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JB/T 8941.2-2014 English PDF (JBT8941.2-2014)

JB/T 8941.2-2014 English PDF (JBT8941.2-2014)

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JB/T 8941.2-2014: Roots type blowers for general purpose. Part 2: Performance test methods

This Part of JB/T 8941 specifies the performance test methods for Roots type blowers for general purpose (hereinafter referred to as blowers).
JB/T 8941.2-2014
GB
MACHINERY INDUSTRY STANDARD
OF THE PEOPLE REPUBLIC OF CHINA
ICS 23.140
J 72
Registration no.. 45838-2014
Replacing JB/T 8941.2-1999
Roots type blowers for general purpose
?€? Part 2. Performance test methods
ISSUED ON. MAY 6, 2014
IMPLEMENTED ON. OCTOBER 1, 2014
Issued by. Ministry of Industry and Information Technology of the
People's Republic of China
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Symbols, units and subscripts ... 8
5 Measuring method and accuracy ... 9
6 Test method ... 12
7 Comparison between test results and specified values ... 18
8 Test report ... 19
Annex A (Normative) Discharge coefficient and expansibility coefficient ... 20 Annex B (Informative) Steam pressure ... 24
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 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.
This Part was proposed by China Machinery Industry Federation.
Roots type blowers for general purpose
- Part 2. Performance test methods
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 Normative references
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. 3.1
standard inlet point
For the representative inlet points specified for each type of blowers, the points change along with the differences in structure and configuration of blowers
NOTE 1 The standard inlet point of single-stage blowers is at the inlet flange. NOTE 2 The standard inlet point of double-stage blowers is at the inlet flange of the first-stage blowers.
NOTE 3 The standard inlet point of packaged blowers is at their inlet starting end. 3.2
inlet condition
the condition that the inlet gas is at the standard inlet point of blowers 3.3
specified inlet condition
the condition of the inlet gas as specified in the product sample or the contract (temperature, pressure, humidity and gas composition)
3.4
standard discharge point
for the representative discharge points specified for each type of blowers, the points change with the differences of structure and configuration of blowers
3.5
specified rotational speed
the number of rotations of the shaft of blowers within unit time under the specified operating conditions
3.6
ambient pressure
the absolute pressure of the atmosphere adjacent to blowers
3.7
inlet pressure
the gas pressure at the standard inlet points, ie. the static pressure of inlet gas 3.8
discharge pressure
the gas pressure at the standard inlet point, ie. the static pressure of inlet gas 3.9
inlet temperature
the stagnation temperature of gas at the standard inlet point
3.10
discharge temperature
the stagnation temperature of gas at the standard discharge point
3.11
ambient temperature
the stagnation temperature of the atmosphere adjacent to blowers but not influenced by blowers
3.12
actual volume flow rate
the volume flow rate of the discharge gas of positive-pressure blowers (or inlet gas of negative-pressure blowers) is measured under the specified discharge pressure of positive-pressure blowers (or inlet gas of negative-pressure blowers); and then it is converted to the volume flow rate under the standard inlet conditions (temperature, pressure, humidity and gas composition).
3.13
shaft power
the power required to drive the shaft of blowers, equal to the sum of theoretical power and mechanical loss, but not including the external driving loss of the devices including couplers and belt drive
3.14
specific energy
the shaft power required for each unit of actual volume flow rate of blowers 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.
5.3 Humidity measurement
Humidity measurement shall be carried out as close to the standard inlet points as possible, with an aspirated psychrometer of accuracy ?? 2%.
5.4 Rotational speed measurement
Use tachometer, photoelectric tachometer or other instruments equipped with a stopwatch; the accuracy of measuring instruments shall not be lower than ?? 0.5%. 5.5 Measurement of flow rate
5.5.1 Use orifice plate measuring device to measure the volume rate of the blower. The structure and dimensions, service limits and installation requirements of orifice plate are specified in GB/T 2624.2-2006.
5.5.2 Orifice plate device can be of corner tapping; its structure and dimensions are specified in GB/T 2624.2-2006.
5.6 Power measurement
5.6.1 Use torquemeter to measure the input power of the blower directly, or obtain the input power of the blower indirectly by multiplying the output power of motor by driving efficiency.
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; a group of measured data shall be read at...

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