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Electronic Type Operation Instructions for Drum Water Level Controller

1. JTD TYPE DIFFERENTIAL PRESSURE TRANSMITTER FIRST STAGE ADJUSTMENT METHOD
1) Perform the method described below in accordance with the Boiler Manual.
2) After JTD-type controller installation, ventilate the piping when boiler pressure is normal.
3) Close the HIGH and LOW sides of the JTD-attached manifold valve, and loosen the drain ( air release ) plug.
4) Verify that DC20V-24V power is being supplied to the wiring terminals S+ and S-.
5) Tighten the plug that was loosened in Step 3, and open both the HIGH and LOW sides of the manifold valve.
6) The water level inside the drum should be kept at the Normal Water Level ( hereafter abbreviated “NWL” ).
7) Connect the digital tester to the JTD terminals CHK+/M- and CHK-/S- using a mA ( milliampere ) DC range.
8) Adjust the current using the zero adjustment switch ( external zero adjuster ) located on the right side of the JTD unit the current displayed on the digital tester reaches 12.00mA DC.
Note: The current value changes when the zero adjustment switch is turned approximately +45 degrees using a flathead screwdriver.
9) Adjust the adjustment screw located at the bottom of the water level gauge scale so that the remote water level gauge indicates NWL.
10) Output Current ( Measuring Range: -200mm to +200mm)
                                       NWL 0.0mm: 12.00mA DC
                                       NWL +200mm: 20.00mADC
                                       NWL -200mm: 4.00mADC
11) Precautionary Points
Be sure that the front cover (lid) is securely closed at all times excluding periods of adjustment. When the front cover is released during adjustment and the like, take necessary precautions to ensure that moisture, oil and dust do not contaminate the interior.
2. MOUNTING THE FIXED LEVEL CONDENSER
A. Mounting Position
The fixed level condenser should be mounted so that the condenser maintains a fixed level of water. In this state, the drum water level can be detected by comparing the level head inside the condenser with that of the drum.
To prevent erroneous reading arising from changes in the relative positions between the drum, water level and fixed level caused by the inclination of ship’s hull (head trim ) , it is desirable to mount the condenser above the centre of the drum water surface.
As shown in Fig. 5 and 6, it is necessary that dimension R should be less than 1500mm toward the stern, and shortest toward both sides of the ship.
B. Piping
B-1 The piping to the condenser should angle upward. However, as shown in Fig. 4, dimension A should be less that than 400mm. If this dimension exceeds 400mm, or if a bent is employed, a downcomer should be provided.
B-2 If the length of the condenser piping is over 400mm, lagging should be provided to decrease the amount of condensation.
C. Mounting the Shut-off Valve
3-1. If the glove valve is used on the condenser side as a shut-off valve as shown in Fig.3, the valve handle should be fitted facing sideways to provide smooth return of drainage to the drum. If the handle is fitted facing upward, drainage may fill the condenser, thereby causing a change in the water level position and subsequent erroneous reading.
3-2. If the shut-off valve on the condenser side is an elbow type valve as shown in Fig.1 and 2, the flange on the outlet side should be fitted to face sideways or upward. If the flange is turned downward, drainage may collect inside condenser.
3. MOUNTING THE DIFFERENTIAL PRESSURE TRANSMITTER ( JTD Type )
A. Mounting Position and Mounting Method
A-1. The transmitter should be mounted lower than the shut-off valve on the water side and as close to the drum as possible so as to facilitate adjustment.
In order to minimize error caused by the rolling of the ship, the transmitter should be mounted so that its front faces the ship’s side.
A-2. In order to ensure that transmitter is free low frequency vibration ( less than 10Hz), the transmitter should be mounted on a sturdy stand or pipe of 50A.
4. PIPING OF DIFFERENTIAL PRESSURE CONDUIT
4-1. Connect the conduit ( 15A ) on the fluctuating level side ( water side ) with the LP side of the differential transmitter. Also connect the conduit (15A) on the fixed level side (steam side ) with the HP side.
4-2. The conduit on the HP and LP sides should be installed in parallel to prevent errors caused by differences with ambient temperature.
4-3. In order to prevent the generation of air pockets in the conduit, care must be taken to install each conduit with an inclination of more than 1/10 to the differential transmitter.
4-4. T o assimilate the ambient temperature, each conduit should not be subjected to lagging.
5. PREPARATION FOR OPERATION
A. Sealing the Conduit against Water
When sealing the conduit, care must be taken so that no air is allowed to remain in the line.
A difference in HP and LP conduit temperature may result in a difference in specific gravity, thereby leading to a wide error in level readings.
Before sealing the conduit, remove the differential transmitter from the manifold valve and fill the diaphragm chambers on both the HP and LP sides with water to extract air. Once restored, seal the line.
A-1. Sealing method used after feeding water to drum
Open the HP and LP side valves as well as the pressure equalizing valve of  the differential pressure transmitter. Open the respective shut-off valves attached to the drum on the steam and water sides.
After allowing the unit to stand in this state for a few hours, close the shut-off valves on the steam and water sides as well as the pressure equalizing valve, then fill the unit with water by removing the plug on top of the condenser. When the unit is completely filled with water, close the plug. Then open each shut-off valve on the steam and water sides.
A-2. Sealing method after the drum pressure is built up
Close each shut-off valve attached to the drum on the steam and water sides, then loosen the bolts of the flange of the conduit of the shut-off valve on the water side to provide air ventilation.
Open the HP and LP side valves as well as the pressure equalizing valve of the differential pressure transmitter and feed the water by removing the upper plug of the condenser. Upon confirming that water is coming out from the conduit flange of the shut-off valve on the water side, tighten the bolts. When the condenser is filled with water, close the plug and the pressure-equalizing valve. Then open each shut-off valve on both the steam and water sides.
Note: After the sealing process has been completed as described as above, confirm the HP and LP status and the conduit temperature difference, verify that the condenser is filled with water, and then start the adjustment process.
B. Electrical Power Supply and Run Mode
The system enters run mode when insulated and stable DC24V power is supplied to the JTD unit.
C. Setting the Measuring Instruments
C-1. Differential pressure transmitter
Although fundamental adjustment of the transmitter had been made before shipment, it is sometimes necessary to make field adjustment depending on the mounting position of the condenser and other circumstances. Adjustment should be made in accordance with Section 6, “ Adjustment “ of the following page.
When a test is to be conducted with related parties present shortly after completion of the aforementioned sealing, or when there a discrepancy with condenser plans, the external zero adjuster of the transmitter should be adjusted so that output of the differential pressure transmitter will coincide with the actual water level. In addition, when coincidence with the actual level is difficult to obtain due to residual air or difference in conduit temperature, it is necessary to re-correct the actual level ( water gauge ) and reading under stabilized conditions 2-3 days after starting drum operation.
C-2  MONITOR   SWITCH(water  level  warning  and  feed  water  pump  start/stop)
        The zero adjuster of the differential pressure transmitter should be adjusted so that the water level indicated equals the desired value and the motor switch provided inside the burner control panel operates at that value.
        Further, the ON/OFF performance of the switch should be confirmed by observing the operating sound, tester and buzzer, etc.
D. Level Controller
     The level controller is provided inside the burner control panel. The unit cannot be set.
E. Caution during operation
     E-1 Water level reading
            Generally speaking , the output signal(water level reading) of the differential pressure transmitter varies to some extent with times of operation, i. e. operation after adjustment vs. operation. The size and time required for stabilization are dependent upon the following  factors:
     a)  The time required for assimilation  of the temperature of each conduit with the ambient temperature.