Specifications

molbox™ RFM™ OPERATION AND MAINTENANCE MANUAL

To determine if a molbox RFM is equipped with the microrange option, check the model

number on the product label on the bottom of the molbox RFM case. If the model number

includes a “-M”, the microrange option is installed.

The microrange option is only active during molbloc-L operation. Mirorange has no effect

on molbloc-S operation or measurement specifications.

3.1.6 REFERENCE PRESSURE TRANSDUCER (RPT)

OVERPRESSURE

3.1.6.1 UPSTREAM AND DOWNSTREAM ABSOLUTE RPTS

Every molbox RFM has two absolute RPTs, one measures molbloc upstream

pressure, the other usually measures molbloc downstream pressure and may

provide a second measurement of molbloc upstream pressure in molbloc-S

operation. In normal operation, they are not used at pressures greater than 600

kPa absolute (87 psia).

Exposing the molbox RFM RPTs to pressures greater than the maximum

operating pressure may damage them. molbox RFM has a system of warnings

and alarms to protect itself from overpressure (see Section

3.6.3.1).

3.1.6.2 DIFFERENTIAL RPT, MICRORANGE OPTION

The microrange option low differential RPT has no overpressure warnings or

alarms in normal operation. It is, to the extent possible, protected from

overpressure automatically and transparently as it is put into and out of service

using the molbox RFM on-board valving.

In run calibration operation (see Section 5.2.4.1), the microrange RPT has an

OVERPRESSURE function whose operation is similar to the absolute RPT

overpressure function (see

Section 3.6.3). Overpressure occurs at about 13.7

kPa (2 psi) differential.

When an overpressure condition occurs

during run calibration of the microrange

transducer, the display of microrange

pressure indicates:

Microrange RPT:

OVERP! kPa [ENTER]

Be sure the pressure conditions that caused the overpressure to occur have

been cleared. Then press [ENTER] to reactivate the microrange RPT.

When using molbox RFM equipped with the microrange option, avoid very rapid

pressurization of one molbloc port. Attempt to open flow isolation valves

slowly. The microrange option low differential RPT is protected from

overpressure automatically by internal valving. However, dumping pressure very

rapidly on one port of the molbloc while the differential RPT is active could

cause a very sudden surge in differential pressure that can overpressure it.