Patent ID: 8463635

Claim:
A method for determining a risk of failure in a people moving device and for determining an inspection interval to mitigate said risk; the method comprising: determining by a computer system an acceptable risk score based on computer readable instructions provided on a non-transitory computer readable medium; determining by said computer system an inspection interval based on said risk score; determining by said computer system an increase in risk score proportional to a time elapsed since a missed inspection in said inspection interval; determining by said computer system a tolerance within said inspection interval based on said increased risk score; and, specifying by said computer system an inspection interval and an inspection tolerance based on said determined schedule and said determined tolerance; wherein said step of determining an inspection interval comprises calculating the inspection interval t m or t L based on equations (3) and (4) for medium and low risk devices, respectively: t M = 12 - 1 0.7 ⁢ LN [ R M 6.7 × 10 - 6 ] ( 3 ) t L = 18 - 1 1.21 ⁢ LN [ R L 4.713 × 10 - 9 ] ( 4 ) where t M and t L are measured in months, and R M and R L are acceptable risk scores; and wherein said step of determining an increase in risk score comprises calculating an increased risk score R M2 or R L2 based on equations (5) and (6) for medium and low risk devices, respectively: R M2 =6.7×10 −6 exp[0.7(12−( t M −od ))] (5) R L2 =2.4×10 −6 exp[1.322(18−( t L −od ))] (6) where od is the time elapsed since said missed inspection.