Some steam traps drain their condensate to shared lines, meaning the behavior of one trap can affect others.
Consider the following example:
When the system is functioning properly, we see condensate traveling through the blue paths to the receiver tank.
When a trap fails, we'll see elevated temperatures near the outlet of the trap. Like this diagram:
In some cases, depending on the plumbing, pressures, and design of the steam system, one trap may be close enough to bias another, that would look like this:
In some cases, this bias only affects the measurement at the sensor, and can be ignored. In other cases, if the trap is designed to work at a specific pressure, such as a Thermostatic, Thermodynamic, Balanced Pressure, or Orifice trap, the change in pressure in the system could be causing an otherwise good trap to fail.
The best strategy to prevent this behavior is to install a check valve downstream from the steam trap.