AU2006222653B2

AU2006222653B2 - Drop hammer rapping device

Info

Publication number: AU2006222653B2
Application number: AU2006222653A
Authority: AU
Inventors: Jiri Jekerle; Volker Paruch
Original assignee: Arvos GmbH
Current assignee: Arvos GmbH
Priority date: 2005-09-23
Filing date: 2006-09-22
Publication date: 2010-06-10
Anticipated expiration: 2026-09-22
Also published as: CN1936489B; CN1936489A; EP1767890A1; DK1767890T3; EP1767890B1; ES2373235T3; DE102005045633B3; ATE523750T1; AU2006222653A1

Abstract

The device has a longitudinal extended rotatable shaft (6), which is held by two supports, and a unit provided for rotation of the shaft. Several radial arms (9) are rigidly connected with a shaft at a distance from each other. A drop hammer (10) has a hammer head (11) and a hammer handle and is fixed at each radial arm at its outer end via a hammer joint (13). The hammer comprises of an anvil or striking handle and is designed with additional weight according to a specific equation.

Description

Pool Section 29 Regulation 3.2(2) AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Drop hammer rapping device The following statement is a full description of this invention, including the best method of performing it known to us: -1 DROP HAMMER RAPPING DEVICE Description The invention relates to a drop hammer rapping device which comprises the characteristics of the preamble to Claim 1. 5 A drop hammer rapping device is disclosed, for example, in DE 3500431A1, this rapping device being used to remove dust deposits on precipitation electrodes and spray electrodes of dry operating electrostatic dust separators. 10 Accumulated ash and other precipitations and deposits are often cleaned from outer surfaces of heat exchanger tubes, for example finned tube walls and tube nests of water tube waste heat boilers, by using mechanical rapping devices which operate on the principle of the drop hammer. Such rapping devices normally consist of a series of drop hammers, each of which strike against an anvil 15 or impact handle which are connected to the tubes to be cleaned or are at least in contact with them. The periodic and sudden loading of the drop hammer, particularly its components the hammer head, handle and hammer joint, very often results in damage to the points on the hammer subject to high loads, e.g. on the hammer joint. 20 It is desirable to provide a drop hammer rapping device on whose drop hammer or hammers the above-mentioned disadvantages are avoided and whose mass distribution is arranged so favourably that when there is an impact against the anvil or impact handle the load in the hammer joint goes to almost zero and the 25 tension in the handle is minimised. According to an aspect of the present invention, there is provided a drop hammer rapping device for rapping and shaking heat exchanger tubes for cleaning their outer surfaces, wherein the device comprises: 30 an elongated rotary shaft, which is retained by at least 2 bearings; a means for rotating the shaft; a number of radial arms which are rigidly connected to the shaft at a certain distance from each other, wherein each arm is rigidly secured -2 essentially at right angles to the shaft at a sequentially increasing peripheral angle related to the preceding adjacent arm; a drop hammer which has a hammer head and a handle and is pivoted on each radial arm at its outer end by a hammer joint; and 5 an anvil or impact handle which is secured to a header of a tubular heat exchanger unit, or is in contact with it, and the drop hammer strikes against its exposed end when the shaft rotates, characterised in that in order to reduce or eliminate a return stroke force generated in the hammer joint during the hammer impact against the 10 exposed end of the anvil or impact handle, the drop hammer is designed with an additional weight according to the relation mz = 'i m,-- rA 'I m, rA - rZ where mz is the mass of additional weight, in kg, 15 mi is the mass of a mass particle or increment related to handle and hammer head, in kg, rz is the radius between the centre of hammer joint and the centre of gravity of additional weight, in metres, ra is the radius between the centre of hammer joint and the 20 impact perpendicular Ns of hammer head, in metres, ri is the radius between the centre of hammer joint and the centre of gravity of the mass particle or increment relative to handle and hammer head, in metres. 25 -2a A drop hammer rapping device according to this aspect of the invention preferably has the following advantages: - Substantial reduction to complete elimination of the return stroke force in the hammer joint at the time of the impact of the hammer against the 5 anvil or impact handle, and hence minimal loading of the handle, the hammer joint and the hammer shaft; - The life of the drop hammer, including that of the hammer joint, is considerably extended. 10 The additional weight applied to the hammer head is advantageously fitted to its side facing toward or away from the hammer joint since sufficient space is provided on these sides for the fitting of an additional weight and here the mass distribution can also be effectively achieved. 15 If it is advantageous to concentrate the mass distribution inside the drop hammer toward the hammer joint, the additional weight can also be fitted to the handle. In an advantageous embodiment of the invention the additional weight is screwed or welded to the hammer head or handle, Whilst the first variant offers 20 the possibility of simple replacement, the second variant offers the advantage of a more long-lived connection. Instead of fitting a separate additional weight to the drop hammer it may be appropriate to form the additional weight from a drop hammer having an extra 25 weight and by mechanical machining of the drop hammer to obtain the required extra weight. This can be achieved, for example, by milling or grinding off material constituting added or excess weight on the hammer head, "Comprises/comprising" when used in this specification is taken to specify the 30 presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

-3 Exemplary embodiments of the invention are explained in greater detail below with reference to the drawing and description. Fig. 1 shows diagrammatically and in a perspective view a heat exchanger tube unit which is designed with an anvil or impact handle for rap cleaning, Fig. 2 shows diagrammatically a plurality of heat exchanger tube units which are cleaned by means of a drop hammer rapping device, Fig. 3 shows diagrammatically a drop hammer rapping device during one complete shaft revolution (3600), Fig. 4 shows diagrammatically a detailed view of a drop hammer rapping device, Fig. 5 as Fig. 4, but an alternative design, Fig. 6 as Fig. 4, but an alternative design. Figure 2 shows a multiplicity of heat exchanger tube units 1, an individual unit being shown in Figure 1 for a clearer representation. Such heat exchanger tube units 1 may, for example, be inserted in waste heat boilers as membrane tube walls or tube nests. Since ash or other deposits accumulate during the operation of waste heat boilers or steam generators designed with heat exchanger tube units 1 on the outer surfaces of heat exchanger tube units 1, which ash reduces the heat transfer to heat exchanger tube units 1 and the working medium circulating in tubes 2 as it continues to accumulate, it is necessary to remove the accumulation of ash.

-4 As illustrated diagrammatically in Figure 2, ash can be removed by means of a drop hammer rapping device 16. Here drop hammers 10 can be raised and rotated or tilted over by a rotary shaft 6 driven by a working means 7, which shaft is supported by at least two bearings 8. When the tilting position is reached drop hammer 10 drops from the highest to the lowest position and strikes or knocks against the anvil or impact handle 4 of the corresponding tube unit 1. Here shaft 6 provided with a number of radial arms 9, depending on tube units 1 to be rapped, which arms, spaced a certain distance apart, are rigidly connected to shaft 6, wherein each arm 9 is rigidly to shaft 6 essentially at right angles to it at a sequentially increasing peripheral angle a related to the preceding, adjacent arm 9. The sequence of the shaft rotation of rapping device 16 and the tilting of drop hammer 10 above shaft 6, and the subsequent falling and rapping of drop hammer 10 against the impact surface or exposed end 5 of the impact handle or anvil 4, is shown diagrammatically in Fig. 3. The anvil or impact handle 4, as also illustrated in Figure 1, is secured to header 3 or is connected to it, which header incorporates all heat exchanger tubes 2 of a heat exchanger tube unit 1. Drives of prior art, such as electromotor, hydraulically pneumatically operated drives or gears etc. may be used as drive means 7. The dropping movement of drop hammer 10 is in principle a rotary movement. The impulse of drop hammer 10 during the impact against the anvil or impact handle 4 is equal to the sum of the impulses of the distributed mass Eml-v in drop hammer 10, the speed of the individual mass particles depending on the radius of the rotary movement of the individual mass particles or increments. During the impact a force, which is directed against the rotary movement of drop hammer 10, acts at the point of impact of drop hammer 10. The force of impact acts on drop hammer 10 with a torque which would generally result, after the impact, in a movement of drop hammer 10 other than a (return) rotation of the drop hammer 10 about hammer joint 13. Handle 12 of drop hammer 10 only remains connected to the pivot by means of an additional force (return stroke force) in hammer joint -5 13, and moves with the desired return rotation. The return stroke force in hammer joint 13 results in stress loading in hammer 12. In order to prevent as far as possible stresses in handle 12, hammer head 11 and in hammer joint 13 that are generated at the time of impact of drop hammer 10 against anvil 4, and often result in damage - generally fractures - at the points subjected to high loads, drop hammer 10 is designed according to the invention with an additional weight 14 according to the relation: mnz = m,-i r,- m, rA rZ where m'. is the mass of additional weight 14, in kg, mi is the mass of a mass particle or increment related to handle 12 and hammer head 11, in kg, r. is the radius between the centre of hammer joint 13 and the centre of gravity of additional weight 14, in metres, r. is the radius between the centre of hammer joint 13 and the impact perpendicular N, of hammer head 11, in metres, r; is the radius between the centre of hammer joint 13 and the centre of gravity of the mass particle or increment relative to handle 12 and hammer head 11, in metres. The return stroke force normally generated inside drop hammer 10 and hammer joint 13 can be minimised, or at best can be completely eliminated by the design of drop hammer 10 according to the invention with an additional weight 14 according to the above relation. Figures 4 to 6 illustrate variants of drop hammer rapping device 16 according to the invention, wherein drop hammer 10 according to Figure 4 is designed with an additional -6 weight 14 which is fitted to the side of hammer head 11 facing away from hammer joint 13, whereas drop hammer 10 according to Figure 5 is designed with an additional weight 13 which is fitted to the side of hammer head 11 facing toward the hammer joint 13. Drop hammer 10 according to Figure 6 is designed with an additional weight 14 which also has a portion 15 which constitutes extra or over-weight. This over-weight portion 15 of drop hammer 10 is machined by milling or grinding or the like until the condition is reached where drop hammer 10 is formed with the additional weight according to the above relation.

-7 List of reference numbers: 1 Heat exchanger tube unit 2 Heat exchanger tube 3 Header 4 Anvil or impact handle 5 Impact face or exposed end of the anvil or impact handle 6 Shaft 7 Means for driving the shaft 8 Shaft bearing application 9 Radial arm 10 Drop hammer 11 Hammer head 12 Handle 13 Hammer joint 14 Additional weight 15 Portion of the additional weight subject to overloading or extra loading 16 Drop hammer rapping device

Claims

1. A drop hammer rapping device for rapping and shaking heat exchanger tubes for cleaning their outer surfaces, wherein the device comprises: 5 an elongated rotary shaft, which is retained by at least 2 bearings; a means for rotating the shaft; a number of radial arms which are rigidly connected to the shaft at a certain distance from each other, wherein each arm is rigidly secured essentially at right angles to the shaft at a sequentially increasing peripheral 10 angle related to the preceding adjacent arm; a drop hammer which has a hammer head and a handle and is pivoted on each radial arm at its outer end by a hammer joint; and an anvil or impact handle which is secured to a header of a tubular heat exchanger unit, or is in contact with it, and the drop hammer strikes against 15 its exposed end when the shaft rotates, characterised in that in order to reduce or eliminate a return stroke force generated in the hammer joint during the hammer impact against the exposed end of the anvil or impact handle, the drop hammer is designed with an additional weight according to the relation 20 mz= m, r,- r i rA - rz where mz is the mass of additional weight, in kg, mi is the mass of a mass particle or increment related to handle and hammer head, in kg, 25 rz is the radius between the centre of hammer joint and the centre of gravity of additional weight, in metres, ra is the radius between the centre of hammer joint and the impact perpendicular Ns of hammer head, in metres, -9 ri is the radius between the centre of hammer joint and the centre of gravity of the mass particle or increment relative to handle and hammer head, in metres.

2. The drop hammer rapping device according to claim 1, characterised in 5 that the additional weight is fitted on the side of the hammer head facing away or toward the hammer joint,

3. The drop hammer rapping device according to claim 1, characterised in that the additional weight is fitted to the handle.

4. The drop hammer rapping device according to any one of claims ] to 3, 10 characterised in that the additional weight is screwed or welded to the hammer head or the handle.

5. The drop hammer rapping device according to any one of claims ] to 3, characterised in that the additional weight is formed from a drop hammer having an extra weight and by mechanical machining of the drop hammer 15 for obtaining an additional weight.

6. A drop hammer rapping device substantially as hereinbefore described with reference to the accompanying drawings. ALSTOM TECHNOLOGY LTD WATERMARK PATENT & TRADE MARK ATTORNEYS P27688AU00