Assembly | Flow Switches
SPECIFICATIONS
The 8590C series Flow Sensors are averaging pitot tubes that provide accurate, convenient flow rate sensing and include a DP pressure switch. They are designed to be inserted in the pipeline through a compression fitting and are furnished with a 0.16”wc – 1.2”wc DP pressure switch and test ports. There are multiple sensing points that take the measurements and a built-in averaging capability which compacts the design.
Setting range: 0.16 to 1.2"w.c. Ambient Fluid Temperature Limits: 150 °F Operating Pressure: 7 psi max Electrical Rating: 5A resistive, 3A inductive @ 120VAC, 1A @ VDC SPDT Pressure Switch Enclosure Rating: NEMA 4 Pressure Switch Agency Approval: FM
SIZING INSTRUCTIONS Using the differential pressure equation below, calculate the dp generated by the sensor under normal operating conditions. Select the appropriate assembly from table 4, checking to ensure that the calculated sensor dp is within the pressure range (0.16 to 1.2"w.c.)
Note: the column on the right side of the table 4 defines velocity ranges to avoid. Continuous operation within these ranges can result in damage to the flow sensor caused by excess vibration.
TABLE 4
Item
Pipe Size
Pipe ID (inches)
Flow
Velocity Ranges Not
Number 8590C-1 8590C-2 8590C-3 8590C-4 8590C-5 8590C-6 8590C-7
(Schedule 40)
Coefficient "K" Recommended (feet per second)
1"
1.049 1.380 1.610 2.067 2.469 3.068 4.026
0.52 0.58 0.58 0.64 0.62 0.67 0.67
146 to 220 113 to 170 96 to 144 71 to 108
1 ¼ " 1 ½ "
2"
2 ½ "
56 to 85 42 to 64 28 to 43
3" 4"
DIFFERENTIAL PRESSURE EQUATION
= Differential pressure expressed in inches of water column Q = Flow expressed in SCFM as shown in equation K = Flow cœfficient - See values tabulated D = Inside diameter of line size expressed in inches P = Static Line pressure (psia) T = Temperature in degrees Fahrenheit (plus 460 = °Rankine) Ss = Sp Gr at 60°F (15.6°C)
Any Gas
2 x S s x (T + 460) K 2 x D 4 x P x 16,590
(in. WC) = Q
FLOW EQUATION Any Gas Q (SCFM) = 128.8 x K x D 2 x
P x (T + 460) x S s √
Bulletin 8590 Page 8
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