<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (March 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (March 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> Machine maintenance or the preventive maintenance (PM) has the following meanings: </P>

Why do we need to observe regular maintenance