Differential Pressure Flow Meters
ISO 5167 Primary-Element Series, DN15 to DN9000
Accuracy ±0.5 % of flow at factory wet-cal (DN1000+ dry-cal dimensional)
PN0.6 to PN42 MPa, −200 to +800 °C span
Transmitter-flexible · 1:3 to 1:10 turndown
- Six element types; orifice, venturi, nozzle, annubar, balance multi-hole, integral orifice
- Pairs with Rosemount 3051 / Yokogawa EJA / Honeywell ST3000 / Emerson 2051 / ABB 266 the buyer already owns
- One product line reaching DN6000+ bore, 42 MPa pressure, and 800 °C steam, past where velocity and mass meters stop
A differential-pressure (DP) primary element creates a pressure drop that scales with the square of volumetric flow, under ISO 5167 / GB/T 2624. A buyer-owned or factory-supplied DP transmitter reads the signal through impulse lines and a 3- or 5-valve manifold.
Across six element types the series spans DN15 to DN9000, PN0.6 to PN42 MPa, and −200 to +800 °C, at ±0.5 % of flow on factory wet-cal. The orifice covers the high-pressure end; the annubar reaches the largest bores.
Together they cover very-large-bore, high-pressure-steam, cryogenic, and ISO 5167 custody service that velocity and mass meters cannot reach.
Advantages of DP primary elements
Where a mechanical DP primary element is the right call over a velocity or mass meter.
- Widest service range of the common flow-meter principles The annubar element is the only practical meter for power-station main steam, cooling-water headers, and stack / duct combustion gas above DN6000. The orifice element reaches 42 MPa for hydrocarbon mains and wellhead service.
- ISO 5167 / GB/T 2624 governed geometry Beta ratio, tap geometry, and surface finish are built to the same standards that AGA-3 and API 14.3 custody practice references for natural-gas orifice metering. Each element ships with a factory wet-cal certificate listing DN, beta, accuracy code, and serial number.
- Transmitter-flexible; no proprietary handshake Industry-standard impulse-line tappings pair with the buyer’s existing Rosemount 3051, Yokogawa EJA, Honeywell ST3000, Emerson 2051, ABB 266, or equivalent 4-20 mA / HART DP transmitter. The integral orifice element pre-mates a transmitter at the factory with a 3-valve manifold.
- Mechanical primary; no in-pipe electronics to fail at 800 °C The primary element is passive metal; orifice plate, venturi cone, nozzle profile, annubar probe, or balance disc. Electronics live remote on the DP transmitter, isolated from the process by impulse lines and seal pots. No Ex cert is required on the primary itself.
- Selectable head-loss profile Orifice (50–70 % unrecoverable head), nozzle (30–40 %), venturi (10–15 %), and annubar / balance (low, by hole geometry). Head-sensitive service goes to venturi or annubar; lowest-cost custody goes to orifice.
- 5–7 business day lead time, factory direct All six elements ship in this window. Wet-flow calibration on the factory loop is standard; very-large-bore builds (DN1000+) ship with a dry-cal certificate and dimensional records per ISO 5167.
DP primary-element types
Six element types cover the series. Each card targets a distinct service; pick the closest match and the configurator inside each element returns the build code.
Orifice Plate Flow Meter
The broadest-bore, lowest-cost primary in the series. Clean liquid, gas, steam, and natural-gas custody. Corner / D-D/2 / flange taps per ISO 5167-2. The default pick for ISO 5167 / GB/T 2624 service.
View configuration →Venturi Flow Meter
Classical convergent-divergent profile that recovers 85–90 % of the pressure drop. Pick this for low-head pump circuits, large cooling-water headers, and any service where orifice head loss would force a bigger pump.
View configuration →Flow Nozzle Flow Meter
Long-radius nozzle profile resists high-velocity steam erosion better than a thin-plate orifice. Pick for superheated-steam headers, wet-steam-adjacent service, and lines with mild particulate carry-over where orifice life is short.
View configuration →Averaging Pitot Tube Flow Meter
Insertion probe with multiple sensing ports averages the velocity profile across the bore. Hot-tap installable on live lines, scales to DN9000 stack and main-steam service, and adds only minimal permanent pressure loss.
View configuration →Multi-Hole Orifice Plate Flow Meter
Balanced multi-hole disc conditions the upstream flow profile and reduces straight-pipe demand. Quieter than single-bore orifice on gas service, with lower acoustic emission and shorter pipe-run footprint on retrofit projects.
View configuration →Integral Orifice Flow Meter
Factory-built package; small-bore orifice carrier, 3-valve manifold, and DP transmitter assembled and zero/span calibrated at the loop. Ships ready to wire, ideal for small-bore utility lines and OEM skids with tight footprint.
View configuration →When to specify a DP primary element
Match your service against the table below. Out-of-range cases go to vortex, ultrasonic, turbine, Coriolis, or rotameter.
| Service | DP series pick | Alternative |
|---|---|---|
| Very-large-bore process (DN1000 to DN9000) | Orifice (to DN6000) or Annubar (to DN9000) | No velocity or mass meter at reasonable cost |
| High-pressure steam, hydrocarbon main, wellhead (above 16 MPa) | Orifice plate up to 42 MPa | Coriolis ZLMFM up to 41 MPa at smaller DN |
| High-temperature steam, hot flue gas, refinery hot oil (above 350 °C) | Orifice or Nozzle (passive metal primary) | Vortex LUGB only up to 350 °C |
| Cryogenic LNG / LH2 / LOX / LN2 (down to −200 °C) | Orifice or Venturi (mechanical primary) | Coriolis ZLMFM for direct mass |
| Natural-gas custody and allocation metering | Orifice with ISO 5167 / GB/T 2624 wet-cal | Ultrasonic for non-invasive custody |
| Head-sensitive low-head pump or cooling-water circuit | Venturi (10–15 % loss) or Annubar (low loss) | Ultrasonic clamp-on (zero ΔP) |
| Buyer already owns Rosemount / Yokogawa / Honeywell / Emerson / ABB DP transmitter | Any element; transmitter-flexible | — |
| Small-bore utility line on OEM skid, tight footprint | Integral Orifice (factory-mated package) | Coriolis ZLMFM small-bore |
| Retrofit project with limited upstream straight pipe | Multi-Hole Orifice (shorter pipe demand) | Vortex LUGB or Ultrasonic clamp-on |
| Slurry / particulate / abrasive flow | Outside the operating range (taps plug) | Electromagnetic LEA for conductive slurry |
| Wet gas, saturated steam carry-over, 2-phase | Outside the operating range (signal biased) | Coriolis ZLMFM (mass-direct, 2-phase tolerant) |
| Pulsating compressor / reciprocating pump outlet | Outside the operating range (no accumulator) | Coriolis or PD turbine |
| Very-low-flow service below ΔP noise floor | Outside the operating range | Liquid Turbine LWGY or Rotameter LZD |
| High turndown above 1:10 | Outside the operating range | Coriolis (1:200) or Vortex LUGB (1:70) |
Installation rules
These five rules apply across all six DP elements; each element page gives its specific tap arrangement.
- Follow the straight-pipe table per ISO 5167 Single 90° elbow needs 22D upstream at β = 0.5 and 44D at β = 0.75; two elbows out of plane need 50D upstream; control valve needs 30D or a flow conditioner. Downstream is 5D across all disturbances. These numbers are stricter than any velocity or mass meter and are not negotiable; the wet-cal cannot correct profile bias.
- Orient horizontal for liquid + gas, slope impulse lines for steam Horizontal is preferred for clean liquid and gas. For steam and condensable gas, mount horizontally with impulse lines sloped downward 1:10 toward the transmitter so condensate drains. For low-pressure gas, slope impulse lines upward toward the primary so condensate drops back into the line.
- Plumb impulse tubing with isolation and equalising valves Run 8–12 mm OD stainless impulse tubing total length under 5 m to minimize lag. Fit isolation valves at the primary plus an equalising valve at the transmitter; standard practice uses a 3-valve or 5-valve manifold. The 5-valve manifold adds bleed valves for hot-tap zeroing on live service.
- Pair with a transmitter the buyer trusts Industry-standard impulse-line tappings accept any 4-20 mA / HART DP transmitter on the buyer’s approved-vendor list: Rosemount 3051, Yokogawa EJA, Honeywell ST3000, Emerson 2051, ABB 266, or equivalent. The integral orifice element ships pre-mated. For the other five elements the buyer mounts the transmitter within 3 m on a 2″ pipe stand or wall bracket.
- Zero-cal at commissioning under static pressure Pressurise the line through both impulse legs with the equalising valve open. With flow stopped and the primary balanced, zero the DP transmitter and record the baseline offset. Open both isolation valves, close the equaliser, and confirm the loop reads live ΔP before opening flow.
Frequently asked questions
- Orifice plate (DN15–DN6000): lowest cost, broadest bore, loses 50–70 % of the signal as unrecoverable head. For clean liquid, gas, and steam where head is available and ISO 5167 / GB/T 2624 custody matters.
- Venturi: keeps only 10–15 % loss. For low-head pump circuits and large cooling-water headers where orifice loss would force a bigger pump.
- Flow nozzle: 30–40 % loss, but resists erosion better than a thin-plate orifice. For high-velocity steam and lines with mild particulate carry-over.
- single 90° elbow at β = 0.5: 22D upstream, 5D downstream;
- two elbows out of plane: 50D upstream;
- control valve: 30D, or a flow conditioner.
- Slurry or particulate flow plugs impulse lines and taps within hours: use electromagnetic for conductive slurry, or ultrasonic clamp-on for non-invasive readout.
- Wet gas and saturated steam carry liquid into the impulse lines and bias the square-root extraction: use Coriolis for mass-direct 2-phase service.
- Pulsating flow from a PD pump or reciprocating compressor amplifies square-root error: use Coriolis, or add an upstream accumulator and accept a turndown penalty.
Need help sizing a DP primary element?
Send pipe DN, design P/T, fluid composition, min/normal/max flow, and head budget. Reply in 1 day; lead time 5–7 business days.