Annubar Flow Meter Rods: Averaging Multi-Port Differential Pressure Inset Arrays

Quick Answer: An Annubar flow meter rod is an insertion differential pressure flow element with multiple sensing ports across the pipe diameter. It averages velocity pressure to deliver a stable DP signal on gas, steam, and liquid lines from DN50 to DN3000. Silver Automation Instruments supplies complete Annubar rod packages with DP transmitters, manifolds, sizing sheets, and local indicators.

This insertion DP flow meter is sometimes called an averaging pitot tube. The compact multi-port inset array suits existing pipes without cutting the line. A single point probe reads only one velocity point. A multi-port rod places four or more upstream sensing holes and one downstream reference hole inside the pipe. The internal chamber averages the high pressure signals. The transmitter then measures a steady differential pressure.

In practice, most engineers skip the long theory. They ask about pressure loss and installed cost. A customer in Vietnam replaced a 12 inch steam line orifice plate with an Annubar rod. The line ran at 9 bar and 190 degrees Celsius. The old orifice caused 0.3 to 0.5 bar permanent loss. The Annubar rod cut that to below 0.05 bar. The compressor load dropped enough to recover the cost in under seven months.

Why a Multi-Port Averaging DP Rod Works in Real Plants

Process lines are rarely straight for 30 diameters. An averaging rod handles disturbed flow profiles because it samples multiple points, not one. The upstream ports are spaced along the pipe radius or diameter. The downstream port sees the low pressure wake. The differential pressure is proportional to the square of flow rate. A 0 to 12 kPa span covers a 10 inch natural gas line at 20 bar in many applications. The same rod style works on a 4 inch steam header at 8 bar or a 24 inch cooling water line at 6 bar.

We have seen this on customer sites many times. A desalination plant in Oman uses a DN400 Annubar rod on the reject brine line because the pressure drop budget was tight. A palm oil refinery in Indonesia has three rods on steam lines from 6 to 14 bar. A paint manufacturer in Thailand installed one on a DN150 solvent line after a pump discharge with only 8D upstream. All systems report stable signals once the DP range is set correctly.

Common Annubar Configurations Silver Instruments Quotes

We keep three typical model ranges. SIL-AP200 suits clean water, compressed air, and low pressure nitrogen. The rod is 316L stainless steel. The DP transmitter has 0.075 percent of span accuracy and a 4-20 mA HART output. The working temperature is -40 to 250 degrees Celsius. SIL-AP450 covers saturated and superheated steam up to 400 degrees Celsius and 25 bar. It uses a 316L or alloy 600 rod with remote seals and a 3 valve manifold. SIL-AP650 handles wet gas, biogas, and mild chemical service. It uses Hastelloy C276 wetted parts and a PTFE coated rod. The transmitter body can be remote mounted.

These are not floating numbers. We match the rod size, DP span, and material to your actual flow range. Total system accuracy after calibration is usually 1.0 to 1.5 percent of rate. Repeatability is 0.1 percent. That is enough for steam allocation, gas distribution monitoring, compressed air audits, and process balance calculations.

What You Need to Send for a Firm Quote

Send us your fluid type, pipe size in DN, pipe schedule or wall thickness, operating pressure in bar, temperature in degrees Celsius, and normal or maximum flow rate in kg/h or m3/h. Also state whether you need a flanged connection, hot tap, or compression fitting. We return a complete data sheet with rod length, DP range, material, transmitter model, and pricing within one working day.

Call Silver Automation Instruments at +86-25-68650347. WhatsApp is +86-25-52155837. WeChat is +86 15365082610. You can also find product data at flow-meter.com.au. Tell us the pipe size, pressure, temperature, and flow range. We will quote an Annubar rod package that matches your line.

Annubar DP Flow Meter FAQ

Question: What pipe sizes does an Annubar flow meter rod fit?

Answer: Standard products cover DN50 to DN3000. Large ducts and stacks can use custom rod lengths. Provide the pipe inner diameter and schedule. We machine the rod to fit your measurement point.

Question: Can I install an Annubar rod in a short straight pipe run?

Answer: Yes. The multi-port averaging design handles disturbed flow profiles better than an orifice plate. We still recommend 10D upstream and 5D downstream for best accuracy. If your run is shorter, send the piping layout and we will adjust the sizing.

Question: Which fluids work with a multi-port DP rod?

Answer: Clean water, steam, natural gas, compressed air, nitrogen, process gas, and light hydrocarbons work well. Dirty fluids with high solids can clog the sensing ports. In that case we may suggest a purge system or a different flow technology such as electromagnetic or oval gear meters.

Question: How much permanent pressure loss will my system see?

Answer: Usually 0.01 to 0.05 bar depending on the flow rate and pipe size. An orifice plate on the same line often causes 0.2 to 0.5 bar permanent loss. That difference matters on compressor discharge and pump discharge lines.

Question: Do you supply the DP transmitter and installation accessories?

Answer: Yes. Silver Automation Instruments supplies the Annubar rod, DP transmitter, three valve manifold, fittings, flange, and local indicator as one package. We can also add a paperless recorder for pressure and flow logging.

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