Series-VA

Supported Applications

The Dwyer Series VA Variable Area Flowmeters are designed for measuring the flow of compatible gases or liquids. The series features an easy-to-read universal mm scale and is supplied with correlation charts containing calibration data specifically for air (SCFH) and water (GPH). These glass flowmeters include a permanently fused ceramic scale with a vertical locator line to reduce parallax and eye fatigue, along with a thick polycarbonate front shield that provides protection and magnification.

Operating Conditions & Performance

The Series VA offers performance specifications dependent on the specific model family. For models VA1043, VA1243, VA1343, VA25425, and VA25025, accuracy is ±2% Full Scale at 70°F (21.1°C). Repeatability for these units is listed as ±0.25% FS. For models VA1043, VA1243, VA1343, VA25425, and VA25025 operating at 70°F (21.1°C) and 14.7 psia (1 atm absolute), accuracy is ±5% FS.

Operating limits vary by style:

• P and S Style: Designed for pressures not exceeding 200 psig (13.6 bars) and temperatures not exceeding 250°F (121°C).
• T Style: Designed for pressures not exceeding 100 psig (6.8 bars) and temperatures not exceeding 150°F (65.5°C). For T style Teflon flowmeters, standard conditions are considered to be 14.7 psia (1 bar) and 70°F (21 deg C); at pressures or temperatures greater than standard, leak integrity approaches 1x10.
• VAX5XX Models: Operating temperature range is -15 to 150°F (-26 to 65°C).

The series supports a Turn-Down Ratio of 10:1. All meters are factory tested for leakage prior to shipping.

Valve Alignment Requirements

Proper valve positioning is required based on the application:

• Exhaust pressure at Atmospheric conditions: Valve at Inlet.
• Exhaust pressure other than Atmospheric conditions: Valve at Outlet.
• Vacuum: Valve at Outlet.
• Liquid flow: Valve at Inlet or Outlet.

Note: When using a flowmeter with exhaust pressure greater than atmospheric conditions, standard calibrations cannot be used; a calibration for the operating pressure must be obtained. Excessive tightening of valves may damage the orifice.

Configuration Options

The Series VA is available in 65 mm and 150 mm sizes with interchangeable flowtubes. The series supports various housing materials, wetted components, and optional accessories to accommodate different process needs.

Housing and Wetted Materials

• End Fittings: Anodized aluminum, 316 SS, brass, or PTFE.
• Flowtube: Borosilicate glass.
• Floats: Glass or SS (stainless steel). Optional float materials include sapphire, Carboly, and tantalum.
• Float Stops: PTFE.
• Packings: Fluoroelastomer (none on VAX5XX models).
• O-rings: Buna-N on aluminum and brass models; fluoroelastomer on SS models; PTFE on VAX5XX models.

Process Connections and Valves

The standard process connection is two 1/8" female NPT. The flowmeters feature a standard 6-turn needle valve for flow rate control. High precision metering valves with non-rising stems are available as options (VA81 through VA86) to provide high sensitivity control and resolution at very low flow rates.

Accessories and Options

• Mounting: Acrylic tripod for single meter (Model VA7).
• High Precision Valves (316 SS):
  • VA81: 0.42 SCFH capacity.
  • VA82: 0.85 SCFH capacity.
  • VA83: 2.12 SCFH capacity.
  • VA84: 4.87 SCFH capacity.
  • VA85: 13.14 SCFH capacity.
  • VA86: 45.55 SCFH capacity.
• Calibration Certificates:
  • NISTCAL-FL1: NIST traceable calibration certificate for variable air flowmeters.
  • NISTCAL-FL2: NIST traceable calibration certificate for variable water flowmeters.

Dimensions by Size

• 65 mm: 5-1/2" [139.7] overall height.
• 150 mm: 9-13/16" [249.24] overall height.

Key Product Differences

The Series VA encompasses several distinct model families differentiated by material construction, scale length, and valve inclusion.

• Metal 65 mm Scale: Models such as the VA1043 (Aluminum), VA1243 (SS), and VA1343 (Brass) are available with glass or SS floats. These models support flow rates ranging from 0.104 SCFH to 89.2 SCFH for air.
• Metal 150 mm Scale: Models such as the VA20429 (Aluminum), VA22429 (SS), and VA23429 (Brass) offer higher flow capacities, with air ranges up to 93.9 SCFH.
• PTFE 65 mm Scale: Models such as the VA1545 are available with or without a valve (e.g., VA1505). These units utilize PTFE end fittings and support air flow rates from 0.220 SCFH to 49 SCFH.
• PTFE 150 mm Scale: Models such as the VA25425 are available with or without a valve (e.g., VA25025). These units support air flow rates from 0.104 SCFH to 18.39 SCFH.

The model number guide follows the format: VA<MODEL> - <MATERIAL> - <FLOAT>. For example, VA1043 denotes a specific configuration within this series structure.