Many factors are involved in selecting a probe for continuous level transmitters and multiple point controllers.There are electrical, chemical, and mechanical aspects to be considered.
Electrically, a ground reference (such as the vessel wall) must be present and the probe must be built to provide proper response.
Chemically, the probe must be compatible with the process material.It must be immune to attack and must offer no chance of contaminating the process.
Mechanically, the probe must be able to withstand the pressure and temperature extremes of the application.In addition, turbulence, consistency, viscosity, abrasion and mounting configuration may also play a role in probe selection.A flexible probe is required where probe lengths exceed 236 inches or where physical restrictions (i.e., lack of headroom) prevents installation of a rigid probe.
Even though all of these factors may demand consideration when selecting a probe, most applications are easily defined and the proper probe can be quickly selected.
Probe Selection Guide
Listed at right and below are the nine most common types of application and the probe recommended for each.Please refer to the following pages for a complete description of each system.
Conductive Liquids ~ 100 Micromhos/cm or Higher (water-based liquids)
System
Vessel
Consistency1
Sensor
Model No.
Wetted Surfaces2
I
Metal
Any
Rigid
L101
316 SS & Kynar™ or Teflon™
II
Metal
Any
Flexible
L109
316 SS & Kynar or Teflon
III3
Non-Metal
High
Rigid
L127
316 SS & Kynar or Teflon
IV3
Non-Metal
Low
Flexible
L113
316 SS & Kynar or Teflon
V3
Non-Metal
High
Flexible
L115
316 SS & Kynar or Teflon
Non-Conductive Liquids ~ 5 Micromhos/cm or less (hydrocarbons, solvents, etc.)
System
Vessel
Consistency1
Sensor
Model No.
Wetted Surfaces2
VI
Any
Low
Rigid
L107
316 SS & Kynar™ or Teflon™
VII
Any
Medium
Rigid
L102
316 SS & Kynar or Teflon
VIII
Any
High
Rigid
L127
316 SS & Kynar or Teflon
IX
Any
Any
Flexible
L115
316 SS & Kynar or Teflon
NOTES:
1.Consistency: The tendency for a liquid to coat or cling to the probe.
2.If 316 SS is not compatible, use a probe with appropriate covering on all wetted surfaces.
3.If customer can supply metal ground rod to a level at or below bottom of probe, then System Ior II applies.
Materials of Construction
NPT vessel connections are 316 Stainless Steel.Special alloys can be provided.
Seals are Teflon.
Ground elements on Systems III through IX are Stainless Steel.
Flanges are Carbon Steel (standard), Type 316 or 304 Stainless Steel (optional).