0 Introduction
This standard provides guidance on all aspects of the sampling of processed natural gas. Unless otherwise stated, all pressures up to 15MPa in this standard are given as gauge pressures.
The determination of the composition and the properties of the gas is highly dependent on the sampling technique. Also of great importance are the design, construction, installation and maintenance of the sampling system as well as the conditions of sample transfer and transport.
These guidelines cover sampling strategy, details of sampling methods, the choice of sampling method and sampling equipment.
This document is intended for use in sampling is not described those cases where as part of the analytical procedure. This document concentrates on sampling systems and procedures. Analyses from the samples collected using these systems and procedures may be utilized in many different ways, including calculations to determine the calorific value of the gas stream, identification of contaminants contained in the gas stream, and compositional information to determine whether or not the stream meets contractual specifications.
Warning-The use of this standard may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability or regulatory limitations prior to use.
All sampling activities shall comply with national and local safety regulations.
1 Scope
The purpose of this document is to provide concise guidelines for the collection, conditioning and handling of representative samples of processed natural gas streams. It also contains guidelines for sampling strategy, probe location and the handling and design of sampling equipment.
It considers spot, composite (incremental) and continuous sampling systems.
This document gives consideration to constituents such as oxygen, hydrogen sulfide, air, nitrogen and carbon dioxide in the gas stream.
This document does not include sampling of liquid streams or streams with multiphase flow.
Traces of liquid, such as glycol and compressor oil, if present, are assumed to be intrusive and not a part of the gas to be sampled. Their removal is desirable to protect the sampling and analytical equipment from contamination.
This document can be used for custody transfer measurement systems and allocation measurement systems.
Foreword I
ISO Foreword II
0 Introduction
1 Scope
2 Definitions
3 Principles of Sampling
4 Safety Precautions
5 Technical Considerations
6 Materials Used in Sampling
7 General Preparation of Equipment
8 Sampling Equipment
9 Spot Sampling
10 Direct Sampling
11 Incremental Sampling
Annex A (Informative) Use of a Block Valve in Direct Sampling
Annex B (Informative) Cleaning of Steel Sampling Cylinders
Annex C (Informative) Procedure for Low-pressure Sampling into Glass Cylinders
Annex D (Informative) Procedure for Sampling by the Fill-and-empty Method
Annex E (Informative) Procedure for Sampling by the Controlled-rate Method
Annex F (Informative) Procedure for Sampling by the Evacuated-cylinder Method
Annex G (Informative) Student's t-table
