Polyurethane and Rubber Screening Glossary of Terms

Select the first letter of the word from the list above to jump to appropriate section of the glossary.

- A -

abrasion

Wear due to friction.

aperture

The clear opening size, as in length, width or diameter of the opening. Apertures may also involve special shapes such as rectangular (oblong) or triangular configurations.

aperture pad

The device (tooling) utilized in the molding process that determines the shape and size of the aperture. One aperture pad usually provides a multiple of individual apertures.

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- B -

blinding

Filling in and clogging of the screen apertures. This problem when encountered, may be corrected by increasing the "taper" or "draft angle" of the apertures.

When replacing wire cloth with Polyurethane, describe in detail the nature of any blinding problems. With the correct taper angle (draft) blinding problems can usually be eliminated.

bridge

The material between the apertures at right angles to deck flow, also referred to as the cutting edge.

bridge depth

This term defines the thickness (in depth) of the bridge between the apertures.

buffer strips

See "crown bar cover".

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- C -

crown

The arc of the screen support surface to facilitate screen tensioning, determined by the various heights of the crown bar rails (stringers) provided on the screening deck.

crown bar cover

A protective layer of rubber or polyurethane, contoured to fit over the crown bar rails of a vibrating screen deck to prevent wear of the rails and screen while allowing uniform tensioning of the screen. Also referred to as "buffer strips" and "channel rubber" or "channel polyurethane".

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- D -

dam

A device installed at right angles to the flow of material to enhance screening by slowing the travel of media across the screening surface.

dewatering

The separation of liquids and solids. Solids travel over the screen while liquids pass through screen apertures.

draft

Tapered relief provided on the vertical element of bridge and rib components. The draft angle utilized in most applications is two degrees per side.

Blinding problems encountered utilizing woven wire screens should be significantly reduced or eliminated with the use of polyurethane.

durometer

This term is used to express hardness, typically preceded with the value and shore scale, i.e. "85 Shore A Durometer".

 

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- E -

elastomer

Elastic substance occurring naturally, as natural rubber, or produced synthetically, as polyurethane.

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- F -

fast taper

Draft angle, typically four degrees per side utilized to prevent blinding.

flow

Material traveling across the screen surface.

flow divider

A device installed on the screens top surface running parallel with flow to prevent material from traveling down the screens length over areas which have no aperture openings.

Flow dividers are not required with Flowmax Modular Systems.

flow restrictor

See-"Retarder Bar"

formed edge

Edge preparation provided on the sides of a screen panel parallel to flow, to facilitate clamping and tensioning.

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- I -

impact panel

A solid panel (screen Module) without apertures, used in areas subject to severe impact, typically located directly under the feed chute.

injection molding

A method frequently utilized in the manufacture of polyurethane screen segments. While this method is extremely cost effective when producing sizable quantities of a given aperture specification, the properties of the injection molded polymers (thermoplastics) do not offer the superior characteristics of "open cast" (thermoset) polyurethane's.

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- L -

long slots

Rectangular (slotted) openings (apertures) with the length aligned parallel to the length of the screen deck in direction of material flow. Also referred to as "slots long" and "slots wf".

Long slots are used to increase throughput (open area) when particle sizing is less critical.

See-"short slots"

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- M -

maximum overs

The maximum size material that will contact the screens surface.

See-"overs".

module

A replaceable screen segment (element), typically provided in square 12" x 12" or rectangular 12" x 24" sections.

module thickness

Modules may be provided in various thickness' which govern the overall strength and impact resistance. Industry standards include 30mm, 40mm, 50mm and 60mm.

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- O -

open area

The ratio of useable openings (apertures), to the total area of a module expressed as a percentage. Many systems require clamping devices which cover the edges and/or a portion of the apertures on each module. With reference to these systems the published open area is often misleading, as the loss of open area utilized for fastening is not taken into account.

Flowmax systems do not require external clamping methods such as locking pins or clamps. Published open areas reflect the actual effective screening area.

open cast

The method of manufacture utilized to obtain maximum wear characteristics in polyurethane modules.

opening

See-"aperture".

overs

Material that is "over" (larger than) the screen aperture (opening) size which travels across the screens surface without passing through.

Also referred to as "oversize material".

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- P -

percent open

Percentage of useable open area.

plugging

Near size particles trapped in screen apertures (openings) preventing passage of under size particles. This problem commonly occurs when using wire or perforated plate screens.

Polyurethane screens are less susceptible to plugging due to the advantage of having tapered relief openings.

See-"blinding".

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- R -

Retarder bar

Similar to a dam in purpose, yet smaller. Used to restrict the flow of material, balance distribution and break friable lumps. Also referred to as "flow restrictor".

rib

The area between each aperture on a module, running parallel with deck flow.

As rib width is increased, strength will increase while open area will decrease proportionately.

rib depth

This term defines the thickness (in depth) of the ribs between apertures.

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- S -

shore hardness

The scale by which a polyurethane screen module or component is measured for hardness, typically expressed as "shore A".

As the hardness is increased, abrasion resistance tends to increase while impact resistance decreases proportionately.

As the hardness is decreased, abrasion resistance tends to decrease while impact resistance increases proportionately.

short slots

Rectangular (slotted) opening (aperture) with the length of the slot aligned at a right angle to the direction of material flow. Also referred to as "slots s" and "slots cf"

Short slots are used to increase throughput (open area) when particle size is critical.

See-"long slots"

skid bar

Running parallel to flow, a wear surface raised above the screen to prevent maximum oversized material from coming into contact with the screen surface.

 

slow taper

In ideal conditions where no blinding problems have been experienced, a slow taper (two degrees included angle) may be utilized to increase open area.

split aperture

Aperture "rib" section is split, allowing considerable flexure as an aid to prevent screen blinding.

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