How to Estimate Blast Costs – A complete Guide
Whether you’re a factory, fabricator, or painter you may blast as a part of your process. To be able to be successfully profitable while blasting you have to be able to understand your costs so that you can properly bid on any sandblasting project. For those who have been blasting a while this will most likely be a review, for those who haven’t blasted before this should serve as a guide to help determine the cost you can expect to incur when sandblasting.
This method should provide the best results but requires you being able to blast a sample of your product in advance to determine the factors below. If you can this will provide the greatest insight into what blasting will cost you.
Cost of Compressed Air
Sandblasting requires a huge volume of compressed air whether it be from a gas or electric driven compressor your compressed air will be one of the highest expenses next to your blast media. A rough estimate of electric driven compressed air operating costs can be determined using one of the following formulas.
Electric Driven Air Compressor Costs
Formula 1 – This formula requires a bit more information but should provide better detail on the costs of operating your electric air compressor. Remember this formula would have to be applied during all states of operation including at rest, during blasting, and during blasting with other equipment being used (if applicable)
Cost ($) = (bhp) x (0.746) x (# of operating hours) x ($/kWh) x (% time) x (% full-load bhp) Motor
BHP stands for – motor full load horsepower (this can be higher than what is listed on the motor, check the manual for greater detail)
0.746 refers to a conversion factor between horsepower and kilowatts
$/kwh – price of electricity per kilowatt hour
%time – this refers to the percent time running at this level
Percent full load BHP – percent of full load BHP at the operating level
Motor Efficiency – Motor Efficiency at the given operating level
Formula 2 – This formula will also give you an idea of compressed air operating costs
- Length of time your compressor runs (this can be determined by observing the compressor during blast and seeing how long it runs in a given hour) you can also use a shorter time frame and estimate the hourly run rate. For the greatest precision consider averaging the run time over a longer time period (like a week)
- Determine the watts your compressor will consume per hour, take the voltage of the power for the compressor x the amps the compressor will use this will give you total watts per hour.
- Find total kilowatt hours (kwh) the compressor will consume. To find the total kwh you can look on the name plate or calculate using step 2 and dividing by a 1000. Once you have kilowatts per hour you can multiply by the total hours of operation that you found in step 1
- Multiply kwh by your electricity rate (which is usually given in price per kwh).
Diesel Driven Tow Behind Air Compressor Costs
You can estimate cost by determining how much production you got done in the given test time. Take the total surface area and divide by the production achieved. Multiply by the time taken in test. This will give you approximate compressor run time. Take the total run time and divide by hours. Multiply the hours by the gallons of diesel used per hour. Multiply diesel cost per gallon x total gallons of diesel used for price estimate.
Blast Media Cost
The cost of your blast media will depend on the total size of the product you blast, the profile you will achieve, and the effectiveness of the blast operator. For tips on maximizing blast performance you can download our complete guide to blast equipment. Ideally, you will blast a portion of a product to achieve the pattern you need. You can determine the amount of media that was used by only putting a given portion in the blast pot and seeing how much you finish before running out of media.
Once you have an idea of how much media you used for the given area you can figure out the total surface of the product size you will be blasting. Take the total surface and divide it by the area you got with the test. Multiply the result by the amount of media you used (40 lbs, 80 lbs) to determine total lbs of media you will use.
If you will be recovering media like with steel grit or steel shot you can assume you will reuse the media about 100 – 200 times which will mean you will need significantly less media but will typically use atleast 1 ton as this is a standard media delivery.
Blast Operator Cost
When performing the test on an area of the product you will want to determine how long the operator took to perform the given area. You then want to take the total area of the project you calculated for blast media and divide that by the area that was achieved in the test. Multiply the result by the time it took to finish the test area to get an estimate of the total time for the project. Multiply this by the hourly rate of your labor to determine the overall operator cost.
Blast Equipment Costs
You will also want to include costs for equipment and equipment replacement. Common equipment that wears includes blast nozzles, lense covers, and blast hose. To have a rough estimate of blast nozzle costs you will want to divide the estimate of total blast time by the expected life of the blast nozzle. Round the result to the nearest whole number as this will provide an estimate of the number of blast nozzles you will use. Blast hose is harder to estimate life of use, lense covers will often be used frequently and it is good to consider a fair number of them in a given blast project. They are a few dollars a piece typically.
** Remember to always consider changes in the product shape/ face and other factors to ensure your estimates are as accurate as possible
Method 2 – Use pre-published estimates for blast costs
If you want a quick and easy weight to get close estimates, you can use a pre published reference manual for blast surface costs. They estimate rough costs based on the type of surface, profile you will achieve, and similar factors. Remember their numbers are based on a variety of factors and could be different than your own. It can be wise to check with both manuals to see if the numbers are similar.
Reference Source 1
Reference Source 2
Ultimately estimating blast costs can be challenging. Always ensure you leave room for error. These tips should provide a beginning point to determine a rough idea of blast costs. If you need help with blast equipment as you consider a blast project contact us today.