TABLE OF CONTENTS Mechanical systems
Process connections
Pneumatic and electronic systems
Grounding
Calibration systems
Programmable electronic systems
Valves
This chapter contains troubleshooting hints drawn from experience with typical problems. Though they are important to remember, they are not complete descriptions or explanations.
Mechanical systems have links and levers that can become loose, bent, or fall out of calibration. Check mechanical instruments for the following:
Make sure that all links and levers are straight and secure.
Make sure the doors on mechanical instruments are always closed tightly.
Keep all instruments away from vibrations, particularly switches, gauges, and mechanical instruments.
Watch out for damage caused by over-range transients (bent links or levers or overextended bellows).
Process connections and impulse lines are a major cause of field instrument problems. Here are some tips to bear in mind:
Small ports can become plugged up, even by apparently clean liquids.
Keep process tap purges running.
Arrange connections so that it can be easily determined whether they are plugged, and so that they can be easily rodded out or cleaned out.
Bubbles, improper fill, and temperature variations in the wet legs of transmitters can cause recurring problems.
Make sure that instrument manifolds are installed properly and do not get plugged up. They typically have small ports.
Transmitters too close to hot service will fail sooner rather than later.
Do not use mechanical snubbers on transmitter inputs. They will plug up.
Make sure that all tubing is properly supported and that piping is...
