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Type：CX-PTM pitot tube meter
Illustrate：The Pitot tube meter is based on the principle of Pitot tube, which is determined by the product of the average flow velocity and effective section area of pipe.
CX-PTM pitot tube meter
Operation principle
In general, the flow velocity distribution in the pipe is uneven. For the fully developed fluid, the velocity distribution appears on an exponential law. In order for accurate calculation, the entire circle section is divided into a number of half circles and half rings with the same area. The detect rod in the sensor is made of a hollow metal tube. A number of holes are drilled in the rod at the face-flow side which are located in the center of each divided sections and represent flow velocity of each section. Due to the total pressure tapping is interconnecting, total pressure be transmitted to each point and averaged, be guided to high-pressure terminal through total pressure tube and be transmitted to the positive pressure room. When the sensors correctly installed on long straight pipeline, there no vortex in the flow cross-section and the static pressure of the entire section can be considered as constant. Detected holes are located on the back or side of the sensor which represent the static pressure of the entire section. The static pressure is transmitted from low-pressure terminal to the negative pressure chamber of sensor through the static-pressure tube. Since square of the differential between the positive and negative pressure chamber is proportion to the average flow of section, the flow can be get from the pressure differential. Based on this relationship, the flow can be calculated according to the formula as the following by Bernoulli equation and continuity equations
Qv=α﹒ε﹒（π／4）﹒D2﹒（2∆P／ρ1）0.5
Qm=α﹒ε﹒（π／4）﹒D2﹒（2∆P﹒ρ1）0.5
where：Qv： volume flow Qm： mass flow
α：structure coefficient of the sensor
△P：differential pressure
ε：fluid inflate coefficient
ρ：density of fluid
For uncompressed fluid ε=1 For compression fluid ε﹤1
If D、△P、ρ1 are using SI unite ,the unite of QV is M3∕S and Q1 is ㎏∕S.
The sensor structure coefficient α and the inflation coefficient was known in the calibrate equipment
and noted in quality certification.
Basic structure
The sensor basic structure, as shown in Figure 1
The shape of detect rod section contain circle section, rhombus section, oval section, etc.
Their flow coefficients are stable and low energy consumption.
Model and specification
| spectrum standard | explanation | |||||||
| CX-PTM-ZW- | Pitot tube Flowmeter | |||||||
| Sensor type | W | Pitot tube Flowmeter | ||||||
| D | Delta Flowmeter | |||||||
| A | Pitot tube Flowmeter | |||||||
| Material type | Y | liquid | ||||||
| Q | gas | |||||||
| Z | steam | |||||||
| Liquid temperature | 2 | ＜200℃ | ||||||
| 5 | ＜500℃ | |||||||
|
Liquid pressure |
1 | ≤1.6MPA | ||||||
| 2 | ≤2.5MPA | |||||||
| 3 | ≤4.0MPA | |||||||
| 4 | ≤6.3MPA | |||||||
| 5 | ≤10.0MPA | |||||||
| 6 | ≤25.0MPA | |||||||
| Structure type | 1 | typeⅠ，see 4.2.1 | ||||||
| 2 | Type Ⅱ，see 4.2.2 | |||||||
| 3 | Type Ⅲ，see 4.2.3 | |||||||
| 4 | Type Ⅳ，see 4.2.4 | |||||||
| 5 | Type Ⅴ，see 4.2.5 | |||||||
| Accuracy | 1 | Level 1.0，see 4.2.8 precision table | ||||||
| 2 | Level 1.5，see 4.2.8 precision table | |||||||
| 3 | Level 2.5，see 4.2.8 precision table | |||||||
| Connection style | 1 | Thread connection | ||||||
| 2 | Flange connection | |||||||
| Caliber | S | Indicate in number，see 4.2.6 sensor nominal diameter series | ||||||
The sensor nominal size in the following series：
25，（32），40，50，（65），80，100，（125），150，200，250，300，350，400，500，
600，700，800，900，1000，1200，1400，1600，2000，2500，3000mm
（Number in brackets are generally not recommended to customers.）
The sensor nominal pressure in the following series：
1.6，2.5，4.0，6.3，10，25MPa。
Sensor accuracy grade (see table below)
| Accuracy rating | 1.0 | 1.5 | 2.5 |
| Basic error limits Ea | ±1.0 | ±1.5 | ±2.5 |
| Repeatability(％) | 0.1 | 0.2 | 0.5 |
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