GB1558834A - Repair of metallic components - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THE REPAIR OF METALLIC COMPONENTS (71) I, JOHN KENDELL HOWARD HALL, of Audley End, 18 Fernbank Road, Ascot, Berkshire, SL5 8ED, a British Subject, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the repair of metallic components, for example, the repair of worn dredge pump casings by replacement of material.

edge pump casings tend to wear from abrasion by the materials passing through the casings.

Hitherto, when excessive wear has taken place, several courses of action have been available, namely: a) Replacement of the pump casing.

However, this normally involves cutting a hole in the side of the dredger.

b) Welding a plate sleeve into the pump casing. However, a plate sleeve has a limited life.

c) Build-up of material within the pump casing by welding. One such method has been developed in the U.S.A. and involves the use of a welding machine. (The McKay Dredge-o-Matic). The machine is set up within a pump casing and a welding head attached to a rotating telescopic arm carried by the machine is rotated by a follower which engages in a scroll corresponding to the interior of the pump casing.

This process has two disadvantages however, namely that large input of heat generated by the welding can cause cracking and/or distortion of the component, and that it tends to be expensive.

According to one aspect of the present invention, a method of repairing a worn metallic component, for example, a dredge pump casing, comprises making a pattern corresponding to a mass of material to be replaced, using the pattern to cast a body of replacement material and then securing the cast body to the component.

The pattern may be made in situ and to this end maybe made by the use of expanded plastics material.

The invention also comprises the cast body manufactured whilst performing the novel method of repair and further comprises a worn metallic component repaired by the said method.

The various aspects of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a side view of a dredge pump casing, Figure 2 is an enlarged view, in section, taken on the lines II--II of Figure 1, but with added components, and Figure 3 is a fragmentary view, in section, illustrating a repaired portion of the casing.

With reference to Figure 1, a dredge pump casing 1 has areas of excessive abrasive wear, A, B and C. Rather less wear takes place between said areas.

With reference to Figures 2 and 3, in order to replace the whole, or substantially the whole of the worn material, patterns 2 are made, each of which patterns corresponds to the mass of material to be replaced at a particular area of wear. Each pattern 2 is then used to cast a body 3 (Figure 3) of replacement material, moulded to the worn contour of the casing, which is subsequently secured to the casing 1 at the corresponding point of wear.

In further detail, to replace the worn material, one or more formers 4 are first made, preferably of G.R.P.

(Glass-reinforced plastics material), whereby the "inner surface" of a former corresponds to the original profile of the casing 1.

The cavity at a selected area of wear and the inner surface of the former 4 are coated with a release agent and the former 4 place in position so as to cover the cavity. The former 4 is then held in place by a pair of cramps 5 located by the usual securing bolt holes (not shown) formed in the sides of the casing 1. The cramps 5 carry height-adjustable pillars 6 which are made to hold the former 4 in place. Lateral adjusting screws (not shown) are carried by the pillars 6 so as to provide for lateral adjustment of a former 4.

A pattern 2 is made is situ from expanded plastics material but expanded polystyrene may be used as an alternative. The expanded material is produced by placing a suitable resin and catalyst in a container provided resin catalyst in a container provided with a nozzle. The container is then shaken so as to mix the ingredients whereby the expanded material is formed, and the expanded material introduced between the former 4 and adjacent material of the pump casing 1, using the nozzle of the container.

After the expanded material, has set to form the pattern 2, both the former 4 and pattern 2 are removed. Conventional moulding techniques are then employed, using the pattern 2, so as to produce the cast body 3. (Figure 3).

Subsequently, the cast body 3 is secured in place, for example, by pins, bolts, studs, or as shown in this example, by laterally-extending welding 10. As also shown in Figure 3, the edges of a body 3 are preferably chamfered whereby adjacent parts of the contiguous bodies overlap with the bevels sloping downstream of fluid flow through the pump. Use of the bevelled edges results in protection of the welding 10 from the "scouring" action of material passing through the pump, as water flowing through the casing 1 passes over the bodies 3 and is not forced between them. The overlapping arrangement also results in interlocking of the contiguous bodies 3.

If additional securing of bodies 3 is required, this can be done by perforating the casing 1 and securing the bodies 3 from outside, using welding. All gaps can be subsequently filled by welding to provide a neat surface contour. Where such welds are subject to wear they are preferably hard-faced.

The make pattern/make cast body technique is repeated for material replacement at all worn areas, including exessive wear areas B and C so that the interior of the pump casing is eventually "plated" by interfitting cast bodies 3 of varying shape.

A rotatable jig may be provided to assist welding. Rotation of the jig enables the material worked on to be turned to a horizontal position and enables all welding to be carried out in the down hand position.

Bodies 3 can be cast from the same material used to manufacture the pump casing 1, or, where possible, from more wear resistant material.

Calculations indicate that the invention reduces the cost of repairing a pump casing by a substantial amount. Typically, the current cost of using a welding machine amounts to 90 pence/pound for electrode material, plus welding current, plus welder's time. Using the present invention, the cost of producing a cast body 3 is expected to amount to 60 pence/pound.

In addition, the invention avoids the heavy inputs of heat and so avoids cracking and/or distortion.

Preferably, if a new, i.e. unworn casing 1 is available, formers 4 can be produced therefrom.

Local welding, (welding 10), unlike the build-up welding process referred to above, does not cause cracking and/or distortion.

Where barrelling of the casing has taken place, precision cast cheek plates can be fitted in addition to the bodies 3.

WHAT I CLAIM IS: 1. A method of repairing a worn metallic component, for example, a dredge pump casing, comprising a pattern corresponding to a mass of material to be replaced, using the pattern to cast a body of replacement material and then securing the cast body to the component.

2. The method of Claim 1, wherein the pattern is made in situ.

3. The method of Claim 1 or 2, wherein the pattern is made of expanded plastics material.

4. The method of Claim 1, 2 or 3, wherein a plurality of interfitting bodies are used.

5. The method of Claim 4, when applied to a component subjected in use to a flow of fluid, wherein the bodies have bevelled edges whereby adjacent parts of the bodies overlap, the arrangement being such that the bevels slope downstream of the fluid flow.

6. A metallic component repaired by the method claimed in any one of Claims 1 to 5.

7. A worn pump casing repaired by the method claimed in any one of Claims 1 to 5.

8. The cast body of replacement material, per se, manufactured whilst performing the method of Claim 1, 2 or 3.

9. A method of repairing a worn metallic component, substantially as hereinbefore described, with reference to Figures 1, 2 and 3 of the drawings accompanying the Provision Specification.

10. A worn metallic component, repaired by the method of Claim 9.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. former 4 is then held in place by a pair of cramps 5 located by the usual securing bolt holes (not shown) formed in the sides of the casing 1. The cramps 5 carry height-adjustable pillars 6 which are made to hold the former 4 in place. Lateral adjusting screws (not shown) are carried by the pillars 6 so as to provide for lateral adjustment of a former 4. A pattern 2 is made is situ from expanded plastics material but expanded polystyrene may be used as an alternative. The expanded material is produced by placing a suitable resin and catalyst in a container provided resin catalyst in a container provided with a nozzle. The container is then shaken so as to mix the ingredients whereby the expanded material is formed, and the expanded material introduced between the former 4 and adjacent material of the pump casing 1, using the nozzle of the container. After the expanded material, has set to form the pattern 2, both the former 4 and pattern 2 are removed. Conventional moulding techniques are then employed, using the pattern 2, so as to produce the cast body 3. (Figure 3). Subsequently, the cast body 3 is secured in place, for example, by pins, bolts, studs, or as shown in this example, by laterally-extending welding 10. As also shown in Figure 3, the edges of a body 3 are preferably chamfered whereby adjacent parts of the contiguous bodies overlap with the bevels sloping downstream of fluid flow through the pump. Use of the bevelled edges results in protection of the welding 10 from the "scouring" action of material passing through the pump, as water flowing through the casing 1 passes over the bodies 3 and is not forced between them. The overlapping arrangement also results in interlocking of the contiguous bodies 3. If additional securing of bodies 3 is required, this can be done by perforating the casing 1 and securing the bodies 3 from outside, using welding. All gaps can be subsequently filled by welding to provide a neat surface contour. Where such welds are subject to wear they are preferably hard-faced. The make pattern/make cast body technique is repeated for material replacement at all worn areas, including exessive wear areas B and C so that the interior of the pump casing is eventually "plated" by interfitting cast bodies 3 of varying shape. A rotatable jig may be provided to assist welding. Rotation of the jig enables the material worked on to be turned to a horizontal position and enables all welding to be carried out in the down hand position. Bodies 3 can be cast from the same material used to manufacture the pump casing 1, or, where possible, from more wear resistant material. Calculations indicate that the invention reduces the cost of repairing a pump casing by a substantial amount. Typically, the current cost of using a welding machine amounts to 90 pence/pound for electrode material, plus welding current, plus welder's time. Using the present invention, the cost of producing a cast body 3 is expected to amount to 60 pence/pound. In addition, the invention avoids the heavy inputs of heat and so avoids cracking and/or distortion. Preferably, if a new, i.e. unworn casing 1 is available, formers 4 can be produced therefrom. Local welding, (welding 10), unlike the build-up welding process referred to above, does not cause cracking and/or distortion. Where barrelling of the casing has taken place, precision cast cheek plates can be fitted in addition to the bodies 3. WHAT I CLAIM IS:

1. A method of repairing a worn metallic component, for example, a dredge pump casing, comprising a pattern corresponding to a mass of material to be replaced, using the pattern to cast a body of replacement material and then securing the cast body to the component.

2. The method of Claim 1, wherein the pattern is made in situ.

3. The method of Claim 1 or 2, wherein the pattern is made of expanded plastics material.

4. The method of Claim 1, 2 or 3, wherein a plurality of interfitting bodies are used.

5. The method of Claim 4, when applied to a component subjected in use to a flow of fluid, wherein the bodies have bevelled edges whereby adjacent parts of the bodies overlap, the arrangement being such that the bevels slope downstream of the fluid flow.

6. A metallic component repaired by the method claimed in any one of Claims 1 to 5.

7. A worn pump casing repaired by the method claimed in any one of Claims 1 to 5.

8. The cast body of replacement material, per se, manufactured whilst performing the method of Claim 1, 2 or 3.

9. A method of repairing a worn metallic component, substantially as hereinbefore described, with reference to Figures 1, 2 and 3 of the drawings accompanying the Provision Specification.

10. A worn metallic component, repaired by the method of Claim 9.