Wire conveyor belts were introduced to fulfil the need of transporting items through conditions that were beyond the capabilities of traditional conveyor belts.With the introduction of the automated processes the need for a conveying system that could offer one or more of the following was identified:

	to withstand temperatures from - 50 up to 1 200°C.
	to provide a good open area thereby allowing good drainage characteristics and when necessary the flow of hot or cold air and steam.
	when required, a good resistance to corrosion and / or acid attacks.
	to provide flexibility plus a good strength to weight ratio, and
	considering the duties it would fulfil it would be reasonably good priced.

It was known that the numerous materials used in the manufacture of woven wire screencloths would provide solutions for the majority of the points above provided an assembly could be developed to actually carry out the task of conveying items. It was this criteria that led to the development of the wire conveyor belts and the various types of belting currently available.

Materials for Wire Conveyor Belts

The most popular materials used in the construction of wire conveyor belts are listed below.It should be noted that the temperatures shown are normal atmospheric conditions within the furnace etc. Considerations for additional contaminants would have to be made for each application considered.

Atmosphere Contaminants

An alloy selected from the chart above must be checked for compatibility with any contaminants which may be present in the furnace atmosphere or the parts being processed through the furnace. Where a contaminant is present which is not compatible with the alloy selected, a choice must be made as to the practicality of removing the contaminant or of changing the alloy.

The preferred solution is to remove the contaminant. Most atmosphere contaminants are at least partially harmful to all standard high temperature alloys. When the alloy is changed, the usual result is only that the degree of attack is lessened. Considering the cost of a belt and the relative short life which frequently results upon exposure to some contaminants, the preferred procedure is to take steps to remove the contaminant rather than change the alloy.

SULPHUR - Sulphur causes rapid deterioration of most high nickel alloys used in high temperature belts. It may be introduced in the furnace by the presence of sulphur-bearing oils on the work being processed, by the atmosphere, or by a sulphur-bearing refractory in the furnace. At temperatures above 920°C, a low nickel alloy such as Incoloy DS or AISI 314 is recommended.

STEARATES - Stearates are frequently used as binders in powder metal compacts. Having a relatively high carbon content, stearates, when they are used in such a manner that they run onto or make frequent contact with the belt, will tend to carburize and embrittle it. When this occurs, the preferred choice is high nickel alloy such as 80-20.

LEAD - ZINC - Lead and zinc are sometimes introduced in the form of lead or zinc stearates which function as binders and lubricants for powder metal compacts.Their reactions of lead and zinc, however, are considerably more severe than that of stearates,and corrective measures should be taken primarily against these elements. The selection of low nickel alloy such as Incoloy DS is suggested or AISI 314 is recommended.

PHOSPHATES - Phosphates may occasionally be introduced on parts being processed and in a reducing atmosphere may tend to attack higher nickel alloys. Again, a low nickel alloy such as Incoloy DS or AISI 314 is recommended.

FLUORIDES - The introduction of fluoride in the furnace normally occurs in the form of the flux used on the parts being processed. Heavy concentrations of fluorides are used in aluminium brazing pastes, but they are also found in some copper brazing pastes and in some frits used by the ceramic industry. Fluorides are, in general, severely detrimental to belt life. The best alloy for this type of service has been found to be columbium stabilised high nickel alloy such as 80-20 Cb.

OILS - OILS present on parts being processed tend to carburize the belt. The best solution to this problem is to use a high nickel alloy such as 80-20. An exception to this rule is the case where the oil is a sulphur-bearing one such as is frequently used as a cutting oil. When this situation exists, the effect of the sulphur is more severe than the effect of the oil, and the best alloy will, in all probability, be lower nickel alloys such as Incoloy DS or AISI 314.

COPPER - In copper brazing applications or during the sintering of copper-bearing powder metal compacts, there is sometimes a tendency for molten copper to run onto the belt surface or collect in pools on the hearth. When this occurs, the copper will penetrate the micro-structure of the belt alloy and cause rapid failure. The best solution, as with the case of other contaminants, is to maintain a state of cleanliness such that copper may not come in contact with the belt. Where this cannot be done, the use of 80-20 is suggested. In addition, experience has shown that in some cases a preoxidizing treatment for the belt will diminish or eliminate the copper penetration.

FLUXES - There are a variety of fluxes used in the various types of processes. One example given previously is a fluoride flux. However, there are a great variety of other with varying effect upon the different alloys. As a general rule, every precaution should be taken to ensure that the fluxes do not drip directly on the belt or form in pools on the hearth. In addition, the fluxes, on occasion, may vaporise in a preheat chamber only to condense on a cool wall of the preheat chamber. The flux then drips on the belt in a highly concentrated form and causes rapid deterioration. Every possible measure should be taken to prevent such an accumulation of fluxes.

Weave Types

Balanced Belting
A BALANCED weave belt, as the name implies, is constructed by joining a left hand and a right hand coil with a crimped or straight crossrod. This construction allows the tensions set up in the left and right hand coil spirals to balance each other out when in operation and reduces tendency of the belt to creep from side to side of the conveyor track. These belts are very popular and have good tensile strength combined with good open area.

Duplex Belting
The DUPLEX weave is manufactured from pairs of coil spirals which are of the same hand I.e. either left or right hand. Because the coil wires are of large diameter and close together, the rod is straight. The heavy construction and good mechanical strength makes this weave popular in high temperature applications.

Double Balanced Belting
The DOUBLE BALANCED belt, although similar to the balanced belt, consists of pairs of interlaced right and left hand spirals. The connector rods are crimped on the more open meshes and straight on the closed meshes. The double balanced belt is suitable for most applications.

Cord Weave
In this belt the coil spirals are fitted very closely together and are joined by up to 4 crossrod pitch. CORD weave belts, because of their close mesh and smooth flat surface are ideal for carrying very small products.

Honeycomb Belting
This is not a wire belt at all but is generally made from flat steel strip although plastic HONEYCOMB can also be supplied. This belt may be driven by inboard sprockets or occasionally friction driven. Because of it open mesh design it is ideally suited for handling products that require washing, stoving, heating, cooking, drying or sterilising.

Chain Link
CHAIN LINK belting is manufactured by a series of either right or left hand spirals each turned into the preceding spiral to form a continuous belt. This type of belting can be all in one direction or made of alternating right and left hand sections, referred to as Sectional belting. The travel of the belt is thus controlled to the extent of preventing displacement of the pulleys because its creep to the right is counteracted by an equal creep to the left. Sectional belting is suggested for frictionally driven conveyors. One-direction weave belts are used primarily on positive chain driven units. Both types of chain link belting are suggested for applications where a belt of low initial cost is required.

Ladder Belting
This low-cost rod-type belting is ideal for processing lightweight products. It is manufactured from 4,5 mm wire and is available in plain, galvanised and stainless steels. SCREEN PRODUCTS furnishes ladder belting from straight line conveyors, and for conveyors having 90° or 180° turns.

Flat Flex
Flat Flex® Belting is a unique design of woven wire belting which is positively driven by sprockets within the wire mesh. By positioning the drive so that the loaded section of the belt is pulled by positive traction under a wide variety of load and speed conditions.

Balanced Belting	Duplex Belting	Double Balanced Belting	Cord Weave

 Installation of Belt

Correct installation procedures must be observed to assure that the quality built into the belt by STAR SCREENS will result in low maintenance and long life. A wire conveyor belt may be pulled into the conveyor by means of a rope which has been previously threaded through the conveyor. This rope should not be attached directly to the belt, but rather should be connected to a pull bar which is, in turn wired or brazed to the belt, as illustrated. If the pulling rope is connected directly to the belt, it is suggested that the first 600 mm of fabric be discarded to prevent the introduction of distorted spirals into the belt.

In addition, the new belt may be pulled into the conveyor by attaching it to the old belt. Where both belts are the same mesh, they may be connected by means of straight rod. Where the meshes are different, they should be wired together across their full width. This method should not be used to pull a belt into an oven or furnace while it is at temperature. As the belt is pulled into the conveyor, coil spirals must lie flat in the plane of the belt after installation i.e. showing no 'bumps'. If tension has been applied before the turned spiral has been discovered, the spiral must be removed to ensure proper tracking of the belt.

After making the belt endless, the joint should be finished by welding. Care must be taken during welding, as excessive heat will burn the wire and damage the belt. After the belt is installed, it should be run without load and under the lightest possible counter-tension required to drive it. This will not only seat the spirals but also will serve as a second check to make certain that all spirals lie flat. After several complete revolutions at this tension level, the counter-tension may be increased to the full operating value in series of steps. Close attention must be paid to the belt during this period as frequent tracking adjustments may be necessary.

Where the belt is to operate at elevated temperatures, it should be tracking satisfactorily at ambient before temperature is applied. In order to properly break in the new belt, the temperature must be applied gradually. One rule of thumb is that the temperature should be increased at the rate of approximately 40°C per hour. During this period, the belt must be watched carefully as continuous tracking adjustments may be required.

Requirements for Ordering Wire Conveyor Belt

STANDARD: the description of the wire conveyor belt is based on the identification of the coil and cross rod, both pitch and wire diameter, and the type of construction is required. The length and width required is attached to the end of the identification code: At STAR SCREENS balance weave with crimped cross rods and welded edges is the standard. When this is required, no further identification is necessary:
Wire Conveyor Belt 5,01(1) / 1,6(2) / 6,3(3) / 1,6(4) x 15m(5) x 1500(6)

Variables: the variables that can be included are:

	Type of material
	Type of construction
	Accessories for wire conveyor belt i.e. chain; flights; side flights, etc.

Wire Conveyor Belt 5,0 / 1,6 / 6,3 / 1,6 x 15m x 1500
NOTE:

	Material AISI 304
	Straight cross rod.
	Ladder selvedge.

When the specification is not known, please request a 'Belt Questionnaire' for your completion with full details.

NOTE: Wire Conveyor belts are supplied to exceed specified width. They are normally supplied one coil pitch smaller, subject to dimensions, etc. In the event of a chain drive, supply the following:

	Type of chain
	Pitch of connecting rods.
	Method of fixing the ends of the rods to the chain.
	Detail all accessories required i.e. flights, side-plates, etc.

FOR MORE INFORMATION PLEASE CONTACT US.

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