Ansul 100/30, Руководство по эксплуатации и обслуживанию

Страница: 32 / 37

FOam sOlUTION CONCeNTRaTION DeTeRmINaTION
Page 2
FOam sOlUTION CONCeNTRaTION DeTeRmINaTION
ReFRaCTIve INDex OR CONDUCTIvITy
This test is used to determine the percent concentrate of a
foam concentrate in the water being used to generate foam.
It is typically used as a means to determine the accuracy of
the system’s proportioning equipment.
This method is based upon comparing foam solution test
sample to pre-measured solutions (Calibration Standard)
that are plotted on a baseline graph of percent concentra-
tion versus instrument reading.
A hand-held refractometer is used to measure the refractive
index of the foam solution sample. Scales on refractome-
ters vary, but what is actually being used to determine
concentration is a change in reading from one pre-
measured solution to another (Calibration Standards
“Curve” vs. Discharge Samples “Reading”). The philosophy
applies when using a conductivity meter which is measuring
the changes in the solution’s conductivity. (Refer to
Proportioning Test Instruments Data Sheet, F-2007003, for
more detailed information about the specific meters.)
A base curve is prepared by using the following apparatus:
1. Four 100 ml or larger plastic bottles with leak-resistant
screw caps
2. One 10 ml (10 cc) measuring syringe
3. One 100 ml graduated cylinder
4. Four or more eye droppers
5. One Test Meter – Model PA 202, 10419, 1500-32
6. Graph paper
7. Ruler or straight edge
Using water and foam concentrate from the system to be
tested, make up three 100 ml calibration standard solutions.
For a 6% concentrate, typically a 4%, 6% and 8% samples;
for a 3% concentrate, typically a 2%, 3% and 4% samples;
and for a 1% concentrate, typically a 0.5%, 1% and 1.5%
samples are made.
Label bottles with percent sample calibration solution that
will be utilized, i.e. 2%, 3% and 4% for a 3% concentrate.
As an example, for the 2% calibration solution sample,
measure 98 ml of system water in the graduate cylinder,
then pour into the bottle labeled 2%. Then with the measur-
ing syringe, transfer 2 ml (2 cc) of the concentrate into the
labeled bottle. Secure the cap on the bottle and shake to
thoroughly mix the solution. Repeat for the 3% calibration
sample (97 ml water and 3 ml concentrate) and for the 4%
calibration sample (96 ml water and 4 ml concentrate).
Increasing sample sizes will increase accuracy relative
to the measurement instrument.
After thoroughly mixing
the foam sample, a meter reading is taken of each percent-
age foam solution sample. It is important that temperatures
between discharge samples and calibration standards have
normalized with temperatures above 50 °F (10 °C) working
best. Each instrument has specific instructions for its
correct operation.
Using the graph paper, plot the meter reading on the X axis
and the percent concentrate reading on the Y axis. This
plotted curve will serve as the known baseline for the
proportioning test. Meters may have different scales and
the plotted resolution should be as large as possible with
the complete range of the calibration solutions known. The
scale you set must be linear.
Collect foam solution sample(s) from the proportioning
system, using care to ensure that each sample is taken at
an adequate distance downstream from the proportioner
being tested. (Usually any place downstream of the first
change in direction is adequate if samples are taken in the
riser room.) Stabilize a water flow through your discharge
device within the known acceptable range for the propor-
tioner and open the concentrate control valve. Take the
sample about 30 to 60 seconds after foam appears from
the test connection. Take meter readings of the sample(s)
and compare readings to the plotted curve to determine the
percentage for each sample.
Per NFPA 11,
Standard for Low-, Medium-, and High-
Expansion Foam,
acceptable ranges of proportioning
systems are not less than the rated concentration and not
more than 30% above the rated concentration or one
percentage point above the rated concentration, whichever
is less. For example, the acceptable range for a 3%
concentrate is from 3 to 3.9%.
Note:
There is some variability dependent on the accuracy
of the meter, the accuracy to which the calibration samples
were made, and if temperatures between calibration stan-
dards and discharge samples have not normalized.
Conductivity is especially susceptible to reading fluctuation,
thus the sample should be continuously stirred until a stabi-
lized reading can be estimated. Care should be taken to
not bump the sides or bottom of the sample container or
contaminate the sample with salts or solids, i.e. dirty fingers
while stirring. The conductivity of water stored in or for
systems can vary throughout a discharge which may affect
results. Conductivity should not be used for sea, salt, or
brackish water supplies. Although conductivity can be the
most accurate means of measuring foam solution in clean
water supplies under ideal conditions, the refractive index
method is best for most real world testing.
If discharge samples are sent to the Tyco Fire Protection
Products Test Lab for analysis, they should be packaged
per the instructions with the Test Kit and sent in for immedi-
ate processing. Largely dependent on water quality and the
type of concentrate used, foam solutions may start to
biodegrade in a short period of time which can affect results
(possibly as little as three to five days with nutrient-rich
water and detergent-based foam concentrates).
The following graphs are examples of typical refractive
index values for various concentrate pre-mixes. Results
may vary depending on the concentrate pre-mix type, site
water supply, and actual concentrate lot number. Therefore,
it is important that a new calibration curve be developed on
each date a proportioning test is required.