BigPatents India

A drop hammer for rapping or shaking heat exchanger tubes (2) for cleaning their outer surfaces, wherein the device comprises an elongated rotary shaft (6), which is retained by at least 2 bearings, a means (7) for rotating the shaft (6), a number of radial arms (9) which one rigidly connected to the shaft (6) at a certain distance from each other, wherein each arm (9) is rigidly secured essentially at right angles to the shaft (6) at a sequentially increasing peripheral angle related to the preceding adjacent arm (9), a drop hammer (10) which has a hammer head (11) and a handle (12) and is pivoted on each radial arm (9) at its outer end by a hammer joint (13), and an anvil or impact handle (4) which is secured to a header (3) of a tubular heat exchanger on anvil or impact handle (4) which is secured to a header (3) of a tubular heat exchanger unit (1), or is in contact with it, and the drop hammer (10) strikes against its exposed end (5) when the shaft (6) rotates, wherein, in order to reduce or eliminate a return stroke force generated in the hammer joint (13) during the hammer impact against the exposed end (5) of the anvil or impact handle (4), the drop hammer (10) is designed with an additional weight (14) according to the relation mZ= sigma miri-rA.sigma mi/(rA-rZ) where mz 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, rz is the radius between the center of hammer joint (13) and the center of gravity of additional weight (14), in matres, ra is the radius between the center of hammer joint 913) and the impact perpendicular ns of hammer head (11), in metres, ri is the radius between the center of hammer joint (13) and the center of gravity of the mass particle or increment relative to handle 912) and hammer head (11), in metres.