IMPORTANT OPC tag names are case sensitive There are eleven columns: Tag This is a short-form name for the gas stream. If omitted, it defaults to 'Stream N' where N goes 1,2,3,4 etc... It is recommended that this be kept relatively short, as this appears in the list box on the main page of the ZCalc Service. Pressure Name of the pressure OPC tag. The format of this tag will depend on the configuration of your OPC server. It could be something like 23PI0034.PV as shown below, or it could be something like RTU5.HoldingReg003.Float The engineering units can be bar, psi or kPa Temperature Name of the temperature OPC tag The engineering units can be degrees Celcius or Fahrenheit Z This is the tag that is to receive the calculated Z value calculated and written by the ZCalc Service. It must therefore be possible to write to this tag in the OPC server. This field can be left blank, in which case the compressibility factor is not written to the OPC server. This may be useful during testing. A warning is given in the log file if this field is blank. Critical Pressure This can be either a constant, or it can refer to a tag in the OPC server Critical Temperature This can be either a constant, or it can refer to a tag in the OPC server Acentric Factor From PVT results EU Pressure Allowable entries are Bar, Psi or kPa, although it is not case-sensitive. Gauge pressure is assumed, although can be made expicit with a trailing "G", or absolute specified with a trailing "A", for example: bar bar G psi A Note that this field is not case sensitive, so "bar g" is the same as "bar G" or "BAR G" EU Temperature Allowable entries are degrees Celcius or degrees Fahrenheit. This can be written with or without a space, for example: degC deg C degF deg F Note that this field is not case sensitive, so "deg c" is the same as "deg C" or "DEG C" Status This is a tag in the OPC server to which the ZCalc service will write the status as a floating point number. This field can be left blank, in which case the status will not be written to the OPC server. A warning is given in the log file if this field is blank. Description A description for the stream (optional)   IMPORTANT The critical pressure (Pc) and critical temperature (Tc) must be specified in absolute units consistent with the engineering units for the actual pressure and temperature. For the pressure, the supported engineering units are: Actual Pressure Critical Pressure bar A, bar G bar psi A, psi G psi kPa A, kPa G kPa For temperature, the supported engineering units are: Actual Temperature Critical Temperature deg C Kelvin deg F Rankine The engineering units used for critical pressure and critical temperature are inferred from the engineering units specified for actual pressure and actual temperature, based on the above table.   Visible at Run Time It is suggested that the service is initially run as visible - this allows the service to interact with the desktop, so it is easier to test the application. The service will be visible if the Visible setting is set to Yes, True or 1. e.g. Visible=Yes In a field installation, it is probably better to set the service so that it is not visible. This can be done by setting the Visible setting to No,False or 0. e.g. Visible=No UpdateIntervalSeconds This specifies the OPC update interval. An interval of 5 seconds is usually sufficient. StartupDelaySeconds This is the length of time the service should wait at startup before attempting to connect to the OPC server. This parameter is useful when the PC is rebooted or powered-up, so that there is some control over the startup of OPC clients.  Account  By default, the ZCalc Service runs under the Local System account: You may wish to change the account for the ZCalc Service, in the event that the OPC server that you are connecting to runs under a different account. Note that you may need to change the OPC server's DCOM settings (using DCOMCNFG) to grant the selected account permission to launch and access the OPC server.    Problems or Questions  Please get in touch by telephone or email in the event of any problems with the installation or operation of the ZCalc Service. Tel: +47 99724942 Alternatively, from 0800 to 1800 Western European time: +47 55009860 Email: