Hook Strip Screens: How Side-Tensioned Screen Panels Work and How to Measure for a Replacement

On a round vibratory separator, a replacement screen drops into a frame and clamps down. A hook strip screen is a different animal. It is a section of woven-wire cloth with a formed metal hook crimped onto two opposite edges, stretched drum-tight across a curved deck and held there by tension rails and bolts on the machine's side walls. Get the tension, the hook style, or the section size wrong and the screen does not just underperform — it flaps, rubs, and tears itself apart in service. This guide explains how hook-strip, side-tensioned panels actually work, and — the part that prevents a wasted reorder — exactly which dimensions you have to capture before you can order the right one.

It is written for the maintenance tech or plant engineer running a horizontal or inclined vibrating screen who needs to understand a tensioned section well enough to reorder it correctly the first time, not for a lab.

What a Hook Strip Screen Actually Is

Start with the construction, because the hook is the whole point. A flat strip of sheet metal is formed into a hooked edge — usually a U-shaped channel — and crimped onto two opposite edges of the screen cloth. Small spot welds near the edge keep that hook attached for the life of the section. One detail practitioners rely on: the bottom leg of the hook is intentionally made slightly shorter than the top, so that when the section is pulled tight the mesh seats cleanly into the rail without deforming at the edge.

Those two hooked edges are what the machine grabs. Tension rails (also called bar rails) hook into the formed edge, and tension bolts on the side walls draw the rails outward, stretching the cloth across the deck until it is drum-tight. That tension is not a finishing touch — it is what makes the screen screen. A loose section vibrates wrong, blinds near the cut point, and breaks wires early.

Side Tension vs. End Tension

There are two ways to mount and tension a hooked section, and confusing them is the fastest way to order the wrong part:

• Side tensioning. The sections run across the direction of material flow, and tension is pulled from the two side walls. A deck usually carries several side-tensioned sections in a row, each one independently tensioned and replaceable from the side bolts — which is why side tension is the faster, more common change-out on production decks. On side-tensioned sections the hook is formed with an opening angle of roughly 45° so the rail seats into the bend.
• End tensioning. A single, longer section runs along the length of the deck and is tensioned from the two ends. Here the hook legs are formed essentially parallel rather than at the 45° side-tension angle.

So a hook "angle" only means something once you say which system it belongs to. A bare "45° hook" is a side-tension hook; an end-tension hook is parallel-legged. State the tension type and the hook geometry together or the number is meaningless — and hook profiles vary between machine makers, so the hook on your deck is defined by your equipment, not by a universal figure.

Why the Deck Is Crowned

A tensioned hook-screen deck is not flat. The tension rails sit higher in the center than at the side walls, giving the deck a crown (also called camber) — a high point down the middle. That curve does three jobs at once. It distributes the load and the tension evenly across the cloth. It holds the wires at the right vibrating frequency, the way a tighter guitar string rings higher. And it presents the high point to the incoming feed, so material lands on the crown and disperses across the full width of the deck instead of channeling down one lane.

Crown is a Goldilocks variable. Too little crown and the cloth loses tension, flaps, and breaks prematurely. Too much crown and the feed sheets off to the sides too quickly, wearing the edges out early. On a double-cambered deck the center hold-down is not optional — skip it and the section breaks early at the center where it is unsupported.

One point that trips up buyers: you do not order the crown into the screen. The section itself ships essentially flat. The tension rails on the deck are what impart the curve, so you order a flat section to the correct hooked dimensions and the machine pulls it into the crown when you tension it.

Hook Type Follows Wire Diameter

The right hook construction depends on how fine the wire is. Heavier cloth and finer cloth fail differently at the edge, so the hook is built differently:

• Heavier wire (roughly 1 mm / 0.039″ and above) uses a standard formed U-channel hook — strong enough to hold the coarse cloth without special reinforcement.
• Finer wire (below about 1 mm / 0.039″) uses a double-folded hook, with the metal folded back on itself at the edges, to keep the delicate fine wires from snapping at the hook line under tension.

This is why "just match the mesh" is not enough to order a hook section: the same opening can be woven in different wire diameters, and the wire diameter helps decide the hook construction as well as the screening behavior. The choice of woven wire itself — from oil-tempered high-carbon spring steel for wear and cost down to stainless 304 or 316 for corrosion or sanitary duty — rides on top of all of that, as does the weave type that determines whether the cloth sizes material or merely filters it.

How to Measure for a Replacement

This is where reorders go wrong. The dimension that defines a hooked section is not its mesh and it is not a single "screen size." Mesh count is openings per inch — a property of the cloth, not the size of the panel. The panel is defined by its overall hooked length, its width, the hook style, and the cloth spec. Here is what a complete reorder actually needs:

Manufacturers have their own sizing conventions for the length call-out — designated in catalogs as SPA (measured between the outsides of the hook strips, used for side tensioning), SPI (between the insides, for end tensioning), and SPIA (inside hook to the outside of the flat tensioning bar). The takeaway for the floor is simpler than the codes: whether you measure outside-to-outside or inside-to-inside depends on how the section is tensioned, so record the tension type along with the number.

And here is the honest reality every screen shop will tell you: you often cannot read these dimensions reliably off a worn, stretched, installed section. A panel that has been tensioned and run for months has distorted, and a worn hook is hard to gauge. If the hook itself is torn off or chewed up — common on the very section you are replacing — measure to the side-plate seat instead and flag that the hook is gone. The dependable move when anything is uncertain is to (1) give the equipment brand and model so the spec can be looked up, (2) photograph the seat area, rails, and machine nameplate, or (3) send the worn section in as a physical sample and let the supplier match it. Report the measured number and the machine and let the supplier set the tension allowance — do not pre-shrink the dimension yourself, or you can end up with a section that will not seat. That is exactly how ScreenerKing already handles round-screen reorders in how to measure a replacement screen — sample and model beat a guessed measurement every time.

How Hook Screens Fail

Most tensioned-screen failures trace back to tension, the rails, or the wrong section size — not the cloth itself:

• Loose tension. Shiny rub marks where the section meets the rails mean it is moving when it should be locked tight. Under-tensioned cloth flaps and breaks wires early. New sections settle under vibration, so re-tension a few hours after a fresh install.
• Missing or under-torqued bolts. The stretches of cloth next to a missing tension bolt are the ones that break first. Keep the bolt pattern complete and torqued.
• Worn or bent tension rails. A rail that can no longer hold the hook will destroy good cloth. New liners on a worn rail do not fix it — replace the rail.
• Lost crown. A flattened camber means lost tension and lost support across the deck. Check the crown when sections keep failing in the center.
• Wrong section size. An undersized or oversized section cannot be tensioned correctly no matter how good the cloth is — which loops straight back to measuring it right.

Over-tension is its own failure mode: crank past spec and you snap hooks and wires instead of stretching the cloth. More tension is not "more better." The target is drum-tight to spec, not maximum. For catching wear before it cascades into a deck failure, the same logic that drives bearing-failure detection applies to screen sections: inspect, look for the early tells, and change on a schedule rather than on a breakdown.

Tensioned Wire or Modular Media?

Hook-tensioned woven wire is not the only way to deck a vibrating screen, and the trade-off is worth naming. Tensioned wire gives the highest open area, the most throughput, and the finest separations — and it wears and breaks, which is why it is built to be changed. Modular polyurethane or rubber panels bolt down instead of hooking and tensioning; they last far longer and run quieter, but they give up open area and the finest cuts. That decision is laid out in full in polyurethane screen panels vs. wire mesh. If you are staying with tensioned wire, the cloth-grade standards behind the wire you choose are covered in market grade vs. mill grade vs. tensile bolting cloth, and how that cloth performs once it is tight and running is the subject of screen tension and separation efficiency.

Frequently Asked Questions

What is a hook strip screen?

It is a section of screen cloth with a formed metal hook crimped onto two opposite edges. The hooks engage tension rails on a vibrating screen's side walls, and tension bolts pull the section drum-tight across a crowned deck. It is the standard screening surface on horizontal and inclined vibrating screens, as opposed to the drop-in clamped screens used on round separators.

What is the difference between side tension and end tension?

Side tensioning runs the sections across the material flow and pulls them tight from the side walls, usually with several independently replaceable sections per deck. End tensioning runs one longer section along the length of the deck and pulls it from the ends. Side-tension hooks are formed at roughly a 45° opening angle; end-tension hooks have parallel legs. The two are not interchangeable.

How do I measure a hook strip screen for a replacement?

Capture the overall length measured hook tip to hook tip, the usable width, the tension type and hook style (side vs. end, U-channel vs. double-folded), the mesh or aperture opening, the wire diameter, and the weave and alloy. Mesh alone does not define the panel. Because a worn, installed section distorts, the most reliable approach is to provide the machine brand and model, send clear photos, or ship the old section in as a sample.

Why is my screen deck curved instead of flat?

That curve is the crown, or camber — the deck is intentionally higher in the center. The crown distributes tension evenly, holds the wires at the correct vibrating frequency, and lets incoming feed disperse across the full width instead of channeling. Too little crown lets the cloth flap and break; too much wears the edges early.

Can I just order a hook screen by the mesh size?

No. Mesh count is the number of openings per inch of cloth — it is not the size of the panel and it does not by itself fix the opening, because the opening also depends on wire diameter. A hook section needs its overall hooked length, width, hook style, mesh, wire diameter, weave, and alloy to be ordered correctly. An original sample or the equipment make and model is the fastest way to pin all of that down.

Why does a tensioned screen break wires near the edges?

Usually tension or hardware, not bad cloth. Loose tension lets the section move and rub against the rails; a missing or under-torqued bolt leaves the adjacent cloth unsupported; a worn or bent tension rail cannot hold the hook; and a flattened crown loses support across the deck. Over-tensioning also snaps wires and hooks. Re-tension new sections a few hours after install once they have settled.

Spec the Section, Not Just the Mesh

A hook strip screen lives or dies on three things the mesh number never tells you: the hooked length that fits your machine, the hook style that matches your tension system, and the wire that survives your material. Capture those along with the opening and you order right the first time; skip them and you reorder twice. ScreenerKing is expanding its screen lines beyond round separators, and the team specs replacement screen sections the same way it specs every screen — from the real part, not a guess. If you are trying to identify or reorder a tensioned screen section, the surest path is to send the worn section as a sample, share your equipment make and model, or photograph the deck and nameplate. Call 866-265-1575 or contact ScreenerKing to talk through a tensioned screen section. (Online screen ordering is coming soon.)