A head sealing apparatus for forming a seal between the top peripheral edge of a substantially vertically-oriented opening and a top surface of an industrially-sized object when the object is positioned within the opening, the apparatus comprising: a vertically moveable head seal configured to extend downwards over the opening and contact the top surface of the object, and a vertically moveable counterweight arrangement for balancing the load of the head seal so that the height of the head seal is adjustable to allow for variations in the height of the object, wherein the vertically moveable counterweight arrangement comprises first and second counterweights (161, 163) for balancing the weight of the head seal and configured to move relative to each other, the first counterweight being configured to balance the weight of the head seal in an operable position, the head sealing-apparatus further comprising a roller tube wherein a first cable is further attached to and configured to be wound around the roller tube, the head sealing apparatus being characterized in that the second counterweight is configured to contact the first counterweight to limit the upward movement of the first counterweight relative to the second counterweight; and in that the head sealing apparatus further comprises a motorised roller tube, wherein a second cable attached to the second counterweight is further attached to and configured to be wound around the motorised tube wherein the motorised roller tube and the second counterweight are configured to move the head seal between a retracted position and the operable position wherein, in use, with the head seal in the retracted position, the weight of the head seal biases the first counterweight upwards against the second counterweight wherein the motorised roller tube is configured to be activated to wind the second counterweight in an upward direction, so that the first counterweight moves upward with the second counterweight wherein the upward movement of the first and second counterweights causes the head seal to move downwards towards the top surface of the object until the first counterweight balances the weight of the head seal. a vertically moveable head seal configured to extend downwards over the opening and contact the top surface of the object, and a vertically moveable counterweight arrangement for balancing the load of the head seal so that the height of the head seal is adjustable to allow for variations in the height of the object, wherein the vertically moveable counterweight arrangement comprises first and second counterweights (161, 163) for balancing the weight of the head seal and configured to move relative to each other, the first counterweight being configured to balance the weight of the head seal in an operable position, the head sealing-apparatus further comprising a roller tube wherein a first cable is further attached to and configured to be wound around the roller tube, the head sealing apparatus being characterized in that the second counterweight is configured to contact the first counterweight to limit the upward movement of the first counterweight relative to the second counterweight; and in that the head sealing apparatus further comprises a motorised roller tube, wherein a second cable attached to the second counterweight is further attached to and configured to be wound around the motorised tube wherein the motorised roller tube and the second counterweight are configured to move the head seal between a retracted position and the operable position wherein, in use, with the head seal in the retracted position, the weight of the head seal biases the first counterweight upwards against the second counterweight wherein the motorised roller tube is configured to be activated to wind the second counterweight in an upward direction, so that the first counterweight moves upward with the second counterweight wherein the upward movement of the first and second counterweights causes the head seal to move downwards towards the top surface of the object until the first counterweight balances the weight of the head seal.