Vertical Curves

Vertical curves come in two different styles, concave and convex. Both types of curves create belt operational problems when the curve is designed with a shorter radius than required by use of a very low modulus fabric. This fabric is extremely elastic or stretchy. These types of conveyor frames are rare and are usually designed around a low modulus fabric.

The simple concave curve is designed around Radii from around 300 feet to 800 feet. This is the type of curve that may create lift off problems. Lift off results from the curve being designed or built with a radius usually being 100 feet or 200 feet short of ideal. Lift off problems from this type of conveyor can be solved fairly simply.

Concave curve conveyors that have a hard start usually lift off at start up if the belt is empty. A soft start with an extended time delay to full RPM is the first step to keeping the belt in the idlers. The next step is the installation of a hold down roll in the curve area. The preceding picture utilizes a hold down roll at the beginning of the curve and another roll in the middle of the curve. The hold down roll is set above the belt, so as not to interfere with product movement. The roll should only touch the belt when lift off occurs with an empty belt.

The last step, if needed, is to select a heavier belt. The increased belt weight will also help keep the belt laying in the idlers. The increase in belt weight will normally not require any change in motor horsepower or take-up weight.

Важная характеристика английского научно-техничес-кого стиля, которая отражается в отборе и использовании языковых средств, заключается также в его стремлении к краткости и компактности изложения, что выражается, в частности, в довольно широком использовании атрибутивных сочетаний. Неправильное понимание этих конструкций нередко приводит к нелепым ошибкам в переводе. Встретив в тексте сочетание: а remote crane или a liquid rocket, переводчик должен распознать в них эллиптические формы сочетаний a remote-operated crane и a liquid-fuelled rocket. Прочитав, что A non-destructive testing college is to open in London this October, он должен помнить, что открывающийся колледж вовсе не будет неразрушающимся (non-destructive) или испытательным (testing), а будет готовить специалистов в области неразрушающих методов испытания материалов. Аналогичным образом low-pressure producers могут оказаться производителями полиэтилена методом низкого давления.