The meter retrofit at this industrial gas installation was recorded during a scheduled replacement of an older metering assembly. The existing skid had been in service for several years, and the replacement work involved a different meter configuration while retaining the existing pressure-control section. The site was supplying gas to a continuous process plant, so the operating readings before and after the meter change were closely compared during the commissioning record.
The upstream pressure was around 16.4 bar when the site was first checked in the morning. After the pressure-control section, the downstream gauge was showing 4.92 bar. Gas demand was comparatively low at that time, with the flow indication moving around 145 Nm³/h. Later in the inspection, production demand increased and the flow reached approximately 385 Nm³/h. The pressure-control section remained stable during the change, although a small movement in outlet pressure was visible on the local gauge.
The replacement metering assembly included High Pressure Flow Meters connected to an electronic volume correction arrangement. The existing High-Pressure Gas Regulators remained in service upstream of the metering section. This made the retrofit useful for comparing the behavior of the new metering equipment with the pressure conditions already established by the station.
The retained High-Pressure Gas Regulators set the pressure pattern for the new meter section
The regulator section showed a fairly consistent outlet pressure throughout the retrofit observation. At the beginning of the inspection, the inlet pressure was 16.4 bar and the outlet was 4.92 bar. When the industrial load increased, the inlet pressure moved down to 15.9 bar for a short period, while the regulated pressure settled around 4.86 bar.
The movement was gradual rather than sudden. There was no visible repeated hunting of the regulator during the higher-flow period. The pressure gauge needle moved slightly when the plant load changed and then returned toward its previous position.
Outlet pressure remained comparatively steady during production loading
At approximately 310 Nm³/h, the downstream pressure was recorded at 4.88 bar. When the demand increased to approximately 390 Nm³/h, the pressure dropped briefly to 4.83 bar before recovering to around 4.87 bar. The response was more noticeable on the mechanical gauge than on the digital pressure display.
The High-Pressure Gas Regulators were therefore operating under a changing inlet and flow condition while maintaining a relatively narrow outlet pressure range. The observation was relevant to the meter retrofit because the pressure input to the metering system was not completely static during the commissioning period.
High Pressure Flow Meters showed stable registration after the changeover
The new High Pressure Flow Meters were observed through several different loading conditions after the meter section became operational. During the lower-load period, the flow indication moved between approximately 128 and 155 Nm³/h. Once the main production equipment started consuming gas, the indication increased steadily and reached around 372 Nm³/h.
The meter display was compared with the electronic volume correction system during the observation. The raw volume and corrected volume were not expected to remain identical because the correction system was applying the measured pressure and temperature conditions to the gas volume.
The meter index at the beginning of the recorded period was approximately 6,418,290 m³. By the end of the observation, the accumulated index had moved to approximately 6,419,075 m³. The electronic corrected volume showed a different accumulated value because it represented gas volume at the configured reference conditions.
Low-flow indication had more visible movement
During the first production period, the gas demand remained below 160 Nm³/h. The High Pressure Flow Meters showed small changes in instantaneous flow as individual process burners cycled. The variation was visible on the display but did not correspond to any unusual pressure movement across the regulator section.
At this stage, the flow indication changed more frequently than during the later sustained-load period. The mechanical meter index continued advancing normally, while the corrected volume display responded to the pressure and temperature signals being received by the electronic correction system.
Higher loading produced a steadier flow trend
Once the production line reached a sustained operating condition, the flow indication remained between approximately 350 and 390 Nm³/h for a longer period. The trend on the monitoring panel became much smoother, and the pressure transmitter also showed less frequent movement.
The temperature transmitter was indicating approximately 31.2°C during the higher-flow period. The pressure transmitter showed 4.87 bar. These values were visible alongside the corrected volume information, making the relationship between operating pressure, temperature, and calculated gas volume easier to observe.
The volume correction display moved with pressure and temperature
The electronic correction system showed a correction factor of approximately 1.16 during the early part of the retrofit inspection. As the gas temperature increased from approximately 26.9°C to 31.2°C, the correction factor changed gradually.
The pressure signal also moved slightly as the industrial load changed. At one point, the transmitter showed 4.83 bar before returning toward 4.87 bar. The correction factor followed the combined pressure and temperature input rather than remaining fixed.
This difference was noticeable when the mechanical meter index was compared with the corrected volume display. The mechanical index represented the measured gas volume at the meter, while the electronic display accounted for the configured reference conditions.
Transmitter readings remained close to the local instruments
The local pressure gauge showed approximately 4.86 bar while the electronic transmitter displayed 4.84 bar during one of the comparison readings. Later, the gauge showed 4.88 bar and the transmitter was at 4.87 bar.
The temperature transmitter was also checked against the local temperature indication. The difference remained small during the recorded comparison. The wiring terminals inside the correction panel appeared clean, and there was no visible moisture around the signal-entry section.
Filter differential pressure increased with the replacement meter loading
The dry gas filter installed upstream of the metering section showed a differential pressure of approximately 0.05 bar during the lower-flow period. As the flow increased above 350 Nm³/h, the differential moved toward 0.12 bar.
The filter housing showed no visible external leakage. The accessible drain area was dry, and there was no noticeable accumulation around the housing connection. The pressure difference remained stable during the sustained-flow period rather than continuing to rise while the plant was operating.
The filter condition was recorded as part of the retrofit observation because pressure loss through the filtration section affects the pressure available to the metering equipment. In this case, the change in differential pressure followed the change in gas flow and remained within the operating pattern observed during the visit.
Valve response remained unchanged during the meter retrofit
The slam shutoff assembly upstream of the metering section remained in its normal position during the main operating period. Its position indication corresponded with the physical mechanism, and no unexpected movement was observed while the plant load changed.
A controlled functional test was also recorded separately during the commissioning work. The trip mechanism responded without visible hesitation, and the reset movement was completed normally. The downstream pressure indication changed as expected during the test condition and returned to the operating range after the pressure-control section was restored.
The safety relief valve showed no evidence of unwanted discharge during normal operation. The surrounding pipework and valve connections were dry, with no visible gas leakage indication around the accessible joints.
The meter enclosure condition was different from the older installation
The previous meter assembly had accumulated dust around the enclosure and cable entry areas. During removal, some dirt was visible around the external gland plates, although the internal terminal section remained comparatively clean.
The replacement arrangement had a new electronic connection enclosure with separate pressure, temperature, and communication wiring. The terminal screws were visually intact, and the communication modem showed a normal connection indication during the final monitoring period.
The difference was particularly noticeable when the electronic volume display was compared with the older installation records. The new system provided a clearer relationship between flow, pressure, temperature, and corrected volume, while the retained regulator section continued producing the familiar pressure pattern seen before the retrofit.
The final readings settled after the production load reduced
Near the end of the site visit, the industrial process load reduced from approximately 380 Nm³/h to around 210 Nm³/h. The inlet pressure returned to approximately 16.3 bar, while the downstream pressure settled at 4.91 bar. Gas temperature had reduced to approximately 29.6°C.
The High Pressure Flow Meters continued registering the lower flow without any sudden interruption in the displayed trend. The High-Pressure Gas Regulators also remained steady as the demand reduced, with the outlet gauge returning close to the morning reading.
The final meter index and corrected volume values were entered into the commissioning record, along with the pressure and temperature readings. The communication panel showed a normal indication, the terminal enclosure was closed, and the panel cover was secured. The calibration kit was packed back into its case after the last comparison reading, with the downstream gauge sitting at approximately 4.91 bar before the site was closed for the day.
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