Picking point

The wax blocking point is the lowest temperature at which film disruption occurs across 50% of the waxed paper surface when the test strips are separated. The picking point is the lowest temperature at which the surface film shows disruption. Blocking of waxed paper, because of the relatively low temperature at which it may occur, can be a major problem for the paper coating industry. The wax picking and blocking points indicate an approximate temperature range at or above which waxed surfaces in contact with each other are likely to cause surface film injury. 

At the initial pick point, when the vessel is still horizontal, the load is shared between the lifting lugs and the tail beam or lug, based on their respective distances to the vessel c enter of gravity. As the lift proceeds, a greater percentage of the load is shifted to the top lugs or trunnions until the vessel is vertical and all of the load is then on the top lugs. At this point the tail beam or shackle can be removed. 

The worst case is dependent on the tjqje of vessel and the type of attachments. For e.xample, there are three types of trunnions described in this procedure. There is the bare trunnion (Type 3), where the wire rope slides around the trunnion itself. While the vessel is in the horizontal position (initial pick point), the load produces a circumferential moment on the shell. Once the vessel is in the upright position, the same load produces a longitudinal moment in the shell. At all the intermediate angles of lift there is a combination of circumferential and longitudinal moments. The designer should check the two worst cases at 0° and 90° and several combinations in between. 

The minimum lift location is the lowest pick point that does not overstress the overhanging portion of the vessel. The maximum lift location is the highest pick point that does not overstress the vessel between the tail and pick points. These points become significant when locating the lift points to balance the stress at the top lug, the overhang, and the midspan stress. 

When the pick point is immediately above the tail pivot point... 

Boom and Jib pick points. The point(s) of attachment of rigging to a boom (or boom sections or jib or jib sections) must be suitable for preventing structural damage and facilitating safe handling of these components. 

Where a substantial amount of excavation is required in the danger zone, it is advisable to dig one or more trial holes to find the cable and then work along it from the trial holes to expose it. Careful manual methods should be used to avoid damage to the cable. Surface construction may require the use of power tools to break up the surface for removal, in whieh ease it is advisable to fit the bit with a collar to prevent deep penetration and no drilling should be done immediately above the cable. Sharp-pointed tools sueh as pieks should not be used immediately adjacent to the cable even if it is armoured, as the pick points are capable of penetrating between the strands of wire armour and through badly corroded steel tape. 

The type of spray nozzle chosen is important for optimum performance (Kost et al. 1985). The pick-point flushing system with solid-stream (jet) nozzles is the most effective at suppressing respirable dust near the shearer operator s position. The pick-point system with cone-type sprays has been shown to be only 70% as effective. In the Kost study, downwind concentrations were essentially the same for all systems. 

The test strip is printed at a precisely defined plate pressure while being accelerated through the printing zone. The location of the first picking point and the position at which picking is visible right across the test strip are determined by inspection and analyzed quantitatively with the aid of a computer program. 

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