RU2627280C2 - Method of hygrometer calibrating and checking - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measuring equipment and can be used in all industries for verification, and calibration of hygrometers, and also to measure dew point temperature (DPT) of natural gas (air) under working pressures in laboratory conditions. Method performs gas circulation in closed system under pressure, close to pressure in hygrometer under operating conditions, required DPT above phases interface flat surface in closed volume is achieved by creation of hydrodynamic balance between steam and condensed phases of water/frost. Using mirror-type in-series reference hygrometer DPT are measured and compared with calibrated hygrometer DPT measurements.

EFFECT: technical result is providing possibility of various types hygrometers checking at operating pressures up to 10 MPa, as well as higher accuracy of set DPT using standard laboratory equipment.

1 cl, 1 dwg

Description

The invention relates to measuring equipment and can be used in all industries for verification, calibration, comparisons of condensing hygrometers, as well as for measuring the dew point temperature (TTR) of natural gas (air) at operating pressures in the laboratory. It is also possible to use the invention for checking other types of hygrometers.

A device for calibrating and calibrating hygrometers (RF No. 2008704, publ. 02.28.1994), which implement the two-pressure method to produce gas with known humidity, is known. The principle of operation of the device is to saturate the gas with moisture at elevated pressure and a stable temperature, followed by an isothermal decrease in pressure to the operating pressure of the primary moisture converters.

Its disadvantages are large size and weight, operation at low excess pressures, a large amount of consumables (liquid nitrogen, purified air, special filter driers, condensers, etc.).

Famous calibration complex "KONG" (Seleznev S.V., Derevyagin AM, Agaltsov A.G., Stepanov A.R., Efimov R.N., Mikhailov Yu.V., Gubanov V.A., Istomin V.A. . / Science and technology in the gas industry No. 1, 2003, pp. 43-50). The principle of operation of the “KONG” calibration complex is to create a closed volume in which the required dew point temperature (hereinafter referred to as TTR) is achieved by creating hydrodynamic equilibrium between the steam and condensed phases of water. When a dew point meter is installed (without a sampling device) on a sample chamber, a closed volume is created between the camera and the meter sensor, in which there is a condensation mirror. The temperature of the mirror is controlled by a three-stage "Peltier element". Working gas in contact with the mirror takes its temperature and saturates above the surface of water or ice, having previously condensed on the mirror. The gas is circulated in the measuring chamber due to thermal diffusion between the cooled mirror of the complex and the sensitive element of the transducer due to the cyclic operation of the transducer in the heating / cooling mode. A measure of the moisture content of the created vapor-air mixture is the dew point equal to the temperature of the condensation mirror.

The disadvantage of the KONG calibration complex is that the KONG complex is designed for only one type of KONG-PRIMA hygrometer, it operates at atmospheric pressure and only in air. The disadvantages include large errors in determining the temperature of the dew point.

The objective of the invention is to remedy the above disadvantages.

The technical result of the use of the invention is the calibration of different types of hygrometers, improving the accuracy of the specified TTR.

The specified technical result is achieved by applying the method of calibration and calibration of the hygrometer, including the creation of a closed volume in which the dew point temperature is achieved by creating a hydrodynamic equilibrium between the vapor and condensed water / hoarfrost phases over the flat phase interface, ACCORDING TO THE INVENTION, circulate natural gas (air) in a closed system under pressure close to the pressure in the hygrometer under operating conditions, set the flowmeter and measure its flow rate, the reference gy a mirrored type gyrometer, connected in series to the calibrated hygrometer, measure the dew point temperature and determine the errors of the calibrated (calibrated) hygrometer, while the set dew point temperature for negative temperatures is determined by the formula

TT = TTR / K,

Where

TT - temperature in the thermostat;

TTR - set dew point temperature at negative temperatures;

K is a coefficient that takes into account the difference in TTR over water and hoarfrost.

The advantage of such a “ring” scheme over the flow-through is the high stability of the set TTR and quick access to the set point, in addition, it is possible to supply natural gas to the system.

The method is illustrated by the drawing, which shows a system for calibration and calibration of the hygrometer reference mirror-type hygrometer.

The system consists of:

1 - separator (heat exchanger);

2 - a liquid thermostat of industrial design (type Thermotest-05-2 or a temperature calibrator KT-1M (on Peltier elements) with the ability to maintain a given temperature);

3 - a temperature sensor for measuring the exact temperature of the carrier in the thermostat 2 (cooler on Peltier elements) or the temperature of natural gas (air) directly at the output of the separator 1 to determine the desired TTR;

4 - saturator (vessel with water);

5 - calibrated hygrometer;

6 - pump to create a constant flow up to 10 l / min;

7 - reference hygrometer mirror type;

8 - rotameter with flow regulator for measuring and creating the necessary gas duct (flow) through calibrated 5 and reference 7 hygrometers,

9 - pressure sensor;

10 - cylinder with natural gas (air) under pressure;

11, 12, 13 - valves for connecting and disconnecting the saturator and additional humidification of natural gas (air);

14 - valve to relieve gas pressure from the system;

15 - valve for removing gas from the system;

16 - valve for supplying gas to the system.

The method of calibration and calibration of the hygrometer is as follows.

A calibrated hygrometer 5 and a reference mirror-type hygrometer 7 are connected to a system for calibrating and calibrating a hygrometer under pressure 7. The system is filled to a working pressure of up to 10 MPa with natural gas (air) with open valves 11, 12, 13 and closed valves 14, 15 from cylinder 10 through the valve 16, after which the valve 16 is closed. The pressure in the system is controlled using a pressure sensor 9. In the liquid (or Peltier elements) thermostat 2 set the required temperature to which natural gas (air) will be cooled in the separator 1 and maintained at a predetermined value. The required TTR of natural gas (air) in the separator 1 is achieved by creating a hydrodynamic equilibrium between the steam and condensed water phases (at temperatures above zero) and becomes equal to the temperature of the walls of the separator 1 (temperature in thermostat 2), excess moisture settles on the walls of the separator 1. To stabilize TTR in the system provide gas circulation by turning on the pump 6, rotameter 8 regulate the necessary flow of natural gas (air) in the system. The reference mirror-type hygrometer 7 measures the dew point temperature and compares it with the TTR measurements of the calibrated hygrometer 5, determines the errors of the calibrated (calibrated) hygrometer.

At temperatures below zero, water in the separator 1 settles in the form of hoarfrost. To set the required TTR in the temperature range below zero with an accuracy of ± 0.1 ° C, for example, in the temperature range from -1 ° C to -22 ° C, you can use the averaged coefficient K = 1.117 (a more accurate coefficient for negative temperatures at each point at setting the dew temperature on hoarfrost is calculated according to GOST 8.811-2012). The temperature in thermostat 2 is calculated by the formula

TT = TTR / K,

Where

TT - temperature in thermostat 2;

TTR - set dew point temperature at negative temperatures;

K is a coefficient that takes into account the difference in TTR over water and hoarfrost.

If necessary, if the TTR of the supplied gas to the system from the cylinder 10 is lower than the set temperature in the thermostat 2, it is necessary to moisten the natural gas (air). To moisturize, the flow of natural gas (air) is passed through the saturator 4 by opening the valve 11, 13 and closing the valve 12. If the natural gas (air) is sufficiently saturated, when the TTR becomes equal to the specified TTR, open the valve 12 and close the valves 11, 13 for exclusions of further humidification of natural gas (air).

To control the set temperature of the dew point, a temperature sensor 3 is used to measure the exact temperature of the coolant in thermostat 2 (cooler on Peltier elements) or (and) the temperature of natural gas (air) directly at the outlet of the separator 1.

Claims (6)

A method for calibrating and calibrating a hygrometer, including creating a closed volume in which the required dew point temperature is achieved by creating a hydrodynamic equilibrium between the steam and condensed water / hoarfrost phases over a flat phase interface, characterized in that they circulate natural gas (air) through a closed system under pressure close to the pressure in the hygrometer under operating conditions, set the flowmeter and measure its flow rate, a reference mirror-type hygrometer, connected in series to overyaemomu hygrometer produce measuring dew point temperature and the determined error verified (calibrated) of the hygrometer, the dew point temperature is given by for negative temperatures determined by the formula TT = TTR / K, Where TT - temperature in the thermostat; TTR - set dew point temperature at negative temperatures; K is a coefficient that takes into account the difference in TTR over water and hoarfrost.

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