Table of Contents

  1. Scope
  2. Codes and Standards
  3. Environmental Conditions
  4. Design and Construction Details
  5. Nameplate
  6. Inspection and Testing
  7. Requirements for Transport and Storage
  8. Documentation
  9. Notes

1. Scope

This specification/requisition covers the minimum technical require­ments for the design, manufacturing, testing, supply and documentation of meterruns, complete with orifice plate, orifice flanges, studbolts, gaskets and end connection flanges. It is the responsibility of the vendor to ensure that the equipment is suitable for the service conditions stated in this requisition.

2. Codes and Standards

The meterruns shall comply with the requirements of this requisition, the relevant data sheets and of other applicable specifications, codes, standards, attachment II, etc. as stated below.

Order of priority of given requirements: national and/or local requirements shall govern in case they are more stringent than this requisition.

DIN 50049 Edition *: Material testing certificates
ISO 5167 Edition * : Measurement of flow by means of orifice plates, nozzles and venturi tubes inserted in circular cross section conduits running full.
** : Pipe flanges and fittings


3. Environmental Conditions

Location : ***
Temperature : normal : °C
  maximum : °C
  minimum : °C
Relative humidity    
  min/max : **
Rainfall : design  
  intensity: * mm/h  
Wind : max. velocity: :* km/h


4. Design and Construction Details

All meterruns shall be suitable for outdoor service in a petrochemical plant, which is located in a * area.

Piping and process data are detailed per item on the instrument specification sheets in attachment II.

Further details shall be as per ISO 5167.

4.1 Orifice Meterruns

The pressure rating of the complete assembly, shall be equal or better than the flange rating.

The materials of the meterrun orifice plate and the flange rating/­facing shall be as specified per individual item (preferably **).

The standard type orifice plate shall be a concentric square edge plate in accordance with standard drawing.

The vendor is responsible for sizing the orifice plate conform ISO standard 5167 and shall submit calculations for review (see attach­ment II).

4.2 Orifice Flanges

The design and machining shall avoid sharp corners and notches on the assembly.

Flange facing shall be smooth finished with a roughness in the range of 3.2 Ra to 6.3 Ra regardless of gasket type.

Orifice flanges for orifice run installation should be so constructed, machined and attached to the pipe that the inner surface of the passage extends through the orifice flange so that there is no recess at the orifice plate.

The flange bore and the section of pipe shall be of the same internal diameter.

4.3 Selection of Pipe for Meterrun

a. Standard Application
- Meterrun pipe shall be selected from commercially available piping material.
- The selection shall be based on more visual inspection on the following points:
- Pipe section is straight over the required minimum straight length.
· The pipe bore is circular over the entire length.
· The inside surface of the pipe section should be free from pitting, grooves and not be encrusted.
· Rough internal welds, longitudinal or circumferential are not allowed.

b. High Accuracy Applications
- In addition to the selection requirements as applicable to meterrun piping for standard applications the assembly for high accuracy applications shall comply with the following requirements of ISO recommendation R5167. The requirements will be applicable to the meterrun assembly including orifice flanges and the attached pipe sections.
- Grooves, scoring pits, ridges, shoulders, distortions, etc. which affect the inside diameter more than the specified tolerance shall not be permitted. When these measurements are exceeded, the irregularities may be corrected by filling-in, grinding or filing.
- Pipe sections may be specially selected from commercial pipe.
- Fifteen diameters of the special pipe upstream of the orifice is sufficient and standard pipe of same schedule and published inside diameter may be used for added straight length.
- For smaller sizes (2, 3 and 4 inches) the pipe sections shall preferably cover the entire straight length required
- Alternatively, wherever the highest accuracy is required, the upstream internal diameter of the pipe shall be bored for a distance of at least 4 diameters. Wall thickness shall not deviate more than 12.5% of the published dimensions.
- Each section of meterrun piping shall have its average internal diameter stamped on a stainless steel nameplate welded to the flange.

4.4 Installation Requirements

4.4.1 Welding Procedures

Reduction of the diameter of the pipe or distortion caused by welding should be eliminated.

If there is any internal roughness at the welds of the assembled meterrun, it should be ground smooth and flush with wall of pipe.

Flanges must be welded to pipe concentrically with flange faces exactly at 90 to center line of pipe although a tolerance of 3.5 mm per meter is permitted.

Flanges should be so oriented that the jackbolts are diametrically opposite. Bolt holes of all flanges shall straddle the vertical centerline of the assembled installed meterrun.

4.4.2 Mounting

The inside diameter of the gasket must not be smaller than the inside diameter of the pipe, and the gasket must be positioned concentrically.

A pair of break-out flanges may be installed, without affecting accuracy, at a minimum of 5 diameters downstream from the orifice to allow inspection of the orifice run.

4.4.3 Storage

Internal surfaces of the pipe sections shall be preserved to prevent corrosion during storage and installation.

For protection during shipment and outdoor storage flange faces and butt weld ends shall be protected/enclosed by steel plates and/or plastic cups.

5. Nameplate

The following items shall be permanently marked on the upstream face of the orifice plate handle:
- "Upstream"
- Rating and facing
- Line size
- Measured bore (d) radius (r)
- Plate material
- Orifice tag number
- Orifice type

6. Inspection and Testing

All equipment shall be given complete visual inspection and check of measures.

Vendor shall submit his standard test and inspection procedure in his proposal.

Inspection shall be made at the place of manufacture by the purchaser prior to shipment.

Acceptance of shop tests shall not constitute a waiver of requirements to meet field tests under specified operating conditions, nor does inspection relieve the vendor of his responsibilities in any way whatsoever.

Vendor shall supply material certificates in accordance with DIN 50049.3.1.B.

7. Requirements for Transport and Storage

For protection during transport and field storage, equipment shall be provided with suitable packing to protect against rough handling.

The equipment shall be packed securely for domestic or export shipment as specified. Lifting points or lugs shall be clearly marked. The equipment shall be properly identified with item and serial numbers. All material shipped separately shall be identified with securely fixed and corrosion tags indicating the item and serial number for which it is intended.

Meterruns shall be shipped, fitted loosely together as complete units, so that there is no possibility of mixing items.

8. Documentation

Vendor shall submit documents and drawings in accordance with the requirements as specified, in attachment I, "Vendor Furnished Documents".

9. Notes

  1. Vendor shall submit all data which is marked with a single asterisk (*) on attachment II.
  2. Vendors quotation shall include orifice plate calculations for all items on attachment II.
  3. Where insufficient data is specified to calculate beta, vendor shall take beta = 0.5.