The steam flowmeter has strict requirements for the measured medium

1. Steam flowmeter is generally only used to measure single-phase fluid with low viscosity

2. The medium fluid measured by steam flowmeter should be in turbulent state

3. At present, most of the bearings of steam flow meters are ball bearings, so there are high requirements for the cleanliness of the measured medium. If the medium contains particulate impurities, it will make the bearing wear quickly. If it contains fiber impurities, it will wind around the steam blade, affecting the normal rotation of the flowmeter. In practical application, an effective filter can be installed in front of the steam flowmeter.

Use and installation instructions of steam flowmeter

The following problems should be paid attention to when selecting the diameter of steam flowmeter

When selecting the diameter of steam flowmeter, the working flow rate of medium should be between 15% and 70% of the measuring range of the flowmeter. When the measured medium flow rate is less than 15% of the measurement range of the selected flowmeter, the medium fluid velocity in the pipeline is slowly in the laminar flow state, and the measurement linearity of the flowmeter becomes poor, so it is difficult to achieve the required measurement accuracy. When the flow rate under medium condition is greater than 70% of the measurement range of the selected flowmeter, the rotation speed of the flowmeter will change greatly, which will accelerate the wear of the bearing and bracket, and affect the service life of the steam flowmeter.

Problems needing attention in installation of steam flowmeter:

1. The uneven distribution of medium fluid velocity and vortex flow are the main reasons that affect the measurement accuracy of steam flowmeter. To eliminate the uneven velocity and vortex flow, it is necessary to have a long enough straight pipe in front of the steam flowmeter. It is generally required that there is a straight pipe section of more than 15d upstream and 4D straight pipe downstream of the steam flowmeter to ensure the measurement accuracy. If the upstream flow cannot meet the requirements due to the limitation of the installation site, a tube speed rectifier can be installed on the upstream straight pipe section.

2. The installation point of steam flowmeter shall not have strong mechanical vibration and strong electromagnetic interference. During welding and installation, welding slag and flange sealing gasket shall not protrude into the pipeline. The control valve of flow meter upstream must be set as full open ball valve or gate valve, so as to avoid affecting the flow state of the measured medium.

3. The steam flowmeter can be installed horizontally, obliquely or vertically, and its flow characteristic curve will change with the installation mode. In order to obtain high precision measurement, horizontal installation must be adopted. If it is necessary to adopt vertical installation, the steam flowmeter shall be re calibrated and the instrument coefficient shall be reset.

Problems needing attention in maintenance and calibration of steam flowmeter:

1. Most of the faults of steam flowmeter are abrasion of flowmeter bearing and jamming of impeller. Users only need to replace bearing or remove debris on impeller. However, the steam flowmeter is a precision instrument with tight assembly, and the instrument coefficient will change after replacement or re assembly. Therefore, in order to ensure the measurement accuracy, the instrument coefficient should be re calibrated and changed after the replacement of accessories or re assembly.

2. With the increase of operation time or replacement of parts, the instrument coefficient of steam flowmeter will change, so it is necessary to calibrate the steam flowmeter. Two problems should be paid attention to in calibration

a. The fluid medium used in calibration must be the same medium or medium with similar viscosity as the measured medium;

b. If the steam flowmeter is used in the place where high measurement accuracy is required, the calibration should be carried out as a whole with the straight pipe section of the flow meter upstream and downstream to eliminate the additional error of the straight pipe section before and after the steam flowmeter.

Editor in charge: WV

Leave a Reply

Your email address will not be published. Required fields are marked *