JPH0275186A - Sheath heater fitting structure - Google Patents

Abstract

PURPOSE:To apply the maximum face pressure to the inner diameter side end face for sealing, prevent the occurrence of a crevice, and prevent the occurrence of the crevice corrosion in stainless steel by forming the cross section shape of a sealing packing into a trapezoid which is thicker on the inside than on the outside. CONSTITUTION:A flange section 7 fitted with a cease heater 6 is fastened and fixed with multiple fixing bolts 9 via a circular sealing packing 8 on a heater fitting seat face 2 openly fitted to a stainless can 1. The packing 8 is formed into a trapezoidal cross section structure which is thicker on the inner diameter side than on the outer diameter side, thus the face pressure of the seal face is made maximum at the inner diameter side 8a section, and the infiltration of water into the can is prevented. The occurrence of crevice corrosion which is most feared of IN stainless steel can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the structure of a stainless steel can electric water heater, and particularly to a suitable sheathed heater mounting structure that does not cause crevice corrosion.

[Conventional technology]

The shape of the sealing gasket of the conventional sheathed heater mounting portion is a ring-shaped plate gasket 19 or an O-ring shape 20, as shown in FIGS. 8(a) and 8(b). When the seal is tightened using this seal, a gap is created between the seal and the seal seat at the A part and the mouth part, as shown in FIG. 4(a) Φ). Incidentally, related devices of this type include, for example, Utility Model Publication No. 5805-1985 and Utility Model Application Publication No. 58-58.
No. 15150 etc. are mentioned.

[Problem to be solved by the invention]

The above conventional technology only considers sealing performance, and does not take into account the prevention of gaps on the sealing surface.
There was a problem with crevice corrosion of metals, especially stainless steel. To explain this point with reference to FIG. 4, the sealing area between the sealing surface 17a on the sheathed heater side and the packing on the sealing surface 12a on the mounting seat side is as follows. The inside of is open in the radial direction and is the smallest,
A gap occurs in the part. In the case of (b), a gap such as a mouth portion is clearly visible even in the illustration. When these gaps are formed, there is a problem in that corrosion of the sealing surface (generally referred to as crevice corrosion) progresses from the gaps, leading to water leakage.

An object of the present invention is to provide a structure that prevents the occurrence of gaps on the sealing surface. In particular, in the case of stainless steel materials, this crevice corrosion is significant, so a sealing structure that does not generate any crevices is required.

[Means to solve the problem]

The above object is achieved by providing a structure in which the sheathed heater is attached and sealed using a substantially trapezoidal cross section of the annular packing around the seal.

[Effect]

The sealing padkin, which has a roughly trapezoidal cross-sectional shape, is
When installed tightly between the heater mounting side seat surface and the sheathed heater flange, the long side (inside) of the gasket cross section
Since the tightness is wider on the short side (outside), the surface pressure against the heater mounting seat surface becomes larger. As a result, water can be completely sealed on the long side of the gasket that comes into contact with water, so there is no gap between the gasket and the heater mounting surface, and crevice corrosion can be prevented. can.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

■ is the can body, 2 is the heater mounting seat opened and attached to the can body 1, 8 is the water supply port provided at the bottom of the can body l, 6 is the hot water supply port provided at the top of the can body 1, and 5 is the hot water storage part , 6 is the sheathed heater inserted and attached to the can body 1, 7 is the sheathed heater 6 7272
Section, 8. d Seal packing, 9 is a fixing bolt.

With the above structure, the temperature of the water in the hot water storage section 5 is raised by the sheathed heater 6 to become hot water, and the sheathed heater 6 is pushed up by the water supplied from the water supply port 8 and hot water is supplied from the hot water supply port 4. is fastened to the heater mounting seat surface 2 via an annular seal packing 8 with a plurality of fixing bolts 9. Here, the seal packing 8 has a substantially trapezoidal cross-sectional structure in which the thickness on the inner diameter side is larger than the thickness on the outer diameter side. Therefore, when the seal packing 8 is sandwiched between the sealing surface 2a of the heater mounting seat surface 2 and the sealing surface 7a of the sheathed heater flange 7, the edge 8a of the long side of the sealing packing 8 is Short side 8
The compression allowance is larger compared to b, and the sealing surfaces 2a and 7a
The surface pressure acting on the surface is maximum at part 8a. As a result, the water contact part is completely sealed with these 88 parts, and the BI
Water does not enter the section 8b which is radially outward from the section A.

According to this embodiment, since the seal portion can be tightened without creating a gap, it is possible to prevent crevice corrosion in the water-contacted portion.

Particularly when the mounting surface is made of stainless steel, the effect of preventing crevice corrosion is remarkable.

〔Effect of the invention〕

According to the present invention, by making the cross-sectional shape of the sealing packing substantially trapezoidal in which the thickness on the inner diameter side is larger than the thickness on the outer diameter side, the maximum surface pressure is applied at the end surface on the inner diameter side of the sealing packing. Since it can be sealed, it is possible to prevent gaps from forming on the sealing surface. As a result, there is an effect of preventing the occurrence of crevice corrosion, which is the most feared problem in stainless steel.

[Brief explanation of the drawing]

Fig. 1 is an enlarged exploded view of a sheathed heater mounting structure according to an embodiment of the present invention, Fig. 2 is a configuration diagram of a can body to which the sheathed heater of the present invention is attached, and Figs. 3(a) and 3(b) are prior art. FIGS. 4(a) and 4(b) are cross-sectional views of the seal gasket shown in FIG. 8, in which the seal gasket shown in FIG. 8 is installed. 2... Heater mounting seat surface 2a... Heater mounting seat seal [iU 7a... Sheathed heater flange sealing surface 8a... Seal seal long side end point 8b.
・Leakage point on the short side of the seal seal.

Claims (1)

[Claims] In the mounting structure of the sheathed heater part that is tightened and sealed with a sealing packing interposed on the stainless steel sheathed heater mounting seat, the cross-sectional shape of the sealing packing is as follows.
A sheathed heater mounting structure characterized by having a substantially trapezoidal shape in which the inner width dimension is larger than the outer diameter width dimension.