Surface Overlays

 

See “Thick Overlay Checklist”

Temporary & Permanent Surface Overlays

Given a smooth sealed surface and a supply of air at the right pressure and volume, air caster technology can be sized to lift and move any load. Following these floor guidelines will ensure trouble-free performance for your equipment for years to come.

 

Proper operation of air caster systems is achieved on concrete that is smooth-troweled and sealed. This document covers how to correct larger surface areas that are damaged or cannot be sealed to create a suitable operating surface for the proper operation of air caster equipment.

  • For instructions on how to correct or create a suitable operating surface, see EI-13 “Cracks, Joints and Holes in Concrete”.
  • For information on original/new floor specifications or surface continuity, consult EI-14 “Floor Surface Specifications – Concrete Floors”
  • For information on achieving sealed concrete floors, consult EI-16 “Concrete Surface Treatments”

TEMPORARY SURFACE OVERLAYS – Introduction

Quite often, part or all of the proposed travel path may be unacceptable for air caster operation. Older or deteriorated floors, wood block floors, rough and porous shipping docks, doorway thresholds or chipped and cracked surfaces may be encountered. Upgrading or resurfacing may be impractical or uneconomical, especially if the move is a one-time, infrequent occurrence.

Temporary overlays of a suitable material are used in order to provide a smooth, non-porous and continuous surface. If the existing floor has the load bearing strength required, relatively thin material can be used, such as 24-ga sheet metal, non-embossed vinyl linoleum or 14 mil. (0.36mm) plastic. The roughness of the underlying surface must be considered as thin overlay materials may take on the underlying texture. (See “Overlay Use – Thin”)

For very rough surfaces, low load bearing capacities or open gaps, drains, tracks, etc., thicker, self-supporting overlay materials must be used. Quarter inch (¼”) (6mm) steel plate, butt-welded and ground has the strength for many of those conditions. Supplementary supports may be necessary for proper load distribution. (See “Overlay Use – Thick”)

Gaps at railroad tracks can be filled with plaster of paris, wet sand or any load bearing material and then overlaid with thin material.

 

OVERLAYS ARE REQUIRED ON:

– SEVERELY DETERIORATED CONCRETE FLOORS
– WOOD BLOCK AND PLANK FLOORS
– UNTREATED ASPHALT
– DOORWAY THRESHOLDS AND EMBEDDED PROJECTIONS
– SERIOUSLY CHIPPED AND CRACKED SURFACES

EXAMPLES OF OVERLAY MATERIALS:

FOR SURFACES WITH FULL LOAD-BEARING CAPACITY (THIN):

– 24 GAUGE SHEET METAL (GALVANIZED STEEL OR ALUMINUM)
– VINYL LINOLEUM (NON-EMBOSSED)
– 14 MIL PLASTIC

FOR ROUGH SURFACES WITH MINIMAL LOAD-BEARING CAPACITY (THICK):

– ¼” STEEL PLATE BUTT-WELDED AND GROUND
– SEALED or SMOOTH – PAINTED PLYWOOD or MASONITE

OVERLAY MATERIALS Clean, UN-corroded “slick” surface materials strong enough to bridge surface irregularities without being damaged by the air pressure load of the air casters are suitable as temporary surfaces. Thickness of material depends upon its stiffness, underlying roughness and air pressure load. Overlays, with tape applied, can handle major crevices and other defects.

OVERLAY USE – THIN Overlays less than .020”(.5mm) thick:

  • Edge beveling or tapering is usually not required (depends on air caster diameter and list).
  • Be sure edges are free of burrs or sharp corners that might wear, cut, or tear the torus fabric. Start with the dull side of a sheared edge or use a deburring tool or exacto knife.
  • Overlap edges by shingling in the direction of travel so the air casters step down from one sheet to the next (see diagram). Shingle the sheets in the direction of the move.
  • Arrange sheets so that air casters cross the fewest number of joints. Sheets should be selected which are wider than the air casters in use. Ensure individual sheets are secure – especially if drive wheel force will be acting on them.
  • Particular care should be taken where several sheets join together at odd angles such as in turning corners, so joints are infrequent and “stack” heights are reduced.
  • Taping: Tape the edges with aluminum foil tape (not duct tape) to facilitate air caster transition onto the overlay. We recommend taping leading and trailing edges to minimize air loss and ensure trouble-free passage. In some cases, experienced operators may tape only the leading edge. See “Aluminum Tape” section for full tape instructions.
OVERLAY USE – THICK

Overlays greater than .020”(.5mm) thick:

  • Thicker sheets of metal that are overlapped should have the edges beveled to 1:10 to 1:20, then ground smooth.
  • Bevel edges with 1:20 taper and deburr. (Taper of 1:10 will generally work, however, 1:20 or greater is preferred).
  • Ensure individual sheets are secure – especially if drive wheel force will be acting on them.
  • Always step down in direction of travel (refer to diagram – previous page).
  • Use vinyl “T” extrusion to seal butt joints of plywood panels (use painted panels only) or metal plates on construction and expansion joints. Duct tape applied to the underside of the gap may be used to secure the overlays in alignment.
  • Tape per “Overlay Use – Thin”

THICK OVERLAY CHECKLIST
– BEVEL EDGES TO 1:20
– EDGES & TAPERS FREE OF BURRS
– SHINGLE IN DIRECTION OF TRAVEL
– USE “T” STRIPS TO SEAL BUTT JOINTS
– TAPE EDGES
 

 

 

THIN OVERLAY CHECKLIST

– SHINGLE IN DIRECTION OF TRAVEL
– EDGES FREE OF BURRS & SHARP CORNERS
– FEWEST OVERLAP CROSSINGS
– AVOID LENGTHWISE OVERLAP TRAVEL
– MINIMUM STACK HEIGHTS
– TAPE EDGES

 

TEMPORARY OVERLAY OF CRACKS OR JOINTS

If bigger surface overlays are not an option for you, you may utilize a temporary overlay for smaller cracks. There are two effective options: aluminum tape or narrow, sheared metal strips. Check the full travel path of the Air Casters to determine all affected areas.

ALUMINUM TAPE: Taping can be a quick method for overcoming smaller floor defects for short-term passage of air caster floated loads. This works well for smaller cracks, joints or holes – in either single or multiple layers. There are two main considerations: the width/area/ depth of the defect and the expected air caster pressure when traversing the repaired defect.

Tape to Use: Suggested is 2-inch (50mm) or wider tape of 2mm (0.08-inch) thickness (or better) dead soft aluminum with 3mm (0.12-inch) acrylic adhesive layer and with release liner so foil doesn’t wrinkle as it unrolls – available from many industrial supply houses.

Applying Tape – Single Layer: If the joint/crack is 1/8-inch (3mm) or less wide, and the expected air caster pressure is less than 13 psi (.90bar), one layer of tape should be sufficient.

  • Clean floor surface with a solvent (isopropyl alcohol, MEK, etc.) – the adhesive on the tape will hold firmest on a clean surface. Note: If the tape is not properly applied, the air pressure will get under the tape and blow out any sand or filler material
  • Use rag or roller to smooth tape and push out bubbles. Caution: aluminum tape edges are sharp.
  • Test the taped surface for compatible air caster operation before regular moves.

Applying Tape – Multiple Layer: If the surface can be taped effectively, multiple layers of tape can be used to provide sufficient strength to bridge larger voids and resist higher air pressure loads.

  • Support: If possible, fill crack, joint or hole with sand or wood or other removable substance to support tape.
  • Layers: The number of layers will depend on the width of the gap and the support available. A few examples are given below – call ASE for more information.
    1) If the joint/crack is 1/8-inch (3mm) or less wide, and the expected caster pressure is less than 13 psi (.90bar), one layer of tape should be sufficient. If more than two Air Casters will cross this gap, add one or more extra layers and inspect after the first crossings for tape integrity. If the air casters are working above 13 psi (.90bar), start with two layers and add more if more than two air casters use the tape. When the cracks are 1/4-inch (6mm) wide, start with three layers and add more per above 2) A 1/4 – 3/8-inch (6-10mm) crack with clean edges can be bridged with 3-4 layers of 0.12-inch (3mm) tape for use with 25 psi (1.7bar) air casters. Note: For applications requiring moves across larger cracks, gaps, or steps, ask your representative if the increased capabilities of the Gap master would be right for you.
  • The multiple layers should be slightly staggered creating steps to ease transition, with steps facing away from the direction of travel and so that air casters climb only one tape edge at a time. Keep all layers of tape over the crack/joint itself so that full thickness of stack-up provides strength.
  • Follow all other tape application guidelines in the “Applying Tape – Single Layer” section above.

SHEARED STRIPS: For straight joints or wider gaps, .020-inch (24-ga.) sheared strips can be an effective temporary solution for air caster usage. Smooth galvanized sheet is a good choice.

  • Width: Typically 4-inch (100mm) wide sheared strips work well on joints – and are also easy and economical to obtain from a sheet metal shop.
  • Edge beveling or tapering is usually not required (depends on air caster diameter and list). However, be sure edges are free of burrs or sharp corners that might wear, cut, or tear the torus fabric. Start with the dull side of a sheared edge or use a deburring tool or exacto knife.
  • We recommend taping leading and trailing edges to prevent air loss. Important: Apply tape to both edges of sheared strips per the above “Aluminum Tape” section above.
  • Strips need to be sufficiently longer than the diameter of the air caster will be traveling over them – either covering the entire load width or just the path of the air casters.
  • Gap crossing air casters are furnished without landing pads and may be fixed-mounted or slide mounted. For best results and reduced air flow, smooth and round off all gap and step edges if possible. *Capacities shown are maximum.