# Red Room - Session 7

## 10:30 to 11:30 a.m. Wednesday April 22, 2015

### Mixed Weibull Distribution as Best Representative of Forced Outage Distribution to be Implemented in BlockSim RBD

When a Reliability Block Diagram (RBD) is required, the failure distribution and outage distribution are requested as inputs for each block. Should field data exist, the two distributions can be obtained by managing data in the most appropriate manner. While the failure distribution is often a right-censored data set, the outage distribution is always a time-to-failure distribution obtained through the RRX interpolation. Moreover, as the reliability approach is conservative, the three-parameter Weibull (3P) assumption is welcome because the gamma value, in this particular circumstance, guarantees a minimum outage duration. However it has been noticed that while the two-parameter Weibull (2P) sometimes might not be conservative enough, the 3P could be too conservative with the risk of declaring a lower target than the actual one and hence with the consequence of not being commercially competitive. The proposed approach applies and develops the mixed Weibull application, where each subpopulation distribution comes out from a single data set, which represents a step forward after the traditional 2P and the more conservative 3P.

**Key Words:** RBD, Reliability Block Diagram, RRX, Rank Regression on X, Weibull 3P, Weibull with 3 Parameters, Weibull 2P, Weibull with 2 Parameters, LNG, Liquefied Natural Gas, GTL, Gas To Liquid (a refinery process), OEMs, Original Equipment Manufacturers, BCL, Barrel Centrifugal Compressor

Elisa Carlucci and Leonardo Tognarelli

GE Oil & Gas

Italy