Assembly | Flow Switches
8590B — PITOT PURGE SWITCH ASSEMBLY
INPUT
Flow (scfh) Duct Area (ft^2) Elevation (ft) Fluid Temperature (deg°F) Static Pressure ("w.c.) OUTPUT
The 8590B Pitot Purge Switch Assembly is a device used to monitor air flow. The assembly consists of a pitot tube and a differential pressure switch with an adjustable setting. With the adjustable setting on the pressure switch, a specific flow can be set. This assembly is ideal for applications where proof of air purging is required. The advantage of the adjustable setting for purge applications is that purge time can be controlled thus keeping the air volume to a specific value so startup can occur sooner. The standard pitot tubes can be used with duct sizes between 3” and 28”. The pitot tube and interconnecting tubing construction is 304 stainless steel. The differential pressure switch comes with an adjustable setting between 0.16 to 1.2”w.c. or 0.4 to 4"w.c. which covers a large range of pipe velocities. A compression fitting is included with the pitot tube and allows for adjustable insertion depth and a ½” NPT process connection or a flat washer type connection for rectangular or square ducts (washer type mounting requires access to interior of duct). The differential pressure switch comes pre-assembled to the pitot tube so no additional tubing is needed. The setting of the pressure switch can be verified with the pressure taps on the assembly. The static pressure port runs parallel to the sensing tube which is inserted into the duct. The sensing tube is to be inserted half way into the duct with the tip directed into the air stream. The pitot tube also has permanently etched insertion depth graduations for ease of installation. Enter the operating conditions in the INPUT section to calculate the pressure switch setpoint. For purging applications the flow should be based on 80% of the firing rate.
Pressure switch setpoint ("w.c.)
SPECIFICATIONS
Setting Ranges: 0.16 to 1.2"w.c. 0.4 to 4" w.c.
Ambient Fluid Temperature Limits: Pitot Tube 1500°F, Pressure switch 150°F
Operating Pressure: 7 psi
Electrical Rating: 5A resistive, 3A inductive @ 120VAC, 1A @ 24-48 VDC SPDT
Pressure Switch Enclosure Rating: NEMA 4
Pressure Switch Agency Approval: FM
Bulletin 8590 Page 5
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