Gas Chromatograph & Sample Handling System Upgrade

Summary

This project represents the delivery of one of New Zealand’s most complete, analytically correct, and technically robust fiscal metering analysis systems.

It has been engineered, installed, and validated to the highest standards applicable to custody transfer gas metering, hazardous area operation, and analytical sampling integrity.

The system comprises a fully redesigned and upgraded sample extraction pathway, heated transport system, integrated Sample Conditioning Cabinet, and a Rosemount 770XA gas chromatograph installed as a cohesive, API and GPA compliant analytical train.

Every part of the installation; mechanical, analytical, and electrical has been fully tested, verified, and independently inspected. All compliance records, drawings, SDoCs, hazardous area dossier, inspection sheets, and design documentation accompany this handover package.

The result is a turnkey, fully validated, operationally reliable, and future-proof fiscal analysis system.

System Architecture

Sample Extraction & Regulation (Pipeline Take-Off)

Genie 750 Direct Drive Probe (DDP) with membrane tip
Installed downstream of all instrumentation to reduce turbulence
Fully vertical installation for gravity-assisted liquid shedding
Extraction conducted under pipeline conditions
A bespoke Field Analytical Conditioning Enclosure maintains stable thermal conditions (≈50 °C) and preserves vapour-phase integrity before and after pressure reduction.
pressure-regulated using a GENIE GHR analytical regulator with pre- and post-regulation heat exchangers to control temperature across the pressure drop.

Heated Sample Transport

Heated Thermon SE-1F1-43-7-ATP-028 bundle
Maintains a minimum 16 °C margin above HCDP
Provides consistent thermal environment through 13 m run to analyser shelter
Reduces condensation risks and transit lag

Sample Conditioning Cabinet

Free-issue CCL / Emerson supplied

Dual filtration: 2 µm particulate + liquid-blocking membrane
Heated cabinet with temperature control (~50 °C)
Flow control and bypass for lag reduction
Uniform delivery conditions to GC
Final short heated connection to analyser

Rosemount 770XA Gas Chromatograph

Installed and commissioned by MNZ
Method: C9+ +hydrocarbon dew point (5-minute cycle)
Carrier & actuation gas setup verified
Fully integrated with the S.C. cabinet

This constitutes a fully compliant, high-performance analytical pathway.

Analytical Design Philosophy

The System was designed to meet or exceed industry requirements for accurate gas quality and fiscal metering analysis.
The design is based on:

Standards & References

API MPMS 14.1 - Collecting & Handling of Natural Gas Samples
GPA 2166 - Obtaining Natural Gas Samples
API MPMS 21.1 - Electronic Gas Measurement
Custody transfer best practice for C1–C9+ and hydrocarbon dew point analysis

Representative Sampling Requirements

Extraction at pipeline conditions
- Membrane-separating probe operating at true flowing temperature and pressure
- Liquid removal before any pressure drop
Strict hydrocarbon dew point control
- Full vapor-phase integrity maintained during pressure regulation
Heated and controlled sample transportation
- Thermon BSX heated bundle
- Temperature margin controlled from probe to GC
Uniform conditioning before analysis
- Sample Conditioning Cabinet applies identical conditions to process sample and calibration gas
Minimised dead volume, lag, and thermal gradients
Designed for traceability, repeatability, and long-term analytical stability

This analytical chain is engineered to deliver lab-quality consistency in a field environment.

Hydrocarbon Dew Point Control

The Field Analytical Conditioning Enclosure is designed to achieve robust vapor-phase integrity with stable heated conditions from the pipeline pressure through to sampling pressure at the gas chromatograph this ensures representative sampling of heavier hydrocarbons.