Vibrating Screen Sizing Guide + Free Excel Calculator
Learn how to size vibrating screens step by step using the VSMA method. Ideal for mining and processing professionals—includes a free Excel calculator.
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| Section summary |
|---|
| 1. Vibrating
screen sizing calculation methodology STEP by STEP |
| 2. Vibrating screen sizing Excel calculator |
This page provides a detailed methodology for calculating the size
of vibrating screens, essential for optimizing efficiency and
productivity in mining, quarrying, and mineral processing
operations. The calculations are based on a formula developed by the
Vibrating Screen Manufacturers Association (VSMA), which
incorporates various factors to ensure accurate and reliable
results.
The process involves analyzing feed characteristics, calculating key
parameters, adjusting for specific conditions, and applying the VSMA
formula to determine the required screening area. This guide is
designed to assist professional engineers in accurately sizing
vibrating screens for their operations.
By following the step-by-step instructions outlined below, engineers will be able to:
-
Analyze Feed Characteristics: Understand the size distribution and bulk density of the feed material.
-
Calculate Key Parameters: Determine factors such as the flow rate of material, oversize and half-size percentages, and screening efficiency.
-
Adjust for Specific Conditions: Account for variables like wet screening, material weight, and the shape of screen openings.
-
Apply the VSMA Formula: Use the formula to calculate the required screening area.
Additionally, an Excel calculator is provided to simplify the process, allowing engineers to input their specific parameters and obtain precise results efficiently.
This page aims to equip engineers with the knowledge and tools necessary to accurately size vibrating screens, ensuring optimal screening processes and operational efficiency.
2. Vibrating screen sizing calculation methodology STEP by STEP
How to determine the size required for a vibrating screen ?
The calculation is based on a formula given by VSMA, this is based on correlations determined by an association of vibrating screen manufacturers :Screening Area (ft2) = U / (A x B x C x D x E x F x G x H x J)
Where:
- U = Amount in STPH of material in feed to deck that is smaller than a specified aperture
- A = Basic capacity (STPH)
- B = Oversize
- C = Halfsize
- D = Deck location
- E = Wet screening
- F = Material weight
- G = Open area of media
- H = Shape of opening
- J = Efficiency
| Factor | Explanation |
| A | Predetermined rate of material in STPH through a square
foot of a specified opening when feed to deck contains 25%
oversize (factor B) and 40% halfsize (factor C) Basic Operation conditions : - feed to deck contains 25% oversize and 40% halfsize - Feed is granular free flowing material - Material weighs 100 lb/cu.ft - Operating slope of the screen inclined screen 18-20° with flow rotation ; horizontal screen 0° - Objective screening efficiency = 95% |
| B | Actual % of material in feed to deck that is larger than a specified aperture (adjusts factor A to suit actual conditions) |
| C | Actual % of material in feed to deck that is one half the size of a specified aperture (adjusts factor A to suit actual conditions) |
| D | Applies for multiple deck screens. Total screening area is available for top deck separation. Time delay for material to pass to deck and 2nd or 3rd deck leaves less effective area available. This factor is expressed in a % of the top deck effective area. |
| E | Applies when the water is sprayed on the material as it moves down the screening deck (typically 5-7 GPM per STPH of solids). |
| F | Applies for weights other than 100 lb/cu.ft, it is calculated as lb/cu.ft (actual) / 100 |
| G | Applies when the open area of the screening surface is less than the reference used for factor A |
| H | applies when rectangular opening are used. Slotted or oblong openings will pass more material per square foot than square opening. |
| J | Applies when the target screening efficiency is < 95% |
Interactive VSMA Vibrating Screen Calculator
FOR EDUCATIONAL PURPOSES ONLY — NO WARRANTY — ALWAYS CONSULT A REPUTABLE SCREEN MANUFACTURER1. Process Feed Specifications
2. Sizing Factors
| Flow rate of material < opening (U): | - STPH |
| Basic capacity Factor A: | - |
| Oversize Factor B: | - |
| Halfsize Factor C: | - |
| Deck Location Factor D: | - |
| Wet Screening Factor E: | - |
| Material Weight Factor F: | - |
| Media Open Area Factor G: | - |
| Opening Shape Factor H: | - |
| Efficiency Factor J: | - |
3. Sizing Result
- ft²
Recommended standard size: -
Step 1 : Define the characteristics of your feed
It is important to analyse 1st the characteristics of the feed, especially :
- The size distribution and especially the % of the feed that is larger than the aperture you consider, and the % of the feed that is half of the size of the aperture you consider
- The bulk density of the feed material
Step 2 : Calculate U which is the flowrate of material smaller than the aperture considered
You have defined the size distribution of the feed, so you know the %weight of material whose size is < than the aperture. Multiplying by the total feed flowrate will give the parameter U.
Step 3 : Calculate the parameter A
Use the following table based on the target aperture
| Surface Square opening (inch) |
% Open Area | STPH Passing / sq ft (parameter A) |
| 4 | 75.00% | 7.69 |
| 3 1/2 | 77.00% | 7.03 |
| 3 | 74.00% | 6.17 |
| 2 3/4 | 74.00% | 5.85 |
| 2 1/2 | 72.00% | 5.52 |
| 2 | 71.00% | 4.9 |
| 1 3/4 | 68.00% | 4.51 |
| 1 1/2 | 69.00% | 4.2 |
| 1 1/4 | 66.00% | 3.89 |
| 1 | 64.00% | 3.56 |
| 7/8 | 63.00% | 3.38 |
| 3/4 | 61.00% | 3.08 |
| 5/8 | 59.00% | 2.82 |
| 1/2 | 54.00% | 2.47 |
| 3/8 | 51.00% | 2.08 |
| 1/4 | 46.00% | 1.6 |
| 3/16 | 45.00% | 1.27 |
| 1/8 | 40.00% | 0.95 |
| 3/32 | 45.00% | 0.76 |
| 1/16 | 37.00% | 0.58 |
| 1/32 | 41.00% | 0.39 |
Step 4 : Calculate parameter B
Determine the % of oversize vs the aperture used in the screen. To note that the factor B is equal to 1 for 25% oversize as it is the reference conditions.
| %oversize | Factor B |
| 5 | 1.21 |
| 10 | 1.13 |
| 15 | 1.08 |
| 20 | 1.02 |
| 25 | 1 |
| 30 | 0.96 |
| 35 | 0.92 |
| 40 | 0.88 |
| 45 | 0.84 |
| 50 | 0.79 |
| 55 | 0.75 |
| 60 | 0.7 |
| 65 | 0.66 |
| 70 | 0.62 |
| 75 | 0.58 |
| 80 | 0.53 |
| 85 | 0.5 |
| 90 | 0.46 |
| 95 | 0.33 |
Step 5 : Calculate the factor C
Factor C is determined by measuring the % of half size vs the screen aperture in the feed. Note that factor C is equal to 1 for 40% as it is the reference conditions.
| %halfsize | Factor C |
| 0 | 0.4 |
| 5 | 0.45 |
| 10 | 0.5 |
| 15 | 0.55 |
| 20 | 0.6 |
| 25 | 0.7 |
| 30 | 0.8 |
| 35 | 0.9 |
| 40 | 1 |
| 45 | 1.1 |
| 50 | 1.2 |
| 55 | 1.3 |
| 60 | 1.4 |
| 65 | 1.55 |
| 70 | 1.7 |
| 75 | 1.85 |
| 80 | 2 |
| 85 | 2.2 |
| 90 | 2.4 |
Step 6 : Calculate parameter D
- For top deck : D = 1
- For second deck : D = 0.9
- For third deck : D = 0.8
Step 7 : Calculate the factor E
Apply only when water is sprayed. Dependent on the screen opening.
| Opening (inch) | Factor E |
| 1/32 | 1 |
| 1/16 | 1.25 |
| 1/8 | 2 |
| 3/16 | 2.5 |
| 1/4 | 2 |
| 3/8 | 1.75 |
| 1/2 | 1.4 |
| 3/4 | 1.3 |
| 1 | 1.25 |
Step 8 : Calculate the factor F
Measure the bulk density of the incoming material. Then use the table to determine F,
| lb/cu.ft | Factor F |
| 150 | 1.5 |
| 125 | 1.25 |
| 100 | 1 |
| 90 | 0.9 |
| 80 | 0.8 |
| 75 | 0.75 |
| 70 | 0.7 |
| 60 | 0.6 |
| 50 | 0.5 |
| 30 | 0.3 |
Step 9 : Calculate the factor G
G is actually defined as the following ratio :
(% open area of screen surface used in the application) / (% open area in reference chart of factor A, for same aperture)
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Step 10 : Calculate the factor H
H depends on the shape of the openings of the actual screen used :
- Square : 1
- Short slot (3 to 4 times width) : 1.15
- Long slot (more than 4 times width) : 1.20
Step 11 : Calculate the factor J
Based on the screening actual target screening efficiency. Note that 95% is 1 as it is the reference condition.
| Efficiency considered (%) | Factor J |
| 95.00% | 1 |
| 90.00% | 1.15 |
| 85.00% | 1.35 |
| 80.00% | 1.5 |
| 75.00% | 1.7 |
| 70.00% | 1.9 |
Step 12 : Calculate the actual capacity of the screen
Screening Area (ft2) = U / (A x B x C x D x E x F x G x H x J)
Step 13 : Calculate that the overall screen area, combined with the width of the screen considered gives an acceptable discharge end depth
It is key that the depth of the material bed at the end of
the vibrating screen be not too high (typical < 4*aperture
size). Use this calculator
(vibrating screen DBD - Discharge End Bed Depth Excel
calculator) to make sure it is acceptable, if not, redefine
the screen width.
2. Vibrating screen sizing Excel calculator
What are the key process parameters to consider ?
Please access here the vibrating screen sizing Free Excel calculation tool : tool access
Warning : this calculator is provided to illustrate the concepts mentioned in this webpage, it is not intended for detail design. It is not a commercial product, no guarantee is given on the results. Please consult a reputable designer for all detail design you may need.
Download Vibrating Screen Sizing Excel Spreadsheet (VSMA Method)
Get the sorting and classification template offline. Apply standard VSMA calculations, select deck location parameters, density scales, and open area ratios. For educational purposes only.
Sources
VSMA
Frequently Asked Questions (FAQ)
How is the required screening area of a vibrating screen calculated?
The required screening area is calculated using the standard VSMA formula: $\text{Screening Area } (ft^2) = U / (A \cdot B \cdot C \cdot D \cdot E \cdot F \cdot G \cdot H \cdot J)$. This equation relates the rate of feed material smaller than the opening ($U$) to basic deck capacities and multiple correction coefficients including oversize, halfsize, deck position, material density, media open area, and target separation efficiency [Vibrating_Screen_Size_Calculation.html].
Why does the bulk density of the material affect vibrating screen capacity?
A material's bulk density directly dictates the volumetric bed depth travelling across the screen deck. The basic capacity rating (Factor A) is derived based on a standard dry material weighing $100\text{ lb/ft}^3$ [Vibrating_Screen_Size_Calculation.html]. For lighter or heavier materials, the mass capacity is adjusted proportionally using Factor F ($F = \rho_{bulk} / 100$) to prevent an excessive material depth at the discharge end [Vibrating_Screen_Size_Calculation.html].
How does wet screening affect vibrating screen sizing?
Injecting high-pressure water sprays (typically 5-7 GPM per STPH of solids) helps wash away fine particles adhering to coarse media, increasing the basic passing capacity. The wet screening correction (Factor E) scales up the theoretical passing rates by factors up to 2.5 depending on the aperture size, effectively reducing the overall physical screening area required to achieve clean classification [Vibrating_Screen_Size_Calculation.html].