Watts 909 Serie Manual De Instalación & Mantenimiento página 4

Testing — Reduced Pressure Zone Assemblies
Follow the requirements of each test when performed to ensure
successful installation, operation, and maintenance of the backflow
preventer.
Test No.1
Purpose: To test check valve No. 2 for tightness against reverse flow.
Requirements: Valve must be tight against reverse flow under
all pressure differentials. Slowly open the 'high' valve A and the
'vent' valve C, and keep the 'low' valve B closed. Open test No.
4. Indicated pressure differential is expected to decrease slightly.
If pressure differential continues to decrease (until the vent opens)
check valve No. 2 is reported as 'leaking.'
Test No. 2
Purpose: To test shutoff No. 2 for tightness.
Requirements: After passing test No. 1, continue to test No. 2 by
closing test cock No. 2. The indicated pressure differential is expected
to decrease slightly. If pressure differential continues to decrease
(approaching 'zero'), shutoff No. 2 is reported to be 'leaking.'
Test No. 3
Purpose: To test check valve No. 1 for tightness.
Requirements: Valve must be tight against reverse flow under all
pressure differentials. Close 'high' valve A and open test cock No. 2.
Close test cock No. 4. Disconnect vent hose at test cock No. 4.
Open valves B and C, bleeding to atmosphere. Then closing valve B
restores the system to a normal static condition. Observe the pres-
sure differential gauge. If there is a decrease in the indicated value,
check valve No. 1 is reported as 'leaking.'
Test No. 4
Purpose: To test operation of pressure differential relief valve.
Requirements: The pressure differential relief valve must operate to
maintain the 'zone' between the two check valves at least 2psi less
than the supply pressure. Close 'vent' valve C. Open 'high' valve
A. Open the 'low' valve B very slowly until the differential gauge
needle starts to drop. Hold the valve at this position and observe the
gauge reading when the first discharge is noted from the relief valve.
Record this as the opening differential pressure of the relief valve.
NOTICE
The differential gauge needle MUST drop slowly. Close test
cocks No. 2 and No. 3. Use 'vent' hose to relieve pressure from
the test kit by opening valves A, B, and C. Remove all test
equipment and open shutoff No. 2.
For repair kits and parts, refer to Backflow
Prevention Products Repair Kits & Service Parts
price list PL-RP-BPD at watts.com.
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Figure 4. Ball Type Test Valves
(A)
Low Hose
(White or Red)
High Hose
(Yellow)
Test Cock No. 3
Test Cock No. 1
Test Cock No. 2
(C)
(B)
Needle
Valve
Vent Hose
(Blue)
Test Cock No. 4