LNG CUSTODY TRANSFER ANALYSIS
by Gas Chromatograph, Calorimeter and Densimeter
For LNG custody transfer it is now a common practice to determine the composition, density and WI by
direct on line GC plus indirect lab analysis methods. A precise sampling according to the requirements of the
ISO 8943 standard is prerequisite for both analysis.
SAMPLING PROBE and VAPORIZER
This superinsulation system is designed for providing
thermal insulation by hight vacuum and enthalpy rise is controlled to be inferior of the subcooling degree.
In the vaporizer, LNG transformation in supercritical
state eliminates fractionated vaporization which would
generate fluctuations in the gas composition during
WI, composition and density measurements with better repeatability than 0.01 mj/m3 (ISO 6976) and
reproductibility lab / process GC better than 0.15%
SPOT & CHARGE SAMPLING SYSTEM
ISO 8943-1991: LNG continuous sampling method
ISO 8943-2004: draft of sampling with piston
EN 12 838: test to assess the LNG sampling
At vaporizer outlet sample gas is flow controlled
and accumulated in constant pressure piston floating cylinder holder.
Purging device is operated for the removal of any
residual gas from previous operations and the spot
transportation containers are automatically charged every hour during the transfer in compliance with
the fill and empty method Annex D of ISO 10 715.
Charge transportation containers at the end of
transfer are automatically fed at 7 barg pressure
within the same method.
The system processing is controlled via a solenoid
valve actuator bus manifold and sampling sequence with alarm history are reported on the controller
screen with data acquisition by keyboard. Customer data interchanges for maintenance acquisition and
SCADA are supported by Data Highway through Modbus or other protocol.