PS-G-19—Provisional specifications for the verification, reverification, installation and use of the primary elements of orifice meters

Category: Gas
Issue date: 2021-08-17
Effective date: 2021-08-17
Revision number: N/A
Supersedes: N/A


Table of contents


1.0 Purpose

The purpose of these provisional specifications is to establish requirements for the verification, reverification, installation and use of the primary elements of orifice meters.

2.0 Scope

These provisional specifications apply to the primary elements of orifice meters used in trade or custody transfer applications, with the exception of those for which conditional permission has been granted for use in service without verification and sealing.

3.0 Authority

These provisional specifications are issued under the authority of subsection 12(2) and section 18 of the Electricity and Gas Inspection Regulations.

4.0 References

5.0 Definitions

Diameter ratio (beta ratio)
(rapport des diamètres [rapport bêta])

The diameter of the bore of the orifice plate divided by the internal diameter of the meter tube.

Note: The diameter ratio at flowing conditions (β) is used in AGA Report No. 3, first edition, 1969, and second edition, 1985. The diameter ratios at reference conditions (βr) and at measured conditions (βm) are used in AGA Report No. 3, Part 2, fourth edition, 2000 and fifth edition, 2016.

Flow conditioner (AGA Report No. 3, Part 2, fifth edition, 2016, 3.1.9)
(tranquilliseur d'écoulement)

Flow conditioners can be classified into two categories: flow straighteners or flow conditions.

A device that effectively removes the swirl component from the flowing stream while redistributing the stream to produce a pseudo fully developed flow profile and the flow conditions that accurately replicate the orifice plate coefficient of discharge database values.

Flow straightener (AGA Report No. 3, Part 2, fifth edition, 2016, 3.1.9)
(stabilisateur d'écoulement)

A device that effectively removes or reduces the swirl component of a flowing stream, but may have limited ability to produce the flow conditions necessary to accurately replicate the orifice plate coefficient of discharge database values.

Note: Flow straighteners are named "straightening vanes" in AGA Report No. 3, first edition, 1969 and second edition, 1985.

Meter tube (AGA Report No. 3, Part 2, fifth edition, 2016, 3.1.10)
(conduite du compteur)

The straight sections of pipe, including all segments integral to the orifice plate holder, upstream and downstream of the orifice plate.

Orifice meter
(compteur à orifice)

A flow meter composed of a primary element, secondary components required to complete the installation of the meter (e.g. flow recorder/computer, pressure/temperature transducer) as well as the required connections, which are installed at the operational location.

Orifice plate (AGA Report No. 3, Part 2, fifth edition, 2016, 3.1.15)
(plaque à orifice)

A thin square-edged plate with a machined circular bore, concentric with the meter tube inside diameter, when installed.

Orifice plate holder (AGA Report No. 3, Part 2, fifth edition, 2016, 3.1.19)
(porte-plaque à orifice)

A pressure containing piping element, such as a set of orifice flanges also known as an orifice flange union (OFU) or an orifice fitting, used to contain and position the orifice plate in the piping system.

Primary element (AGA Report No. 3, Part 2, fifth edition, 2016, 3.1.20)
(élément primaire)

The orifice plate, the orifice plate holder with its associated differential pressure sensing taps, the meter tube, and the flow conditioner, if used.

Reverification
(revérification)

Any subsequent confirmation of a meter's conformance to legal requirements following its initial verification of conformance to those same requirements, performed upon expiration of the meter's reverification period (i.e. seal period).

Verification
(vérification)

All of the operations carried out by an inspector or accredited organization to confirm that a meter entirely conforms to legal requirements.

6.0 General

6.1 Mandatory verification and reverification

All the primary elements of orifice meters described in the scope of these provisional specifications are subject to mandatory verification and reverification.

6.2 Inspection location

6.2.1 Verification

The components of the primary element of an orifice meter may be initially inspected at a location other than the operational location (e.g. factory). In such case, the following information must be provided to the local district office or regional office of Measurement Canada (MC):

  • The name and contact information of the end user; and
  • The operational location (if possible) where these components are to be installed.

The primary element of an orifice meter that has been inspected and verified at a location other than the operational location qualifies to be placed in service, but the following requirements must be met:

  • The contractor or owner must obtain the authorization of the local MC district or regional office; and
  • The orifice meter installation must be verified within one year of installation.

6.2.2 Reverification

The primary element of an orifice meter must be inspected for the purpose of reverification at the operational location.

6.3 Verification triggering events

Any exchange of a component of a verified primary element is deemed to be a verification triggering event and must be reported by the contractor or owner to the local MC district or regional office. However, pursuant to section 8.1, the exchange of the orifice plate is not deemed to be a verification triggering event where the following requirements apply:

  • The thickness of the orifice plate intended for use must be within the maximum and minimum allowable range; and
  • The orifice plate bore thickness and differential pressure tap hole tolerances and limits must be satisfied.

6.4 Nonconforming primary elements

Any component of the primary element that fails to meet all applicable requirements of these provisional specifications or that possesses a defect which could affect its ability to meet the specified requirements must:

  • be classified as nonconforming; and
  • not be accepted for use in trade.

Where applicable, the verification stamp(s) of any nonconforming component of the primary element must be cancelled to indicate rejection.

A nonconforming primary element must be corrected (e.g. by restricting or reducing the diameter ratio) and reinspected, or the orifice meter must be removed from service.

7.0 Administrative requirements

7.1 Registration of orifice meters

Each orifice meter must be registered with the local MC district or regional office:

  • in paper or electronic format; and
  • on an annual basis or at the request of MC.

The following information must be provided to the local MC district or regional office:

  • Name and contact information of the contractor or owner;
  • Station name and location;
  • Date of installation;
  • In-service date;
  • Edition of AGA Report No. 3 originally used to manufacture or build the primary element;
  • Minimum and maximum sizes of orifice plates that may be used;
  • Meter tube:
    • Identification number assigned by the contractor or the owner;
    • Applicable configuration of AGA Report No. 3;
    • Maximum diameter ratio (βr or β, where applicable) to be used; Nominal pipe size and schedule;
  • Orifice fitting (where used):
    • Manufacturer's name or registered trademark;
    • Model number or type designation;
    • Serial number;
    • Notice of approval number;
    • Maximum operating pressure;
    • Nominal pipe size;
  • Flow straightener (where used):
    • Type designation;
    • Outside diameter;
    • Length;
  • Flow conditioner (where used):
    • Manufacturer's name or registered trademark;
    • Model number or type designation;
    • Serial number;
    • Notice of approval number.

7.2 Modifications to verified primary elements

The local MC district or regional office must be informed of any of the following significant changes to verified primary elements:

  • Replacement of the orifice fitting;
  • Modification to the meter tube configuration; and
  • Addition, removal or replacement of a flow conditioner.

7.3 Marking requirements

7.3.1 General

All required markings must be capable of withstanding the effects of the environment for the service life of the orifice meter and must be readily accessible and legible.

7.3.2 Meter tube

The following information must be indelibly marked on the meter tube:

  1. Identification number assigned by the contractor or the owner;
  2. Flow direction;
  3. Published inside diameter or the reference meter tube internal diameter (Dr);
  4. Edition of AGA Report No. 3 and number of the figure corresponding to the meter tube configuration;
  5. Thickness of the orifice plate (E); and
  6. Maximum diameter ratio (βr or β, where applicable) to be used.

Note: Where an orifice fitting is used, items e and f are not applicable.

7.3.3 Orifice plate

The following information must be indelibly marked on the orifice plate, without distorting the plate:

  • Manufacturer's name or registered trademark;
  • Model number or type designation;
  • Serial number;
  • Contractor's or owner's registration number;
  • Thickness of the orifice plate (E); and
  • Nominal inside diameter (d) or reference orifice plate bore diameter (dr), to the nearest one thousandth of an inch, marked on the downstream side of the orifice plate's handle or the outer perimeter of the orifice plate.

    Note: The symbol dr is used in AGA report No. 3, Part 2, fourth edition, 2000 and fifth edition, 2016. In prior editions, the symbol d is used.

7.3.4 Orifice fitting

Where an orifice fitting is approved, it must be marked in full accordance with all applicable location, legibility and marking requirements of specification S-G-03 and any additional marking requirements included in the applicable notice of approval.

Where the markings section of the orifice fitting's notice of approval makes reference to particular requirements of specification LMB-EG-08, these requirements are superseded by those of specification S-G-03.

7.3.5 Flow conditioner

Where a flow conditioner is used, the marking requirements of specification S-G-04 apply.

7.3.6 Verification marks

Upon initial verification and reverification, each component of the primary element must be marked with a verification mark or stamp, as set out in Table 1.

Note: The mark may be done using a special steel punch designed to produce an imprint that uniquely identifies the meter verifier and the year of verification.

Table 1: Location of verification marks on the primary element
Component Verification mark location
Orifice plate On the downstream face, near the outer edge of the plate and without distorting the plate.
Orifice fitting Near the nameplate.
Meter tube On the outer edge of either flange or near the nameplate.
Flow conditioner On the outer edge of the tube bundle or near the nameplate.

7.4 Sealing requirements

7.4.1 General

Where the requirements of section 8.0 have been met, the primary element of an orifice meter must be marked as per section 7.3.6.

7.4.2 Flow conditioner

Where a flow conditioner is used, the sealing requirements of specification S-G-04 apply.

7.5 Reverification period

The initial and subsequent reverification periods for orifice meters are as prescribed in bulletin G‑18.

8.0 Technical requirements

8.1 General

MC authorizes and makes mandatory the specifications and requirements of AGA Report No. 3. The dimensional measurements of each component of the primary element must be verified and not exceed the tolerances prescribed in the applicable edition of AGA Report No. 3.

8.2 Standard applicable prior to the issuance of these provisional specifications

A primary element manufactured or built prior to the issuance of these provisional specifications must be verified in a manner consistent with the requirements of the edition of AGA Report No. 3 that was originally used to build or manufacture it unless:

  1. it has been upgraded or redesigned to conform to AGA Report No. 3, Part 2, fifth edition, 2016; or
  2. a flow conditioner was added to it.

If the exception listed in item a applies, the primary element must be verified in a manner consistent with AGA Report No. 3, Part 2, fifth edition, 2016.

If the exception listed in item bapplies, the primary element must be verified in a manner consistent with the requirements of the edition of AGA Report No. 3 that was originally used to build or manufacture it. However, the meter tube configuration (i.e. the pipe lengths upstream and downstream of the flow conditioner) must conform to the installation requirements set out in the notice of approval of the flow conditioner.

8.3 Standard applicable after the issuance of these provisional specifications

A primary element must be manufactured or built and verified in a manner consistent with the requirements of AGA Report No. 3, Part 2, fifth edition, 2016.

8.4 Installation and use

8.4.1 General

The primary element must be free of:

  • any physical damage, defects in manufacturing or material deficiencies which could affect its ability to comply with usage requirements;
  • dirt, debris and other foreign substances, both internally and externally.

8.4.2 Meter tube

The meter tube must:

  • be installed either horizontally or vertically and, if installed vertically, the gas must flow downward;
  • be configured in a manner consistent with the installation requirements of the applicable edition of AGA Report No. 3;
  • not use pipe taps after the issuance of these provisional specifications.

8.4.3 Limits of the diameter ratio (β)

The diameter ratio (β) must be within the limits specified in Table 2.

Table 2: Limits of the diameter ratio (β)
Standard Limits
AGA Report No. 3, first edition, 1969
  • Meter tube using pipe taps: 0.20 ≤ β ≤ 0.67
  • Meter tube using flange taps: 0.15 ≤ β ≤ 0.70
AGA Report No. 3, second edition, 1985
AGA Report No. 3, Part 2, fourth edition, 2000
  • 0.10 ≤ βr ≤ 0.75
AGA Report No. 3, Part 2, fifth edition, 2016
  • Meter tube manufactured or built prior to the issuance of these provisional specifications: 0.10 ≤ βr ≤ 0.75
  • Meter tube manufactured or built after the issuance of these provisional specifications: 0.15 ≤ βr ≤ 0.67

8.4.4 Orifice fitting

Where an orifice fitting is used, it must:

  • be of a type approved by MC;
  • conform in every technical respect to the notice of approval; and
  • be installed as required by the device's notice of approval or as recommended by the manufacturer, as applicable.

8.4.5 Flow conditioner

Where a flow conditioner is used, the requirements of specification S-G-04 apply.

8.4.6 Flow straightener

Where a flow straightener made of a tube bundle is used, it must be circular and conform to the requirements of the applicable edition of AGA Report No. 3.