ST51/ST51A Mass Flow Meters

Mass Flow Meter Summary

The Model ST51 and ST51A are a compact, low cost solution for accurate, repeatable flow measurement of biogas, digester gas, landfill gas, methane and natural gas as well as air, compressed air or nitrogen. This insertion-style flow meter has no moving parts and is available in probe lengths for installation into pipe diameters from 2.5 inches to 24 inches [63 mm to 610 mm]. It is easily connected into the pipe via a 1/2 inch or 3/4 inch NPT compression fitting. ST51 uses constant power thermal dispersion drive technology, with a slightly heated sensor, which uniquely provides a subtle drying effect on the sensors that results in effective measurement in moist gas applications.
 
The ST51 Series electronics are housed in rugged, IP67 rated enclosure with dual conduit ports in either NPT or M20 threading. The instrument comes standard with dual 4-20 mA outputs and a 500 Hz pulse output. The model ST51A includes HART as well as a higher process temperature service range, NAMUR compliant 4-20 mA outputs and SIL compliance rating. The transmitter/electronics can be integrally mounted with the flow element (probe) or be remote mounted to best match your installation situation. The complete instrument carries global Ex agency approvals for Division l/Zone 1 installations.
 
The ST51 flow sensing element features precision, platinum RTD in small diameter, "equal-mass," all-metal thermowells to provide superior accuracy, repeatability and fast response.

Applications

  • Landfill gas recovery (LMG)
  • Wastewater treatment plant digester
  • Coal mine methane recovery
  • Air/compressed air with totalized flow
  • Livestock and dairy farm on-farm biogas recovery
  • Biogas: biomass fermentation and recovery
  • Biomass gasification

Specifications

Media Compatibility:
  • Biogas
  • Digester Gas
  • Methane
  • Methane Composition Gases
  • Natural Gas
  • Air
  • Compressed Air
  • Nitrogen
  ST51 ST51A
Dual 4-20 mA outputs
4-20 mA per NAMUR NE43   
HART I/O  
500 Hz pulse output
Process operating temperature To 250°F [to 121°C] To 350°F [to 177°C]
Maximum remote distance 50' [15 m] 100' [30 m]
SIL compliance rating  
WarrantyStandard 1 year 2 years
  • Agency Approvals:
 
FM, FMc: Class I, Division 1, Groups B, C, D; T4 Ta = 60°C
Class II/III, Division 1, Groups E, F, G; T4 Ta = 60°C; Type 4X/ IP66
Class I, Division 2, Groups A, B, C, D; T4 Ta = 60°C
ATEX, IECEx: Zone 1, Zone 21
II 2 G Ex db IIC T6...T1 Gb
II 2 D Ex tb IIIC T85°C... T300°C Db; IP66/IP67
Ta = -40°C to +65°C
Other: EAC (TRCU) Russia, CE Marking, CRN
SIL (ST51A): SIL 1 compliant; Safe Failure Fraction (SFF) 78.5% to 81.1%
Pipe/Line Size Compatibility: 2" to 24" [51 mm to 610 mm]

Flow Rate: 0.3 SFPS to 400 SFPS [0,08 MPS to 122 MPS]

Accuracy: (at calibrated conditions) 
  • Standard: ± 2% reading, ± 0.5% full scale 
  • Optional:  ± 1% reading, ± 0.5% full scale

Temperature Coefficient: (at calibrated conditions) 
With optional extended temperature compensation; valid from 10% to 100% of full-scale calibration
  • Flow: Maximum ± 0.015% of reading/ºF up to 350ºF [±0.03% of reading/ºC up to 177ºC]

Repeatability: ± 0.5% reading

Temperature Compensation: 
  • Standard: 40°F to 100°F [4°C to 38°C];
  • Optional:  0°F to 350°F [-18°C to 177°C]

Turndown Ratio: 3:1 to 100:1

Warranty: 
ST51: 1 year
ST51A: 2 years


Flow Element

Installation: Insertion

Type: Thermal dispersion

Material of Construction: 316 stainless steel body with Hastelloy-C thermowell sensors, 316 stainless steel compression fitting with teflon or stainless steel ferrule.

Pressure (Maximum Operating without Damage): 
  • Stainless steel ferrule: 500 psig [34 bar(g)]
  • Teflon ferrule: 150 psig [10 bar(g)]

Operating Temperature: 
  • Stainless steel ferrule

    ST51: 0°F to 250°F [-18°C to 121°C] 
    ST51A: 0°F to 350°F [-18°C to 177°C] 

  • Teflon ferrule: 0°F to 200°F [-18°C to 93°C]

Process Connection: 1/2" MNPT or 3/4" MNPT with stainless steel or Teflon ferrule

Insertion Length (Field Adjustable):
  • 1" to 6" [25 mm to 152 mm]
  • 1" to 12[25 mm to 305 mm]
  • 1" to 18[25 mm to 457 mm]


Flow Transmitter

Enclosure: 
Rating: NEMA 4X, IP67
Material:
Standard – aluminum, polyester powder coated
Optional – 316 stainless steel
Conduit/Cable Port: Dual 1/2″ NPT or M20x1.5

Operating Temperature: 0°F to 140°F [-18°C to 60°C]

Input Power: 
DC: 18 Vdc to 36 Vdc (6 watts max.)
AC: 85 Vac to 265 Vac (12 watts max.; CE Marking approval from 100 Vac to 240 Vac)

Analog Output Signals: Dual 4-20 mA, user assignable to flow rate and/or temperature and a 0-500 Hz pulse output for total flow; ST51A output #1 has fault indication per NAMUR NE43 guidelines, user selectable for high (> 21.0 mA) or low (< 3.6 mA)

Bus Communications (ST51A): HART (version 7); FieldComm Group certified; available over output #1; DD file included

Communication Port: RS-232C

Digital Display (Optional): Two-line x 16 character LCD; displays measured value and engineering units; top line assigned to flow rate, second line user assignable to temperature reading, as flow totalizer or alternating; display can be rotated in 90° increments for optimum viewing orientation

Installation and Mounting: Integral with sensor element or remote mountable
up to 50′ [15 m] with Model ST51, and up to 100′ [30 m] with Model ST51A
 

Certification/Approvals

ATEXBelGIMCEFMcEACIEC/IECEx
 
  • ATEX
  • BelGIM (Products)
  • BelGIM (Pattern)
  • CE
  • FMc
  • FM
  • HART
  • EAC/TR CU
  • IECEx