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Troubleshooting the Blast Cleaning Process


Troubleshooting The Blast Cleaning Process

troubleshooting blast cleaning process

Guidelines for controlling the three basic blast cleaning operating variables

These three variables account for as much as 90% of all problems adversely affecting quality of finish, cleaning productivity, and operation costs.

porper blast pattern aim

  • 1) Check location of blast-pattern “hot spot” regularly. (Test-blast a metal target plate placed at normal work height for 20-30 seconds. Hot spot should be approximately 8” in advance of wheel center-line.)
  • 2) Inspect daily, degree of wear of wheel components:
    • Impeller: Change when leading edges exceed ⅛" wear.
    • Control Cage: Change when beveled edge exceeds ¼" wear
    • Vanes/Blades: Change when grooving is ½ thickness of blade.

Excess wear of wheel components distorts blast pattern and causes “hot spot” to shift (10% shift can cause 25% loss of cleaning efficiency.)

  • 3) Do not permit sand or excess fines in the work mix. (2% Sand content can double wear rate on wheel components.)
  • 4) Establish records of parts replacement vs. wheel hours operated, so preventative maintenance can be utilized.

balanced work mix

  • 1) Screen analyze work-mix weekly.
  • 2) Add new abrasive every operating shift.
  • 3) Do not allow abrasive spillage/leakage to accumulate; return to machine daily.
  • 4) Check Separator/Ventilating system regularly:
    • Scalp screens: Holes? Blockage?
    • Shred Plates: Holes? Be sure a full abrasive curtain exists.
    • Keep dribble valves on all separator or expansion-trap discard pipes.
    • Dust Collector Pipes: Check for dust buildup in pipes.
  • 5) Check separator and dust-collector baffle settings regularly to be sure air-flow is correct.

full anrasive flow

  • 1) Add new abrasive every operating shift and maintain hopper level above ⅔ full always.
  • 2) Keep all paper, cardboard, plastic, wood, and other trash out of the blast cleaning equipment
  • 3) Be sure scalp screens are clean and not plugged.
  • 4) Check wheel components daily for excess wear.
  • 5) Check feed control valve to be sure it is functioning properly.
  • 6) Check for worn or loose drive belts.
  • 7) Post the “Full Amps” target above each ammeter. Record actual readings every shift.
  • 8) Keep ammeters in good working order at all times.

ervin spot check gauge

Check to see where top of work-mlx levels off. = X Mark X on the scale at right

The best protection against inefficient operation is to make frequent analysis of your blast cleaning operations.

FEED HOPPER LEVEL: When too low: Runs the risk of insufficient feed to wheels; Indicates work-mix is out of balance, and cleaning-profiling will be poor.

AMMETER READINGS: If below full-rated amps, wheel is being short-changed. For each amp below full-rate, approximately 30 lbs of abrasive is not thrown. What isn't thrown can't clean-profile your work.

TARGET POUNDS PER WHEEL-HOUR: SAE-quality cast steel shot or grit, in a properly operated system, should equal .35 lbs per hp per wheel hour usage rate. (Example: wheel hp at 40, times .35 equals 14 lbs per wheel hour usage. If usage is at 21 lbs/wh, consumption is 50% higher than it should be.)


W/M x in green-zone represents optimum operation, with respect to:

  • Cleaning-profiling finish: Productivity; and Abrasive consumption.
  • W/M x above the green zone means the w/m is too coarse for efficient and effective cleaning-profiling - Result:
    • Spotty cleaning-profiling, finish too rough, parts warpage, breakage;
    • Blast-cycle time can be 25% to 100% more than normal, or re-blast is required;
    • Equipment wear/tear can increase greatly
    • Shot and grit consumption can increase easily as much as 100%, or more.
  • If the w/m x is in the yellow zone, it is an indication the operation has serious problems - but, when x in the red zone, it means the operation is flirting with disaster.

When the operations analysis indicates trouble - it's time to review the ERVIN TROUBLESHOOTING GUIDELINES shown on the reverse side.

Download a PDF of the full poster here.

or Call Ervin Today at 1-800-748-0055

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P: (734) 769-4600 / TF: (800) 748-0055 / F: (734) 663-0136
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Ann Arbor, MI 48108

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