Meriam Laminar Flow Elements (LFE)

Meriam Laminar Flow Elements (LFE) are ideal for measuring low gas flow rates from 0.2 SCCM to 2250 SCFM. They are inherently accurate and repeatable, and are traceable to NIST for calibration. With a turndown ratio of 20:1 or higher, they produce a nearly linear relationship between differential pressure and flow rate. This combination makes LFE an excellent choice for gas flow measurement.


Performance

Standard LFE calibration accuracy is ±0.72% of reading (not a percentage of full scale), traceable to the National Institute of Standards and Technology (NIST). The rugged construction and absence of moving parts ensure stable LFE calibration. Only physical damage or particle deposition within the element can cause calibration drift.

Standard Accuracy: ±0.72% to ±0.86% of reading

Repeatability: 0.1%

Response Time: 16 ms

Turndown Ratio: 20:1 using precise DP devices; higher turndown ratios achievable with precision DP equipment


Utility

LFE can be used to measure flow rates for a variety of gases and applications. Standard models measure air flow from as low as 0.2 SCCM (5.9 E-06 SCFM) up to 2250 SCFM under standard conditions. Custom models are available for air flows up to 15,000 SCFM. Stainless steel or aluminum materials make LFE compatible with most gases. Flow rates for gas mixtures can also be measured when the percentage of component gases and mixture properties are known.


Applications

LFE is suitable for most clean and non-condensing gas flow applications. They excel in critical gas flow measurement applications and serve as excellent calibration standards due to their inherent accuracy, stable calibration, excellent response time, and repeatability. LFE is used to calibrate turbine flow meters, variable area flow meters, flow regulators, mass flow meters, thermal anemometers, and more. Gas flow measurement for demanding flow control is a common application. Other applications include leak detection and quantification, design and testing of discrete components, automotive engine and emissions testing, and door/window leakage testing.


LFE Matrix

The LFE matrix can be constructed from individual stainless steel tubes or stainless steel foil windings. These tubes are sufficiently long relative to their inner diameter to ensure laminar flow within each tube. The result is a nearly linear relationship between differential pressure (DP) and flow rate. The DP generated in the matrix responds very quickly to flow changes. All DP represents a permanent system pressure loss, but LFE is sized to produce no more than 8 inches of water column under maximum flow conditions. The individual tube diameters are very small, so the flowing gas must be clean and dry to maintain calibration. Most LFE models are available with filtered inlet versions to keep the matrix clean and calibration constant.


Calibration and Analysis

Meriam LFE are calibrated with air under atmospheric conditions, referenced to 29.92 inches of mercury absolute (760 mm Hg absolute) and 70°F (21.1°C). Each completed element is calibrated and traceable to the National Institute of Standards and Technology. Meriam LFE provides repeatable flow curves expressed in SCFM versus inches of water differential pressure. Correction factors are included to cover inlet pressure ranges from 26 to 36 inches Hg absolute and inlet temperatures from 50°F to 150°F. For special flow applications, we request that you contact Meriam and provide complete flow information. The rated accuracy* of all Meriam LFE is a percentage of the actual reading; no other equipment offers a wider percentage of full-scale flow tolerance.

Available Accuracy Levels:

Commercial Calibration: ±0.72% of actual reading (±0.86% of reading for full-scale flows of 1000 SCFM or higher)

Master Calibration: ±0.64% of actual reading (±0.70% of reading for full-scale flows of 1000 SCFM or higher)

Independent Laboratory Calibration: ±0.50% of actual reading or better, please inquire