cable news: cross linked cable inspection should consider special factors-非凡电子娱乐

in recent years, silane crosslinked polyethylene cable material (hereinafter referred to as xlpe), because of its simple manufacturing equipment,

the technology has the advantages of mature technology, convenient operation, low cost and so on.

currently commonly used xlpe, one is the two step xlpe,

in the production of insulated wire core, the silane grafted polyethylene (pe) and the catalyst masterbatch were mixed in a certain proportion,

the utility model is extruded in an ordinary extruder, and then cross-linked in hot water or steam, and the other one step xlpe is produced by the cable material manufacturer,

all the raw materials are mixed in a special way according to the proportion, and the cable factory directly completes the grafting and extrusion of the insulating wire core at the same time,

and then complete the crosslinking under natural conditions. the common point of the two xlpe is that without special extrusion equipment, the crosslinking process is relatively simple,

as long as the raw materials and process conditions meet the requirements, it can be made into insoluble, non fusible thermosetting plastics. compared with thermoplastic pe,

the thermal deformation and mechanical properties at elevated temperature, environmental stress cracking, aging resistance, chemical resistance and so on have been improved or improved,

and the electrical performance is still kept unchanged, and the long-term working temperature of the cable from the original 70 c to = c,

therefore, the ability of short time withstand current of the cable is improved. to sum up, xlpe low voltage cable has become the main products of cable manufacturers in recent years.

as the third party inspection agency inspection of the cable is also increasing year by year, how to accurately provide such products, such as thermal expansion and aging performance test results,

inspectors face a number of special circumstances, the following analysis:

first, the problem of xlpe insulation thermal stretch anomaly. i often find in the detection,

the elongation of the xlpe cable insulation under the thermal elongation test at 200 deg c exceeds the standard requirements,

or the sample into the oven within a very short period of time to fuse, if immediately with the original retest, the results are very good reproducibility,

if in accordance with the routine, as long as the test method is correct, sampling correctly, according to the results of the test can determine the conclusion,

but for xlpe, there may be a lot of risk. because the crosslinking process of xlpe is related to temperature, humidity and time,

insulation thickness and other factors related to the slow chemical changes in the process, in particular, naturally cross-linked xlpe insulation,

it is affected by the above factors, there will be a big difference in the time to complete the cross-linking, it is possible in the specified test period,

natural crosslinking. once the natural crosslinking has been completed over time, its performance may meet the requirements of national standards.

for such cases, the author believes that the current situation in the sample reflects the premise, can not be eager to determine,

instead, it should provide a condition to promote crosslinking of the sample - soaking in hot water at 90 deg c c = 2 to for 4 hours and then for thermal expansion test.

practice has proved that the results of this test can be used as the basis for judgment. it is worth mentioning that individual manufacturers one-sided pursuit of commercial profits,

pe and pe are similar to xlpe, and the pe can be regarded as xlpe, but no cross link can be generated by the condition of crosslinking,

it is not in the performance of the xlpe requirements, which can not be hatched with stones is a reason. this requires the inspectors should have the ability to identify true and false, good or bad xlpe.

in fact, through the observation and accumulation, we can according to the sample in the fuse time, the melting point of oven to distinguish whether a test sample belongs to owe crosslinking, inferior xlpe,

or use pe? however, as third party inspectors, it is impossible to draw conclusions from experience, must be based on the actual data to determine.

second, the problem of excessive change rate of xlpe thermal aging test. during the test, if the sample is obtained, make the sample immediately,

often appear after aging tensile strength, elongation at break rate exceeds the phenomenon, the results must be careful to determine.

this phenomenon is not entirely due to poor performance caused by aging, it may be because the xlpe has not yet fully cross-linked (xlpe cable material from the extension of the hot water can be placed in the time curve can be seen),

when the heat is qualified, it does not mean that the sample is fully crosslinked, and the xlpe is still in the process of cross-linking, which results in the increase of tensile strength,

the elongation at break decreased and the final change rate exceeded. due to the completion of the aging time is longer, once the trial is over and then find the problem is more trouble,

therefore, it is necessary to make the sample completely cross-linked and then aging test.

to sum up, it can be seen that the thermal expansion and thermal aging of xlpe should be taken into account. personnel engaged in the third party inspection, neither hasty conclusion for the test results,

because of this there is a qualified product misjudgment as a risk of failure; nor because the conclusions are difficult to avoid these two tests do not do,

this is likely to allow substandard products or counterfeit products missing. therefore, it is necessary to exclude the samples which have not been cross-linked or completely crosslinked before the two tests are carried out.

we advocate the use of scientific and rational means of testing, to provide a fair and reliable test results.