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Shanghai Shang Shaft Bearing Quality Inspection Institute Co., Ltd.

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Address: 301 Shangxue Road, Jiading District, Shanghai

Laboratory management six "control"

2021-03-31 10:14


Control of standard procedures


Standard procedures are the basis for testing and judgment. Various channels should be adopted to collect new standards in time to ensure that the standard version on which the testing work is based is currently valid. At the same time, the new and old standards should be analyzed and compared, and according to the new requirements of standard procedures, basic work such as the transformation and configuration of instruments and equipment and the implementation of new standards should be done well.


For this reason, it is necessary to formulate basic technical standard equipment specifications for the laboratories under their jurisdiction, clarify the basic technical standards that should be equipped for various tests of the businesses under their jurisdiction, ensure that the coverage of major business standards reaches 100, realize standard scientific research and standard experiments, and avoid quality accidents caused by defects in experimental design to the greatest extent.



Sample Control


The state of the test sample shall meet the requirements of the standard.


1. The sample should be representative, and the sampling should be carried out by random sampling method.

For example, drilling mud and cement tests stipulate that bagged cement should take equal samples from not less than 20 bags of cement in this batch, with a total amount of at least 12kg. It is not advisable to take half a bag or the whole bag of cement as test samples at one time, which does not meet the standard requirements.


2. The number of samples is related to the accuracy of the test results.

The number is too small, the test error increases, so the standard has requirements on the number of material samples. In the actual test work, it is necessary to strengthen the control of the number of tests. If the standard requires parallel tests, the samples shall be divided into separate tests. If only one test is done, the data shall be pieced together and reported, which shall be strictly prohibited.


3. The size of the sample is related to the accuracy of the test results, and the size of the sample must meet the standard requirements.

The size (length) of the metal material sample is specified in the "Metal Material Room Temperature Tensile Test Method" used in the downhole tool tension and torsion test. If the length of the sample does not meet the standard requirements, it is obviously not in conformity with the specification requirements to complete the test only by adjusting the upper and lower jaw positions of the universal material testing machine.


Instrument control


Instruments and equipment and various measuring instruments are the most basic tools in the detection work. Its integrity and accuracy will directly affect the accuracy of the detection data, and also affect the evaluation of the quality of the project.

1. Control of measurement standards.

The establishment, replacement, sealing and cancellation of laboratory measurement standard instruments or calibration devices shall establish complete technical files and comply with the relevant procedures of the JJF1033 Measurement Standard Assessment Specification. The weekly inspection rate of standard instruments of measurement is 100 per cent, which is in line with the requirements of the JJF1033.


2. Test instruments and equipment for mandatory metrological verification specified by the state

All must be submitted for inspection and timely inspection. After inspection, the calibrated instruments shall be rechecked to check whether the calibration data meet the use requirements..


3. For some parts that are not within the scope of strong inspection, calibration specifications shall be formulated by oneself.

For some test instruments and equipment that are not within the scope of strong inspection and for which the state has not yet formulated calibration specifications, calibration specifications shall be formulated according to the instrument instructions, relevant technical specifications, relevant metrological verification regulations, etc., as the basis for regular self-calibration, and the accuracy of measurement data shall be controlled. Such as: cement compression fixture, cement test screen usually must also be self-calibration, otherwise the test results also have a great impact.


4. In addition to verification (calibration), regular maintenance and inspection.

Attention should also be paid to the regular maintenance and inspection of instruments and equipment and various measuring instruments. For example, if the gap between the cement mixer blade and the pot is checked monthly, if any problem is found, it should be stopped immediately and can only be used after the metrology department has re-verified (calibrated) and meets the requirements.



Standard Material Control


The laboratory shall establish relevant systems to effectively control the whole process of purchase, acceptance, storage, distribution and use of standard substances and standard materials, as well as the disposal of waste standard substances, so as to ensure that the standard substances are used within the validity period and that their measurement performance such as fixed value accuracy, uniformity and stability meet the testing requirements.


To purchase high-quality standard materials and standard materials, you should choose a qualified and capable service provider, and obtain the corresponding qualification and ability certification documents. A list of qualified suppliers is established for some long-term and important suppliers, and these suppliers are used as fixed users to ensure the relative stability of the test materials. For example, standard sand for construction tests is generally only one designated seller in a region. When purchasing standard sand, one must ask the seller for sales authorization and certificate of conformity. Do not buy some fake standard sand for cheap, thus affecting the quality of the test work.



temperature and humidity control


Temperature and humidity have a certain influence on the performance of some materials, so the environmental conditions for material testing are clearly stipulated in the standard and must be observed.

For example, the "Test Method for Strength of Cement Mortar (ISO) Method" for the indoor test of thermal recovery cement blocking and channeling stipulates that the temperature of the laboratory shall be kept at 20 ℃ 2 ℃ and the relative humidity shall not be less than 50% when the test body is formed. The temperature of the test body curing box with mold shall be kept at 20 ℃ 1 ℃, and the relative humidity shall not be less than 90%. The water temperature of the test body curing pool shall be within 20 ℃ 1 ℃. In order to strengthen the temperature and humidity control of the laboratory, the laboratory can establish a set of temperature and humidity control system and control measures according to its own conditions, and the unit with conditions adopts automatic temperature and humidity control system as far as possible.




Quality Control


The test work should be repeated test, comparison test, ability verification and other methods to offset the impact of test errors on the test results, improve the quality of laboratory work.


1. Repeated test

Repeatability is the error of the test results obtained from the same sample test in the same laboratory under basically the same conditions.

For example, the repeatability of the cement compressive strength test method is quantitatively expressed by the error of the test results obtained by the same sample in the same laboratory, in the same operator, the same standard sand, and in a short time interval. For the determination of 28-day compressive strength, the repeatability of a qualified laboratory under the above conditions is expressed as a coefficient of variation, which is required to be between 1% and 3%.


2. Comparison test

The comparison test in the laboratory is the comparison of the test results obtained by different personnel in the laboratory, using the same instrument and equipment, and using the same sample test. The comparison test in the laboratory is easy to operate and is conducive to improving the detection ability of the test personnel.


The systematic error of the laboratory can be eliminated through the comparison test between laboratories, which cannot be eliminated by the comparison of repeated tests and the operation of different personnel in the same laboratory. Through this comparison, find out the reasons for the deviation, timely correct and improve the operation, temperature and humidity environmental conditions and equipment factors caused by various deviations.


3. Capability verification

In order to effectively control the internal quality of the laboratory and raise the testing ability to a higher level, it is better to participate in the ability verification test of the national laboratory certification and accreditation body after comparison and improvement. Only through the ability verification can we understand the real level of ourselves in the testing project, find problems, take measures, correct and rectify as soon as possible.