Thursday, December 1, 2011

Coriolis flowmeter for custody transfer

The CNGmass Coriolis flowmeter series from Endress+Hauser is approved by NTEP in the U.S. and five other international standards organizations for custody transfer of compressed natural gas (CNG) and for fueling vehicles with CNG.

Available in three common sizes from 3/8 to 1 in., the CNGmass measures mass flow up to 330 lb/min (150 kg/min) at fluid temperatures up to 257F (125C) and pressures to 5,080 psi (350 bar). The instrument measures direct mass or corrected volume flow with 0.5% accuracy to meet custody standards. It also outputs temperature and density. Because the Coriolis flowmeter is a balanced two-tube design, it is insensitive to pipeline vibrations, and can be installed without taking inlet or outlet runs into consideration.

When used for custody transfer, the flowmeter is verified on site using reference measurements approved by the local authority for legal metrology controls. The flowmeter must be locked for custody transfer measurements and sealed by authorized personnel, but it can easily be converted back to normal measurements. The flowmeter is approved for custody transfer by NTEP (U.S.), PTB (Germany), NMi (Netherlands), METAS (Switzerland), BEV (Austria) and MC (Canada).

The CNGmass flowmeter carries approvals for use in hazardous areas from UL, ATEX, FM, cCSAus and NEPSI. The transmitter housing is powder-coated aluminium, the sensor housing is acid-and alkali-resistant 304 stainless steel, and all process connections are 316 or 316L stainless steel.

A multi-color LED on the transmitter housing indicates, by various colors and flashing intervals, the status of the instrument and the process conditions—such as creepage, system working/not working, custody transfer mode started, or explicit Modbus messages.

Output options for the CNGmass 8DF/8FF include pulse/frequency signal, 4-20mA current with HART, 30Vdc status output for fault or power supply failure, or MODBUS RS485 output in accordance with the EIA/TIA-485 standard designed for custody transfer applications in dispensing or fueling in the compressed natural gas industry. The MODBUS output contains flow rate, totalizer, temperature and density information, system or process notifications, and security status identification.

Four configuration methods exist for this product. Endress+Hauser’s FieldCare software can be used for on-site configuration, verification and diagnostics. The instrument can also be configured via HART, manually via the local display, or with a plug-in EEPROM

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