restricted, however, to route that involves some degree of vertical fall.
OPERATIONS MANAGEMENT-MATERIAL OPERATIONS MANAGEMENT-MATERIAL
HANDLING HANDLING
Endless chain conveyors: These conveyors are usually driven by Endless chain conveyors: These conveyors are usually driven by an electrican electric motor and
motor and, as a , as a consequence, are usually more expensive than gravityconsequence, are usually more expensive than gravity conveyors. They
conveyors. They have several imphave several important advantages, howevortant advantages, however. er. TheseThese
conveyors can move materials up as well as down, and the progress of the conveyors can move materials up as well as down, and the progress of the materials can be
materials can be closely controlled. Iclosely controlled. In addition, special n addition, special carrying devices andcarrying devices and containers can be attached to the
containers can be attached to the chain. Frequently, production tasks such aschain. Frequently, production tasks such as dip painting, cleaning and washing may be performed as the c
dip painting, cleaning and washing may be performed as the c onveyor moves.onveyor moves.
Finally, by varying the speed of the
Finally, by varying the speed of the conveyor at different points, or by conveyor at different points, or by buildingbuilding loops into it, work-in-process inventory may be stored
loops into it, work-in-process inventory may be stored between operatingbetween operating stages.
stages.
Belt conveyors: Belt conveyors are also driven by electric motors. These beltsBelt conveyors: Belt conveyors are also driven by electric motors. These belts are usually made of some flexible material such as rubber. However, special are usually made of some flexible material such as rubber. However, special belts are used in many industries.
belts are used in many industries. In the baking industry, for example, In the baking industry, for example, Teflon- Teflon-coated metal is utilized to prevent sticking. The belt passes over rollers, which coated metal is utilized to prevent sticking. The belt passes over rollers, which normally create a trough in the centre of the belt where the materials are
normally create a trough in the centre of the belt where the materials are concentrated. Conveyors of this sort are used
concentrated. Conveyors of this sort are used mainly for transporting bulkymainly for transporting bulky material. Baggage is moved from
material. Baggage is moved from the ground to the baggage compartments of the ground to the baggage compartments of airplanes and shipped by conveyor belts. They are also
airplanes and shipped by conveyor belts. They are also used to move oresused to move ores from the min face to work areas. Stock brokerage firms and insurance
from the min face to work areas. Stock brokerage firms and insurance companies even use them to route papers
companies even use them to route papers to various parts of their to various parts of their buildings.buildings.
When work is to be performed, however, the materials must be taken from the When work is to be performed, however, the materials must be taken from the belt and later replaced when the
belt and later replaced when the work is completed.work is completed.
106
Other conveyor equipment: Pipelines are often employed for moving liquidsOther conveyor equipment: Pipelines are often employed for moving liquids and gases such as gasoline and natural gas.
and gases such as gasoline and natural gas. Pneumatic tubes are used in sPneumatic tubes are used in someome firms for rapid dissemination of internal
firms for rapid dissemination of internal communications.communications.
Screw conveyors have been successfully used to lift materials in both grain Screw conveyors have been successfully used to lift materials in both grain elevators and food-processing industry to move delicate foods in steady elevators and food-processing industry to move delicate foods in steady streams without damage.
streams without damage.
Industrial trucks: Industrial trucks which represent the Industrial trucks: Industrial trucks which represent the second category of second category of material handling equipment, are vehicles powered by hand, fuel or
material handling equipment, are vehicles powered by hand, fuel or electricity,electricity, which are capable of transporting materials horizontally between any
which are capable of transporting materials horizontally between any twotwo points. As opposed to a conveyor, a truck
points. As opposed to a conveyor, a truck is able to more is able to more from one location tofrom one location to any other location so long as suitable trav
any other location so long as suitable traveling surface is eling surface is available and its pathavailable and its path of travel is not obstructed. For
of travel is not obstructed. For this reason, the prevalent method of this reason, the prevalent method of handlinghandling material in a firm engaged in intermittent manufacturing is by means of trucks.
material in a firm engaged in intermittent manufacturing is by means of trucks.
The variabl
The variable path of travel e path of travel they are able to follow permits them to transportthey are able to follow permits them to transport materials from one work station to any of a number of other work stations at materials from one work station to any of a number of other work stations at which a subsequent operation is scheduled to be performed.
which a subsequent operation is scheduled to be performed.
A second desirable feature of trucks is that they occupy a given amount of space A second desirable feature of trucks is that they occupy a given amount of space
intermittentl
intermittently. Ty. This means that a certain amount of space in a given location ishis means that a certain amount of space in a given location is required to house a truck for only as long as the truck is in that location. As required to house a truck for only as long as the truck is in that location. As soon as the vehicle is moved, the space is free for other uses.
soon as the vehicle is moved, the space is free for other uses.
OPERATIONS MANAGEMENT-MATERIAL OPERATIONS MANAGEMENT-MATERIAL
HANDLING HANDLING
As in the case of conveyors, there are many types of trucks,
As in the case of conveyors, there are many types of trucks, and each of these canand each of these can be equipped wi
be equipped with a variety of ath a variety of attachments. But the most important ones are asttachments. But the most important ones are as follows:
follows:
Hand operated vehi
Hand operated vehicles, tractors, platform trucks, cles, tractors, platform trucks, forklift trucks, straddle carriers.forklift trucks, straddle carriers.
When the loads are not too heavy
When the loads are not too heavy and the hauls are short, maand the hauls are short, manual equipment maynual equipment may be used. However, when the load size and
be used. However, when the load size and weight and the distances to beweight and the distances to be traveled are great, powered equipment is
traveled are great, powered equipment is used. Today, most industrial trucksused. Today, most industrial trucks are powered. They are generally equipped with forks
are powered. They are generally equipped with forks or platforms that can beor platforms that can be raised or lowered to facilitate the movement and storage of materials, and for raised or lowered to facilitate the movement and storage of materials, and for this reason the loads are generally placed on pallets or skids.
this reason the loads are generally placed on pallets or skids.
Cranes and hoists:Cranes and hoists:
The third classification of material
The third classification of material handling equipment consists of cranes andhandling equipment consists of cranes and hoists. This equipment is able to mov
hoists. This equipment is able to move materials vertically e materials vertically and laterally in anyand laterally in any area of limited length, width and height. It is used primarily when material must area of limited length, width and height. It is used primarily when material must be lifted prior to being moved from
be lifted prior to being moved from one point to another. These points mayone point to another. These points may represent different work stations or different
represent different work stations or different locations at a single work locations at a single work station.station.
For example, if a part is large or heavy, the operator may find it nec
For example, if a part is large or heavy, the operator may find it nec essary toessary to use a hoist to aid him
use a hoist to aid him in loading or unloading the machine. Subsequently, ain loading or unloading the machine. Subsequently, a crane may be used to move the part to another work-station.
crane may be used to move the part to another work-station.
108
One of the advantages of cranes and hoists is that they are able to transport objects through One of the advantages of cranes and hoists is that they are able to transport objects through
the overhea
the overhead space in the d space in the plant. Consequentlyplant. Consequently, , space is utilized, which would otherwise bespace is utilized, which would otherwise be unused, and floor space is freed for other uses. To
unused, and floor space is freed for other uses. To illustrate, it might be illustrate, it might be possible to move apossible to move a large heavy casting by means of a truck from one work-station to another. However, this large heavy casting by means of a truck from one work-station to another. However, this would create a need for wide aisles at
would create a need for wide aisles at appropriate locations in the plant. If a floor appropriate locations in the plant. If a floor space isspace is at a premium, a more desirable alternative would be to
at a premium, a more desirable alternative would be to transport the item through the air bytransport the item through the air by means of a crane which would either eliminate the
means of a crane which would either eliminate the need for certain aisles or, at least,need for certain aisles or, at least, permit the use of aisles which may be required for the movement of smaller objects. But permit the use of aisles which may be required for the movement of smaller objects. But there are cases in which cranes and hoists are used, not because they free floor
there are cases in which cranes and hoists are used, not because they free floor space butspace but because they are the best available means of positioning material in a particular location.
because they are the best available means of positioning material in a particular location.
However, when considering cranes and hoists, it is important to keep in
However, when considering cranes and hoists, it is important to keep in mind that any one unitmind that any one unit of this equipment is capable of serving on a
of this equipment is capable of serving on a limited area.The size and shape of this arealimited area.The size and shape of this area will vary with the kind of
will vary with the kind of crane or hoist being used. Nevertheless, the equipment iscrane or hoist being used. Nevertheless, the equipment is somewhat more flexible in this respect than are conveyors
somewhat more flexible in this respect than are conveyors, , but not a flexible as but not a flexible as areare industrial trucks. A
industrial trucks. Also, lso, it will be found it will be found that cranes and hoists are as likely to that cranes and hoists are as likely to be usedbe used intermittent
intermittently as in ly as in continuous production.continuous production.
Again, there are many types of equipment which are placed in the crane and hoist category.
Again, there are many types of equipment which are placed in the crane and hoist category.
However, the most common ones are the following: overhead bridge cranes, gantry cranes, However, the most common ones are the following: overhead bridge cranes, gantry cranes, jib cranes, elevators, lifts, chain hoists, air hoists, electric
jib cranes, elevators, lifts, chain hoists, air hoists, electrichoists.hoists.