Rosemount 3095, Product Manual

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Level Controller Overview and Installation
TAP CONSIDERATIONS When the Level Controller is oriented on its side, the Coplanar
™
flange
may be mounted to ensure proper venting or draining. Mount the flange
so that the drain/vent connections are on the top half of the flange for
liquid service.
CAUTION
In elevated temperature services, it is important that temperatures at
the Coplanar process flanges not exceed 250 °F (121 °C).
Impulse Piping The piping between the process and the controller must accurately
transfer the pressure in order to obtain accurate control. In this
pressure transfer, there are five possible sources of error: leaks, friction
loss (particularly if purging is used), trapped gas in a liquid line, and
temperature-induced or other density variation between the legs.
The best location for the Level Controller in relation to the process pipe
depends on the process itself. Consider the following guidelines in
determining controller location and placement of impulse piping:
• Keep impulse piping as short as possible.
• Slope the impulse piping at least one inch per foot (8 centimeters
per meter) upward from the controller toward the process
connection for liquid.
• Avoid high points in liquid lines.
• Make sure both impulse legs are the same temperature.
• Use impulse piping large enough to avoid friction effects and
prevent blockage.
• Vent all gas from liquid piping legs.
• Avoid purging through the controller.
• Keep corrosive or hot (above 250 °F (121 °C)) process material out
of direct contact with the sensor module and flanges.
• Prevent sediment deposits in the impulse piping.
• Avoid conditions that might allow process fluid to freeze within
the process flange.
Diaphragm Seals Because instrument response time is directly proportional to capillary
length, and the fill fluid volume in the capillary changes with
temperature to affect the output, care must be taken to optimize
performance:
• Keep the capillary length as short as possible.
• Mount a controller with one seal at the same level, or below the
seal and process connection. Use direct mount when possible.
• In vacuum applications, mount the controller below the lower tap
to ensure proper operation. This requirement applies to both one-
and two-seal systems.
• Avoid mounting seals and capillaries in direct sunlight.
• Keep the capillary lengths equal when two seals are involved.
• Rezero the controller on a seasonal basis.
• Never attempt to disconnect the seals or capillaries. Doing so will
void the warranty.