Decrease haul truck wash time

[JP123]

Hi,

To perform any maintenance on 240 tons trucks in the wash bay, the trucks require considerable heating time to ensure the water doesn't freeze to the trucks during winter time. The building is heated.

Is there any other way to heat the truck faster than in 6 hours using steam heaters from the building? Does somebody know references for calculations?

Thank you.

 

[sreid]

1) The hotter the air, the better.

2) Have fans blowing the hot air everywhere.

 

[IRstuff]

How about just using the steam to clean the trucks?

TTFN

FAQ731-376

 

[ivymike]

How about using water with an anti-freeze agent in it for washing? That pink stuff they squirt on planes might be expensive, and I don't know how it compares to your heating and service bills...

better yet, how about washing the trucks, then letting them cool, then coating them in a protective layer of ice to avoid future washing?

 

[JP123]

the truck used are carrying rocks and soil to produce iron ore. During the winter the climate can drop down to -40 deg C.

I think heating the building properly and using hot water will be a good idea.

But i have to calculate how long it is gonna take to warm up the steel of the truck before washing it and prevent the water to freeze.

Any tips?

 

[IRstuff]

Do consider that the heat transfer rate of water or steam can be considerably higher than air heating.

Another option would be to install radiant heaters, which would allow additional degree of control.

TTFN

FAQ731-376

 

[athomas236]

I do not know much about your operation, but it seems that when the truck arrive at the maintenance bay they should be hot because some one has driven the truck there.

So the engine block, radiator, gear box, differential and the driver's cab will all be at their various operating temperatures which will be greater than 15C. So the problem then becomes not how to heat the truck up but how to stop it cooling down.

The only parts that would be at minus 40C would be the load carrying and structural members of the truck. So I suggest heated parking bays that are within individual but adjoining insulated buildings with double doors in series with an air seal to minimise draught losses.

I also suggest that hot air blowers are provided to make good the heat losses from the parking bay and heat up the cold sections of the truck.

The heat losses from the building can be easily calculated.

The heat required to heat the cold sections would need you to estimate the weight of cold parts and calculate the heat required as the weight times temperature rise (minus 40C to 25C say) times specific heat of steel (0.47kJ/kg C) divided by the time that want to take to heat the truck.

The capacity of the air blowers could then be estimated from the sum of the heat to maintain building temperature and the heat to warm the trucks.

This analysis is not complete because it does not consider the heat transfer between the air in the building and the cold truck parts so you need to do this to confirm that air at 25C will give a heat transfer rate that will heat the truck in the required time.

Note this approach turns the question round so you are not trying to establish the time to heat the truck to trying to design a system that will heat the truck in the time you require.

athomas236

 

[JP123]

good point!
yes the truck arrive at the wash bay. The motor is hot but the steel frame, which as to be washed before any maintenance, is cold, very cold! And it has to be warm up before washing it to prevent freeze on the steel frame. I want the truck to be warmed and washed into 2 hours. I will strat with that data 0.47kJ/kg C.

Thank you.

 

[rmw]

I've seen rows of gas fired radiant heaters used in coal truck/trailer bays but the temperatures weren't but about -20F. The goal wasn't to wash the equipment, just to heat the equipment enough to knock the hanging ice off the bay enough to be able to work on it.

rmw

 

[athomas236]

There is this guy called Harold in Manitoba who has a mug containing water at nearly 100C. He is outside where the air temperature is minus 40C and throws the water into the air. Almost none of the water hits the ground.

Interesting ?

See ling below

Regards,

athomas236

http://www.newton.dep.anl.gov/askasci/gen01/gen01738.htm

 

[amorrison]

Forced air at 15mph velocity will increase heat transfer into the trucks metal surfaces 5 times faster than having no air velocity (i.e. Natural convection). Thus your defrosting time theoretically will be one fifth.

To get a good velocity for a large truck surface at a large distance away the best solution I can recommend is LARGE drum fans – 42 inch diameter or larger.

Some drum fan suppliers are here but most seem to have only the smaller diameter ones

http://images.google.ca/images?gbv=2&svnum=10&hl=en&q=drum+fan

Also see

http://www.bosstoolsupply.com/index.asp?PageAction=VIEWPROD&ProdID=9360

seems to be one supplier of 42 inch fans.

You could even put the fans in banks of four to get more air volume and
more “air throw“ distance from the fans. Install the fan bank on a set of wheels to move them around easily.

Drip proof motors on the fans is recommended – also electrical power cord safety considerations for wet environment.

Beware that the heat that goes into the truck has to come from somewhere so the air in the truck room might become a bit cold. This will draw heat from the concrete floor and walls – but this should be ok- as the room heater will eventually warm everything up again.

PS. If the ice falls off in heavy pieces and wrecks the fans – don’t blame me <)).

Good luck.

 

[JP123]

Thanks amorrison! I'll beware of falling ice!

 

[KMRDMECH]

Radiant heat is actually one of the better ideas that I've seen, but depends on the ability of the trucks to absorb the radiant energy. Most heavy-haul trucks I've seen are usually a bright yellow. But a DIRTY truck might be a better black body. You could potentially use radiant heat to heat the surfaces. Steam cleaning would be the best means using water.

The best method might be radiant pre-heat, keeping the ambient air in the building above freezing, and steam-cleaning.

 

[dcasto]

I like ivymike's answer. It would be an expensive retro fit, but on a new installation, the way to go. Look at the airlines, they deice the planes with a glycol solution and trust me, they recover everydrop.

 

[amorrison]

Some additional suggestions.

1. Make sure there is enough intake area on the fan suction side for you to get good airflow - One fan diameter above the "floor" is good.
2. If you decide to use a bank of four fans in a 2X2 square aim the fan output airflow in a little (say 15 degrees)to the centerline of the bank - this will get the airflows to join in together to produce a longer "throw".