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Defining Stripe Removal Processes – Is it a Grinder?

Grinder Talk

The term “grinder” is a term many use to describe ALL mechanical eradicators.  This is not correct.   In this article, we  describe the various common mechanical stripe removal processes that are commonly mislabeled as a Grinder.

Removal can be defined by its rotation. Vertical and rotary removal or eradication machines will create all 10 profiles in the surface profile chart (SP1-SP10). Most surface-preparation and traffic-line removal work can be accomplished using either vertical or drum-style removers.

Rotary Erasing is a simultaneous vertical and horizontal, floating to planing, rolling-cutting-action on the pavement. Rotary-style eradicators (erasers or grinders) use the same rotation as a water-blaster.   Markings that are soft to brittle can be abraded and scraped off the surface, leaving an “Erased”, bevel-edged, feathered appearance without grooving or undulation patterns associated with drum-style eradicators.

Drum-style eradicators used for scarification, planing, milling or grooving. The vertical cutting action of these removers create a sharp-edge surface profile best for preparing surfaces prior to installing stripes, coatings, overlay or repair materials. When removing stripes, drum style rotation often leave a deep surface scar that allows water to pool, creating false or ghost-lines where the prior marking was located.

In many instances, a combination of both removal rotary and drum styles are used by stripers to achieve the final desired surface finish profile required by the design engineer.

grinder

Defining Rotary and Drum Style Stripe Removers

Grinder (Rotary):

Actually a rotary process that produces a rubbing or frictional force applied against a hard surface through a grinding process using stones, discs, or blocks embedded with diamonds that wear away the paste, fines and aggregates at a uniform rate to produce a nearly flat (SP 2) surface. Removal is accomplished by the rotation of abrading stones or discs applied under pressure at right angles to the surface. The grinding stone or disc is moved across the surface until the desired effect of smoothing surface irregularities is achieved.

Erasers (Rotary):

Rotary Erasing is a simultaneous vertical and horizontal, floating to planing, rolling-cutting-action on the pavement. Markings that are soft to brittle can be abraded and scraped off the surface, leaving an “Erased”, bevel-edged, feathered appearance without grooving or undulation patterns associated with drum-style eradicators.

The Rotary Eraser removal tool can be outfitted with select cutters each held on a spindle at a pre-set pitch and down pressure to control the angle and depth of cut.

The Eraser’s chassis includes cut-depth caster wheels that can be engaged by the operator to remove markings in a sweeping side-to-side action. This oscillating action peels and pushes the markings off the surface, at a glancing angle, to keep unstable surfaces sound.

Traditional drum style scarifiers beat the markings deep into the surface, which cause surface bruising and cracking.

Operators can select from a variety of multi-pin cutter options that can be quickly installed on the Eraser to match the marking being removed and the final pavement surface profile required. These multi-pin cutters rotate consistently at speeds up to 2500 RPM.

The forward, backward and/or side-to-side travel speed of the machine is determined by the operator. After testing the material tensile strength, thickness and road surface characteristics, the operator sets the adjustments and moves the equipment by walking, riding or driving to spread the shear force of the multi-pin cutting action over a smaller or larger area.

This movement, faster or slower, can be quickly paced by the operator so materials reacting to heat like thermoplastic and tapes remain cool and surfaces like “Open Graded Friction Courses” stay in place.  This controlled cutting surface contact time is designed to keep the surface cool and break up only the marking materials while leaving sound surfaces unaffected.

The operator has absolute control over performance and surface micro-cracking by (1) cutter selection, (2) surface pressure, (3) pitch angle, (4) cut depth and (5) travel speeds.  To reduce possible surface micro-cracking on friction coarse while removing thick paints, fewer oscillating pin cutters may be used for removal, applying shorter contact time or increased speed to break up the coatings keeping the surface sound with multiple passes.  Reducing speed and increasing contact time will apply the full concentration force for aggressive removal to increase removal speeds but can also influence surface breaking.

Planer (Drum or Rotary):

Also known as an impact rotomiller, it is a rotating drum with teeth that strike the surface with great force, fracturing the material into chips and dust in depths ranging from ¼” to 4” with the surface roughness determined by the number and size of teeth, plus the size and weight of the machine, typically producing an SP 8 – 10 profile. Planning produces a rough, fractured surface with the teeth producing a linear striation-grooving pattern. Driving the equipment in a straight path across the surface and adjusting the depth of the cutting drum prepare the surface.

Scarifier (Drum):

Primarily used for profiling and removal of hard surfaces and brittle coatings up to 1/8” thick, with multiple passes required for deeper removal. Equipment can be outfitted with cutter drums or non-cutter drums. Cutter drums consists of toothed cutters and spacers assembled on steel shafts mounted at the perimeter of a drum that rotates at high speeds and flails to fracture or pulverize the surface and produce vibration. The types of cutters selected and their array on the cutting drum, rotation and travel speeds spread the cutting shear force over a larger area resulting in controlling the surface contact time leaving sound surfaces unaffected while fewer pin cutters oscillating will produces longer contact time and concentrate the force of the tools resulting in more aggressive removal. The selection of the appropriate cutters and their in-line or offset spacing patterns with the direction of rotation and rate of lineal travel determines the removal finish and cut depth range. Best removal action is pulling machine backwards in opposite drum rotation position and overlapping passes to produce uniform cut depths and profiles. Scarifiers attached to dust collection vacuum systems provide little airborne dust during operation with a following up use of a vacuum wand or broom truck for containing any remaining left contaminants.

Groover (Drum):

Diamond Shavers or Groovers are similar to scarification equipment with diamond segmented blades stacked together on a drum arbor that rotate at speeds up to 3000 RPM with little or no vibration. This removal style is ideal for leveling or grooving into surfaces up to 1/8” per pass, without microcracking the surface. The drum arbors can also be spaced to cut through thick, resilient coating systems for further surface preparation. The selection of the appropriate diamond grit, hardness spacing patterns with the up-cut direction of drum rotation, and rate of lineal travel determines the removal performance. The diamond blade segments have aggressive grit compositions for dry cutting operations, and are available in different hardness grades for the surface hardness and materials being grinded, and are consumed during the process and require changing as they wear out.

Dust-Free Removal (Drum/Rotary):

Any removal without water produces dust. A vacuum attached to any style eradicator (drum or rotary) will contain all airborne dust from the job-site.  To pickup any remaining materials requires the use of a secondary wand or a sweeper broom truck.  Since Drum or Rotary Eradicators remove stripes without water, the surface remains dry for any immediate re-striping thus shortening the work-zone closure.   No water use means surface-prep and stripe removal can be a year round operation.

 

three types

Surface Profile Chart, Removal Selection Guide and Stripers Toolkit:

The surface profile chart (SP1 – SP10) aids both stripers and inspectors in assuring that the MUTCD requirements for removing all traces of prior markings are met. Read more here.

To help stripers and specifiers in their equipment and cutter tool selection, please visit here.

Create All 10 Surface Profiles

SMITH has developed a new method to measure the effectiveness of preparing surfaces for successfully installing new pavement markings and removing markings that meet MUTCD guidelines that will directly benefit stripers, material suppliers, engineers and the public. Follow this link to the striper’s Pavement Marking Removal Toolkit to help stripers win more bids, assure stripes last longer, satisfy the engineer, and improve your bottom line.

If you own a grinder, scarifier, planer, eraser or shaver and are looking to achieve the right surface profiles, click here

Questions to Consider?

  • Is it fair that stripers are being held responsible for producing a quality stripe if they don’t have responsibility for the surface on which their stripe is being applied?
  • Should the responsibility for prep-before-stripe be better defined in contracts?
  • Should prep-before-stripe be separated from the striping contract, as a paid line item, and not considered incidental to the contract?
  • Is it true that contractors base their bid price on what is paid for and inspected?

Join us in our mission to help make our roads safer and last longer through paid surface preparation practices.  Agencies investing  in proper surface preparation work will benefit with longer lasting pavement markings.   Not paying for the hard work of removal, that no one wants to do, is simply not working.

 
© 2017 SMITH Surface-Prep Solutions - 1610 S. Dixie Highway, Pompano Beach, FL 33060-8913
Toll Free: 1-800-653-9311 | Ph: 954-941-9744 | Fax: 954-545-0348
Specifications and data are subject to change without notice.