Regulating stations

The process of reducing gas pressure with an expander is an isen-tropic process, which is able to recover both the energy from the gas pressure and also the gas temperature. A conventional gas regulator station is an isenthalpic process, which only reduces pressure. As a result, an expander system produces much lower gas temperatures downstream compared to a pressure regulator operating under the same pressure conditions. 

San Diego Gas Electric s expander is installed in parallel to a major city gate station. This type of system could be installed on a pressure reducing station supplying natural gas to an electric power plant. Large regulator stations serving industrial customers are another possible application. 

The loeation that was finally seleeted was the Mission Regulator Station. This was one of the three eity gate stations supplying the distribution loop from tlie transiuission system. Mission is on tlie southern end of tlie 16-in. transiuission line, whieh was rated at 795 psig maximum. 

Operation of the unit has proven to be successful. The generator is started and stopped by the dispatcher in the control center. It is also designed to automatically shut down if the electrical output drops below a predetermined level. Due to the widely varying conditions in the pipeline, there are times when the generator is started and stopped once or twice a day. At other times, it runs continuously for two or more weeks. There has been no impact on the operation of the existing regulator station resulting from the operation of the expander. The transfer of flow as the expander starts and stops has not caused any pressure excursions downstream of the station. 

The need for auxiliary heating is another factor that must be carefully evaluated. Due to the nature of the thermodynamic process, the gas discharging from an expander is at a much lower temperature than gas discharging from a regulator station operating within the same pressure bounds. If temperatures downstream of the expander are allowed to drop too low, potential problems may arise, such as hydrate formation and material compatibility. 

Detailed requirements for pressure-regulating stations are contained in two Institution of Gas Engineering publications ... 

GR-5.23.3 Maintenance of Pressure-Limiting and Pressure-Regulating Stations... 

Every distribution system supplied by more than one district pressure-regulating station shall be equipped with devices that record the hydrogen pressure in the district. 

On distribution systems supplied by a single district pressure-regulating station, the operating company shall determine the necessity of installing such devices in the district, considering the number of customers supplied, the operating pressures, and the capacity of the installation. 

Each vault housing a pressure-limiting, pressure-relief, or pressure-regulating station shall be examined to determine its condition each time the equipment is examined and tested in accordance with para. GR-5.23.3. For any vault which personnel enter, the atmosphere shall be tested for combustible gas. If the atmosphere is hazardous, the cause shall be determined. The vault shall be examined for adequate ventilation. The condition of the vault covers shall be carefully examined for hazards. Unsatisfactory conditions disclosed shall be corrected. No welding maybe done if a combustible gas mixture is present. Maintenance work performed in the vault shall be in accordance with procedures developed per para. GR-5.23.3, with particular consideration given to the monitoring of the atmosphere and safety protection for personnel in the vault. 

Addresses piping transporting aqueous slurries between plants and terminals and within terminals, pumping, and regulating stations. 

Parallel to this line an older DN 700 and DN 500 line is located to which the meter- and regulator stations supplying the Georgian market are connected. 

Pressure limiting and regulating stations inspection and testing 192.739... 

Pressure limiting and regulating stations telemetering or recording gauges (for gas pressure) 192.741... 

Pressure limiting and regulating stations testing of relief devices 192.743... 

Apart from a pressure reducing and regulating station, natural gas does not require any treatment at the cement works either. 

Gaseous fuel for cement kilns is predominantly natural gas, the properties of which are given in Table 1. It is supplied by pipeline at pressures ranging from 10 to 70 bar, which are reduced to between 3 and 10 bar in a pressure regulating station for use in the cement works. 

FIG. F-26 Pressure regulating station (PRS) upstream of vertical dry scrubber. (Source Peerless.)... 

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