The key way to improve the measuring precision of orifice flanges

Orifice flanges are widely used in flow measurement systems to measure the flow of liquids and gases in pipelines. To ensure high accuracy in these measurements, it is essential to adhere to specific guidelines regarding the pipeline setup and the installation of orifice plates. Below are two key areas to focus on for improving the measurement accuracy of orifice flanges:

Custom ASTM A182 F316 316L ASME B16.36 orifice flange

1.Pipeline Requirements

National standards provide strict technical requirements for the length, straightness, roundness, and internal surface roughness of the measuring pipes. If the minimum required length of the pipeline is not met, it can cause deviations in the flow measurement. The magnitude of this deviation is influenced by the orifice diameter ratio (β) and the Reynolds number.

To avoid these measurement errors, a flow straightener must be installed in the straight pipe section upstream of the orifice plate. The flow straightener helps to stabilize the flow and eliminate disturbances, ensuring accurate flow readings. Adhering to these pipeline standards is crucial for maintaining measurement accuracy.

ANSI ASME B16.36 orifice flange

2.Installation Requirements

The orifice plate’s entry face must be installed perpendicular to the pipeline’s axis, with a deviation of no more than 1 degree. Additionally, it is critical to install the orifice plate in the correct direction to avoid incorrect flow readings. Standards dictate the acceptable alignment tolerances, and failure to meet these standards can lead to measurement errors.

The sealing gasket between the orifice flange, the orifice plate, and the pressure tapping device must not exceed a thickness of 0.03D (where D is the pipe diameter). Moreover, the gasket must not intrude into the straight pipe section or the pressure tapping cavity, as this could obstruct the pressure ports or alter the measurement location, affecting accuracy.

For new installations, the orifice plate should only be installed after the pipeline has been purged and operated for a few days. This precaution helps prevent the orifice plate from being damaged or contaminated by liquids or solid particles present in the gas, which could interfere with accurate flow measurements.

By following these key pipeline and installation requirements, the accuracy of orifice flange-based flow measurement systems can be significantly improved. Ensuring proper pipeline length, installing a flow straightener, maintaining perpendicular alignment of the orifice plate, and carefully controlling the gasket placement are all essential steps in minimizing measurement errors and enhancing the reliability of flow data.