<8. Maintenance>
8-4
IM 01C25W05-01EN
2. Apply reference pressures of 0%, 50%,
and 100% of the measurement range to the
transmitter. Calculate the errors (differences
between digital voltmeter readings and
reference pressures) as the pressure is
increased from 0% to 100% and is decreased
from 100% to 0%, and confirm that the errors
are within the required accuracy.
Note: If the output mode is square root, apply reference
pressures of 0%, 6.25%, 25%, 56.25%, and 100% of the
measurement range to the transmitter.
8.4 Disassembly and
Reassembly
CAUTION
Precautions regarding Frameproof Type
Instruments
1. Flameproof type transmitters must be, as
a rule, removed to a non-hazardous area
for maintenance and be disassembled and
reassembled to the original state.
2. For flameproof type transmitters, turn the
Allen head bolt clockwise with an Allen
wrench to unlock the cover, and then remove
the cover. When a cover is closed it should
be locked by a shrouding bolt without fail.
Tighten the shrouding bolt to a torque of 0.7
N·m {7 kgf·cm}.
Allen head bolt
(shrouding bolt)
F0802.ai
Figure 8.2 Allen head bolts
This section describes procedures for disassembly
and reassembly for maintenance and component
replacement.
CAUTION
Always turn OFF power and shut off and release
pressures before disassembly. Use proper tools
for all operations.
Table 8.2 shows the tools required.
Table 8.2
Tools for Disassembly and Reassembly
Tool
Quantity
Remarks
Phillips screwdriver
1
JIS B4633, No. 2
Slotted screwdriver
1
Allen wrenches
3
JIS B4648
One each, nominal 3,
4 and 2.5 mm Allen
wrenches
Wrench
1
Width across flats,
17 mm
Torque wrench
1
Adjustable wrench
1
Socket wrench
1
Width across flats,
16mm
Socket driver
1
Width across flats,
5.5mm
Tweezers
1
8.4.1 Replacing the Integral Indicator
This subsection describes the procedure for
replacing an integral indicator. (See Figure 8.3.)
CAUTION
Users are prohibited modifying the construction
of a flameproof type transmitter. As such, the
user is prohibited from using a flameproof type
transmitter with its integral indicator removed, or
from adding an integral indicator to a transmitter.
If such modification is absolutely required,
contact Yokogawa.
■ Removing the Integral Indicator
1. Remove the cover.
2. While supporting the integral indicator with one
hand, loosen its two mounting screws.
3. Dismount the LCD board assembly from the
CPU assembly. When doing this, carefully pull
the LCD board assembly straight forward so as
not to damage the connector pins between it
and the CPU assembly.
■ Attaching the Integral Indicator
1. Align both the LCD board assembly and CPU
assembly connectors and engage them.
2. Insert and tighten the two mounting screws.
3. Replace the cover.
