Venturi Tube Material Selection Criteria Design – Flow Measurement

This article is about Venturi Tube Material Selection Criteria Design for Flow Measurement of Instrumentation and Control Systems as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.

Venturi Tube Material Selection Criteria Design – Flow Measurement

Material Receiving General Checklist for Instrumentation & Control

General Requirements

1. Purchase Order and Instrument specification sheet criteria shall be confirmed and compared with instrument stainless steel tags / labels and nameplates, and shipment checked for damage, prior to acceptance of the shipment
2. Verify that all the instruments are from technically acceptable vendors (Attachment 1)
3. Verify that the convergent section B, and the throat, C, be joined as one part or comply with the following: (Refer to Attachment 2) a) For machined convergent, the throat and the convergent section be manufactured from one piece of material. If made in two separate parts they shall be assembled before the internal surface is finally machined.
   b) There shall be no step in diameters between the divergent section E, and the throat, C. This can be established either visually or by touch. (PIP PCCFL001 Sec 3.4.1; ASME MFC 3Ma 2007 sec. 4.4.3)
4. The hole on the inside wall of the pipe shall be circular and the edges shall be flush with the internal surface of the pipe wall and as sharp as possible. (PIP PCCFL001 Sec 3.4.1; ASME MFC 3Ma 2007 sec. 4.4.4.4)
5. To ensure the elimination of all burrs or wire edges at the inner edge, rounding is permitted, but shall have a radius less than one-tenth of the pressure tap diameter. No irregularity shall appear inside the connecting hole, on the edges of the hole drilled in the pipe wall, or on the pipe wall close to the pressure tap. (PIP PCCFL001 Sec 3.4.1; ASME MFC 3Ma 2007 sec. 4.4.4.4)
6. The pressure taps shall be cylindrical over a length at least 2.5 times the internal diameter of the tap measured from the inner wall of the pipeline. (PIP PCCFL001 Sec 3.4.1; ASME MFC-3Ma-2007 sec. 4.4.4.5)
7. For the ASME venturi tube (Refer to Attachment 2) with an “as-cast” convergent section, the spacing between the upstream pressure taps situated on the entrance cylinder (A) and the plane
   of intersection between the entrance cylinder (A) and the prolongation of convergent section (B) shall be:
   (a) 0.5D ± 0.25D for 100 mm ≤ D ≤ 150 mm
   (b) 0.5D (+0.0D, -0.25D) for 150 mm < D ≤ 1200 mm (PIP PCCFL001 Sec 3.4.1; ASME MFC 3Ma 2007 sec. 4.4.4.6)
8. For ASME venturi tube (Refer to Attachment 2) with a machined convergent section and with a rough-welded convergent, the spacing between the upstream pressure taps and the plane of intersection between the entrance cylinder, A, and the convergent section, B (or their prolongations) shall be 0.5D ± 0.05D. (PIP PCCFL001 Sec 3.4.1; ASME MFC 3Ma 2007 sec. 4.4.4.6)
9. For all types of ASME venturi tube (Refer to Attachment 2) , the spacing between the plane containing the axes of the points of breakthrough of the throat pressure taps and the intersection
   plane of the convergent section, B, and the throat, C (or their prolongations) shall be 0.5d ± 0.02d. (PIP PCCFL001 Sec 3.4.1; ASME MFC 3Ma 2007 sec. 4.4.6)
10. Venturi meter materials and construction shall be compatible with the process fluid and applicable piping codes (PIP PCCFL001 Sec 3.4.2).
11. Flow calculations for proprietary venturi meters shall be provided by manufacturer. (PIP PCCFL001 Sec 3.4.3)
12. Minimum straight run pipe length requirements shall be in accordance with Table 3 (Attachment 3). Comment: Where owner approves additional metering uncertainty, minimum piping run lengths may be in accordance with ASME-MFC-3M. (PIP PCCFL001 Sec 3.4.4).

International Standard and Codes for Instrumentation Accessories

1. Turbine Meter Material Selection Criteria Design & Flow Measurement
2. Pitot Tube Design Requirement in Process Industry
3. SAES-J-002 – Technically acceptable instruments, 23 June 2008
4. SAES-J-003 – Instrumentation Basic Design, 16 January 2008
5. SAES-J-100 – Process Flow Metering, 05 April 2008
6. Standard Drawing Orifice plates 990-J- AB-036094 Sheet 1& 2 of 2 rev 16
7. PIP PCCFL 001 – Flow Measurement Criteria , August 2006, Process Industry Practices Process Control,
8. ASME MFC-3Ma-2007 – Measurement of fluid flow in pipes using orifice, nozzle, and Venturi

1. Attachment 1: Technically Acceptable Instruments, SAES-J-002, 23 June 2008

2. Attachment 2: Geometric Profile of ASME Venturi Tubes, ASME MFC 3M, 2004

3. Attachment 3: Minimum Straight Run Lengths for Venturi Tubes and Flow Nozzles Per ANSI/API (ISO 5167-3) PIP PCCFL001 August 2006