The Dwyer RMB-56 is a Rate-Master Series RM polycarbonate variable area flowmeter that reads 50 to 500 SCFH air on a 5 in. (127 mm) direct-reading scale. It is the standard model without a valve and has 1/4 in. female NPT connections.
Specifications verified October 12, 2026 against Dwyer DS-RM Rev. 3 (2/21), Bulletin F-43 (FR# 440197-00 Rev. 26, 8/23) and the Dwyer Series RM product page.
Best For
- Direct reading of 50 to 500 SCFH air with no conversion charts
- Air samplers and gas analyzers
- Pollution monitors
- Cabinet purging
- Medical equipment
- Panel mounted, surface mounted or piping-supported installations
Warranty
DwyerOmega limited warranty: free from defects in material and workmanship under normal use for one year from delivery, or such other period as specified in a product-specific warranty supplied with the product. Team Zot supports warranty claims at 855-825-2811 or sales@zotsupply.com.
Key Features
Direct-Reading SCFH Scale
The 5 in. (127 mm) scale reads 50 to 500 SCFH air directly, eliminating troublesome conversions.
Interchangeable Body
Within a model series the flowmeter body can be swapped without disturbing the piping, simplifying range changes and cleaning.
Stainless Steel Backbone
Absorbs piping torque to reduce installation damage and cost.
Shatter-Proof Polycarbonate Body
Durable body built for long operating life.
High Repeatability
Precision injection molding around a precision tapered pin, with integral flow guides that stabilize float movement.
Graduations on Both Sides
Scale graduations on both sides of the indicating tube give an instant flow reading.
ZOT Supply is an authorized distributor of Dwyer products.
Technical Specifications
| Series | Rate-Master Series RM, Model RMB |
| Flow Range | 50 to 500 SCFH |
| Calibrated Media | Air |
| Scale Length | 5 in. (127 mm) |
| Accuracy | 3% FS |
| Valve | None (standard model, no valve) |
| Process Connection | 1/4 in. female NPT |
| Pressure Limit | 100 psi (6.9 bar) |
| Temperature Limit | 130°F (54°C) |
| Service | Compatible gases and liquids |
| Wetted Materials | Body: polycarbonate; O-rings: neoprene and Buna-N; metal parts: stainless steel; float: stainless steel, black glass, aluminum, K monel or tungsten carbide depending on range |
| Calibration | Factory calibrated |
| Mounting Position | Vertical, inlet at bottom rear, outlet at top rear |
| Mounting Options | Through-panel (flush), surface mounted, or supported on piping |
| Panel Cutout (Flush Mounting) | 8-9/16 in. high x 1-5/16 in. wide (21.75 x 3.33 cm) |
| Surface Mounting Panel Holes | pipe 5/8 in. (1.59 cm), bolt 9/32 in. (0.71 cm) |
| Mounting Holes | 1/4-20 thread |
| Clamp Bolt Torque | 5 in-lb maximum |
| Dimensions (see drawing) | A 8-1/2 in. [215.90 mm]; F 1-3/4 in. [44.45 mm]; J (back width) 1-1/4 in. [31.75 mm]; K 8-3/4 in. [222.30 mm]; L 1-1/2 in. [38.10 mm] |
| Weight | 13 oz (368.5 g) |
| Compliance | Meets the technical requirements of EU Directive 2011/65/EU (RoHS II) |
Documentation
Frequently Asked Questions
What flow range does the Dwyer RMB-56 measure?
The Dwyer RMB-56 reads 50 to 500 SCFH air on a 5 in. (127 mm) direct-reading scale.
How accurate is the Dwyer RMB-56?
Accuracy is 3% of full scale (3% FS).
What are the pressure and temperature limits of the RMB-56?
The RMB-56 is rated to 100 psi (6.9 bar) and 130°F (54°C). Do not exceed these limits.
How is the Dwyer RMB-56 mounted?
Mount it vertically with the inlet at the bottom rear and the outlet at the top rear. It can be mounted through the panel using an 8-9/16 in. high x 1-5/16 in. wide (21.75 x 3.33 cm) cutout, surface mounted, or supported on rigid piping. Do not exceed 5 in-lb on the clamp bolts.
Does the Dwyer RMB-56 include a flow control valve?
No. The RMB-56 is the standard model without a valve. Valved versions add -SSV (stainless steel valve) after the range code.
Do SCFH readings on the RMB-56 need correction for pressure and temperature?
Yes, when operating conditions differ from standard. The SCFH scale is calibrated to standard conditions of 14.7 psia and 70°F. Correct the observed reading with Q2 = Q1 x square root of ((P1 x T2) / (P2 x T1)), using absolute pressure and temperature measured at the flowmeter exit.
What size are the process connections on the RMB-56?
The RMB-56 has 1/4 in. female NPT connections. Inlet and discharge piping should be at least as large as the connection (1/4 in. IPS).
What fluids should not be used with the RMB-56?
Caustic solutions, antifreeze (ethylene glycol) and aromatic solvents should not be used, and solutions of acids, bases or salts with a pH below 5.0 or above 8.5 should be avoided. Keep the installation away from strong chlorine atmospheres and solvents such as benzene, acetone and carbon tetrachloride.
Can the RMB-56 be cleaned without removing the piping?
Yes. First make sure the flowmeter is unpressurized and drained of any liquid. Remove the four mounting bracket screws and pull the body forward; the piping connections stay intact. Clean the flow tube and body with pure soap and water and a soft brush.
