Characteristics and principles of steam orifice flowmeter

1Characteristics and principles of steam orifice flowmeter、working principle：

The fluid filled in the pipeline flows through the throttling device inside the pipeline, causing local contraction near the throttling element, increasing the flow velocity, and creating a static pressure difference on both sides upstream and downstream.
Under the condition of known parameters, the relationship between differential pressure and flow rate can be derived based on the principle of flow continuity and Bernoulli equation to obtain the flow rate. The schematic diagram of its measurement principle is as follows:

C - Non dimensional outflow coefficient
D - Diameter of the orifice or throat of the throttling element under working conditions
D - Inner diameter of upstream pipeline under working conditions
QM - Mass flow rate Kg/s
Qv - Volume flow rate m3/s
The diameter ratio d/D is dimensionless
Density of fluid Kg/m3
The coefficient of expandability is dimensionless

IICharacteristics and principles of steam orifice flowmeter、Product Structure:
Composition of throttling device
1. Throttling components: standard orifice plate, standard nozzle, long diameter nozzle, 1/4 circular orifice plate, double orifice plate, eccentric orifice plate, circular orifice plate, conical inlet orifice plate, etc
2. Pressure collection device: ring chamber, pressure collection flange, clamping ring, pressure pipe, etc
3. Connecting flanges (flanges according to national standards, various standards, and other design departments) and fasteners.
4. Measuring tube

Several pressure measurement methods for standard orifice flow meters:

1. Ring chamber pressure standard orifice plate:

It belongs to the standard orifice plate. Due to the implementation of ring chamber pressure measurement, measurement accuracy has been improved and the length of small straight pipe segments required for installation has been shortened, making it widely applicable in various departments.

2. Individual drilling and pressure measurement for corner joints:

It belongs to the standard orifice plate. When the pipe diameter is above 400 millimeters, this form is often used. The pressure measurement methods include drilling holes separately on the flange, using circular pressure equalization rings, or using square pressure equalization rings. The orifice plate can be in the form of a handle hole or a non-standard circular hole plate.

3. Flange pressure measurement:

It belongs to the standard orifice plate. Regardless of the diameter of the pipeline, the centers of the upstream and downstream pressure tapping holes are located at 1 hour (25.5mm) each from the end faces on both sides of the orifice plate. This form is commonly used in refining systems.

4. Radial distance pressure measurement:

It belongs to the standard orifice plate. The pressure measurement method is pipeline pressure measurement. The center of the upstream pressure tapping hole is located at twice the inner diameter of the pipeline in front of the orifice plate. The center of the downstream pressure tapping hole is located at a distance of half the inner diameter of the pipe from the rear end face of the orifice plate.

5. Small caliber orifice plate:

Belongs to non-standard orifice plate. Used for measuring fluids within a diameter of 10mm to 50mm.

6. Double orifice plate:

It is composed of two standard orifice plates installed at a certain distance from each other in a straight pipe. In terms of the direction of the flow, the front orifice is referred to as the auxiliary orifice plate, while the rear orifice plate is referred to as the main orifice plate. The cross-sectional ratio m1 of the auxiliary orifice plate is greater than that of the main orifice plate. Two orifice plates form a nozzle with a liquid wall. It is used for flow measurement of low Reynolds number fluids or high viscosity fluids.

7. Circular perforated plate:

It belongs to non-standard orifice plates and is suitable for measuring the flow rate of fluids that are dirty, have air bubbles, or contain solid particles. Its measurement accuracy is relatively low.

8. Conical inlet orifice plate:

Belongs to non-standard orifice plate. The angle between the circular cone and the centerline is 45 °. This conical inlet orifice flowmeter is suitable for applications with very low Reynolds numbers, but the pipe size must not be less than 25 millimeters.