 29,213 CMH
Note: If masonry shaft is of reinforced concrete, 10% leakage factor is adequate (iii)
The airflow of fan selected: = 30,000 CMH
(B)
A 30 storey office building with 2 staircases constructed from ground floor up to roof level. Both staircases are connected to fire fighting lift lobbies, which in turn are connected to accommodation areas. There is only one single leaf door per floor for staircase. As for fire fighting lift lobby, there is only one single leaf door separating each lift lobby and the accommodation areas. There is one door connecting the lift lobby to a service shaft. However, this is not to be taken into account as it is opened into an enclosed area. Therefore, there are 30 doors in total for both staircase and fire fighting lift lobbies. Refer to Figure 14.1
(i) The staircase and lift lobbies will be independently pressurised. (ii) All pressurisation shafts are not provided with sheet metal ductwork. (iii) According to UBBL, the no. of opened doors shall be minimum 2 nos. or no. of doors at 10% of the total floors (worst condition), whichever is higher. Hence, for this case study, there will be 3 floors where all staircase and lift lobby doors are assumed to be opened. (iv) The design of pressurisation system shall be based on constant speed fan with pressure relief system.
(i) Design criteria based on MS1472 (ii) Leakage Area Calculation: Based on 50 Pa pressure differential and interpolation of data from Table 3 and 4 (MS1472). Size Type Of Door
Leakage
Height
Width
(mm)
(mm)
Per Door (CMH)
Case A
Single leaf opening into a pressurised space
2
0.8
210
Case B
Single leaf opening outwards from a
2
0.8
420 630
pressurised space Case C
Double leaf opening into pressurised space
2
1.6
Case D
Double leaf opening outwards pressurised spac
2
2
Ref: MS1472
No. of single leaf doors opening into pressurised area
=
No. of single leaf doors opening outwards from an pressurised area
=
No. of double leaf opening into pressurised space
=
No. of lift landing doors
=
(i)
(Case A) Air leakage for 30 no. of door = 210 CMH x 30
(ii)
6,300 CMH
=
0 CMH
=
0 CMH
(Case B) Air leakage for 0 no. of door = 420 CMH x 0
(iii)
=
(Case C) Air leakage for 0 no. of door = 630 CMH x 0
Refer to Equation (14) of sub-section 5.3.2.3 of M51472 Equation: Qd = Qc x F / n where, Qd
is the air leakage from one lobby past one lift door,
Qc
is the air leakage for an isolated lift door (value taken from Table 4 or derived from Qc = 0,0496 x (PE)1/2 where PE is the pressurisation level for the lobby,
F
is the factor depending on vent size in lift shaft and taken from the appropriate column of Table 6 (MS 1472),
N
N is the number of pressurised lobby openings into the lift shaft Hence, when applied to;
(iv) (Case D) (assume lift shaft vent size = 0.16m2) F= Qd (for 1 lobby)
2.66 m3/s
= Qc x F / n = 0.0496 x (50)½ x 2.66 m³/s x 3600 / 30 = 112
No. of Lift
=
CMH 1
Total Leakage 112 CMH x 30 Landings x 1 Lift
Total Air leakage = 6300 + 0 + 0 + 3360
=
3,360 CMH
=
9,660 CMH
(C)
(i)
The total no. of doors is 30. Therefore, the design calculation shall consider 3 nos. of opened single leaf doors. No. of opened single leaf doors
=
(ii)
The size of each door is
m (H)
m (W)
(iii)
Therefore, area of door is
(iv)
Based on design criteria of 1 m/s air flow through door when the door is opened, air flowrate
1.6 m²
1.6m² x 1.0 m/s x 60 sec x 60 mm = (v)
5,760 CMH
For 3 opened doors, the air quantity = 5760 CMH x3 =
17,280 CMH
14.8.2.5 Selection of Capacity for Pressurisation Fan (i)
The minimum air required = (C) + (D) = 9660 + 17280 CMH
(ii)
Add
leakage factor (masonry shaft)
=
26,940 CMH
=
33,675 CMH
Note: If masonry shaft is of reinforced concrete, 10% leakage factor is adequate (iii)
The airflow of fan selected:
=
34,000 CMH
(D)
