IP 476: Petroleum liquids - Automatic pipeline sampling (ISO 3171: 1988)

Overview:

Scope

This International Standard recommends procedures to be used for obtaining, by automatic means, representative samples of crude oil and liquid petroleum products being conveyed by pipeline.

NOTE - Although throughout this international Standard the term crude oil is used, this should be taken to include other petroleum liquids where the technique and equipment are also applicable.

This International Standard does not apply to the sampling of liquefied petroleum gases and liquefied natural gases.

The principal purpose of this International Standard is to give guidelines for specifying, testing, operating, maintaining and monitoring crude oil samplers.

The sampling procedures for crude oil are intended to provide representative samples for the determination of
a) the oil composition and quality;
b) the total water content;
c) other contaminants that are not considered to be part of the crude oil transferred.

If the sampling procedures for a), b) and c) are in conflict, separate samples may be required.

NOTE - The results of the laboratory analysis may be used for calculating adjustments to the declared quantity of crude oil transferred. The procedure for carrying out the adjustments does not form part of this International Standard.

Sample handling is included, covering all aspects following collection to the transfer of the sample to laboratory apparatus.

This International Standard describes the practices and procedures believed at the present time to be the most likely to lead to representative sampling and hence to accurate water determination. However, the accuracy of the water determination on pipeline samples obtained using automatic samplers will depend upon the arrangement and characteristics of all the various elements making up the sampling system, and on the accuracy of the subsequent analytical procedures.

A theoretical technique for evaluating the combined accuracy of the automatic sampling system and the analytical test is given in clause 16. A practical test procedure for field use is described in clause 15.

Normally, the acceptable accuracy limits for a particular automatic sampling system will be specified in agreement between the interested parties.

Table 4 of clause 15 classifies the performance of automatic sampling systems by ratings based on the accuracy of practical test results. These ratings may be used as a guide to possible performance and as a basis for individual agreement.