Measurement Specialties 9116 - Manual (Page 25)

Pressure Systems, Inc. Model 9116 User’s Manual
Page 16 www.PressureSystems.com
2.3.6.4 LEAK Mode Inputs
The purge/leak charge valve design includes a leak check feature capable of testing the
integrity of user pneumatic connections as well as those within the Model 9116 module. For the
leak mode to be used, all RUN mode pressure inputs must be dead ended (closed) by the user.
When the Model 9116 is commanded into the LEAK-CHARGE position, the CAL input port will
be pneumatically connected to module run side inputs. Common reference modules will
connect only the numbered run side inputs to CAL (RUN REF is not charged). True differential
(reference per port) modules will connect both the measurement input and reference port to
CAL. While in the LEAK-CHARGE position, a test pressure may be applied through the CAL
port which will charge the dead ended run side tubulation.
Note
Test pressures applied to the CAL port during the leak check
operation must not exceed the full scale pressure of any internal
transducers.
Once the lines are charged, the Model 9116 may be commanded back to the RUN position.
This will reattach the charged run side lines to their corresponding internal transducer.
Consecutive pressure readings from the Model 9116 will now allow user calculation of the line
leak rates. Once returned to the RUN position, lack of a pressure indicates a gross leak. A
slowly declining pressure indicates a slight leak. A leak is more difficult to detect as tubing
volume increases. In the case of true differential units where both sides of the sensor are
pressurized with the leak test pressure, an initial differential pressure of 0.0 psi should be
measured when the unit is placed in the RUN position. If the measurement or RUN side of the
channel leaks at a rate greater than the reference side, a resulting negative differential pressure
will be measured. Likewise, if the reference port tubing leaks at a rate greater than the
measurement side, a resulting positive differential pressure will be measured.
2.3.6.5
Supply Air
The Model 9116 modules require an 80 psig minimum dry air (or inert gas) supply which is used
to shift the internal calibration valve between its different positions. Each module contains a
fitting marked “SUPPLY” for this input. Internal solenoid valves direct this supply pressure to
the proper control port on the calibration valve as required by instrument commands. The
absence of sufficient supply air to the module will prevent the calibration valve from shifting into
requested positions (i.e., RUN, CAL, PURGE, LEAK-CHARGE).
WARNING! Supply air should not exceed 125 psi (875 kPa). Excessive pressure
may damage the internal solenoids.