Flow Measurement · Glossary

What is Straight Pipe Run?

multiples of pipe diameter (D)Flow Measurement

Straight pipe run is the length of unobstructed pipe needed before and after a flow meter for an accurate reading.

Straight Pipe Run Explained

Bends, valves, reducers and pumps distort the velocity profile and create swirl. Straight pipe lets the profile recover before the meter.

Requirements are given in pipe diameters. They depend on the meter type, the upstream fitting and, for DP elements, the beta ratio. Flow conditioners can shorten them.

Straight Pipe Run: Typical Values

Orifice, single 90° bend (ISO 5167-2)	about 6 D at β 0.2 up to 44 D at β 0.75
Magnetic meter (typical maker data)	about 5 D upstream, 2 D downstream
Coriolis	usually none required

Calculators for Straight Pipe Run

CalculatorStraight Pipe Run CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Straight Pipe Run?

Straight pipe run is the length of unobstructed pipe needed before and after a flow meter for an accurate reading.

What if there is not enough straight pipe?

Use a flow conditioner, choose a meter less sensitive to profile such as a coriolis or cone meter, or accept and state a higher uncertainty.

Is downstream straight pipe needed?

Yes, but less. A valve or fitting just after the meter can still affect it.

Learn more on the blog

What factors affect the stability of flow meter readings?

A practical guide on instrumentationblog.in with more detail on straight pipe run and how it is applied on real plants.

Read Full Article

More Flow Measurement Terms

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