Viking VFT - Section 9 - Foam Concentrate Level Measurement

BLADDER TANK MODEL VFT & FT
INSTALLATION, OPERATION AND
MAINTENANCE MANUAL
(
foam concentrate inside the bladder
)
TECHNICAL
MANUAL
F_032216 16.1 | TM1.3.1.1/14032016/en
The Viking Corporation, 210 N Industrial Park Drive, Hastings MI 49058
Telephone: 269-945-9501 Technical Services: 877-384-5464 Fax: 269-818-1680 Email: techsvcs@vikingcorp.com
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Page 25 of 35
SECTION 9 – FOAM CONCENTRATE LEVEL MEASUREMENT
Level checking of bladder tanks cannot be performed under normal standby/operational conditions.
Isolation of the bladder tank from the system and shell water drown down is always required.
The Viking bladder tanks are equipped with a foam concentrate level indicator (hydrometer) at its bottom (10) in gure 3.3.1). From
the level measurement the foam volume of the tank can be easily calculated.
The lever indicator bases its measurements on the column weight generated by the foam concentrate. As a consequence, the
range of pressure this device is designated to measure is within few (typically 6) meters of liquid column.
To check the foam concentrate level the following operations must be performed:
1. Close the water (11) and foam concentrate (12) cut-off valves;
2. Completely drain the water from the region outside the bladder by rst opening the water drain valve (7). Once the water
pressure has been reduced, carefully open water vent valve (2) and foam vent valve (4) to allow the pressure inside the tank
to equalize. Depending on the system conguration, the presence of foam from valve (7) could be caused by migration back
through the water supply piping. In the event of bladder failure, a solution of water and foam may consistently ow through
valve (7), all the necessary measures to avoid environmental contamination must be taken. Further details regarding a Bladder
Integrity Check can be found in section 10.5.
3. Once the water pressure and water column weight have been eliminated (steps 1. & 2.), move the handle of the 3-way valve
(9) from its normal position shown on the right hand side of gure 9.1.1 (i.e. when the bladder tank is in operation) to the
measurement position shown on the left hand side of gure 9.1.1.
4. Take the reading of the level indicator. The number indicated on the scale equates to the height, in metres, of the foam
concentrate above the hydrometer’s lower diaphragm section. As most of the foam concentrates have a specic gravity equal
to that of water within few %, the reading will indicate the foam level above the hydrometer position (expressed in meters).
Should the foam density

foam
differ signicantly from that of the water
ρ
water
, the foam level position above the hydrometer
h(m) can be calculated by the formula:
h(m)=

water
/

foam
x h
reading
(m)
5. Move the handle of the 3-way valve (9) from the measurement position to the normal position. This operation will avoid that the
bladder tank pressure is transmitted to the hydrometer and will drain the foam concentrate from the hydrometer line.
6. To place the bladder tank back in service (using lling device).
A water supply hose should be connected to the water ll/drain valve (7). Water must then be transferred into the tank, by
slowly opening valve (7) and venting air through valves (2) and (5) always ensuring the pressure is less than 1 kPa at pressure
gauge (6).
Water lling must continue until water, free of air bubbles, is drained though valve (2) and until foam concentrate, after some
seconds, is drained through the valve (5).
Close the valves (7), (2) and (5). The bladder tank condition is described in gure 7.3.8;
NOTICE