Maintenance; Overview; Preventive Maintenance Practices And Schedules; Inspecting And Cleaning Barrier Diaphragms - Honeywell ST 700 User Manual

5.1 Overview

This section provides information about preventive maintenance and replacing damaged parts. The
topics covered in this section are:
•
Preventive maintenance of the meter body barrier diaphragms and process piping to the
Transmitter.
•
Replacement of damaged parts such as the Transmitter Printed Wiring Assembly (PWA) and
meter body

5.2 Preventive Maintenance Practices and Schedules

The ST 700 Transmitter does not require any specific maintenance at regularly scheduled intervals.
However, it is recommended that you perform these typical inspection and maintenance routines on a
schedule that is dictated by the characteristics of the process medium and if blow-down facilities or
purge systems are being used.
•
Check piping for leaks.
•
Clear piping of sediment or other foreign matter.
•
Clean the Transmitter process heads, including the barrier diaphragms.

5.3 Inspecting and Cleaning Barrier Diaphragms

Depending on the characteristics of the process medium, sediment or other foreign particles may
collect in the process head cavity/chamber and cause faulty measurement. In addition, the barrier
diaphragm(s) in the Transmitter meter body may become coated with residue from the process
medium. The latter is also true for external diaphragms on flange-mount and remote seal type
Transmitters.
In many cases, you can readily remove the process head(s) from the Transmitter meter body to clean
the process head cavity and inspect the barrier diaphragm(s). For flange-mount and remote seal
diaphragms, you may only need to run a purge line in the tank to rinse off the face of the
diaphragm(s).
The following procedure comprises the general steps for inspecting and cleaning barrier diaphragms.
You may have to modify these steps to meet your particular process or transmitter model
requirements. Figure 19 shows an exploded view of a Differential Pressure (DP) Transmitter meter
body for reference. For disassembly/reassembly purposes, Gauge Pressure (GP) and Absolute
Pressure (AP) Transmitters are similar.
It is recommended that you remove the Transmitter from service and move it to a
clean area before disassembling it.
Revision 2.0

5 Maintenance

ST 700 Smart Pressure Transmitter User's Manual Page 33