266CRH / 266CRT, 266CSH / 266CST MULTIVARIABLE PRESSURE TRANSMITTER  |  OI/266CXX/MODBUS-EN REV. A  83 
 
 
 
 
Mounting / dismounting the operating 
button unit 
 
M10804-01
1
2
3
4
5
 
Figure 4:  Operating button unit 
 
1.  Unscrew the fastening screws of the name plate and swing 
the name plate to the side to obtain access to the local 
operating elements. 
2.  Unscrew the fastening screws 
1 of the button unit that hold 
the spring-loaded plastic part. 
3.  Remove the seal 
3 that is located below the plastic cover of 
the button unit. 
4.  Now the three operating buttons 
4 and the springs 5 can 
be taken out. 
 
 
Mounting / dismounting the LCD display 
Refer to Opening and closing the housing on page 25 and 
Rotate the LCD display on page 26. 
 
1.  On the side of the electronics module / LCD display, unscrew 
the housing cover. 
2. Fit on the LCD display. Depending on the install position of 
the multivariable transmitter, the LCD display can be fit on in 
four different positions. Consequently it can be rotated by 
± 90° or ± 180°. 
3.  Screw on the housing cover hand tight. 
 
 
 
 
 
 
Removing / installing the process flange 
 
1.  Unscrew the fastening screws of the process flanges in cross 
pattern (hexagon socket wrench AF 13 mm (0.51 in). 
2.  Carefully take off the process flanges so that the separating 
diaphragms are not damaged. 
3.  Clean the separating diaphragms, and if necessary the 
process flanges with a soft brush and a suitable cleaning 
agent. 
 
NOTICE 
Potential damage to parts! 
Components can be damaged using the wrong cleaning tools. 
•  Do not use any sharp-edged or pointed tools. 
 
4.  Insert new O-rings into the process flanges. 
5.  Fit the process flanges onto the measuring cell. 
  The flange surfaces of both process flanges must be 
positioned in one plane and at right angles to the electronics 
housing (vertical process flanges are the exception). 
6.  Check the thread of the screws for the process flanges for 
ease of movement. To do this, screw on the nuts by hand to 
the screw head. If this is not possible, use new screws and 
nuts. 
7.  Lubricate the screw thread and the seat of the threaded 
union, for example with ‘Anti-Seize AS 040 P’ (supplier: 
WEICON GmbH & Co.KG, Münster, Germany). 
 
Note 
For the oil-free and grease-free version, after installation of the 
process flange, the measuring chambers must be cleaned again. 
 
8.  Installation of the process flanges: 
•  First tighten the screws / nuts of the process flanges 
with a torque wrench to a pre-tightening torque of MJ = 2 
Nm (0.2 kpm), working in a cross pattern. 
•  Then tighten the screws / nuts of the process flanges 
with a pre-tightening torque of MJ = 10 Nm (1.0 kpm), 
working in a cross pattern. 
•  Retighten all screws / nuts (in a cross pattern), this time 
with a total tightening angle of ήA = 180°; in two steps, 
90° for each step. 
  Some transmitters have size M10 screws. Tighten these 
screws with a total tightening angle of ήA = 270°; in three 
steps, 90° each step.