Pressure calibrator molbloc-S®

temperaturegas flowfor flow meters

Product overview
molbloc-S® is a high-precision sonic nozzle calibration device for use with molbox1+ Flow Terminals and molbox RFM Flow Monitors. Mass flow through the molbloc-S is proportional to upstream absolute pressure and independent of downstream pressure when critical (sonic) flow is established. Maintaining a sufficiently low back pressure ratio (BPR) is required for valid sonic-flow measurements.

Features at a glance

• Covers flow ranges up to 5,000 slm in N2 and air.
• Extends the operating range of molbloc/molbox™ calibration systems with high accuracy at medium and high flows.
• Compatible with molbox1+, existing molbox1 terminals and COMPASS software.
• Critical-flow venturi (sonic) nozzle principle validated by gravimetric calibration.
• Low sensitivity to contamination.
• Measurement uncertainty: ±0.125% of reading with molbox1+; ±0.2% with molbox1.
• Calibrations available for air, N2, Ar, He and many specialty gases; humid-air density compensation supported.
• Excellent rangeability (10:1 turndown) with molbox1+S or molbox models with vacuum capability.
• Redundant absolute upstream pressure measurement to reduce uncertainty and improve reliability.
• Integral gas temperature conditioning and measurement; continuous real-time reading; can be fully automated.

molbloc-S ranges
The molbloc-S flow ranges are defined by the pressure-to-flow conversion ratio K_F (sccm/kPa), relating mass flow to upstream absolute pressure. Calibrations are performed over upstream pressure ranges depending on type: LP 20–200 kPa (3–30 psia), SP 50–500 kPa (7–70 psia) or HP 200 kPa–2 MPa (30–300 psia). To maintain critical flow the downstream pressure must be low enough that the Back Pressure Ratio (BPR = downstream absolute pressure / upstream absolute pressure) stays below an allowable upper limit, which depends on Reynolds number. Using a downstream vacuum pump can extend the usable flow range by lowering downstream pressure.

Specifications – Standard molbloc-S Calibrations – Used with molbox1+ and molbox2 terminals
Normal operating temperature: 15 to 35 °C
Storage temperature: -25 to 35 °C
Normal upstream operating pressure ranges: 20–200 kPa abs (LP) or 50–500 kPa abs (SP); HP: 200 kPa–2 MPa abs (usable with molbox1+S only).
Overall flow range: <1 to 5 000 slm
Inlet connections (by model): 1/4 in. VCR™, 1/2 in. VCR™, 1 in. VCR™ or 1 in. NPT (models 1E1-S … 1E4-S etc.).
Outlet connections (by model): ISO‑KF style vacuum flanges (16 mm, 40 mm) depending on model.
Supported gases: Dry air, N2, Ar, He and many specialty gases (see full specifications).

Flow Measurement (summary)
Range: Dependent on molbloc size and pressure calibration range.
Required Back Pressure Ratio: 0.4 to 0.9 depending on Reynolds number.
Calibration gases: Standard — Dry air. Options: N2, Ar, H2, He, N2O (availability varies). Dry air calibration required for humid-air operation.
Pressure calibration ranges: LP 20–200 kPa abs; SP 50–500 kPa abs; HP 200 kPa–2 MPa abs (HP with molbox1+S only). Flow specifications valid from 10% to 100% of molbloc full scale.
Resolution: ±0.0015% of FS
Precision: ±0.06% of reading
Predicted one-year stability: ±0.05% of reading
Measurement uncertainty: ±0.2% of reading (Premium: ±0.125% with molbox1+).

Included with each molbloc-S

• molbloc-S flow element
• Shipping and storage case
• Soft, reusable VCR O-rings for upstream connection; ISO‑KF centering ring, clamp and overpressure ring for downstream connection; mounting instructions
• Standard uncertainty calibration at SP with air and accredited calibration report

Technical specifications

• Brand: Fluke
• Commercial name (series): molbloc-S®
• Example models / available K_F values: 1E1-S (KF 10), 2E1-S (KF 20), 5E1-S (KF 50), 1E2-S (KF 100), 2E2-S (KF 200), 5E2-S (KF 500), 1E3-S (KF 1000), 2E3-S (KF 2000), 5E3-S (KF 5000), 1E4-S (KF 10000)
• Overall flow capability: <1 to 5 000 slm
• Operating temperature: 15 to 35 °C; storage: -25 to 35 °C
• Pressure calibration types: LP (20–200 kPa), SP (50–500 kPa), HP (200 kPa–2 MPa) — HP with molbox1+S only
• Measurement uncertainty (typical): ±0.2% of reading (standard); ±0.125% (premium, with molbox1+)
• Resolution / precision: ±0.0015% FS resolution; ±0.06% precision
• Interfaces: VCR or NPT inlet options by model; ISO‑KF vacuum flange downstream options
• Supported gases: Air, N2, Ar, He and many specialty gases
• Compatibility: Designed for use with molbox1+, molbox1 terminals (v4.0+), molbox2 terminals and molbox RFM monitors; compatible with COMPASS software