Container spray booth build?

[ian]

Hi Albert

looking at your other posts, your "shed in the garage" is really a small scale industrial set-up -- though we both know it's just a well funded "hobby".
So I can't see you settling for anything less than small scale industrial for your spray finishing.

However, you should seriously look at contracting a professional to do your finishing. While the rate might appear exorbitant, in reality it should represent a fraction of the value add from applying a spray finish. If the professional would charge you $200 to apply a finish, you should be looking to cost your own finishing at a similar (if not higher) rate, which at a cost of $200 per item should represent a $400 (or more) increase in the piece's value. If the client is not prepared to stump up for the additional value (i.e. cost to them) then you have to ask why you would invest in a booth.
If the client is only prepared to pay $100 more for a finish that costs $200 then accepting only $100 means that you are going backwards.

[ian]

I've googled a bit about spray finishing ...

https://gfsboothblog.com/2013/03/26/...n-performance/

"It is more common for the ventilation performance of a spray booth to be specified by the average velocity through the booth or in the vicinity of the painter and product. From the design velocity you can calculate ventilation flow rates and air changes.
For example, if your booth is 16 feet wide by 14 feet tall and is a cross draft design, typical velocity in the booth would be 100 feet per minute (fpm). The total flow through the booth would be 22,400 cubic feet per minute (cfm) (16 x 14 x 100). The volume of the booth is 8960 cubic feet (16 x 14 x 40). The air changes can be calculated by dividing the flow rate by the volume. In this example, the air changes would be 2.5 air changes per minute (22400 / 8960).

These sorts of numbers equate to the air flow velocity in the one spray finishing booth I've used.
For a 8' x 8' x 20' container, your fan (after accounting for the resistance of all the particle filters and exhaust air cleaners would need to pull 1600 cubic feet per minute)

The link also gives an example for a down draft design and cautions that

"the ventilation rate shall be able to maintain the concentration of flammable vapors in the exhaust below 25%."

and suggests that maintaining less than 25% may require additional air flow.


https://www.toolsusa.com/blog/how-mu...booth-require/

"The real issue with air flow in a spray paint booth is having adequate air. A 14’ wide x 9’ tall x 26’ long spray paint booth will exhaust at least 13,104 cubic feet of air per minute. Running this spray booth for twenty minutes requires 262,080 cubic feet of available air. This requires a building at least 17,472 sq ft with 15’ ceilings or 10,483 sq ft with 20’ ceilings. This issue of an undersized building can be addressed with booth design and/or an air make-up unit. "

bearing in mind this is written for North America where, during winter, pulling sub-zero outside air into a building is undesirable, but the principle still applies


In terms of filters, How to Calculate Spray Booth Air Flow

Proper airflow is not only necessary for the protection of the operator, but is necessary to achieve the desired finish quality. Flow that is too low will not draw the overspray to the filters. Much of the overspray will end up on the part as dry spray (rough finish). If the flow is too high, solvent tend to evaporate too quickly resulting in dry spray.
To calculate the amount of exhaust air needed for the booth, a simple calculation is used.
CFM = Booth Face Area in square feet multiplied by the required flow (typically 100 FPM)
For example, and 8 X 10 filter bank (80 square feet) would require an exhaust of 8000 CFM (100 X 80) to achieve the required 100 FPM velocity.

and although not an NZ or Australian standard, the information here NFPA Ventilation Standards - Paint Booth Technologies - Industrial & Automotive Paint Booths should be a useful guide.

[Albert]

Hi Albert

looking at your other posts, your "shed in the garage" is really a small scale industrial set-up -- though we both know it's just a well funded "hobby".
So I can't see you settling for anything less than small scale industrial for your spray finishing.

However, you should seriously look at contracting a professional to do your finishing. While the rate might appear exorbitant, in reality it should represent a fraction of the value add from applying a spray finish. If the professional would charge you $200 to apply a finish, you should be looking to cost your own finishing at a similar (if not higher) rate, which at a cost of $200 per item should represent a $400 (or more) increase in the piece's value. If the client is not prepared to stump up for the additional value (i.e. cost to them) then you have to ask why you would invest in a booth.
If the client is only prepared to pay $100 more for a finish that costs $200 then accepting only $100 means that you are going backwards.

Thanks Ian!
Sometimes I am not even sure I needed it or I wanted it lol

I think having my own booth so I can hire someone as a contractor to do the painting for me. I can pay a painter an hourly rate rather than pay him $200 for a piece.

[Albert]

I've googled a bit about spray finishing ...

....and although not an NZ or Australian standard, the information here NFPA Ventilation Standards - Paint Booth Technologies - Industrial & Automotive Paint Booths should be a useful guide.

Thanks again Ian!

over the weekend I have found a professional spray painter who will be helping me to set up my booth.

he is dismantling his booth (retiring) and I have bought some of the stuff I need from him (I have actually bought a 800mm diameter Hison extractor fan from him already), the flow rate of the fan is about 17000m3/hr at 15mm of water pressure, or 20400 m3/hr at 5mm of water pressure, this is high for the size of my containter booth(usable volume of around 8m3) but I will have a VSD on the fan so I can adjust the speed of the fan. Its better to have a bigger motor than too small. here is the fan curve of the Hison fan, mine is 28 deg pitch.

Hison Fan curve.jpg

my booth will be at the back of the property rather than on the drive way.

Sitting on the driveway is asking for neighbours attention. having it at the back of the property meaning I will need to put money down on the compressed airline and a power supply. but it will be out of sight.

Will upload photo as I go.

[ian]

I think having my own booth so I can hire someone as a contractor to do the painting for me. I can pay a painter an hourly rate rather than pay him $200 for a piece.

a word of caution

I don't know about Auckland, but in Sydney hiring a contractor to work in a spay booth you own (or rented) would mean that you ceased to be a "well funded hobbyist" and became a "home based business".
In the areas of Sydney that I am familiar with, your existing scale is possibly beyond what is would be tolerated (or even permitted) as a home based business not to mention the wall of workplace safety and compliance issues that would tower over you as soon as you became an "employer"


Personally I think your better option is to contract an external provider to do the finishing.
Issues associated with speed and volume of air flow through the booth, filter performance, gun selection and finish preparation, spray pattern, clean-up, work health and safety, etc are all yours if you own the booth and just contract the labour to spray the finish.

[Albert]

a word of caution

I don't know about Auckland, but in Sydney hiring a contractor to work in a spay booth you own (or rented) would mean that you ceased to be a "well funded hobbyist" and became a "home based business"..... etc are all yours if you own the booth and just contract the labour to spray the finish.

yes I know if I start to employ people I become "Person Conducting Business Under Taking" with the new health and safety legislation in NZ... if I provide proper health and safety gear and training then I am all good. its just matter of time before I have to do this properly.

its a long way before I produce enough items require someone else to do the spray painting anyway. the booth will be modular so if I ever want to sell my house to a permanent location, I will just put it on a truck and leave.

At the moment I am on the border of permitting - local authority's bottom line is that I am not doing this as my full time job and the impact on the environment is within reasonable tolerance. will have to put a lot of filter on the spray booth to ensure no smell/fume is seen.

[ian]

... if I provide proper health and safety gear and training then I am all good.

what might trip you up under that scenario is showing that you are "qualified" to provide the training and competency assessment. Doing so might require that you hold a fistful of formal qualifications