When an air line needs a clear local flow indication, choosing the correct flow range matters as much as choosing the meter itself. The Dwyer DR4243 is a direct-reading glass flowmeter from the Series DR4, built for higher-capacity flow measurement with a visible scale and an adjustable needle valve.

DR4243 at a glance

Choose the range around your normal flow

Start with the minimum, normal and maximum flow expected during operation. The DR4243’s published air range is 0.5–11 SCFM, with a 10:1 turn-down ratio across the Series DR4 range family. A meter that is much larger than the process flow can leave the normal operating point near the low end of its scale, where small changes are harder to judge. A meter that is too small can push normal operation toward or beyond full scale.

Use the stated air range as a selection reference, not as a universal reading for every gas or condition. Gas composition, pressure and temperature can affect the relationship between a variable-area meter’s indication and actual flow. If your operating conditions differ from the catalog reference, ask the supplier or manufacturer to confirm the appropriate range and correction method.

Check accuracy and reading conditions

Dwyer specifies ±10% of full-scale accuracy at 70°F (21.1°C) and 14.7 psia (1 atmosphere absolute). Repeatability is specified separately at ±0.25% of scale reading. Accuracy describes closeness to the reference value under stated conditions; repeatability describes how consistently the instrument returns to a reading. Do not treat the repeatability figure as the measurement accuracy.

The instrument has a borosilicate glass flow tube, a 316 stainless-steel float, PTFE float stops and stainless-steel end fittings with fluoroelastomer O-rings. The series also uses a reflective background and magnifying lens to make the scale easier to read. Check material compatibility with the actual gas and installation before use.

Plan the installation before ordering

Series DR4 flowmeters are intended for vertical mounting, and the DR4243 connection is 3/8 in female NPT. Confirm that the pipe connection, available clearance and mounting orientation suit the installation. Check that system pressure remains within the published 200 psig (13.8 bar) limit and temperature stays within 250°F (121°C). Follow the manufacturer’s installation instructions and avoid subjecting the glass tube to pressure or temperature conditions outside its rating.

DR4243 or a lower-flow model?

Choose the DR4243 when the required air flow fits its specified range and the process benefits from the stainless-steel, valve-equipped configuration. Series DR4 includes other model codes and ranges, including models intended for water service, so do not assume that every DR4 variant has the DR4243 air scale. Confirm the complete model code, medium, range and end-fitting material on the quotation.

For a smaller air or water flow point, compare the scale and mounting needs with the Dwyer RSF024V flowmeter guide. Its published maximum rates differ from the DR4 high-flow range, so select by the application’s expected operating point rather than by appearance alone.

A quick checklist before purchase

• Is the medium air, and does 0.5–11 SCFM (20–320 SLPM) cover the expected operating range?
• Are the catalog reference conditions appropriate for the gas and process?
• Do the 3/8 in female NPT connection and vertical mounting fit the installation?
• Are operating pressure, temperature and wetted materials compatible?
• Does the quotation identify the DR4243 model and valve-equipped stainless-steel configuration?

Review the Dwyer Series DR4 manufacturer catalog for the model chart, ratings and installation details, then confirm the exact configuration for your service.