Viking VFT - Check of Bladder Integrity

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
VISIT THE VIKING WEBSITE FOR THE LATEST EDITION OF THIS TECHNICAL MANUAL
Page 30 of 35
10.5 Check of bladder integrity
During the normal operation, if the instructions given in this manual are correctly followed, the bladder is always subject to a virtually
null net pressure as the pressure in the internal area equals that in the external region. This is achieved because the lling and the
normal use procedures described so far avoid the formation of air bubbles inside or outside the bladder. Under this condition it is
extremely unlikely that a bladder rupture will occur.
A periodical check is however recommended to ensure that water and foam concentrate do not contaminate each other, decreasing,
yet not zeroing even in case of bladder rupture, the re ghting performance of the system where the bladder is installed.
The bladder integrity check can be done following these steps and referring to Figure 3.3.1:
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.
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.
3. In the event that a water foam solution is persistently discharged through water drain valve (7), possibly becoming richer with
foam concentrate as the discharge continues and resulting almost in a pure foam concentrate discharge at the end, then the
bladder integrity is likely to be compromised and further investigation is required (step no. 4).
If only water or a lean foam solution is discharged, not resulting in a pure foam concentrate ow and ending in water ow only
then the bladder is probably unimpaired. In this case please jump to step 6 in Section 9 or make the additional check detailed
in step 4.
Note: An initial discharge of water and foam solution, made particularly evident by the foaming properties of the foam concentrate
is normal if a CCV is not installed and the bladder tank operates in automatic mode (see Section 8.). This is because pressure
uctuations such as those caused by jockey pumps, combined with small leaks through the system piping network, may cause
some water ow through the ratio controller. This ow sucks some foam concentrate and generates water foam solution through the
ratio controller. This solution may pass to the water side of the bladder tank through valve no. (11).
4. If the water drain valve (7) discharges foam concentrate or sufcient doubt still exists regarding bladder integrity, then the
bladder needs to be pressurized with air to assess its status;
Remove the foam vent valve (4) and assemble the lling device in place of it (gure 3.3.1).
Connect a compressed air source having the features described in 7.2(e) to the lling device valve (5)
Close the water drain valve (7) and open the water vent valve (2).
Start the air compressor or open the installation’s air network valve to inate the bladder to 1kPa.
5. Scenario 1 - The time taken to achieve 1 kPa is variable depending on size and foam concentrate volume of the bladder. If it is
not possible to achieve 1 kPa on gauge (6) then a bladder rupture has occurred and the bladder must be replaced. For bladder
tank replacement operations refer to Paragraph 10.6.
Scenario 2 - Once 1 kPa air pressure inside the bladder is achieved on gauge (6), record the time and the temperature at the
tank shell. After 60 minutes record the air pressure inside the bladder and the temperature of the tank shell. Should the drop of
pressure exceed 0.3 kPa temperature adjusted (i.e pressure inside the bladder less than 0.7 kPa, temperature adjusted), the
bladder has a leak and must be replaced. For bladder tank replacement operations refer to Paragraph 10.6;
Scenario 3 – If the 1 kPa air pressure inside the bladder is retained over 60 minutes then the bladder is undamaged and the
tank can be put back into service. Restore water outside the bladder conditions following steps 6 & 7 from Section. 9.
Note: It is vital that the individual carrying out the bladder integrity check fully understands the working concept of the bladder
tank and the steps given in 10.5. This is because any deviation in the checking process could give a false conclusion leading to
unnecessary remedial work or placing a damaged bladder back in service.