JP3648986B2 - insulator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an insulator in which a metal fitting is bonded to a porcelain with a mortar, and obtains an insulator in which the mortar is not easily altered.
[0002]
[Prior art]
A conventional insulator will be described with reference to FIGS. 3 is a plan view of the insulator, and FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3 and 4, an insulator 1 for tightening a primary bushing wire of a transformer is shown as an example. The insulator 1 includes a porcelain 3 having a hole diameter portion 3a that is concave in cross section, and the hole diameter portion 3a. It consists of a metal fitting 5 as a columnar member which is bonded by a mortar 7 and has a hollow portion 5a.
[0003]
The manufacturing method of the insulator 1 comprised as mentioned above is demonstrated below. A metal fitting 5 is inserted into the hole diameter portion 3a of the porcelain 3, and a gap between the hole diameter portion 3a of the porcelain 3 and the metal fitting 5 is filled with mortar 7 in which water, cement, and sand as an aggregate are mixed at an appropriate ratio. The porcelain 3 and the metal fitting 5 are bonded by curing the mortar 7 by natural drying inside, and the insulator 1 is completed.
[0004]
[Problems to be solved by the invention]
However, the mortar 7 of the insulator 1 configured as described above may cause radial cracks (hereinafter referred to as hair cracks) from the metal fitting 3 to the outside over time, and the insulator 1 is functionally functional. It is conceivable that the above problem will occur.
[0005]
The cause of the occurrence of hair cracks is that thermal stress is applied to the mortar 7 due to the difference in the coefficient of linear expansion between the mortar 7 and the metal fitting 5 and radial cracks (hereinafter referred to as hair cracks) are generated from the metal fitting 5 toward the outside. It is estimated to be. That is, if the material of the metal fitting 5 is, for example, brass, the coefficient of linear expansion is 2.08 × 10 ⁻⁵ . Similarly, that of the porcelain 3 is 0.31 × 10 ⁻⁵ , and the surface portion of the metal fitting 5 is contracted. On the other hand, the surface portion of the porcelain 3 is considerably smaller than the metal fitting 5, and the difference between the two becomes the thermal stress of the mortar 7 and it is estimated that hair cracks occur in the mortar 7. A separate application was filed as a proposal for this measure.
[0006]
However, when the inventor subsequently studied, the cause of the occurrence of hair cracks in the mortar 7 was, in addition to the thermal expansion of the metal fitting 5, firstly expanded cracks due to the alkali-aggregate reaction of sand, and secondly, the cement Cracks due to delayed expansion, and thirdly, cracks due to frost damage of the mortar 7 are conceivable. Therefore, there is a problem that the cracks occur again unless measures are taken according to such other causes.
[0007]
This invention was made in order to solve the said subject, and it aims at providing the insulator with which a hair crack does not occur easily in mortar.
[0008]
[Means for Solving the Problems]
The insulator according to the first invention is a columnar columnar member made of metal, a porcelain having a hole diameter portion into which the columnar member is loosely inserted, and the columnar shape formed by loosely inserting the columnar member into the hole diameter portion of the porcelain. a insulator comprising a mortar filled into the gap between the outer peripheral surface and the opening part of the ceramic member, the mortar, cement 100 wt%, silica sand 200 wt%, 70 wt% water, admixtures 0. The mortar was blended at a ratio of 8% by weight , and the mortar was poured into the gap between the surface of the columnar member inserted loosely into the porcelain and the hole diameter portion, and the columnar member and the porcelain were bonded. Is.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
First, among the above estimated causes, first, expansion cracks due to alkali-aggregate reaction of sand were confirmed by the following experiment. According to the latest Canadian accelerated mortar bar test (CSAA 23.2-25A, 1994) with high detection sensitivity, ASTM formwork (2.54 × 2.54 × 28.6 cm) was subjected to post-powder particle size adjustment. Aggregate (4.75 mm to 0.15 mm, 5 stages) and 600 g of cement, 1350 g of aggregate, and 300 g of water are mixed to prepare mortar 7, and after pre-curing, in an alkaline solution at 80 ° C. (1 N NaOH) After soaking, the expansion rate of the mortar 7 was measured as shown in FIG. In this test, the expansion rate of 0.15% after 2 weeks is regarded as harmful, so the result of FIG. 5 is determined to be harmful.
[0012]
When the mortar 7 was sliced into thin pieces and confirmed with a polarizing microscope, a chart 17 as a substance showing an alkali-aggregate reaction was confirmed as shown in the schematic diagram of the polarizing microscope in FIG. Therefore, it is conceivable that drying shrinkage of the cement paste overlaps with the cracks 17a, and cracks occur in the porcelain 3.
[0013]
Second, the following experiment was conducted on delayed expansion of cement. Cement paste packed in ASTM formwork (2.54 × 2.54 × 28.6 cm) is pre-cured and then boiled in an autoclave (2 Mpa = 216 ° C.) for 3 hours, and reduced in pressure and cooled (from 90 ° C. to 23 ° C. As a result of measuring the rate of change in the length, the expansion coefficient was 0.00 (%), which is 0.8% or less according to the Portland cement quality standard ASTM C150.
[0014]
Thirdly, in order to confirm the frost damage of the mortar 7, the cocoon 1 is subjected to a freezing state (-20 ° C. to −25 ° C. for 7 hours) and a thawed state (5 ° C. to 10 ° C. for 12 hours) as one cycle. As it was confirmed that no hair cracks were generated in the mortar 7 even after 10 cycles, it is estimated that this is not the cause.
[0015]
Since the other cause of hair cracks in the mortar 7 has been confirmed as expansion cracking due to alkali aggregate reaction as described above, an embodiment of the present invention embodying this countermeasure will be described with reference to FIGS. . FIG. 1 is a plan view of an insulator showing an embodiment according to the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG. In the figure, the same reference numerals as those in the prior art denote the same or corresponding parts, and a description thereof is omitted.
[0016]
1 and 2, the mortar 107 of the insulator 100 is generated using a material that easily causes an alkali-aggregate reaction, for example, silica mineral such as opal and cristobalite and sand that is an aggregate not containing volcanic glass. . Here, in order to obtain such sand, for example, standard sand (specified in JIS cement test -1993) manufactured from natural silica sand produced in Toyoura-gun, Toyoura-gun, Yamaguchi is suitable. In addition, when the metal fitting 5 consists of brass etc., it is preferable to apply | coat the varnish as a corrosion inhibitor to the surface of the metal fitting 5 in order to prevent the corrosion of the contact part of the metal fitting 5 and the mortar 107.
[0017]
It is known that the alkali concentration in concrete is, for example, 3.0 kg / m ³ or less (JIS A 5005-1993). However, the alkali concentration of the mortar 107 must be such that the mortar 107 is poured into the gap between the hole diameter portion 3a of the porcelain 3 and the metal fitting 5 to bond the porcelain 3 and the metal fitting 5 with a predetermined strength.
[0018]
On the other hand, the mortar 107 has a characteristic that the adhesive strength decreases as the alkali concentration decreases, and conversely, the mortar 107 has a characteristic that the viscosity decreases as the alkali concentration increases. Here, the alkali concentration of the mortar was 3.44 kg / cm ³ , and it was confirmed that no cracks occurred in the mortar 107 even when a torque of 250 to 300 kgcm was applied to the metal fitting 5. In this case, the mortar 107 is mixed with 100 g of cement, 200 g of silica sand, 70 g of water, and 0.8 g of an admixture to obtain the above alkali concentration.
[0019]
【The invention's effect】
According to the first invention, a columnar columnar member made of metal, a porcelain having a hole diameter portion for loosely inserting the columnar member, and the columnar member formed by loosely inserting the columnar member into the hole diameter portion of the porcelain. The mortar is filled with a mortar filled in the gap between the outer peripheral surface of the porcelain and the pore diameter portion of the porcelain. The mortar is composed of 100% by weight of cement, 200% by weight of silica sand, 70% by weight of water, and 0.8% of an admixture. Since the mortar was poured into the gap between the surface of the columnar member loosely inserted in the porcelain and the hole diameter portion and the columnar member and the porcelain were bonded , the metal fitting was attached to the porcelain. The mounting workability is improved, and further, the alkali aggregate reaction of the mortar is suppressed, the expansion of the mortar is reduced, and there is an effect of obtaining an insulator in which the crack is unlikely to occur in the mortar.
[Brief description of the drawings]
FIG. 1 is a plan view of an insulator showing an embodiment according to the present invention.
2 is a cross-sectional view taken along the line II-II in FIG.
3 is a plan view of a conventional insulator. FIG. 4 is a cross-sectional view taken along arrows IV-IV in FIG.
FIG. 5 is a characteristic curve diagram showing an alkali aggregate reaction of mortar.
FIG. 6 is a schematic view of a photograph of a mortar flake taken with a polarizing microscope.
[Explanation of symbols]
3 Porcelain, 3a hole diameter part, 5 metal fitting (columnar member), 100 insulator, 107 mortar.

Claims (1)

A columnar columnar member made of metal, a porcelain having a hole diameter portion for loosely inserting the columnar member, an outer peripheral surface of the columnar member formed by loosely inserting the columnar member into a hole diameter portion of the porcelain, and a hole diameter of the porcelain An insulator with a mortar filled in a gap with the part,
The mortar, cement 100 wt%, silica sand 200 wt%, 70 wt% water, as well as compounding the admixture in a proportion of 0.8 wt%, and the surface of the columnar member of the mortar is loosely inserted into the porcelain An insulator characterized by being poured into a gap with the hole diameter portion and bonding the columnar member and the porcelain .

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