API MPMS 4.8 pdf download Manual of Petroleum Measurement Standards Chapter 4.8 c) the mechanical or electrical components of the meter have been opened, changed，repaired,removed. exchanged, or reprogrammed; d) changes in operating conditions have occurred, such as fiuid type, density, viscosity,temperature , pressure, or flow rate. 6 Frequency of Meter Proving The frequency required for proving varies from several times...