Lifts Flashcards
What is defined as a ‘lift’ under the lift regulations 1997?
An appliance serving specific levels, a car moving
- Along guides which are rigid
- along a fixed course even when it does not move along guides which are rigid (scissor lift)
List the Regualtions or Codes for Lifts in the UK?
Lift Regulations 1997
Supply of machinery (Safety) Regulations 2008
Building Regulations Part M
Disability Discrimination Act 2004
BS5655 Selection, installation and location of new lifts
BS ISO 4190 2010 Lift installations
BS8300 2009 Design of buildings for disabled persons
BS EN 81-70 2003
BS EN ISO 25745 Energy performance of lifts
What is the up peak when sizing lifts?
The Up Peak is the peak time for occupiers of the building to use the lifts. This is considered as a 5 minute period during the morning rush.
Essentially the number of people arriving to use the lift in a 5 minute period.
What is the formula for the required capacity on the lift installation during the up peak?
RC=P5 * Pocc
Where:
RC=Required Capacity
P5= number of persons using the lift in a 5 minute period
Pocc= number of occupants above the ground floor level
What is the Round Trip Time (RTT)
The RTT is the total time it takes for the lift to complete one cycle, that is leave the ground floor and carry passengers to the desired level and then come back down again to the ground floor.
Define the RTT in 5 minutes?
300/RTT
Define Transport Capacity?
Transport capacity is the number of identical lifts serving the ground floor loft lobby (L) and the number of people we expect on average to enter the empty lift at ground floor (P)
TC= L.P/RTT in a 5 minute time period the equation is 300L.P/RTT
P is taken as around 80% of the rated lift capacity. Don’t round P to nearest decimal place when used in the following equation:
RTT<300L.P/P5.Pocc
RTT is the sum of?
1) actually in motion between ground floor visited during an average cycle- the highest floor doesn’t mean the highest floor of the building. The lift will be accelerating and decelerating for most of it’s time between floor
2) stationary at the ground floor and at each upper floor it visits during an average cycle. Including doors opening, doors closing and passengers leaving and entering.
How is RTT expressed mathematically?
RTT=2Hdf/V+(S+1){tc+to+tf-df/V} + 2Ptp
Where:
H= number of floors traversed on the upward journey
df= distance between floors (m)
V= rated lift speed
S = the probable number of floors visited other than ground level
tc= is time taken for doors to close at each floor
to= is time taken for doors to open at each floor
tf= flight time- the time taken to taken to travel between two adjacent floors
P= average number of passengers entering lift at ground floor
tp= average time it takes for passenger to leave the lift
How do you calculate H- the highest floor visited during an average cycle?
Using probability theory:
N-1
H = N - Σ (i/N)p
i=1
How do we calculate S- the probable number of floors visited by the lift
Using probability theory:
S= N={1-(1-1/N)^p)
What is the V in the equation for RTT and how can it be determined?
V is the rated speed of the lift in m/s hence the V for velocity. You can use standard lift speeds given BS5655 Part 6 2011. Most lifts require the lift to get from the ground floor to the highest floor within 20-30s
What is tf in the RTT equation and how can it be determined?
Tf is the flight time, that is the the time taken for the lift to travel between floor to floor (df). Typical values for flight time can be found in CIBSE Guide D
What is tc and to in the RTT equation and how can they be determined?
tc and to are the time taken for doors to close and open depending on door width and type of door (side opening or centre opening). Values can be found in CIBSE guide D.
What is P in the RTT equation and how can it be determined?
P is the number of passengers expected to enter the lift at the ground floor when the lobby is reasonably crowded. P is usually 80% of the rated lift capacity from the manufacturer.
