Several problems of steam metering and their solutions
Steam is one of the important energy sources for enterprise production. It is the main heat energy for urban central heating and an important indicator for economic accounting. Therefore, the accuracy of steam metering is particularly important.
In order to solve the problem of heating for employees, the company has updated the original boiler equipment, adding 4 new boilers (2 sets of 25t/h, and another 2 sets of 35t/h). The DCS realizes the automatic control of the boiler system, and the product is saturated steam.
Analysis of problems and influencing factors
Starting from the boiler ignition operation in November 2010, the steam flow often shows the maximum value, and the differential pressure signal measured by the differential pressure transmitter exceeds 20 mA. The same is true when the load is low and the actual flow is small. In this case, steam flow measurement does not provide a safety reference for boiler operation, and it cannot be used for cost accounting.
In response to this phenomenon, the design of the project uses a V-cone flowmeter, equipped with an intelligent differential pressure transmitter, and the measurement signal is sent to the DCS for calculation and display.
Steam vortex flowmeter measurement requirements
Keywords: steam vortex flowmeter, saturated steam vortex flowmeter, superheated steam vortex flowmeter
What should I pay attention to when measuring vortex flowmeter? What is the best way to measure steam installation by vortex flowmeter? Can vortex flowmeters be used for steam metering? The vortex flowmeters are evaluated for their measurement performance under single-phase flow conditions. There is currently no single-phase flowmeter for measuring the system variation of two-phase flow. However, the two-phase flow exists objectively, and its influence on flow measurement is unavoidable. Despite the difficulties, people are still trying to study the mechanism of its influence on flow measurement, and take corresponding countermeasures to improve the accuracy of flow measurement.
First, steam flow measurement difficulties
During long-distance transportation, dry steam will partially condense due to heat loss, resulting in reduced steam dryness and become wet steam. The gas-liquid two-phase flow structure in the horizontal pipe is related to the gas-liquid two-phase volume ratio and the flow velocity. In the steam pipe, since the volume ratio of the condensed water in the wet steam is small, the drain pipe drawn from the bottom of the horizontal pipe is made. , can receive a good hydrophobic effect. When the flow rate is particularly high, it will also behave as a circular flow, that is, there is a liquid film on the pipe wall, and the central part of the pipe is a gas core with droplets. Due to the influence of gravity during horizontal flow, the lower liquid film is higher than the upper pipe. The thickness of the wall, in the vertical ascending pipeline, the basic structure of the gas-liquid two-phase flow has a fine bubble flow structure, a bullet-like flow structure, a block flow structure, a ring-shaped flow structure with fibers, and an annular flow structure.
Installation of plug-in electromagnetic flowmeter
The plug-in electromagnetic flowmeter sensor installation upstream straight pipe section is not less than 5D (D means pipe diameter), the downstream straight pipe section is not less than 2D:
1. Vertical installation. When the sensor is inserted into the pipeline, it should be less than 5° from the vertical diameter of the pipeline section. It is suitable for measuring the cleaning medium with small vibration of the pipeline.
2, inclined installation, the axis of the sensor and the axis of the pipe to be tested is 45 °, suitable for large pipe diameter and measuring the flow of liquid containing other impurities in the medium, the installation method is small, not suitable for entanglement.
There are two ways to insert the insertion point of the electromagnetic flowmeter sensor: one is inserted into the central axis of the pipe to be tested (ie 1/2 times the diameter of the pipe); the other is inserted into the inner wall of the pipe at 1/4 of the pipe.
1. Clean the welding slag and burrs of the base of the pipe to be tested.
2. Turn off the upstream flow control valve or use low pressure water supply.
3. Install the DN50 ball valve on the mounting base. Pay attention to the long cavity of the ball valve. Check whether the ball valve can be fully open and fully closed. Install the screw seat, compression nut and rubber sealing ring onto the ball valve and loosen the positioning nut. Insert the sensor into the rod through the ball valve and insert it into the pipe to be tested. At the same time, it should be noted that the direction of the sensor direction indicator rod should be consistent with the flow direction of the fluid. Ordering Information Please specify the name of the tested medium, working pressure, medium temperature, flow rate (flow rate) range, pipe diameter and the pipe network to be tested.