S-G-03–Specifications for the approval of type of gas meters, ancillary devices and associated measuring instruments

Category: Gas
Issue date:
Effective date:
Revision number: 1
Supersedes: LMB-EG-08 and S-G-03


Part 19: Densitometers

Table of contents


1.0 Scope

This part of the Specifications applies to measuring instruments submitted for approval and used for the measurement of absolute gas density.

2.0 Metrological requirements

The applicable requirements of Part 1, section 7.0 shall apply unless otherwise stated in this section.

2.1 Maximum permissible errors

The following MPEs shall apply at any point within the density range for which approval is sought (see Part 19, Table 1).

Part 19, Table 1: Maximum permissible errors
Test conditions MPE
Reference ± 0.3%
"Other than reference" ± 0.5%

3.0 Technical requirements

In addition to the applicable requirements of Part 1, section 8.0, the following shall apply.

3.1 Filters

Where the design of the measuring instrument is such that foreign matter in gas can adversely affect its operation or impair its accuracy, the manufacturer shall incorporate suitable filters.

3.2 Gas flow passages

The inlet and outlet connections and the gas passages of a densitometer so equipped shall be of sufficient size to ensure minimal pressure drop with adequate gas flow through the densitometer in order to respond rapidly to changes of density in the metered gas.

4.0 Marking requirements

In addition to the applicable requirements of Part 1, section 9.0, the following shall apply.

4.1 The following information shall be marked on the nameplate, where applicable:

  1. Operating density range;
  2. Minimum required gas flow through the densitometer;
  3. Output signal characteristics and, where linear, signal to density conversion factor;
  4. Additional necessary information identified by MC.

5.0 Performance tests

The applicable requirements of Part 1, section 12.0 shall apply unless otherwise stated in this section.

5.1 Test conditions

5.1.1 Operating conditions
5.1.1.1 Reference and "other than reference" working pressures (pw)

Variation of the flowing gas pressure shall produce densities corresponding to 10%, 50% and 90% of the nominal range of density for the measuring instrument.

5.1.1.2 "Other than reference" working temperatures (tw)

The following flowing gas temperatures shall apply (see Part 19, Table 2).

Part 19, Table 2: "Other than reference" working temperatures
"Other than reference" ambient temperature "Other than reference" working temperatures
Low ambient temperature: -30 °C -10 °C
High ambient temperature: 40 °C 30 °C
5.1.2 Flow rate

The flow of gas through the densitometer, where applicable, shall be set at a minimum rate specified by the manufacturer or at zero flow where not specified.

5.1.3 Test medium

Chemically pure, dry nitrogenFootnote 19-1 shall normally be used as the test gas.

5.2 Evaluation tests

5.2.1 At reference conditions, tests shall be performed at the flow rate specified in 5.1.2 with test medium as specified in 5.1.3 at working pressures as specified in 5.1.1.1 (see Part 19, Table 3).

5.2.2 At "other than reference" conditions, tests shall be performed at the flow rate specified in 5.1.2, with test medium as specified in 5.1.3 at working temperatures as specified in 5.1.1.2 (see Part 19, Table 3).

Part 19, Table 3: Accuracy testing
Flow rate (Q) Test medium Working pressure (pw) Working temperature (tw) Environmental conditions
Qmin or zero where not specified Chemically pure dry nitrogen As specified in 5.1.1.1 Reference Reference
As specified in 5.1.1.2 "Other than reference"

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