G 492 Technical Rule - Standard 06/2021 -PDF-file-

Gas Measuring Systems for an Operating Pressure up and including 100 bar

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  • DVGW
  • 30 pages
  • available as PDF only
  • 2nd edition 2021
  • 1
  • 1
  • 512140
ST

This Technical Rule G 492 governs planning, manufacturing, assembly, testing, commissioning and operation, as well as decommissioning and disposal of gas measuring systems of up to 100 bar1 in gas transportation and distribution systems and stations supplying commercial, industrial, or other comparable facilities.

1 Scope of Application

2 Normative References

2.1 DVGW Sets of Rules

2.2 DIN Standards

2.3 International Standards

2.4 PTB Sets of Rules

2.5 Acts

2.6 Ordinances (national)

2.7 Ordinances (EU)

2.8 Other Regulations

3 Terms, Symbols, Units, and Abbreviations

3.1 System

3.1.1 Measuring System for the Determination of Gas Concomitant Substances

3.1.2 Measuring System for the Determination of Gas Quality

3.1.3 Gas Measuring Station

3.1.4 Mobile Gas Measuring Station

3.2 Pressure

3.3 Flow-Rates

3.3.1 Flow-Rate

3.3.2 Flow-Rate Qb

3.3.3 Maximum Flow-Rate Qb,max

3.3.4 Minimum Flow-Rate Qb,min

3.4 Standard System Operating Conditions

3.5 Personnel Qualification

3.5.1 Qualified Person (QP)

3.5.2 Expert / Technical Expert (TE)

4 Quality and Managements Systems

4.1 General

4.2 Tasked Companies

5 Influence on the Environment

6 Gas Measuring System Installation Space

6.1 General

6.2 Installation Location Layout

6.3 Safety of Installation Location

7 Housing and Casing

7.1 Housing Requirements

7.2 Explosion Protection

7.3 Fire Protection

8 System Design

8.1 General

8.2 Measuring Concept

8.2.1 General

8.2.2 Continuity of Gas Transportation

8.2.2.1 General

8.2.2.2 Availability

8.3 Components and Assemblies

8.4 Stress Analysis

8.4.1 Design Pressure

8.4.2 Supports and Support Structures

8.4.3 Temperature

8.4.4 Gas Velocity

8.5 Gas Meters

8.5.1 General

8.5.2 Displacement Meters

8.5.3 Velocity Meters

8.5.4 Differential Pressure Gas Meters

8.6 Flow Correctors / Conversion Devices Including Sensors

8.7 Recording Devices

8.8 Gas Quality Measuring Systems

8.9 Measuring Data Communication Systems

8.9.1 General

8.9.2 Communication System

8.10 Meter Run

8.11 Shut-off Devices Upstream of the Measuring System

8.12 Gas Meter Bypass Line

8.13 Monitoring Systems

8.14 Switchover Device for the Selection of the Suitable Meter Run

8.15 Flow Straighteners

8.16 Device for Dampening Pulsations and Vibrations.

8.17 Filter and Separator

8.18 Station Heating

8.19 Electrotechnical Devices

8.20 Conformity-assessed/Factory-tested Gas Pressure Regulations Upstream of Gas Meters

9 Overpressure Protection

10 Pre-Commissioning Testing

10.1 General

10.2 Testing of the Measuring System Assembly

10.3 Metrological Documentation

11 Commissioning

11.1 General

11.2 Process Commissioning

11.3 Metrological Commissioning

11.3.1 General

11.3.2 Testing Equipment for Instrumentation

11.3.3 Testing Measuring Systems

11.3.4 Functional Testing of Data Transmission

12 Operation, Maintenance

12.1 General

12.2 Display at the Installation Location

13 Decommissioning and Disposal

13.1 General

13.2 Decommissioning

13.3 Disposal

Annex A (informative) – Visual Examples for Gas Measuring Systems

Annex B (informative) – Part 1 Certificate for Expert Testing of Gas Measuring Systems as defined by Section 10 of DVGW Code of Practice G 492

Annex B (informative) – Part 2 Certificate for Expert Testing of Gas Measuring Systems as defined by Section 11 of DVGW Code of Practice G 492

Further Reading