This document describes the hardware setup and
other recommendations for testing the orifice flow
meters used for verification/calibration of flows into
PM2.5 particulate monitoring instruments. The Chinook
Engineering Streamline flow transfer standard (FTS) is
used by leaving the inlet to the orifice open to
atmosphere and drawing the air flow through the device
utilizing a downstream vacuum source (sub-atmospheric
pressure).
HARDWARE REQUIRED
FTS Adaptor Kit for molbloc-S™
P/N 401932
Installation and Operation Instructions
Carefully slide the Chinook Engineering FTS over
the adaptor until the adaptor “bottoms out” inside
the FTS.
PARTS INCLUDED IN FTS ADAPTOR KIT
SHIPMENT
The following parts are included in the FTS adaptor kit
shipment:
P/N 401932
FTS Adaptor Kit
• molbloc-S elements: Designated 2E2-S and 5E1-S
• End flange conversion kit, 1/4 in. VCR, P/N 401935
(allows the placement of 2E2-S molbloc-S on 1/4 in.
molstic-S)
• molstic-S Platform: Dual, 1/4 in. with low flow metering
valve, P/N FAM0009-01-3, with option -04-2
• Vacuum source and interconnecting hardware
INSTALLATION OF FTS ONTO MOLSTIC-S
1. Chinook FTS 3. Filter
2. FTS adaptor 4. Double female VCR coupler
5. Metering valve
Remove and retain the VCR tube adaptor together
with the double female VCR coupler from the filter
element’s inlet connection, located on the inlet of
the molstic-S. Discard the VCR gasket, which is
for one-time use.
Place the included VCR soft o-ring into the groove
inside of the FTS adaptor.
Connect the FTS adaptor to the filter element’s
inlet connection. Refer to the VCR face seal usage
instructions in the molbloc-S instruction sheet,
document no. 560050, supplied with molbloc-S.
DESCRIPTION QTY PART NO.
Adaptor, FTS to 4VCR 1 123659
1/4 in. VCR Face Seal O-ring 1 101421
APPLICATION NOTES
When operating the 200 sccm/kPaa molbloc-S in
sub-atmospheric conditions, its full-scale flow rate
is 20 slm (STP: 0 °C and 101.325 kPaa) at 101.325 kPaa.
In order to adjust flow through the FTS to the volumetric
flow rate of 16.67 lpm, the inlet absolute pressure to
this molbloc-S will have to be approximately 77 kPaa.
At its lowest volumetric flow rate of approximately 4 lpm,
the inlet absolute pressure will be 20 kPaa.
The 50 sccm/kPaa molbloc-S has full-scale flow rate
of 5 slm (STP: 0 °C and 101.325 kPaa) at 101.325 kPaa,
and will flow approximately 3 lpm at 55 kPaa. At its
lowest volumetric flow rate of approximately 1 lpm, the
inlet absolute pressure will be 20 kPaa.
The regulating valve in the configuration described
above is used to restrict the flow rate and thereby
reduce the molbloc-S inlet pressure. As long as the
vacuum source can maintain the molbloc-S outlet
pressure to that of no greater than 0.5x that of the inlet
pressure, the FTS can be checked at multiple flow
rates down to approximately 2 slm for the
200 sccm/kPaa, and 0.5 slm for the 50 sccm/kPaa
REFERENCE FLOW MEASUREMENT
In order for the molbox or COMPASS for molbox PC
software to properly calculate volumetric flow rate,
the prevailing conditions of ambient temperature,
absolute pressure, and relative humidity of the air
flowing into the FTS must be determined and entered.
If the FTS has the associated instrumentation capable
of measuring these values it should be used for
this procedure. Typically, the ambient temperature,
barometric pressure, and relative humidity of the
(
laboratory in which the calibration takes place can be
measured independently and used for this purpose.
The gas temperature measurement made by the
molbloc-S can be selected for use by either the
molbox or by COMPASS in order to calculate the
FTS flow rate. However, the molbloc-S pressure
measurement should NOT be used in this manner
since the upstream absolute pressure at the
molbloc-S is not the same pressure as the inlet
pressure to the FTS due to the flow control valve
in the hardware setup.
DETERMINATION OF CALIBRATION
COEFFICIENTS
Once the calibration is complete, the data obtained
can be used to recalculate the FTS values of slope (m)
and offset (b). A simple spreadsheet can be produced
to make the following calculations:
FTS indication:
Where:
∆P = Difference between ambient pressure
and FTS pressure tap
= Ambient air temperature in Kelvin [°C + 273.15]
T
amb
= Ambient air pressure in Atm [mmHg/760]
P
amb
m = Slope coefficient
b = Offset coefficient
[marked on FTS label]
[marked on FTS label]
[in. H2O]
Once sufficient calibration data has been obtained, the
“as received” % of reading error can be calculated at
each point as follows:
QQ
−
)
ERR%
=
Q
REFFTS
REF
•
100
The “slope” function in MS Excel can be used to
determine the new “m” slope coefficient. The format of
this function would take the form similar to:
=slope(ref Q data range:FTS indication data range)
The “intercept” function in MS Excel can be used to
determine the new “b” offset coefficient. The format of
this function would take the form similar to:
FTS flow rate:
FTS
IND•=
P
mQ
•=
P
amb
•
amb
TP∆
amb
The predicted “as left” % of reading error can be
determined in the same manner using the new
coefficients of m and b, and recalculating the FTS
indication and volumetric flow rate.
TP∆
amb
b
+
=intercept(ref Q data range:FTS indication data range)
molbloc and molbloc-S are trademarks, registered and otherwise, of DH Instruments, Inc.
Document 560048 030527
DH Instruments, Inc.
4765 East Beautiful Lane
Phoenix AZ 85044-5318
USA
VCR is a registered trademark of the Swagelok Company.
Tel 602.431.9100
Fax 602.431.9559
dhi@dhinstruments.com
www.dhinstruments.com
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