Crystal nVision Lab Reference - Manual (Page 20)

Modules  18
nVision Operation Manual
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PRESSURE MODULE (PM) INSTRUCTIONS
Pressure Connection
Crystal CPF System: Medium Pressure Female (MPF) (1/4” medium pressure tube system with 7/16-20 threads). See our CPF Brochure for further information.
CPF o-ring size and material: AS568A-012, Viton 90 durometer (P/N 3981).
For most applications CPF Fittings can be hand tightened (no tools required). Wrench tightening is recommended (to achieve a metal to metal cone seal) for
applications where chemical compatibility of the process fluid and the o-ring are a concern. Cone seals require only moderate assembly torque to seal up to
10 000 PSI (700 bar). We recommend a tightening torque of 120 in-lbs ±20 in-lbs for our CPF fittings. Please note this is only a fraction of the typical torque
required to seal a 1/4” NPT fitting. If a torque wrench isn’t practical to use, the fittings can be assembled as follows: Hand tighten fitting fully
until the cone has bottomed out. Tighten an additional 20º using a wrench. Apply a small amount of media-compatible lubricant to the gland threads and
male cone to increase fitting life, reduce the likelihood of galling, and promote sealing.
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CAUTION: To achieve CPF maximum allowable working pressures no o-ring substitutions are allowed. See our CPF brochure and
CES-003 CPF Safety Guide available from the website at crystalengineering.net for further detail.
Measuring Vacuum
All versions of the nVision can be used to measure moderate vacuum.
When measuring pressure less than ambient barometric conditions, a minus (-) sign will appear.
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CAUTION: The nVision is not recommended for continuous use at high vacuum.
Water Density (Inches of Water)
The following applies only to models where inches of water is a selectable pressure unit. As shipped from the factory, the nVision is set to display inches of
water corresponding to the density of water at 4°C (39.2°F).
You may require a different water density for your application. CrystalControl allows the user to select the appropriate water density desired
at 4°C (39.2°F), 20°C (68°F), or 15.6°C (60°F) temperatures.
Overpressure Conditions
The nVision will read pressure up to approximately 110% of the rated pressure range. Above 110% of the range the display will start flashing and the readings
will not be reliable. The zero function does not affect when the display starts flashing to indicate overpressure, so depending on the zero value it is possible
that the display can start flashing without the maximum pressure being displayed.
For instance, if a 100 PSI nVision is zeroed when 30 PSI is being applied, it will indicate that the overpressure condition has been reached at 80 PSI (i.e., 110% x
100 PSI – 30 PSI = 80 PSI).
Overpressure can affect accuracy, but the effect is only temporary unless the sensor has been destroyed. See Pressure Module (PM) Specifications for maximum
allowable overpressure ratings.