DP Technology Overview_Shanghai Keyontechs Co., Ltd.

DP Technology Overview

Differential Pressure flow meter is the most widely used type of flow meter. Designed and manufactured according to ISO-5167.

Working Principle

Basic Principle: When a fluid flows through a throttling device, a pressure difference is created before and after the device. The pressure difference is mathematical related to the flow rate. The Differential Pressure signal is guided by the pressure tapping to the transmitter, where the volume flow or mass flow is calculated according to the Bernoulli equation.

Q _m：mass flow rate kg/s

C：discharge coefficient

β：diameter ratio d/D

ε：gas expansion coefficient

d：throttling device hole diameter at the throat m

∆p：differential pressure Pa

ρ：density kg/m3

Flow vs. Differential Pressure Curve

图片43.png

图片44.png

Differential Pressure Flow Meter Comparison

	Balanced Venturi	Orifice	Conditioning Orifice	Nozzle	Venturi	Wedge	Ring Wedge	Pitot Tube
Measurement Fluid	Gas Liquid Steam	Gas Liquid Steam	Gas Liquid Steam	Gas Liquid Steam	Gas Liquid Steam	Gas Liquid Steam	Gas Liquid Steam	Gas Liquid Steam
Diameter	15-3000mm	50-1000mm	25-1000mm	50-500mm	50-1200mm	50-600mm	25-600mm	25-5000mm
Pressure	-253~1000℃	-150~400℃	-150~400℃	-150~400℃	-150~400℃	-150~400℃	-150~400℃	-100~500℃
Temperature	≤24 MPa	≤24 MPa	≤24 MPa	≤24 MPa	≤24 MPa	≤24 MPa	≤24 MPa	≤24 MPa
Straight Run Requirement*	Before 2D After 2D	Before 44D After 8D	Before 2D After 2D	Before 46D After 8D	Before 16D After 4D	Before 7D After 6D	Before 5D After 3D	Before 7D After 3D
Accuracy	0.25%-0.5%	1%~2%	0.5%-1%	1%~2%	1%~2%	1%~2%	0.5%-1%	1%~2%
Long Term Stability	Good	Bad	Medium	Bad	Good	Bad	Good	Bad
Turndown Ratio	>10:1	3:1	5:1	3:1	5:1	3:1	10:1	10:1
Permanent Pressure Loss	10%~30% DP	60%~100% DP	30%-50% DP	60%~100% DP	10%~30% DP	50%~70% DP	50%~70% DP	<10% DP
Dirt Resistant	Good	Bad	Medium	Bad	Good	Medium	Good	Bad
Bi-direction Measurement	Yes	No	No	No	No	No	Yes	No
Measurement Range	Reynolds Number: 2x10^2~10^7	Reynolds Number: >5x10^3	Reynolds Number: >5x10^3	Reynolds Number: 2x10^4~10^7	Reynolds Number: 2x10^5~10^6	Reynolds Number: 2x10^4~10^6	Reynolds Number: >500	Reynolds Number: 2x10^4~10^5
High Speed Flow Measurement	Good	Bad	Bad	Good	Good	Bad	Good	Good
Low Speed Flow Measurement	Good	Bad	Bad	Bad	Bad	Bad	Good	Bad
Devise Size	Medium	Small	Medium	Medium	Large	Medium	Medium	Medium
Price	Medium	Low	Medium	Medium	High	Medium	Medium	Medium
Service Life	Long	Short	Medium	Medium	Long	Short	Long	Short

*Straight Run Requirement depends on β, the list value is based on the biggest β.