Evaluation of the measuring conditions of water meters in the water supply system of St. Petersburg Vodokanal PUE

Summary

The basic parameters of the water flow that affect the results of water flow rate and volume measurements, i.e. fluid aeration, fluctuation of the measured flow rate under actual conditions, deposit formation on the inner surface of the water pipelines etc. are considered. Experimental investigations of the said parameters were carried out; the ways of reducing their effect on the results of measuring water flow rate and volume are suggested. The principal condition of the normal operation of measurement instrumentation should be the adjustment of all the parameters listed in the technical documentation (but not limited to those in the instruction manual) to the operational environment.

Key words

operational environment , water flow parameters , multistaging, transiency , non stationarity , deposits on the inner surface of the water pipelines , validity of the measurement results

Consideration of object ageing in estimating its reliability

Summary

The issues related to the estimation of reliability of nonstationary (ageing) objects that are characterized by increasing failure rate with time are discussed. The lack of methods that could be used in engineering evaluation of the reliability of these objects is stated. The method is suggested that consists in nominal replacing the nonstationary object with fictive stationary one with failure rate constant value that is selected basing on several additional considerations. The relationships readily usable in practice and expressing the reliability index of the fictive objects through the parameters of the ageing characteristics of the actual nonstationary objects were obtained.

Key words

non stationarity , reliability indicator , fictive replacement of objects , replacement criterion , probability of failure-free operation , calculation method