检定规程本规程适用于新制的、使用中和修理后的玻璃转子流量计(以下简称流量计)的检定。 Verification Regulations for Glass Rotameters This regulation is applicable to the verification of newly manufactured glass rotor flowmeters (hereinafter referred to as flowmeters) during use and after repair.
I. Technical requirements
1 Before installation, remove the ejector rods, fillers, etc. for glass rotor flowmeter transportation protection.
2 The glass rotor flowmeter should be installed vertically on the vibration-free pipe, and no obvious tilt is allowed.
3 The glass rotor flowmeter inlet joint should be connected to its small end of the cone.
4 When installing the flowmeter, make sure that the pipe fittings connected to the glass rotor flowmeter are fixed, and the glass tube should not be stressed.
5 The calibration medium should be clean. If necessary, install a filter upstream of the glass rotor flowmeter.
6 When the glass rotor flowmeter installed on the pipeline needs to be cleaned, the cleaning pipeline can be installed. It is recommended to clean the pipeline of the glass rotor flowmeter.
7 When calibrating a gas flow meter, a thermometer and pressure gauge should be installed near the inlet of the flow meter. The minimum division value of the thermometer should not exceed 0.2 ° C, and the measurement accuracy of the pressure gauge should be within ± 1%.
8 The flow standard device must be regularly verified and accompanied by a verification certificate.
9 A dynamic or static flow standard device can be selected. The accuracy of the flow standard device should be at least 1/2 of the allowable error of the flow meter.
10 For the flowmeter whose value is susceptible to changes in liquid viscosity, it should be verified under the actual working conditions of the flowmeter as much as possible.
11 The name of the manufacturer (or factory standard), the name, model, factory number, and date of manufacture of the flowmeter shall be marked on the label of the flowmeter; the temperature and pressure of the calibration medium and the medium shall be marked on the tapered tube (or certificate). .
12 The reading line of the flow meter should be clear. The scale of the flow meter should indicate a percent scale or a flow scale. The scale flow rate Q1 of the flow meter is generally the flow rate at a temperature of 20 ° C for liquids; the flow rate at a standard state (temperature is 20 ° C, atmospheric pressure 辚 1.01325 × 105Pa) for gas.
13 The verification system should have good tightness to ensure no leakage.
(A) appearance inspection
14 In accordance with the relevant provisions of the technical requirements, check whether the flowmeter meets the technical requirements.
(II) Indication verification
15 When no medium passes through the flowmeter, the rotor should be below the lower limit of the reading scale.
16 When verifying that the medium is liquid, open the regulating valve to allow the liquid to slowly flow into the flowmeter and flush away impurities in the tube and the flowmeter. Then, adjust the flow to the upper limit of the flow meter and run it for a period of time until all the gas accumulated in the pipeline is eliminated.
17 Adjust the flow to raise the rotor to the verification point. The reading position of the rotor is shown in Figure 2.
18 During the verification process, the allowable value of the rotor fluctuation (up and down position at a constant flow) should meet the requirements of the following table.
Note: The accuracy level of the glass rotor flowmeter corresponds to its allowable error δ. For example, when δ = ± 1%, the accuracy level of the flowmeter is set to level 1. The allowable value of rotor fluctuation is expressed as a percentage (%) of the upper measurement limit.
19 Check the flowmeter at least five points and check it twice. The flowmeter with the guide rod should be checked for the up and down stroke.
20 The flowmeter can be calibrated by volume method, weighing method and comparison method.
20.1 Volume method:
This method is suitable for the verification of low viscosity liquid and gas flow meters.
20.1.1 Liquid: The liquid flows into the working volume through the flowmeter at a certain flow rate. The volume, temperature and inflow time of the liquid flowing into the working volume are measured, and the actual flow rate Q (m3 / h) of the flowmeter under the calibration state is calculated
Where: V--the volume of liquid flowing into the working volume (m3);
T--Inflow time (h).
20.1.2 Gas: The gas is discharged from the flow standard device and passed through the flow meter. 前面的气体压力、温度。 Measure the volume and time of the exhaust gas, and the pressure and temperature of the gas in the device and in front of the glass tube rotor flowmeter . Calculate the actual flow rate Q (m3 / h) of the flowmeter in the scale state
In the formula: V-the volume of gas discharged in the standard flow device (m3);
T-discharge time (h);
PN, Ps, Pm--respectively under the standard state, the absolute pressure of the gas in the flow standard device and in front of the flow meter (Pa);
TN, Ts, Tm-are the absolute temperature (K) of the gas in the standard flow device and in front of the flow meter under standard conditions.
20.2 Weighing method:
This method is suitable for the verification of liquid flow meters.
The liquid flows into the weighing container through the flowmeter, and the mass, density, temperature, and inflow time of the liquid flowing into the weighing container are measured, and the actual flow rate Q (m3 / h) of the flowmeter under the calibration state is calculated.
In the formula: M--indicated value of standard scale (kg);
ρ--the density of the liquid in the weighing container (kg / m3).
The comparison method uses a standard flow meter as a standard for comparison with a flow meter.
20.3.1 Liquid: Standard flow meters and flow meters shall be of the same type and specification. The verification method is to connect in series and read the calibration flow of the standard flow meter and the flow meter.
20.3.2 Gas: Install the flowmeter downstream of the standard flowmeter and measure the pressure and temperature at the inlet of the standard flowmeter and the flowmeter respectively. Then, calculate the actual flow rate Q (m3 / h) of the flowmeter in the scale state
In the formula: Ps, Pm-the absolute pressure (Pa) of the standard flow meter and the flow of gas;
Ts, Tm-the absolute temperature of the gas at the standard flow meter and the flow meter (K);
QSN--Scale flow rate (m3 / h) of standard flow meter under standard conditions.
21 Indication error of flow meter
Q--The actual flow rate of the flowmeter in the scale state. When comparing the liquid flowmeter (Chapter 20.3.1) with a comparison method, it is the scale flow rate (m3 / h) of the standard flowmeter;
Q1--scale flow of the flow meter (m3 / h);
Qmax--the upper limit flow of the flow meter (m3 / h).
Note: The calculation formulas in Articles 20 and 21 are given under the condition that the test medium and the scale medium are the same medium. If they are not the same medium, another conversion is required.
Processing of test results
22 A flow meter is considered qualified when the following conditions are met.
22.1 The variation of the two verification values at each verification point shall not exceed 1/2 of the allowable error.
22.2 The indication error △ of the flow meter shall not exceed the allowable error δ of the flow meter.
22.3 If the water temperature t at the time of the liquid flowmeter inspection is significantly different from the water temperature t1 at the time of calibration, when the △ value exceeds the δ value, the following formula shall be met:
In the formula: K-correction coefficient of water temperature change (% · ° C-1).
Note: K value is given by the manufacturer.
23 A certified flowmeter shall be issued with a calibration certificate. The verification certificate shall include the name, model, factory number, caliber, flow range, manufacturer, date of verification, and unit for inspection of the flowmeter.
24 The verification period of the flowmeter is determined according to the specific use situation, generally two years.
1 The installation of the flow meter at the work site should meet the requirements of 1 ~ 7.
2 When the viscosity of the working medium of the flow meter and the viscosity of the calibration medium are close to each other and the density is different, the flow correction formula is as follows:
2.1 In the liquid type: Q, Q1--respectively the flow rate of the flowmeter working liquid and the calibration liquid (m3 / h);
ρ, ρ1-the density of the working fluid and calibration liquid of the flowmeter (kg / m3);
ρf--the density of the rotor material (kg / m3).
2.2 In the gas type: Q, Q1--respectively the flow rate of the working gas of the flow meter and the calibration gas (m3 / h);
工作气体和刻度气体在标准状态下密度(kg/m3); ρN, ρ1N--respectively the density (kg / m3) of the working gas and calibration gas of the glass rotor flowmeter under standard conditions;
p--absolute pressure of working gas (P;
T--absolute temperature (K) of working gas.