How to deal with the common problems in the application of orifice flowmeter?There are always many uncertainties in the application life.Orifice plate flowmeter is a process control and measurement instrument widely used in petroleum,chemical industry,metallurgy,electric power,heating,water supply and other fields.What are the problems of orifice flowmeter in use?

 

　　孔板流量計一般容易受被測流體特性、儀表性能安裝及環(huán)境的影響。

 

　　Orifice plate flowmeters are generally vulnerable to the influence of measured fluid characteristics,instrument performance installation and environment.

 

　　由于天然氣本身的性質，會隨著外界環(huán)境溫度的變化而發(fā)生復雜的變化，從而影響流量計的測量精度。對于天然氣的測量，必須首先確定天然氣的工作溫度和壓力。低密度氣體對某些測量方法呈現困難，此時就要改變所選擇的測量方法，或者作溫度和(或)壓力修正，以保證測量準確準確度。

 

　　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,the working temperature and pressure of natural gas must be determined first.Low density gas is difficult for some measurement methods,so it is necessary to change the selected measurement methods,or make temperature and/or pressure correction to ensure the accuracy of measurement.

 

　　孔板流量計本身也會引起的誤差，如孔板入口直角銳利度、管徑尺寸與計算不符、孔板厚度誤差、節(jié)流件附件產生臺階、偏心，孔板上游端面平度，環(huán)室尺寸產生臺階、偏心;取壓位置，焊接、焊縫突出，取壓孔加工不規(guī)范或堵塞，節(jié)流件不同軸度等等。這些因素都有可能影響孔板的重復性，影響測量精度。若儀表輸出特性是非線性的，則這種影響更為突出。

 

　　The orifice flowmeter itself can also cause errors,such as orifice plate entrance right angle sharpness,diameter size and calculation inconsistency,orifice plate thickness error,orifice accessories Produce step,eccentricity,orifice plate upstream end flatness,ring chamber size produce step,eccentricity;pressure taking position,welding,welding seam prominent,pressure taking hole processing is not standardized or blocked,throttle parts of different axes and so on.These factors may affect the repeatability of orifice plate and the measurement accuracy.If the output characteristic of the instrument is non-linear,the influence will be more prominent.

 

　　管線布置的偏離造成的安裝誤差是普遍性的，其產生的主要原因是現場不能滿足直管段要求的長度。雖然孔板流量計安裝能正常使用了，但因所使用環(huán)境條件與預期的情況發(fā)生了改變，使儀表的一些性能參數和硬件方面也隨之發(fā)生了改變，從而會改變流量計測量結果。

 

　　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.Although orifice flowmeter installation can be used normally,some performance parameters and hardware aspects of the instrument have also changed due to the changes of the environment conditions and expectations,which will change the measurement results of the flowmeter.

 

　　孔板流量計按國標規(guī)定進行設計、制造和檢定的標準孔板無需實流標定，精度高、結構簡單、制造成本低，但壓力損失在所有標準節(jié)流裝置中最大，不適用于要求壓力損失小的情況，標準孔板廣泛用于石油、化工、冶金、電力等行業(yè)。

 

　　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.