Meriam 70H_72H High Pressure Wet Tap Accutubes with Integral 3-Valve Head and Optional RTD - Manual (Page 8)

8
The indicator must be placed far enough away from the Accutube to prevent thermal damage from line
heat. Allow 1 ft. of uninsulated instrument piping for every 100
° F of process temperature.
1.2.3.4 Slope the instrument lines to probe at an incline of approximately 1/2”
per foot to prevent air entrapment.
WARNING: DO NOT ATTEMPT TO FILL INSTRUMENT LINES
IF SYSTEM CONNECTING LINES ARE UNDER PRESSURE.
1.2.3.5 Fill the instrument lines with water before connecting the Accutube or
opening block valves.
1.2.3.6 Allow approximately 1/2 hour after system startup for condensate level
to stabilize. Stabilization time may be reduced by section 1.2.3.5
above.
1.2.3.7 Accutubes should not be used for steam applications when the
differential pressure is less than 10” water column.
1.2.4 GENERAL INTERCONNECTION REQUIREMENTS
1.2.4.1 Instrument lines to the Accutube shall be as large as possible in liquid
and steam applications. For Accutube with 1/2” NPT connections,
1/2” pipe or tubing is recommended. Accutubes with 1/8” NPT
connections should use 1/4” pipe or tubing.
1.2.4.2 Use of the optional instrument shutoff valves at the Accutube head are
recommended.
1.2.4.3 Use of a 3-valve manifold is recommended at the indicator to aid
system startup and to ease indicator maintenance and calibration.
1.2.4.4 Where instrument-piping slopes are required, use 1/2” per foot
minimum.
1.2.4.5 The length of the instrument lines does not affect accuracy. Long lines
can, however, dampen the indicator response time.
1.2.4.6 Test the system for leaks after connecting instrumentation to assure that
no leaks exist.
1.2.4.7 In situations where accumulation of sediment or condensation within
the piping is possible, a system drain or pressure blow down should be
performed on a regular basis. Valves are recommended for
indicators/transmitters without drain valves/plug.