Screening Problems Solved

SCREENING PROBLEMS; SOLVED Alex Caruana Aggregate Territory Manager

#1: My Screen and structure keep failing!

#1: My Screen and structure keep failing!

Identifying the symptom is a good start: -

Breaking cross members, frames, feedboxes, Repeated premature bearing failures, Fastener failures, Cracked side plates, Structural damages.

The next step‌. Measure it!

You can only manage what you’ve measured.

-

Orbits (rotation), Amplitude (stroke), Speed, Pedestal movement, Critical Frequency.

Orbits & Amplitudes INCLINE SCREENS & 4 BEARING (CIRCULAR MOTION)

Amplitude/Stroke

Orbits & Amplitudes HORIZONTAL SCREENS (ELLIPTICAL MOTION)

Amplitude/Stroke

Orbits & Amplitudes COMBINATION SCREENS

FAST travel rate

Medium travel rate SLOW travel rate

Orbits & Amplitudes LINEAR MOTION SCREENS

Orbits & Amplitudes

Pedestal Supports – Structural Movement Measuring the pedestals’ movement.

-

Excess motion in any of the directions will cause lost energy, Excess motion will also cause fatigue failure perpendicular to it, ISO standard for vibrating equipment on a fixed structure is the baseline.

Critical frequency ‘peak’ @ 13Hz / 780 RPM Operation at or near such peaks result in screen body damages

#2: Quality Control vs. Production – a Saga!

Measuring points

+ Belt Sampler (plant running)

Belt Cut (plant stopped), Useful for tonnages & efficiency.

Making changes? Make a new pile!

Loader pad

Making QC performance a little easier Save your work!

- Screen layouts, - Crusher settings, - Feed parameters, - Specialty materials, - Don’t look for the magic formula again.

Smaller media = smaller degrees of change.

- Double crown wire = 2x as adjustable, - Small modules, 1’x1’, 1’x2’ etc allow for very fine tuning - Quicker repairs when failures occur.

QC Peace of Mind Finding the longest wearing screen media smooths out your gradation variances

Wear Trend vs. Out of Spec Wire

Synthetic

Oversize

120 100

1 oversize occurrence vs. 6.

80 Wear

Real example based on 2 sets of wire cloth per year, vs. 1 set of Rubber modules every 36 months.

60 40 20 0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324252627282930313233343536 Months

#3: I need More Tonnes!

1” opening wire 56 holes across, 180 holes down

1” opening rubber 72 holes across 8’, 180 holes down

Step #1: Find out your actual open area in place – simply count the open holes.

Step #2: Apply the correct open area panel blend. Feed zone, under spray and flow path have different requirements. This is possible with most media types.

24% Wear Life

Tonnes/Hr

35%

44%

52%

Hybrid decks are excellent at blending wear and high open area too.

Check your bed depth and feed distribution to raise efficiency.

Underloaded

Overloaded Wear line = bed depth

#4: My Media isn’t Working!

Pegging factors: -

Particle shape, Nearsize, Rotation of machine uphill/counterflow, Lacking stroke for the application.

Solutions: -

Self cleaning media opening style, Flexible media material, Adjust rotation downhill/with flow, Adjust stroke upward if appropriate for application and machine.

Blinding: -

Moisture content, Clay content, Rotation of machine uphill/counterflow, Lacking stroke for the application.

Solutions: -

Self cleaning media opening style, Flexible media material, Adjust rotation downhill/with flow, Adjust stroke upward if appropriate for application and machine, Washing.

#5: It’s got Water, now why isn’t it Working?!

Wet Screening can be a lot more efficient,

-

Biggest efficiency increase in finer sizing,

Efficiency with proper Water Application 2.5

Too fine and water just adds turbulence.

2

2

2

1.75 E (x100%)

-

1.75

1.5

1.5 1.3

1.25

1.2

1

1.1

0.5

0 1/32”

1/16”

1/8”

3/16”

5/16” Opening Size

3/8”

1/2”

3/4”

1”

So‌. How much water?

Rule of Thumb: 3-5 GPM per TPH (feed to screen)

@

*Pressure gauge should be placed at the actual spray bars or manifold.

Introduce Water BEFORE the screen!

1/3 of water at headbox

2/3 of water at spray bars

Bottom deck of a triple deck screen with no headbox water L

What is happening in there‌

Head Box Creates Slurry

Feed End Passes Half Sized Material

Discharge End Passes Near Sized Material

Slurry Quickly Passes on Feed End

How do I position my spray nozzles?

• 45 Degree Angle • Towards Feed End • Create Water Dam

• Increase Retention Time of Material Under Water • Critical for Deeper Bed Depths (4:1) • Biggest Impact on Decks with Higher Fines Content

THANK YOU! Let’s talk further…

Alex Caruana Polydeck 519 774 2813