GB 5491-1985 Sampling and subsampling methods for inspection of grain and oilseeds
Some standard content:
National Standard of the People's Republic of China
Inspection of grain and oilseeds
Sampling and sample reduction methods
Inspection of grain and oilseedsMethods for sampling and sample reduction This standard applies to the quality inspection of commercial grain and oilseeds. 1 Sampling tools
1.1 Sampler: also known as grain probe. There are two types: packaged and bulk. 1.1.1 Packaged sampler. There are three types.
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1.1.1.1 Large grain sampler: total length 75cm, probe mouth length 55cm, mouth width 1.5~1.8cm, head is pointed or duckbill, maximum outer diameter 1.7~2.2cm.
1.1.1.2 Small and medium grain sampler: total length 70cm, probe mouth length 45cm, mouth width about 1cm, pointed head, maximum outer diameter about 1.5cm. 1.1.1.3 Powdered grain sampler: total length about 55cm, probe mouth length about 35cm, mouth width 0.6~0.7c, pointed head, maximum outer diameter about 1cm. 1.1.2 Bulk sampler. There are three types.
1.1.2.1 Thin cannula sampler: total length is divided into 1m and 2m, three holes, each hole is about 15cm long, mouth width is about 1.5cm, head length is about 7cm, outer diameter is about 2.2cm.
1.1.2.2 Coarse casing sampler: The total length is divided into 1m and 2m, with three holes, each hole is about 15cm long, about 1.8cm wide, about 7cm long, and about 2.8cm in outer diameter.
1.1.2.3 Electric suction sampler (not suitable for impurity inspection). 1.2 Sampling shovel, mainly used for sampling of flowing grain and oil or inverted bag sampling. 1.3 Container: The conditions that the sample container should have are: good sealing performance, clean and insect-free, no leakage, and no pollution. Commonly used containers include sample tubes, sample bags, sample bottles (wide-mouth bottles with ground mouths), etc. 2 Sampling method
2.1 Unit represents quantity. When sampling, the same type, batch, grade, cargo position, and vehicle (tank) are taken as one inspection unit. Representative quantity of one inspection unit: medium and small grains and oilseeds generally do not exceed 200t, and extra large grains and oilseeds generally do not exceed 50t. 2.2 Bulk sampling method
2.2.1 Warehouse sampling: Bulk grains and oilseeds are divided into zones and set points according to the shape and size of the pile, and the samples are taken in layers according to the height of the grain pile. The steps and methods are as follows:
2.2.1.1 Zone point setting: The area of each zone does not exceed 50m. Each zone has five points in the center and four corners. If there are two or more zones, the two points on the boundary of the two zones are common points (two zones have eight points in total, three zones have eleven points in total, and so on). The points at the edge of the grain pile are set about 50cm away from the edge.
2.2.1.2 Layering: For piles below 2m, there are two layers, upper and lower. For piles between 2 and 3m, there are three layers, upper, middle and lower. The upper layer is 10 to 20cm below the grain surface, the middle layer is in the middle of the grain pile, and the lower layer is 20cm from the bottom. If the pile is between 3 and 5m, there should be four layers. For piles above 5m, the number of layers should be increased as appropriate.
2.2.1.3 Sampling: Sampling is carried out layer by layer, from top to bottom, by area and point. The number of samples at each point should be the same. 2.2.1.4 For bulk extra-large grains and oilseeds (peanuts, broad beans, sweet potato slices, etc.), the method of digging up the pile shall be adopted. According to the principle of “GB 5491--85 issued by the National Bureau of Standards on November 2, 1985 and implemented on July 1, 1986”, representative samples shall be taken out without selection at several points 10 to 20 cm below the grain surface using a sampling shovel. 2.2.2 Sampling of round silos (country): Layer according to the height of the round silo (same as 2.2.1.2), each layer is divided into three circles according to the diameter of the round silo: inner (center), middle (half of the radius), and outer (about 30cm from the silo edge). For round silos with a diameter of less than 8m, each layer has 1, 2, and 4 points for the inner, middle, and outer respectively, for a total of 7 points. For round silos with a diameter of more than 8m, each layer has 1, 4, and 8 points for the inner, middle, and outer respectively, for a total of 13 points. Samples are taken point by point according to each layer.
2.3 Package sampling method
2.3.1 The number of medium and small grain and oilseed sample packages shall not be less than 5% of the total number of packages, and the number of wheat flour sample packages shall not be less than 3% of the total number of packages. The sampled packages should be evenly distributed.
When sampling, use the package sampler with the notch downward, insert it diagonally from one end of the package to the other end of the package, and then take it out with the notch upward. The number of samplings per bag is consistent.
2.3.2 Number of sampling bags of extra-large grains and oilseeds (such as peanuts, kernels, sunflower seeds, sesame seeds, large beans, sweet potato chips, etc.): No less than 10 bags shall be sampled for bags below 200, and 1 bag shall be added for every 100 bags above 200. When sampling, a combination of bag pouring and bag unpacking shall be adopted. Sampling ratio: 20% of the prescribed number of sampling bags shall be taken for bag pouring, and 80% of the prescribed number of sampling bags shall be taken for bag unpacking.
Putting bags: First, place the sampling bag on a clean plastic sheet or on the ground, remove the seams of the bag mouth, slowly put it down, hold the two corners of the bottom of the bag tightly with both hands, lift it up to about 50cm high, drag it down for about 1.5m, and after all the bags are poured out, use a sampling shovel to take out the sample from the middle and bottom of the bag. The number of samples per bag and per point is consistent.
Unpacking: Unsew 3 to 5 stitches of the bag mouth, and use a sampling shovel to take out the required samples from the top. The number of samples for each bag is the same. 2.4 Flowing grain sampling method
For sampling of mechanically transported grain and oil, first determine the number of sampling times and the number of samples to be taken each time according to the number of grain and oil to be inspected and the transmission time, and then take samples from the end of the grain flow at a fixed time. 2.5 Sampling method for sporadic collection and payment of grain and oil
For sampling of sporadic collection and payment (including procurement) of grain and oil, you can refer to the above method, combine it with the specific situation, and master it flexibly to ensure that the sample taken is representative.
2.6 Sampling for special purposes: such as grain inspection, pest investigation, determination of processing machinery efficiency and yield test, sampling can be taken as needed.
3 Sampling method
The process of fully mixing the original sample and then taking the average sample or test sample is called sampling. 3.1 Quartering method
Pour the sample onto a smooth and flat table or glass plate, and use two sample dividers to spread the sample into a square. Then scoop up the sample from the left and right sides of the sample to a height of about 10 cm, aim at the center and pour it down at the same time, then change the direction and do the same operation (the center point does not move), and repeat this four or five times to spread the sample into a square of equal thickness. Use a sample divider to draw two diagonal lines on the sample to divide it into four triangles, take out the samples of two opposite triangles, and repeatedly divide the remaining samples according to the above method until the remaining two opposite triangles are close to the required sample weight.
3.2 Sample divider method
The sample divider is suitable for the sample division of medium and small grains and oilseeds. The sample divider consists of a funnel, a sample divider grid, and a sample receiving hopper. The sample is divided into two parts through the sample divider grid.
When dividing the sample, place the clean sample divider steadily, close the funnel switch, place the sample receiving hopper, pour the sample into the funnel from about 5 cm above the funnel mouth, scrape the sample flat, open the funnel switch, and after the sample has flowed out, tap the sample divider shell, close the funnel switch, and then pour the samples in the two sample receiving hoppers into the funnel at the same time, and repeat the above method to mix twice. In the future, use the sample in one sample receiving hopper to continue dividing the sample according to the above method until the sample in one sample receiving hopper is close to the required sample weight. 210
Additional remarks:
This standard was proposed by the Ministry of Commerce of the People's Republic of China. GB5491--85
This standard was drafted by the Grain Storage and Transportation Bureau of the Ministry of Commerce. The main drafters of this standard are Gao Xiuwu, Yang Haoran, Wu Yanxia, and Lv Guifen. 211
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