JPS6246431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The disclosed technique relates to a technique for removing a welded sealing cover of a manhole provided on the side of a tank such as a flat-bottomed cylindrical tank.

Therefore, when opening a manhole for construction, inspection, etc. provided on the side of the tank body of the flat-bottomed cylindrical tank, etc., for inspection, first remove the screwed outer cover of the manhole, and then open the cylindrical body. This relates to a manhole opening method in which gas is disconnected from the airtight lid, and in particular, after purging the accumulated material in the tank, the manhole is entered through the upper manhole of the tank, and an inner lid is attached to the inner end of the cylinder of the side manhole before and after that. Then, a safety gas such as an inert gas is supplied between the inner cover and the airtight cover using a hose passed through the upper manhole to replace the explosive gas, and before and after that, the outer cover is closed. This relates to a method for opening a manhole in a tank, in which the sealing lid is cut and removed without causing any ignition or explosion, and finally the inner lid is removed from the inside or outside.

As is well known, when building a tank, a manhole is provided in the tank body to allow materials to be brought in and out during construction, to allow workers to enter and exit, and to serve as a work entrance and exit during inspections.

For example, in the inner tank frame 2 of the flat-bottomed cylindrical tank 1 shown in FIG. 1, an upper manhole 3 is provided at the top in contrast to the outer tank manhole, and a side manhole 4 is provided at the lower side.

Therefore, of course, the upper manhole 3,
The side manhole 4 also has a cylindrical body 6 for sealing against the liquid storage 5 during operation and for opening during inspection.
An outer cover 7 is screwed and fastened to the flange 10 of the outer end using bolts 8 and nuts 9.

However, even if a gasket or the like is inserted into the outer lid 7, a sealing lid 12 is provided on the cylindrical body 6 to prevent leakage of the stored liquid 5 due to thermal behavior caused by operation over time, and a complete pressure-resistant seal is achieved by welding 13. are doing.

Therefore, during inspection, it is necessary to remove the outer cover 7 and open the sealing cover 12, which usually reduces work efficiency and
Gas cutting means is used for reliability and other reasons.

Of course, upon opening, the gas is cut off after the discharge of stored liquid and gas purge are completed through a predetermined mechanism (not shown); however, in a vast tank space, it may not always be possible to completely purge the residual gas locally. In such cases, gas cutting has the disadvantage that the residual gas may easily ignite and cause an explosion.

The purpose of this invention is to solve the problem of opening the side manhole of a tank based on the above-mentioned conventional technology. Attach the inner lid to the end to seal it, and purge and fill the tank gas by supplying safety gas such as inert gas through the hose, and before and after that, remove the outer lid and close the airtight lid. To provide an excellent method for opening a manhole in a tank by cutting off gas, preventing ignition and explosion, and finally removing the inner cover from either the inside or the outside.

Next, a third embodiment of the present invention that meets the above objectives will be described.
The explanation will be as follows with reference to the drawings below. Note that the same parts as in FIGS. 1 and 2 will be described using the same reference numerals.

In the embodiment shown in FIG. 3, when the tank is in operation, that is, after the tank is constructed, the manhole 4' opposite to the outer tank manhole has a cylindrical body 6 provided on the inner tank side plate 2 that also faces into the tank. ' and a flange 1 at the inner end.
1 and is in an open state.

The outer tank 7 is tightened and screwed onto the outer end flange 10 via bolts 8 and nuts 9, and a sealing lid 12 is sealed and fixed to the inside via welding 13.

In this way, tank operation is performed with the stored liquid 5 stored, and when performing periodic inspection at a predetermined timing, the stored liquid 5 and gas are purged via a predetermined mechanism,
Open the upper manhole 3 (of course open the outer tank manhole), the worker enters, and open the valve 14 as shown in the figure.
An inner lid 18 to which gas hoses 16 and 17 having gas hoses 15 and 15 are sealed is tightly attached to the inner end flange 11 of the cylindrical body 6' via bolts 8 and nuts 9. Gas is supplied to purge and replace residual gas in the space 19 between the inner lid 18 and the sealing lid 12 to fill it.

For convenience of illustration, the outer tank 20 is shown in the figure so that the valves 14 and 15 are set at predetermined operation parts outside the tank.

After completing the replacement, close the valves 14 and 15.
The outer cover 7 is removed by bolts 8 and nuts, and the sealing cover 12 is gas-cut from the outside as shown in FIG.

However, since the space 19 is filled with inert gas as described above, no explosion will occur due to the gas arc, the sealing lid 12 is removed, and the inner lid 18 is finally opened from the inside. As shown in the figure, remove it with the bolt 8 and nut 9, allowing it to move in and out as shown by the arrow, completing the release.

For inspection and repair work, materials are brought in and out and workers are brought in and out from the manhole 4' and the upper manhole 3 as appropriate. After the work is completed, the sealing lid 12 is welded and sealed, and then the outer lid 7 is attached and tightened to resume operation. Be prepared.

It goes without saying that the embodiments of the present invention are not limited to the above-mentioned embodiments. For example, by turning the end flange of the cylinder inward, the bolts can be loosened from inside the cylinder, and after cutting the sealing lid, the bolts can be loosened from inside the cylinder. Various configurations are possible, such as allowing the lid 18 to be removed.
In addition, target tanks include gas tanks, oil tanks, etc. in addition to low-temperature tanks.

Then, the inner cover is fastened to the inner end of the cylinder in advance,
An embodiment of the present invention also includes a mode in which a gas hose is introduced from the upper manhole and connected with a nipple to a screw hole cut into the inner cover for gas replacement.

Also, instead of introducing the gas hose from the upper manhole, a gas cylinder is brought in, connected to the inner lid with a hose, and gas is replaced.

As described above, according to the present invention, when the residual gas after purging the tank is explosive during a tank opening inspection, in the method of opening the side manhole, the gas is first entered through the upper manhole, and before and after that, the side manhole is opened. An inner cover is attached to the inner end of the manhole, and a safety gas such as inert gas or air is supplied between the sealing cover of the cylinder and the inner cover to purge and replace hazardous gas. By doing so, it is ensured that there is no dangerous explosive gas inside the sealing lid to be cut before the gas is cut off, and therefore, when the tank is opened, the contents are not fully discharged and the gas purge is not completed, and residual gas is removed. This is an excellent effect in that gas cutting can be carried out safely even if the presence or absence of gas cutting cannot be confirmed, and the merits of gas cutting can be fully demonstrated.

There is also an advantage that the sealing lid does not fall into the tank after the gas is cut off, and the inner lid can serve as a support.

Therefore, the inner cover has the advantage that it can also be used as a hose support for gas replacement, and depending on the construction, it also has the advantage that the cover of the upper manhole can be used.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of the tank, Fig. 2 is an explanatory diagram of a side manhole according to the prior art, Fig. 3 and the following are explanatory diagrams of one embodiment of the present invention, and Fig. 3 is an explanation of the inner cover set state. FIG. 4 is an explanatory diagram of the closed lid cut away, and FIG. 5 is an explanatory diagram of the manhole in an open state. 1...tank, 2...framework, 4'...manhole,
6, 6'... Cylinder body, 7... Outer lid, 12... Sealing lid, 18
...Inner cover, 3...Upper manhole, 16, 17...Hose.

Claims (1)

[Claims] 1. In a manhole opening method in which an outer cover screwed to the outer end of a cylindrical body of a manhole provided on the side of a tank body and facing into the tank is opened and a sealing cover welded inside the cylindrical body is opened and closed by gas cutting, An inner cover is attached to the end of the cylinder, and a hose is provided to the inner cover through the upper manhole to fill the space between the cylinder inner cover and the sealing lid with safety gas, and the above-mentioned gas is filled before and after the hose. Open the outer lid, remove the airtight lid by gas cutting,
A method for opening a manhole in a tank, characterized in that the inner cover is opened at the end.