JB/T 8941.2-2014Roots type blowers for general purpose - Part 2: Performance test methods (English PDF)

Foreword

JB/T 8941, Roots type blowers for general purpose, is divided into two parts.

-- Part 1. Specification;

-- Part 2. Performance test methods. This Part is the 2nd part of JB/T 8941.

This Part was drafted in accordance with the rules given in GB/T 1.1-2009.

This Part replaces JB/T 8941.2-1999, Roots type blowers for general purpose - Part

1 Scope

This Part of JB/T 8941 specifies the performance test methods for Roots type blowers for general purpose (hereinafter referred to as blowers).

This Part applies to the performance test for Roots type blowers for general purpose.

For the blowers which are used under special working conditions and to transfer special gas, refer to this Standard for the performance test.

2 Performance test methods; and compared with JB/T

8941.2-1999, the main technical changes of this Part are as follows.

-- in accordance with JB/T 2624.2-2006, it deletes the lengths of orifice plate, grid type flow conditioner and straight pipe section in the flow measuring device;

-- in accordance with JB/T 2624.2-2006, it modifies the equations and data of discharge coefficient and expansibility coefficient in Annex A;

-- it adopts GB/T 6075.1-2012, Mechanical vibration - Evaluation of machine vibration by measurements on non-rotating parts - Part 1. General guidelines, as the measuring method of vibration;

-- it changes "The volume flow rate of discharge gas of the blower is measured at the standard discharge points; the flow rate shall be converted to the specified inlet conditions" into "The volume flow rate of the discharge gas of positive-pressure blowers (or the inlet gas of negative-pressure blowers) is measured under the specified discharge pressure of positive-pressure blowers (or the inlet pressure of negative-pressure blowers)";

-- it changes "Use calibrated apparatus, e.g. thermometer, thermocouple, electric resistance thermometer or thermistor with accuracy ± 1 K to insert the pipe or thermowell to measure temperature" into "The accuracy of the calibrated apparatus for measuring temperature is ± 1.0°C. The measuring devices include thermometer, thermocouple, electric resistance thermometer and thermistor";

-- it adds "g) For the type test of the blower, performance curve and noise spectrum analysis charts shall be plotted";

-- it revises part of the words in the original standard.

The following documents are indispensable for the application of this document. For dated references, only the dated editions apply to this document. For undated references, their latest editions (including all amendments) apply to this document.

GB/T 2624.2-2006, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full - Part 2. Orifice plates

GB/T 2888, Methods of noise measurement for fans, blowers, compressors and Roots blowers

GB/T 6075.1-2012, Mechanical vibration - Evaluation of machine vibration by measurements on non-rotating parts - Part 1. General guidelines

GB/T 8941.1, Roots type blowers for general purpose - Part 1. Specification

3 Terms and definitions

For the purpose of this document, the following terms and definitions apply.

5 Measuring method and accuracy

5.2.4 During reading, do not take thermometer from the medium measured. if there is thermowell, do not take it from its thermowell.

5.2.5 The measures shall be taken to make sure.

a) that the thermal insulation adjacent to insertion points and raised connectors is good so that the temperatures of thermowell and measured medium are the same;

b) that the measured medium flow past the sensors or thermometer thermowell of all kinds of temperature measuring instruments (the sensors or thermometer thermowells shall be inserted obliquely against the flow. in extreme cases, the points perpendicular to airflow are allowed);

c) that the thermometer thermowell shall not disturb normal flow.

5.2.6 Thermocouples shall have a welded hot end and shall be calibrated together with conductor in accordance with their intended application scope. The material of thermocouples shall be applicable to the temperature of measured medium and use.

If thermocouples have a thermowell, then the hot end shall be welded to the bottom of thermowell.

6 Test method

6.3.1 Before calculating the measured data, check carefully whether the recorded data is consistent with the working conditions; the fluctuation of the data measured in the test shall not exceed the limits in Table 5.

6.3.2 All readings used in the test shall be continuous.

6.3.3 For a group of readings showing a major fluctuation, abandon the readings at the beginning and end of the test; […]