Ametek PMT 40, Manual

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User Manual
20
Figure 19
LOCKNUT
DIAPHRAGM
LINK
ANGLE L BELL CRANK
BELL CRANK
ANGLE SCREW
MEASUREMENT
LINK
INDICATING
MOVEMENT
DIAPHRAGM
ASSEMBLY
RED POINTER
BLACK POINTER
ELEMENT
MOUNTING SCREW (3)
INDICATING
ASSEMBLY
DIAL
DIAL SCREW
(2)
SHOULDER
SCREW
SET POINT LINK
CONTROL LINK
TRACKING
ADJUST SCREW
RANGE
ADJUST SCREW
SLACK DIAPHRAGM ACTUATED PRESSURE
ELEMENT (Fig. 20)
To remove indication assembly –
unhook
diaphragm link at bell crank. Unhook control
link at its lower end. Remove shoulder screw to
set point link. Remove three element mounting
screws. The upper screw is reached through the
dial.
To remove diaphragm housing assembly –
unhook diaphragm link at bell crank. Remove
three screws securing diaphragm housing
to columns and bracket on back of case.
Reassemble in reverse order.
To adjust overpressure stop – (before
reassembly to instrument) turn overpressure
stop screw counterclockwise, at least three
turn. Apply full scale pressure and turn stop
screw clockwise until water column meniscus is
disturbed. Back off ½ turn.
To clean indicating assembly – same as
Bourdon element.
To calibrate – use a manometer or inclined
manometer of known accuracy to compare
with black pointer readings. Element must be
assembled in case. Disconnect control link
(short link closest to the chassis) from the tab on
the indicating movement. Set bell crank angle
at 90°. Adjust diaphragm link to engage 4 or 5
segment teeth on pinion at Po by unhooking it
at bell crank and turning it clockwise to shorten,
counterclockwise to lengthen. Proceed with
calibration as described under CALIBRATING
AND TRACKING INSTRUCTIONS, except for
the scale shape adjustment. If Pc is too high or
low (item 6 under CALIBRATION OF ELEMENT),
adjust bell crank angle and make appropriate
diaphragm link adjustment to engage 4 or 5 teeth
at Po.
SLACK DIAPHGRAGM ACTUATED
DIFFERENTIAL PRESSURE, VACUUM
ELEMENT, COMPOUND ELEMENT (Fig. 21)
To replace indicating assembly – same as Slack
Diaphragm Pressure Element.
METAL DIAPHRAGM PRESSURE ELEMENT (Fig. 19)
To remove –
remove two screws on back of case holding process connection block. Unhook long
control link from lower tab of bell crank. Remove shoulder screw to set point link. Remove three element
mounting screws. The upper screw is reached through the dial.
The diaphragm assembly may be removed by first disconnecting the diaphragm link and then loosening
the locknut securing the threaded base to the mounting bracket. The replacement diaphragm assembly
must be recalibrated as described below. Reassemble in reverse order.
To clean and disassemble – same as for Bourdon element.
To calibrate –
use a test gauge or column of known accuracy to compare with black pointer
readings. Calibration is best performed in the case. Leave control link (the long link closest to chassis)
disconnected at bell crank. Connect measurement link to bell crank. Loosen bell crank angle screw and
adjust angle to 80°. Lock with screw. Connect diaphragm link to bell crank in the hole which causes
about 4 or 5 segment teeth to be engaged on pinion at Po. Remainder of calibration adjustment is as
described in the CALIBRATION AND TRACKING INSTRUCTIONS.
Figure 27
Figure 26