How to sample and test filter bags? What are the methods of sampling inspection?

The inspection of filter material has three significance: to provide a basis for filter material manufacturers to control product performance and improve product quality; Provide a basis for design and users to select filter media based on evidence; Implement scientific supervision for the management and technical supervision part. Filter material inspection can be divided into self-inspection of filter material production plant, sampling inspection of technical department and product identification inspection.

1. The content and sampling of filter material inspection.

For filter media, the contents that need to be verified and tested are as follows.

1) Appearance inspection of punctures, defects, black spots, jumpers, broken wires, joints, etc.

2) Physical properties such as unit area mass, thickness, amplitude, woven fabric structure, fabric density, non-woven bulk density, porosity, etc.

3) Mechanical characteristics, such as the breaking strength and elongation of the filter material, the elongation of the warp and weft load of the filter material, and the expansion and bursting strength of the filter material.

4) Dust filter characteristics, such as resistance coefficient, static dust removal efficiency, dynamic dust removal efficiency, dynamic resistance of filter material, regeneration resistance coefficient and dust stripping rate.

5) Special functional characteristics such as temperature resistance, corrosion resistance, electrostatic properties, hydrophobicity, etc.

In order to ensure the quality of the filter material, the inspection and sampling of the filter material not only samples the raw material fiber and yarn used in the filter material, and the tracking and quality supervision of the finished product and finished product of the filter material, but also the filter material manufacturer must also conduct sampling inspection on each batch of filter material. 5% of filter media per batch.

From each batch of batch samples, the full width required for the test is randomly cut out as the test sample. In general, the shear position should be at least 3m away from the end of the horse. The length of the sample required for the test is about 6 m.

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The sampling methods include DU

1.Simple random sampling of zhi and dao

2.System sampling.

3.Stratified sampling.

Sampling inspection, also known as sampling inspection, is a statistical method and theory that randomly selects a small number of products (samples) from a batch of products for inspection, and judges whether the batch of products is qualified. It differs from a comprehensive inspection in that the latter requires the entire batch of products to be inspected one by one to sort out the non-conforming products, while the sampling inspection infers the quality of the entire batch based on the test results of the products in the sample. If it is inferred that the batch meets the pre-defined conformity criteria, it will be accepted, otherwise it will be rejected.

Therefore, a batch of products that are considered qualified by sampling inspection may also contain some unqualified products.

First of all, you should be clear: both sampling and sampling methods are methods for investigating population density. The differences between them are:

The survey methods are different depending on the respondents. Sampling methods are used to investigate population densities of plants and animals with weak mobility; Microorganisms should be tested by sampling. Animals with strong mobility should be re-caught with signs.

In addition, let me tell you again: when using the sample method, pay attention to the size of 1 quadrat (100 square meters for trees, 16 square meters for shrubs, and 1 square meter for small plants) and the number of 2 quadrats, 3 samples should be randomized, and 4 counts.

Sampling detection method, hemocytometry counting method, microscopic counting method, the name is different, the sample method and the marker recapture method are the same population density survey method, as for the sampling detection method is a survey method or a method, it remains to be understood.

There are also random sampling, stratified sampling, cluster sampling.

1. Random sampling:

Random sampling requires strict probabilistic principles, with each sampling unit having the same probability of being drawn and reproducible. Random sampling is often used when the population is small, and its main feature is that it is extracted from the population one by one. Random sampling can be divided into simple random sampling, systematic sampling, stratified sampling, and cluster sampling.

2. Stratified sampling:

Stratified sampling refers to the method of dividing the population into disjoint layers [2] during sampling, and then independently extracting a certain number of individuals from each layer according to a certain proportion, and combining the individuals taken from each layer as a sample. The smaller the intralayer variation, the better, and the larger the interlayer variation, the better.

3. Cluster sampling:

Cluster sampling, also known as cluster sampling, is to merge each unit in the population into a number of sets that do not cross and repeat each other, which is called a group. A sampling method in which a sample is then drawn in a swarm as a sampling unit. When applying cluster sampling, it is required that each group should be well represented, that is, the differences between units in the group should be large and the differences between groups should be small.

Sampling methods mainly include: random sampling, stratified sampling, overall sampling, and systematic sampling. In general, if a population contains n individuals, and n individuals are taken as samples (n n) one by one, if each sampling makes the chances of each individual in the population being drawn equal, this sampling method is called simple random sampling.

There are many sampling methods, which can be random sampling, regular sampling, or sequential sampling.

Stratified Sampling Systematic Sampling Simple random sampling.

(Lottery method, random sample table method) is often used when the number of the population is small, and its main feature is to extract from the population one by one;

Advantages: Easy to operate.

Disadvantages: It is too large to implement.

Method (1) Lottery method.

Generally speaking, the lottery method is to number n individuals in the population, write the number on the number tag, put the tag in a container, stir evenly, extract a tag from it each time, and extract n times in a row to get a sample with a capacity of n.

The lottery method is simple and easy to use, and it is suitable when there are not many in the population. When there are a large number of individuals in the population, it is more difficult to "stir evenly" the population, and there is a high probability that the sample will be poorly representative by the lottery method).

2) Random number method.

Another method that is often used in random sampling is the random number method, which uses random number tables, random number dice, or computer-generated random numbers for sampling.

(1) Simple and immediate sampling: including direct selection method, lottery method, random number table method.

2) Categorical sampling: also known as type sampling or stratified sampling, all units in the population are divided into several classes (groups) according to a certain mark, and then samples are randomly selected in each class.

3) Mechanical sampling: firstly, the sampling population units are lined up in a certain order, and the sampling interval (sampling distance) is calculated according to the number of population units and the number of sample units, and then the sample units are selected according to a certain interval. Since the sampling interval is equal, it is also called equidistant sampling.

4) Cluster sampling: The population is divided into several groups or groups, and then selected in groups, each group contains several sample units.

1 Classified according to the characteristics of product quality indicators

1) Counting sampling method is to take a certain number of samples (samples) from a batch of products, test the quality of each sample in the sample, determine whether it is qualified or unqualified, and then count the number of qualified products, and compare with the specified "qualified judgment number" to determine whether the batch of products is qualified.

2) Measurement sampling method is a method that takes a certain number of samples (samples) from a batch of products, inspects the quality of each sample in the sample, and then compares it with the specified standard value or technical requirements to determine whether the batch of products is qualified.

2 Classified by the number of sampling inspections

According to the number of sampling inspections, it can be divided into one, secondary, multiple and sequential sampling inspection methods.

1) A sampling method This method is the simplest, it only needs to sample a sample to make a judgment on whether a batch of products are qualified.

2) The second sampling method is to take the first sample for inspection, and if the judgment and inspection of the batch of products can be made accordingly, the inspection will be terminated. If no judgment can be made, a second sample will be taken and a judgment will be made after another test.

3) Multiple sampling method The principle is the same as the secondary sampling method, the sample size of each sampling is the same, that is, n1 = n2 = n3 = n7, but the number of sampling is more, and the number of qualified judgments and unqualified judgments is also more. The ISO2859 standard provides a 7-time sampling program. China's GB2828 and GB2829 have implemented 5 sampling programs.

4) sequential sampling method is equivalent to the limit of multiple sampling methods, each time only one unit of product is randomly selected for inspection, after the inspection is made according to the judgment rules to pass, unqualified or then draw the next unit of product judgment, once the batch of qualified or unqualified judgment can be made, the inspection will be terminated.

3. Classification according to the type of sampling method

Sampling methods can be divided into two categories: adjusted and unadjusted.

The adjustment type is linked by several different sampling programs and transfer rules to form a complete sampling system, and then according to the changes in the quality of each batch of products, the sampling program is replaced according to the transfer rules, that is, the conversion of the normal, tightened or relaxed sampling program, ISO2859, ISO3951 and GB2828 standards belong to this type, and the adjustment sampling method is suitable for the quality inspection of continuous batches of products related to the quality of each batch.

The non-adjusted single sampling inspection scheme does not take into account the quality history of the product batch, and there is no transfer rule in use, so it is relatively easy for quality inspectors to grasp, but it is more suitable for quality inspection of isolated batches.

I will answer this question, and I will answer it if you accept it.

Sampling testing is generally for the same batch of goods in large quantities, can not be tested one by one, a certain proportion of samples are taken for testing.

In addition, medical blood tests are also sampling tests.

Sampling, samples are taken at the project site, and the executor may be Party A, supervision, and testing agency personnel; Sending samples, that is, entrusting personnel to send the samples to the testing institution for testing. If it is a witness sampling project, the sampling can be taken by the construction party, but it must be witnessed by the relevant personnel of the supervision or construction unit, and the sample must also be accompanied by a witness to the inspection and testing institution to ensure the representativeness and authenticity of the sample.