Selection and installation of flowmeter.

With the continuous development of science and technology, many flow meter manufacturers, relying on the modern intelligent and chip technology, using the different laws of physics and the working principle of producing various types of flowmeter. But for work in the production of the first line of measuring instrument engineering personnel, due to the flow meter on-line detection of all kinds of working condition is relatively complicated, the flowmeter selection in some cases is quite difficult. In actual work, it is important to pay full attention to the selection, installation, debugging and use of the flowmeter in the process of use, among which the selection is very important, but the installation is absolutely not careless. If driving system operation, find the work flow instability or think is too low, the credibility of testing data to verify is improper installation defects or flowmeter lectotype, find out the exact causes and changes are not easy. If the selection is correct and the installation is in place, it lays a solid foundation for successful debugging and normal use. Therefore, this paper focuses on the selection and installation of flowmeter, and discusses the success and inadequacy of the selection and installation flowmeter.

To successfully choose good flowmeter, first of all, in the selection of measuring instrument engineering personnel should have enough with technical data and the related information, such as flowmeter selection manual, the selection of flow meter manufacturers samples, correlation flowmeter operation instruction, about the traffic, petroleum chemical instrumentation some books and technical papers, and flowmeter using the experience of peers.

Secondly, the basic requirements of flowmeter selection should be defined: the name and component of the tested medium; Maximum flow, common flow and minimum flow in standard working condition; Highest, common and minimum working pressure; Highest, common and minimum operating temperature; The viscosity of the medium in the working state and the liquid materials are easy to crystallize.

Thirdly, we should discuss with the production technology, power equipment and civil engineering technicians in time to further confirm the requirements of process, equipment and civil construction on flow detection and installation. Such as to set aside enough space for use by the meter installation and maintenance, the power how security configuration, how to ensure the straight pipe length, etc, also reflect the specific difficulties, model selection of the flowmeter potential risks and installation flowmeter must have the basic conditions, because the measuring instrument should be about the production process requirement, product characteristics, equipment level and improve labor productivity.

Fourth, to properly consider the flowmeter lectotype of consistency, if work unit has a long history of the flowmeter to use, and also have a certain amount of flow meter in use, another expansion project, the selection of reference when the original selection experience of success, also can use other types of flow meter, so convenient for the flow unified management and use, reduce the backup timing maintenance flow, has a good economy, but also accumulated some experience with other flowmeter. If the meter is to use on the new project, flowmeter selection on the premise of economy can afford to consider some more advanced, such as the compensation parameters is complete and good performance of compensation flowmeter, in order to constantly improve the level of traffic detection.

Fifth, it is necessary to go to the production enterprise research and to use the unit field to obtain the experience, it is worth mentioning that other people's experience is for reference only, because the operating conditions of the flow meters are very different.

The selection of a specific flowmeter should be considered in terms of its measuring principle, technical parameters, traceability, installation conditions, price level and service capability.

Flowmeter selection is mainly concerned with the principle of flow measurement sensor. The flowmeter of different measuring principle often has different working characteristics, such as measuring accuracy, range, type of application medium, structure characteristic and installation requirement. The determination of the technical parameters of the flowmeter, such as the flow range and calibre, is determined by the production capacity of the engineering system or device. Of course, the measuring instrument technician can also refer to the petroleum chemical process design manual, the common thermal instrument selection manual and other flow type selection books and other materials to determine the flow range and caliber. Large diameter small flow is a common mistake when flowmeter selection, the main reason is often not overestimate the existing production capacity or in the future development potential, is to put more allowance, diameter larger than diameter small insurance ideas.

Work for the general flow meter has small flow instability, low accuracy of weakness, for a similar period, the second phase of the construction of the flowmeter selection, if the pipe size according to the requirements of first and second phase of the overall traffic design, think flow meter according to the first phase of the actual flow range selection for good, if the second phase of expansion, an additional purchase to use as required. Of course, the measurement accuracy of the flowmeter can be improved by the method of pre-shrunk tube expansion. Some special cases get full attention, such as thermal power plants for steam flowmeter trade settlement, due to the size of the steam pipe size in some places and pipeline opening fee directly link, steam users in order to pay less steam pipe opening fee, may the steam flow rate is low, commonly used this flowmeter selection when its common flow and diameter is likely to be small, once put into use, flowmeter has the outrange use risk, which affect the measurement accuracy and service life and may produce unnecessary metering disputes. The maximum allowable error of the flowmeter should be less than twice the allowable error of the object under test, and the resolution properly meets the predetermined requirement, which should be sufficient and not too high. Because of the high accuracy of the flowmeter, it means high prices. It is also necessary to pay enough attention to the normal value traceability, and some flowmeters are highly accurate, or the structure is difficult to trace.

Installation conditions, for measuring easy crystallization liquid flowmeter installation, attention should be paid to some of the material won't crystallization under normal conditions, if the temperature is lower or higher concentration of abnormal conditions, such as by flow in the body will appear crystals, crystal grinding function on the sensor to the influence of some of the flowmeter can be deadly, so when you install, consider the appropriate method and adding auxiliary heating insulation. When installation to the situation of the sealing ring into the pipe, it is better to finished sealing ring or made of sealing ring template, make the sealing ring in rules, some seals should consider to add two ears when producing, in order to convenient unarmed when installation, make sure that the location is correct. In addition, we should not forget to disassemble if the installation condition is convenient. The reality is that the flowmeter is often easy to remove. At the same time, it should also be noted that there are no foreign bodies in the pipe, such as coaxiality and inclination, etc.