JPS6223628B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a rubber-lined cast steel pipe by applying a rubber lining to the inner surface of a flanged cast steel pipe.

Fluid transfer pipes for slurry, crude oil, gas, etc. are usually manufactured by centrifugal casting, and therefore bubble impurities are likely to form on the inner surface of the cast pipe. It is known empirically that the thickness of the unsound layer where air bubbles and impurities are mixed is in the range of 10% from the inner surface, so cast pipes should be cast with an extra thickness in advance so that the inner wall thickness of the tube is 10%. It is common practice to cut the pipe after casting to remove the unsound layer and finish it to a predetermined size, and finally weld flanges to both ends of the pipe.

However, cutting the inner surface of the cast pipe to a thickness of 10% after casting is a waste of material, so a rubber lining layer is formed on the inner surface of the cast pipe to cover the unsound layer. It is also conceivable that the material can be effectively utilized as part of the wall thickness of the fluid transfer pipe. However, when a flange is welded to a cast pipe on which a rubber lining layer has been formed, the rubber lining layer is destroyed by the welding heat input, making it impossible to use it as a fluid transfer pipe. Because of these problems, it has been considered difficult to manufacture flanged cast steel pipes with rubber lining.

In the present invention, flanges are welded to both ends of a straight cast steel pipe in advance, and by forming a protruding part on the inner surface of the flange that slightly protrudes into the inside of the cast steel pipe, the inner protruding part collects a rubber lining agent and then the cast steel pipe is melted. To provide a method for easily manufacturing a flanged rubber-lined cast steel pipe by rotating the pipe and without involving air in the rubber lining agent.

In the manufacturing method of the present invention, a cast steel pipe is manufactured into a straight pipe with both ends open by known centrifugal casting.

Note that in this application, the term "cast steel pipe" includes not only those manufactured by centrifugal force casting, but also cast pipes and steel pipes manufactured by other methods.

The cast steel pipe 1 has flanges 2, 2 welded in advance to openings at both ends, respectively. As shown in the drawing, the flanges 2, 2 have an outer flange portion 3 that largely protrudes outward.
and an inward protrusion 4 that protrudes slightly inward from the inner surface of the tube.

The flanged cast steel pipe 1 is further fitted with a pair of steady rest rings 5, 5 which are divided into two parts, and the pair of steady rest rings 5, 5 are connected in a ring shape by a connecting fitting 6, and the cast steel pipe 1 and the steady rest are connected to each other in a ring shape. The steady rest rings 5, 5 are fixed to the cast steel pipe 1 by weak spot welding at several places between the rings 5, 5, to the extent that they can be easily separated later by hitting the steady rest rings 5, 5 with a hammer.

The cast steel pipe 1 is placed on rotating rollers 8 and 9 of a centrifugal casting machine 7, and one rotating roller 9 has grooves 10 on its circumference.
By applying this, the steady rest ring 5 is held in place, and the cast steel pipe 1 can be rotated while suppressing lateral vibration.

The cast steel pipe 1 is preheated to 100-130° C. before being installed in the casting machine or after being supported on the rotating rollers 8, 9 of the casting machine.

While continuing to preheat the cast steel pipe, add a separately prepared rubber lining agent to the cast steel pipe by a pre-calculated weight.
Pour it inside. In the present invention, since the flanges 2, 2, which are welded in advance to both ends of the cast steel pipe 1, are provided with the inwardly protruding parts 4, the rubber lining agent can reach the bottom of the cast steel pipe 1 while the rotation of the cast steel pipe 1 is stopped. It can be poured quietly so that it collects at a depth of 3 to 6 mm, and air is prevented from being drawn into the rubber lining agent during injection.

The rubber lining agent can be selected as long as it exhibits corrosion resistance for the inner surface of the cast steel pipe, but for example, a two-component urethane elastomer (UTM-1), which is a mixture of polytetramethylene glycol and TDI prepolymer, can be used as the rubber lining agent. Trademark) (manufactured by Toyo Rubber Industries, Ltd.) is used.

The rubber lining agent is prepared by preheating the main agent to 80°C,
Leave the mixture under 5 mmHg for 30 minutes to defoam, then mix the hardening agent heated to 120℃ and melt it, stir for 2 minutes, and leave this mixture under 5 mmHg for 3 minutes. It was degassed.

After pouring the rubber lining agent, the casting machine 7 is driven to gradually rotate the cast steel pipe 1 to uniformly spread the rubber lining agent over the inner surface of the cast steel pipe 1.

The cast steel pipe 1 increases its rotational speed to a predetermined rotational speed so that a centrifugal force of approximately 50 G (G is the acceleration of gravity) acts on the rubber lining agent, and continues to rotate for approximately 1 hour.

The rubber lining agent coats the inner surface of the cast tube to a uniform thickness, and adheres closely to the inner surface of the tube due to preheating of the cast tube 1 and centrifugal force, forming a rubber lining layer 11 with a thickness of about 3 mm.

Thereafter, the rotation of the casting tube 1 is stopped, and the lining layer 11 is heated and dried at 120° C. for 4 hours to harden and complete the lining layer 11.

The extra length of the inwardly protruding portion 4 of the flange 2 that protrudes from the lining layer 11 is cut off, and the third
As shown in the figure, the inner surface of the lining layer 11 and the inner peripheral surface of the inwardly protruding portion 14 of the flange 2 are finished to have the same inner diameter.

After that, the connecting fitting 6 of the steady rest ring 5 is removed, the spot welds that fasten the steady rest rings 5, 5 and the cast steel pipe 1 are broken by hitting with a hammer, and the flanged rubber-lined cast steel pipe is separated from the cast steel pipe 1. can be obtained.

When pouring the rubber lining agent, it is not necessary to particularly finish the inner surface of the cast steel pipe to make it smooth, or to apply any pretreatment or adhesive.The rubber lining agent is poured onto the as-cast surface. As a result, an excellent rubber lining layer 11 can be formed.

As described above, the flange portion 3 is attached to the outside of the flanged lined cast steel pipe by bolts and nuts 12.
When connected to form a pipeline, cast steel pipe 1
The unsound layer 13 remaining inside the pipe is covered by the lining layer 11 and is not exposed to the outside, and contact with the fluid being transferred is blocked, so it will not cause corrosion or cracks, and the transfer pipe cannot be used. There is no problem at all.

Moreover, the flange 2 is welded to the cast steel pipe 1 before lining is applied, and no welding is performed after the lining layer 11 is formed, so the lining layer 11 is not destroyed by welding, and the desired flanged rubber We can manufacture lined cast steel pipes. or,
Since the cast steel pipe can be used by forming the lining layer 11 including the unsound layer 13, there is no need to cast an extra wall thickness during casting as in the conventional method, and the unsound layer 13 can be cut off after casting. It exhibits many excellent effects, such as eliminating the need for removal.

[Brief explanation of the drawing]

Figure 1 is a front view showing the state of implementation of the manufacturing method;
FIG. 2 is a partially cutaway front view of a cast steel pipe in the process of being manufactured, and FIG. 3 is a partially cutaway front view showing how the flanged rubber-lined cast steel pipe is used. DESCRIPTION OF SYMBOLS 1... Cast steel pipe, 2... Flange, 3... Outer flange part, 4... Inward protrusion part, 7... Centrifugal casting machine, 11...
lining layer.

Claims (1)

[Scope of Claims] 1. Flanges that protrude significantly outward from the pipe and project a short appropriate length inward are welded to the openings at both ends of a straight cast steel pipe, and after preheating, a rubber lining agent is applied to the inner surface of the cast steel pipe. A method for manufacturing a flanged rubber-lined cast steel pipe, which comprises: injecting the rubber lining agent into the inner surface of the cast steel pipe by rotating the cast steel pipe at high speed, and drying and hardening the rubber lining layer. 2. The manufacturing method according to claim 1, wherein the cast steel pipe is preheated to 200°C for 1 to 2 hours. 3. The manufacturing method according to claim 1 or 2, wherein the rubber lining agent is a urethane elastomer prepared by stirring and mixing polytetramethylene glycol and TDI prepolymer. 4 The rotational speed after the rubber lining agent is injected into the cast steel pipe is such that a centrifugal force of approximately 50G (G is gravitational acceleration) is maintained on the rubber lining agent for approximately 1 hour. Manufacturing method stipulated by crab. 5. The manufacturing method defined in any one of claims 1 to 4, wherein the rubber lining layer is dried by continuing heating at 120°C for 4 hours.