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Comparison of conventional volume and small volume tube

Number of visits: Date:2016-01-10

  1 Overview

  The conventional volume tube is a one-way or two-way ball type volume tube, the domestic model LJG.

  Small volume pipe system finger piston volume tube.

  In the United States, the small volume tube is introduced into our country at the end of 1980s, the production plant is Smith; Brooks; Waugh; calibron and so on. Kaifeng instrument factory in the early ninety's also produced a small volume tube.

  Kaifeng instrument factory as a flux calibrating equipment production plant, the size of these two types of properties of the tube is not easy to make improper comments, so as not to mislead the user. Now a flow test device manufacturer BOPP company in Germany, the performance of two kinds of volume tube is described as follows.

  2 the performance comparison of the spherical volume tube and the small volume tube

  2.1 ball type volume tube

  A. advantage

  High reliability.

  Simple operation.

  The flowmeter can be used for calibrating the low pulse resolution flowmeter, and only requires that the flowmeter can output 10000 pulses between the switches.

  Check the number of times at one point of the flow.

  Is not sensitive to the reaction of solid particles in the liquid to be detected.

  Low maintenance costs.

  Replacement flexible ball replacement.

  Good reproducibility, better than 0.02%.

  Using four detection switches, can reduce the number of tests.

  B. shortcoming

  Large area.

  One-way hydraulic system.

  2.2 small volume tube

  A. advantage

  Small area.

  And the test time is short, one run in the shortest test time 0.5 seconds.

  The metering cylinder is of electroless nickel plating and has strong corrosion resistance.

  B. shortcoming

  Standard small size, (the maximum standard volume of 300 liters of existing products) does not apply to the verification of low pulse resolution of the flowmeter.

  And the number of run times, this offset the advantages of short verification time, according to the U.S. product sample introduction, a flow point usually to be certified 15 times.

  The relative speed of the sealing member and the moving part of the sliding seal is 1.5m/s, so the sealing element is easy to wear, and the replacement is difficult.

  To be sensitive to the reaction of solid particles in the liquid, which is easy to cause the damage of the piston seal in the metering cylinder.

  High cost of maintenance.

  Using the pulse insertion method can lead to the reduction of repeatability.

  And using pulse insertion method, we must to know the flowmeter output pulse cycle of standard deviation and T, in accordance with the provisions of GB GB/T17286.3, collected in a calibration pulse number n, press type obtained nanoparticles submitted (c t) 2

  According to N and K to determine the flow coefficient, standard volume, o t shall bear meter factory. But the flow meter factory is usually not given, so it is difficult to determine the size of the small size.

  Note: the IP standards in the United Kingdom are as follows:

  If a flow point test 15 failed, you can increase 30 times, if the 30 is still not qualified. The conclusion is that the flowmeter is not suitable for the detection of small volume tube. (but not the flow meter is not qualified)

  About 2.3 pulse interval standard deviation by T

  This suggests there are initially ISO7278/3 (BS6886) regulations when using the piston volume tube, first of all to that the flowmeter output pulse interval of the standard deviation of the 6S t.

  The standard deviation of the pulse interval is the minimum pulse collected in a single stroke

  O t (%) N

  0.5 --------------100

  1.0-------------- 500

  2.5-------------- 2500

  5 --------------10000

  10.0------------- 40000

  15 -------------90000

  Now ISO7278-3 - 1988, has been used in our country

  N=500 (o t) 2

  According to the introduction of IP standard, quality by T turbine is + 1%, and the gear transmission pulse generator by t as high as 10%.

  Appendix A, which is the small drafting group of standard test, figure pulse regularity and 6S t different, irregular degree = (maximum cycle minimum cycle) 2 / average cycle

  A1 - turbine flow meter, generator without regulator

  A2, A3, A4 - the sender of a gear regulator

  3 Comparison of small volume tube and conventional volume tube calibration flow meter

  Is about in 1993, in order to revise the main drafting of China's volume tube verification procedures JJG209, Xie Jiji, and so on, in Yanshan, Beijing petrochemical plant made a test

  Detected flowmeter: DN100 flowmeter, Japan TOKICO products

  Volume tube:

  SVP150 A., the United States Smith products, the standard volume V=57L

  B. ball type volume tube DN150, domestic, standard volume V=728L

  C. ball type volume tube DN250, domestic, standard volume V=2750L

  Measured medium: diesel oil

  Measured medium viscosity: 2.5CP

  Verification flow: 46.4m3/h

  Volume tube DN150 DN250 SVP150

  Instrument constant 9.98053 10.0063 10.0155

  Pulse number 570.62728027521

  Standard deviation Sk 0.00234 0.000058 0.0151

  Repetitive delta K 0.051% 0.0013% 0.39%

  Verification times 301212

  It can be seen that the small size tube test is not qualified, flow meter is not necessarily unqualified, only to indicate that the flow meter using the volume of only 57L small volume tube is not suitable.

  Test records see Appendix B, due to the improper storage of data recorded in the DN250 volume tube.

  About 4 in mass flowmeter verification Keli Austria

  In theory, the mass of the liquid is equal to the product of the density of the liquid and the volume of the liquid. The volume precision of the volume tube can reach 0.05%, and the new technology promotes the success of the high precision on-line density meter. So it is feasible to use the volume tube and the on-line density meter in theory. So the verification regulation of mass flow rate in our country is also given in JJG897 95.

  M= P tVt=, P 20V20------------------------------- (1)

  M - liquid quality

  P T - t temperature in liquid density

  Vt - volume of liquid at temperature T

  P 20 - reference conditions in liquid density, the density is given by

  V20 - the volume of liquid in the reference condition is given by the volume tube.

  Reference condition - 20 C, 101.325Kpa

  If we think that the liquid is incompressible

  P P t= 20 - A (T-20) 20[1-a/ P = P 20 = P 20 V (T-20) - (2)

  P V =1-a/ 20 - (T-20) -------------------------------------------------- (3)

  A--- density of the temperature correction coefficient, according to the national professional standards

  Temperature compensation coefficient density

  The imported densimeter reference condition is the temperature of 60 degrees Fahrenheit (15.55 degrees Celsius), density by 15 P. Conversion from 5 to p 20, this work can only be resolved through the test, liquid is can be compressed, which in turn relates to the pressure correction, these technical details JJG897-95 not given, it is impossible to give, so volume tube and online density meter on online calibration of mass flowmeter is not a theoretical problem, but through practice, accumulated experience, to develop good operating rules.

  Internationally, the oil trade is settled by volume, the volume of oil has been very mature. Flow verification system, which is composed of volume flow meter and volume tube, has been widely used in many countries. Using the method of mass flowmeter and abroad is still in research and development, no mature recognized certification standard, in JJG-897 rules in, of Keli Austrian mass flowmeter calibration method, only general guidance principle, and lack of interoperability, the country has not been used mass flowmeter as trade connection precedent. Therefore, from the reliability, the comparison of the consideration, the oil transfer, still use the GB9109.1~5 standard, it does not occur trade disputes.

  Mass flowmeter off-line verification, usually using the weighing method, abroad France widely adopted this method. The Qilu Petrochemical Austria have Keli to test these 380 meter, flow meter, a set of self weighing verification device.

  For reference only!

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