Gas Valve Seal Control Equipment Ldu 11 - baltur COMIST 122 DSPGM Manual De Instrucciones

GAS VALVE SEAL CONTROL EQUIPMENT
LDU 11...
Use
The LDU 11 equipment.... is used to check the gas burner valve
seal. Together with a standard pressure switch, it automatically
checks the gas burner valve seal before each start-up or after each
shutdown. The seal is checked in two pressure phases of the gas
circuit between the burner two valves.
Operation
During the first phase, called "TEST 1", the pipe between the valves
to be checked must be at atmospheric pressure. In plants without
atmospheric pressure setting pipe, this condition is achieved through
the seal control equipment which opens the furnace side valve for 5
seconds during the "t4" time. When the pressure has been set to the
atmospheric value for 5 seconds, the furnace side valve is closed.
During the first phase (TEST 1) the control equipment "DW"
pressure switch checks that the atmospheric pressure is kept
constant in the pipe.
If there is a blow-by in the safety valve while closing, the pressure
increases, the "DW" switch triggers, the equipment indicates such
increase and enters in fault state and the position indicator blocks
in "TEST 1" position (red light on).
Vice-versa, if the valve is tight and the pressure remains constant,
the device immediately sets the second phase "TEST 2".
In these conditions the safety valve opens for 5 seconds during the
"t3" time introducing the gas pressure in the pipe ("filling operation").
During the second phase the pressure must remain constant. If it
decreases, the burner furnace side valve features a blow-by while
closing (fault), the "DW" pressure switch triggers, and the control
device prevents the burner start-up and stops in shutdown state
(red light on).
If the second phase check is successful, the LDU 11 device.... closes
the internal circuit across terminals 3 and 6 (terminal 3 - contact
ar2 - external U-bolt of terminals 4 and 5 - contact III - terminal 6).
This circuit usually gives the consensus to the equipment start-up
control circuit.
After terminals 3 and 6 circuit closure the LDU 11 programmer...
returns in stand-by position and stops, i.e. is ready for a new check
without changing the position of the programmer control contacts.
Set the "DW" pressure switch to a value equal to half
!
of the gas line pressure value.
Symbol meaning:
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Start-up = operation position
In plants without vent valve = test circuit put under
atmospheric pressure by opening of the burner furnace
side valve.
TEST 1 "TEST 1 " pipe at atmospheric pressure (blow-by check
during safety valve closure).
Test gas circuit put under pressure by opening of the
safety valve.
TEST 2 "TEST 2" pipe at gas pressure (blow-by check of burner
furnace side valve).
I I I
Programmer automatic reset (or stand-by).
}
Operation preset for a new blow-by check.
In case of fault, the control device terminals are not powered, except
terminal 13 which gives remote indication of the fault. After the check,
the programmer automatically returns to the stand-by position and is
preset to carry out a new gas valve seal test (while closing).
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