天津压力变送器性能,孔板流量计存在的问题及解决途径!-西安华恒仪表制造有限公司
天津压力变送器性能,孔板流量计存在的问题及解决途径!
信息来源: 华恒 | [ 2019-05-20 ] 点击量: 187

   孔板流量计存在的问题及解决途径,西安华恒仪表介绍:孔板流量计是将标准孔板与多参数差压变送器(或差压变送器、温度变送器及压力变送器)配套组成的高量程比差压流量装置,可测量气体、蒸汽、液体及天然气的流量,广泛应用于石油、化工、冶金、电力、供热、供水等领域的过程控制和测量。

 
  The orifice plate flowmeter is a high range ratio differential pressure flowmeter consisting of standard orifice plate and multi-parameter differential pressure transmitter(or differential pressure transmitter,temperature transmitter and pressure transmitter),which can measure the flow of gas,steam,liquid and natural gas.It is widely used in petroleum,chemical,metallurgical,electric power,etc.Process control and measurement in heating,water supply and other fields.
 
  1被测流体特性的影响:
  由于天然气本身的性质,会随着外界环境温度的变化而发生复杂的变化,从而影响流量计的测量精度。对于天然气的测量,必须首先确定天然气的工作温度和压力,因为外界温度的变化,会使天然气本身的压力和温度也发生变化,都有可能造成过大的密度变化和压缩系数变化。低密度气体对某些测量方法呈现困难,此时就要改变所选择的测量方法,或者作温度和(或)压力修正,以保证测量准确准确度。
 
  1.The influence of measured fluid characteristics:
  Because of the nature of natural gas itself,complex changes will occur with the change of ambient temperature,thus affecting the measurement accuracy of flowmeters.For the measurement of natural gas,we must first determine the working temperature and pressure of natural gas,because the change of external temperature will change the pressure and temperature of natural gas itself,which may result in excessive density change and compression coefficient change.Low density gas is difficult for some measurement methods.At this time,it is necessary to change the selected measurement methods,or make temperature and/or pressure correction to ensure the accuracy of measurement.
 
  2仪表性能的影响:
  孔板流量计本身引起的误差原因主要有:孔板入口直角锐利度;管径尺寸与计算不符;孔板厚度误羞;节流件附件产生台阶、偏心;孔板上游端面平度;环室尺寸产生台阶、偏心;取压位置;焊接、焊缝突出;取压孔加工不规范或堵塞;节流件不同轴度等等。这些因素都有可能影响孔板的重复性,重复性是由仪器本身原理与制造质量所决定,它在过程控制应用中是重要的指标。而精确度除取决于重复性外,尚与量值标定系统有关。在实际应用中,仪表优良的重复性被许多因素包括流体粘度、密度等变化所干扰,都会影响测量精度。若仪表输出特性是非线性的,则这种影响更为突出。
 
  2.Instrument performance:
  The main reasons for the errors caused by orifice flowmeter itself are:the right angle sharpness of orifice plate entrance;the size of pipe diameter is not consistent with the calculation;the thickness of orifice plate is mistaken;the appendages of orifice plate produce step and eccentricity;the flatness of upstream end face of orifice plate;the size of annular chamber produce step and eccentricity;the position of pressure taking;the welding and welding seam are prominent;the processing of pressure taking hole is not standardized or blocked;the different axes of orifice parts,etc These factors may affect the repeatability of orifice plate.The repeatability is determined by the principle of the instrument itself and the manufacturing quality.It is an important indicator in the process control application.Besides the repeatability,the accuracy is also related to the calibration system.In practical application,the excellent repeatability of the instrument is disturbed by many factors,including fluid viscosity,density and other changes,which will affect the measurement accuracy.If the output characteristic of the instrument is non-linear,the influence will be more prominent.
 
  3流量计安装的影响:
  管线布置的偏离造成的安装误差是普遍性的,其产生的主要原因是现场不能满足直管段要求的长度。
 
  3 Influences of Flowmeter Installation:
  The installation error caused by the deviation of pipeline layout is universal,and the main reason is that the site can not meet the requirements of the length of straight pipeline section.
 
  4环境条件方面的影响:
  孔板流量计按国标规定进行设计、制造和检定的标准孔板无需实流标定,精度高、结构简单、制造成本低,但压力损失在所有标准节流装置中最大,不适用于要求压力损失小的情况,标准孔板广泛用于石油、化工、冶金、电力等行业。
 
  4.Impact of environmental conditions:
  The orifice plate flowmeter designed,manufactured and calibrated according to the national standard does not need real-flow calibration.It has high accuracy,simple structure and low manufacturing cost.However,the pressure loss is the largest in all standard throttling devices,and it is not suitable for situations requiring low pressure loss.The standard orifice plate is widely used in petroleum,chemical,metallurgical,power and other industries.
 
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