Problems with orifice plate flow meters!
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Can a orifice plate flow meter be installed in reverse? What are the consequences of installing it in reverse? Can it be used?
I don’t think it’s possible, because generally during installation, there must be straight pipe distances of (15-40)d and 5d respectively on the upstream and downstream sides; once it’s installed in reverse, these straight pipe distances will likely need to be adjusted accordingly
Generally, it’s not possible; unless the user uses a symmetric orifice plate, flow rate cannot be measured from either direction. In such a case, both edges of the orifice meet the characteristics of the upstream edge of a right-angled orifice plate, and the total thickness of the orifice plate does not exceed that of the orifice itself. Asymmetric orifice plates have angled edges instead. Last edited by casondu on 2009-3-25 at 13:30.]
Orifice plate flow meters must not be installed in reverse; when the orifice plate of a differential pressure flow meter is installed incorrectly, the differential pressure value displayed is lower than that obtained when the orifice plate is installed correctly, resulting in a lower reading on the flow meter.
A orifice plate flow meter is a differential pressure flow measurement device with a high range ratio, consisting of a standard orifice plate in combination with a multi-parameter differential pressure transmitter (or separate differential pressure transmitter, temperature transmitter, and pressure transmitter). It can measure the flow rate of gases, steam, liquids, and natural gas, and is widely used in process control and measurement across industries such as petroleum, chemicals, metallurgy, power generation, heating, and water supply. Application range of orifice plate flow meters:
1. Nominal diameter: 15 mm ≤ DN ≤ 1200 mm
2. Nominal pressure: PN ≤ 40 MPa
3. Operating temperature: -50°C ≤ t ≤ 550°C
4. Range ratio: 1:10, 1:15
5. Accuracy: Class 0.5, Class 1
I. Overview of orifice plate flow meters
Throttling devices, also known as differential pressure flow meters, consist of a primary sensing element (throttle element) and secondary components (differential pressure transmitter and flow display instrument). They are widely used for measuring the flow rate of gases, steam, and liquids. These devices feature a simple structure, ease of maintenance, stable performance, and reliability in operation.
The orifice plate throttling device uses standard throttle elements that can be manufactured directly in accordance with relevant standards: 1. National standard GB2624-81; 2. International standard ISO51673; 3. Ministry of Chemical Industry standard GJ516-87-HK06.
II. Working principle of orifice plate flow meters
When fluid filling a pipeline passes through the throttling device within it, a local contraction occurs near the throttle element, resulting in an increase in flow velocity. This creates a static pressure difference on the upstream and downstream sides of the element. Given the known parameters, the relationship between differential pressure and flow rate can be derived using the principle of fluid continuity and Bernoulli’s equation, thereby allowing the flow rate to be determined. Its basic formula is as follows:
c – discharge coefficient, dimensionless
d – diameter of the orifice or throat of the throttling element under operating conditions
D – inner diameter of the upstream pipe under operating conditions
qm – mass flow rate, Kg/s
qv – volume flow rate, m³/s
ß – diameter ratio d/D, dimensionless
Density of the fluid, Kg/m³
Coefficient of expandability, dimensionless
III. Structure of the orifice flow meter
Components of the throttling device:
Throttling elements: standard orifices, standard nozzles, long-diameter nozzles, 1/4 circle orifices, double orifices, eccentric orifices, notched orifices, orifices with conical inlets, etc.
Pressure extraction devices: annular chambers, pressure extraction flanges, clamping rings, pressure guide tubes, etc.
Connection flanges (**standard flanges, various standards, and flanges designed by other parties), fasteners. Measurement tube: Installation requirements for orifice plate flowmeters: The required straight pipe section is generally 10D in length ahead of the orifice plate and 5D behind it; therefore, when selecting an orifice plate flowmeter, it is essential to choose one that is suitable for the specific conditions at the installation site.
1. Nominal diameter: 15 mm ≤ DN ≤ 1200 mm
2. Nominal pressure: PN ≤ 40 MPa
3. Operating temperature: -50°C ≤ t ≤ 550°C
4. Range ratio: 1:10, 1:15
5. Accuracy: Class 0.5, Class 1
I. Overview of orifice plate flow meters
Throttling devices, also known as differential pressure flow meters, consist of a primary sensing element (throttle element) and secondary components (differential pressure transmitter and flow display instrument). They are widely used for measuring the flow rate of gases, steam, and liquids. These devices feature a simple structure, ease of maintenance, stable performance, and reliability in operation.
The orifice plate throttling device uses standard throttle elements that can be manufactured directly in accordance with relevant standards: 1. National standard GB2624-81; 2. International standard ISO51673; 3. Ministry of Chemical Industry standard GJ516-87-HK06.
II. Working principle of orifice plate flow meters
When fluid filling a pipeline passes through the throttling device within it, a local contraction occurs near the throttle element, resulting in an increase in flow velocity. This creates a static pressure difference on the upstream and downstream sides of the element. Given the known parameters, the relationship between differential pressure and flow rate can be derived using the principle of fluid continuity and Bernoulli’s equation, thereby allowing the flow rate to be determined. Its basic formula is as follows:
c – discharge coefficient, dimensionless
d – diameter of the orifice or throat of the throttling element under operating conditions
D – inner diameter of the upstream pipe under operating conditions
qm – mass flow rate, Kg/s
qv – volume flow rate, m³/s
ß – diameter ratio d/D, dimensionless
Density of the fluid, Kg/m³
Coefficient of expandability, dimensionless
III. Structure of the orifice flow meter
Components of the throttling device:
Throttling elements: standard orifices, standard nozzles, long-diameter nozzles, 1/4 circle orifices, double orifices, eccentric orifices, notched orifices, orifices with conical inlets, etc.
Pressure extraction devices: annular chambers, pressure extraction flanges, clamping rings, pressure guide tubes, etc.
Connection flanges (**standard flanges, various standards, and flanges designed by other parties), fasteners. Measurement tube: Installation requirements for orifice plate flowmeters: The required straight pipe section is generally 10D in length ahead of the orifice plate and 5D behind it; therefore, when selecting an orifice plate flowmeter, it is essential to choose one that is suitable for the specific conditions at the installation site.
Generally, it cannot be installed in reverse, but there is a special case where such a restriction does not apply; I saw this at a factory……
It cannot be installed in reverse; in air separation equipment, a 15D straight pipe section is required before the flow meter, and a 5D straight pipe section is required after it. It generally cannot be installed in reverse.
If one needs to take pressure readings from a throttling device, what installation method is suitable for the pressure transmitter?
Differential pressure type; or it’s better to ask at the instrumentation area