Dwyer STRA User Manual

Series STRA Duct Mounted Airflow Measurement Station

AIR
STRAIGHTENER

[F]

[D]

AIRFLOW

TOTAL PRESSURE

(T.P.) TAKEOFF

1/4˝ COMPRESSION

FITTING

[L]

STATIC PRESSURE

(S.P.) TAKEOFF

1/4˝ COMPRESSION

FITTING

3.25

[H]

[W]

.25˝ RADIUS
BEADED EDGE (TYP)

TOTAL PRESSURE

(T.P.) TAKEOFF

1/4˝ COMPRESSION

FITTING

AIRFLOW

STATIC PRESSURE
(S.P.) TAKEOFF
1/4˝ COMPRESSION
FITTING

[L]

[L+2.5]

[W]

[F]

[H]

TOTAL PRESSURE

(T.P.) TAKEOFF

1/4˝ COMPRESSION

FITTING

STATIC PRESSURE

(S.P.) TAKEOFF

1/4˝ COMPRESSION FITTING

AIRFLOW

8˝

Specifications - Installation and Operating Instructions

CIRCULAR FLANGE DIMENSIONS
Station

Size “D”
8˝ – 15˝
16˝ – 44˝
45˝ – 72˝
73˝ & Over

Flange
Thickness
.064˝
.064˝
.188˝
.188˝

OVAL FLANGE DIMENSIONS (OPTIONAL)
Station

Width “W”
Up to 44˝
Over 44˝

*NOTE: All oval flow stations without
flange have a casing length of 8˝.

Flange
Size “F”
1˝
1-1/2˝
1-1/2˝
2˝

Flange
Thickness
.064˝
.188˝

Casing
Length “L”
8˝
8˝
10˝
12˝

Flange
Size
1-1/2˝
1-1/2˝

*Casing
Length “L”
8˝
10˝

Bulletin F-STRA

RECTANGULAR FLANGE DIMENSIONS
Station

Size “H” or “W”
8˝ – 72˝
73˝ & OVER

SELECTABLE SIZES:

1. OVAL OR RECTANGULAR “H” OR “W” DIMENSIONS IN INCHES CAN BE THE FOLLOWING: 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 40, 44, 48, 52, 56, 60, 66, 72, 78, 84, 90, 96, 102, 108, 114 or 120.

2. CIRCULAR “D” DIMENSION IN INCHES CAN BE THE FOLLOWING: 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 36, 40, 44, 48, 54, 60, 66, 72, 78, 84, 90, 96, 102, 108, 114 or 120

The Series STRA Airflow Measurement Station consists of single or
multiple airflow elements, factory mounted and pre-piped in a casing
designed for flanged connection to the ductwork. The station also incor­porates an airflow straightening section using a honeycomb which has a
1/2 inch opening by 3 inch depth. Standard materials consist of a G90
galvanized casing, 6063-T5 anodized aluminum flow sensors, and 3003
aluminum air flow straightener, suitable for most HVAC applications. The
Series STRA Air Flow Measurement Station has been developed for use in
duct systems having a highly turbulent condition at the point of measure­ment.
The airflow averaging element, utilized in the Series STRA, is a head type
device, which generates a differential (velocity) pressure signal similar to the
orifice, venturi, and other head producing primary elements. The Series
STRA is constructed so that strategically located sensing ports (based on
duct size) continually sample the total and static pressures, when inserted
normal to flow. The total pressures sensed by the upstream ports are con­tinually averaged within the element in an isolated chamber. The static
sensing ports (located where the influence of the velocity head is zero) are
averaged in a se cond i solat ion ch amber. Multiple elements are manifolded
together for connection to a differential measurement device (gage, trans­mitter, etc.) for flow measurement and indication purposes.

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: [phone] e-mail: [e-mail]

Flange
Size “F”
1-1/2˝
2˝

SPECIFICATIONS
Accuracy: Within 2% of actual flow when installed in accordance with

published recommendations.

K Factor: 0.97.
Velocity Range: 100 to 10,000 fpm (0.51 to 51 m/s).
Wetted Material: Elements: 6063-T5 anodized aluminum; Casings: 16

ga G90 galvanized steel, 3003 aluminum air flow straightener.
Temperature Limits: Galvanized Casings and Aluminum Elements
350°F (177°C) continuous operation (in air), 400°F (204°C) intermittent
operation (in air).

Humidity: All Airflow Stations 0 to 100% non condensing.
Process Connections: 1/4˝ compression fittings.

Phone: [phone] www.dwyer-inst.com

Circular Flange Dimensions

Station

Size

6˝ - 15˝
16˝ - 44˝
45˝ - 72˝

73˝ & Over

Circular Stations

Standard circular airflow measuring stations include a 16 gage galvanized
casing with attached 90° connecting flanges as listed above.

Flange

Thickness

0.064˝

0.064˝

0.188˝

0.188˝

Flange

Size

1˝
1-1/2˝
1-1/2˝

2˝

Casing

Length “L”

8˝

8˝
10˝
12˝

Rectangular Flange Dimensions

Station

Size

8˝ - 72˝

73˝ & Over

Rectangular Stations

Standard rectangular airflow measuring stations include a 16 gage galva­nized casing, 8 inches long, with formed integral 90° connecting flanges
as listed above.

Flange

Size

1-1/2˝

2˝

Oval Flange Dimensions (Optional)

Station

Size

Up to 48˝

Over 48˝

Oval Stations

Standard oval airflow measuring stations include an 18 gage galvanized
casing, 8 inches long between beads with 1-1/4 inch connecting sleeve
on each end (10-1/2 inch overall length). Actual O.D. dimensions are 1/4
inch less than specified duct I.D. dimensions.

INSTALLATION

The elements may be installed in any duct configuration. However, the
accuracy of the installation is dependent on the flow conditions in the
duct. The minimum installation requirements for the elements based upon
a uniform velocity profile approaching the duct disturbance for flow rates
less than 2,500 fpm are shown below. Add one duct diameter to the
installation requirements shown below for each additional flow rate of
1000 fpm. These are not ideal locations. It is always best to locate the ele­ments as far as possible from all duct disturbances, with upstream distur­bances being the most critical consideration.

Flange

Thickness

0.064˝

0.188˝

Flange

Size

1-1/2˝
1-1/2˝

Casing

Length “L”

8˝

10˝

ELBOWS

Notes:

Round Ducts:
D = Duct diameter

TRANSITIONS

Rectangular Ducts:

D = 4HW

π

π

H = Duct height
W = Duct width