PMT-IFWyatt Lo-Loss® Flow
Tubes Insert-Type Fabricated Primary Elements


  • Lowest Pressure Loss
  • Light Weight
  • Low Cost of Ownership
  • Custom Designed
  • Short Laying Length
  • Best Documented Flow Tube on the Market


The Wyatt Lo-Loss® PMT-IF is a fabricated insert venturi flow element that offers repeatability and accuracy over a wide range of flow rates and has lower permanent pressure loss than orifice plates, flow nozzles, and any other venturi or flow tube on the market. The PMT-IF can be manufactured from virtually any material. It is designed for insertion within the interior of a pipeline and is secured by the adjacent pipe flanges. This unique design is characterized by longevity of service and flexibility in install-ation and application.


The fabricated insert PMT-IF is designed to measure the flow of gases and liquids with low solids content. It can operate over extreme temperature and/or pressure ranges, and with highly corrosive fluids or gases. The Lo-Loss® fabricated insert has the distinct advantages of minimal weight, cost, and laying length. Typical applications include potable water, cooling water, process fluids, steam, air flow for aeration, and gas flow for combustion applications.

Flow Measurement Accuracy

For pipe Reynolds numbers greater than 100 000 and a normal-ized piping configuration, the Wyatt PMT-IF Lo-Loss® meter provides a flow measurement accuracy of ± 0.25% with indepen-dent flow calibration and ± 1.00% without flow calibration.

Lo-Loss® is a registered trademark of Wyatt Engineering.

PMT-IF Technical Specifications

Headloss Comparison


For pipe Reynolds numbers greater than 100 000 and a normalized piping configuration, the Wyatt Lo-Loss® Meter provides a flow measurement uncertainty of:

± 1.00% for standard meters and
± 0.25% for flow calibrated meters.

Pressure Loss

As shown in Figure 1, the permanent pressure loss of the PMT-IF, expressed as a percentage of differential pressure, is significantly lower than that of short-form and long-form venturis as well.

Beta Ratio

Wyatt Engineering can furnish PMT Lo-Loss® fabricated insert meters in a wide range of diameter ratios (d/D). This provides users with accurate flow measurement over a broad range of flow rates for a given line size.

Temperature Range

The fabricated series of the PMT-IF can operate over the fluid temperature range of -325 °F to +1200 °F (-200 °C to +650 °C).

Pressure Range/Flange Connections

The allowable operating pressure for the PMT-IF is limited only to that of the adjacent pipe flanges. Pressures of 4000 PSIG to 6000 PSIG (27 500 kPaG to 41 350 kPaG) are not uncommon.

Piping Requirements

Designed for full-pipe flow, the PMT-IF can be mounted horizontally or vertically. For recommended upstream piping, refer to Wyatt Engineering Technical Manual for the Lo-Loss® meter.

Energy Considerations

Figure 1 compares the permanent pressure loss of the insert Lo-Loss® design with that of other primary flow elements. Figure 2 illustrates the reduced pumping costs that are realized when using a Lo-Loss® Meter in a typi-cal example. The pressure recovery of the Wyatt Lo-Loss® Meter means reduced pumping costs. High beta ratio Lo-Loss® Meters will recover up to 97.5% of the differential pressure produced. This is two to four times better than typical classical venturi devices, as well as most modified venturi meters.

Using venturi tubes instead of orifice plates can yield significant savings and using the Lo-Loss® meter instead of venturi tubes can realize further savings. For over 40 years, engineers have given their clients the benefits of efficiency and accuracy by doing just that.

PMT-IF Available Options

12” (300mm) Water Line
Flow Rate: 7.5 CFS (212.4 LPS)
∆P = 100” (2540mm) H2 O
Line Temperature: 68°F (20°C)
Pump Efficiency: 100%
Energy Costs: US$0.07/kWh

Annual Pumping Cost Savings

Comparison of Differential Producers

Lo-Loss ® vs. Orifice Plate $1704
Lo-Loss ® vs. Flow Nozzle $1544
Lo-Loss ® vs. Short-Form Venturi $327
Lo-Loss ® vs. Long-Form Venturi $52

Materials of Construction

ConstructionThe nature of the PMT-IF fabricated design allows the flow element to be constructed from practically any material. Examples of some of the alloys employed:

  • Carbon Steel
  • 304 Stainless Steel
  • 316 Stainless Steel
  • Inconel
  • Hastelloy B & C
  • Monel
  • Titanium
  • Chrome Molybdenum
  • Nickel
  • Tantalum
  • Zirconium

Consult your local representative or Wyatt Engineering for information on other materials of construction.