# PAL-VMEA: A Novel Method for Enhancing Decision-Making Consistency in Maintenance Management
## 2 Variation Mode and Effect Analysis (VMEA)
The authors claimed that the upgraded probabilistic VMEA that was proposed could be used to identify, to asses, and to manage different variations to increase the system reliability. Besides, it could be used not only for existing products but also for new product development. In order to investigate and compare how external parameters influence the fuel consumption of an articulated hauler, [PERSON] [27] used VMEA with a view to further apply an experimental design methodology--a two-level fractional factorial test--to create a reduced test plan that focuses on the most interesting parameters during the in service runs. It was concluded that the VMEA method may be useful even if the available information is limited. [PERSON] et al. [35] contended that traditional FMEA is insufficient to consider detrimental variations, which lead to soft failure. Accordingly, the authors presented a method combining the FMEA technique with VMEA, which they named \"F-VEMEA,\" and applied it to the analysis of the characteristics of a jet pipe electrohydraulic servo valve. Since there are several methods for improving the prediction of reliability, being VMEA a relatively new one, [PERSON] and [PERSON] [36] set out to show how VMEA differs from Fault Tree Analysis (FTA) and FMEA in terms of requirements, limitations, and possibilities in the context of product development. It was concluded that the results from FMEA, FTA, and VMEA are somewhat complementary and useful during the whole product development process. [PERSON] and [PERSON] [37] after having applied VMEA to a successful Six Sigma improvement project, proposed a new development, named \"Process-VMEA (P-VMEA),\" providing a framework for identifying, assessing, mitigating, and managing variations in a process. The deliveries of the framework were mainly directed towards decision-makers and aim to strengthen fact-based decisions. In their conclusions, however, the authors conceded that it was a statistical complex tool that required high knowledge about variation and how to conduct the analysis of data. Besides, due to restricted time, the P-VMEA had been applied only to one industrial case and needed further validation. According to [PERSON], [PERSON], and [PERSON] [38], who have applied VMEA in the context of Ocean Harvesting Technologies (OHT) while carrying out the gear design for the rack pinion mechanism of a gravity accumulator device, this novel methodology proved to be useful where previous experience in designing was absent, allowing adequate safety factors to be set so the desired reliability could be achieved. As a result of evaluating two design criteria for the structural reliability of the double rod pretension cylinder in a half-scale prototype Wave Energy Converter (WEC), [PERSON] and [PERSON] [39] concluded that the VMEA methodology can be a good basis for condition monitoring, where the accumulated equivalent fatigue load can be monitored and the uncertainties may be updated based on operational data. This gives the possibility to predict the remaining life and its uncertainty, which can be a valuable input to maintenance planning. As presented, despite being a method with several applications and great potential, the use of VMEA for the area of maintenance and system reliability is still marginal.