firetruck stainless tank fabrication need help

[parlee]

hello,hope i posted on the right thread i chanced upon the forum while searching for informations about stainless steel tank welding, I belong to a volunteer fire brigade here in the philippines, we help our government's fire services. as a volunteer group, we have our own fire fighting equipments, 1 pumper and 1 tanker which holds about 13,000 liters of water,( I'll post some pics later). right now we are planning to build another tanker truck in which the stainless tanks size is
16ft x 4ft height x 6 ft width. based on our experience on our other tanker which was done by using stick welding by local welders, it is prone to cracking on the spot welds, in which every now and then we have to repair. this time, by building this new truck, we are researching a lot of infos and opinions so as to minimize our maintenance once this truck is operational. what type of welding should we use, stick, tig and mig are all available here. Thanks

 

[parlee]

these pics are from our old truck

 

[rtbcomp]

Welcome to the forum.

Love the pics! Flip-flops and a baseball cap - our health & safety would be taking smelling salts after visiting your site!

From the pics I assume the tank has a waterproof liner so the welds themselves don't need to be watertight?

 

[parlee]

Welcome to the forum.

Love the pics! Flip-flops and a baseball cap - our health & safety would be taking smelling salts after visiting your site!

From the pics I assume the tank has a waterproof liner so the welds themselves don't need to be watertight?

thanks for the reply sir, that's the way our workers do their thing here in the philippines Safety?? they don't know the word. kidding aside, i guess we lack safety basics awareness.. back to the tank. It doesn't have a waterproof liner so the welds should be watertight.

 

[^neo^]

The problem you have is the sheets need welding on both side as the flexing of the sheets from the water moving around will crack the welds in no time.
The only way i can see round it using the design you've got is to fully weld it to the angle frame.
Have you got any baffles welded into it, or is it just the angle supports?

 

[malcolm]

Do you have any photos to show the cracking?

If they are fatigue cracks it would suggest there is movement in the structure. A flat panel might move in and out as you fill/empty the tank, or drive around corners. Most water tanks have a curved shape for this reason. If you used thicker steel rolled into a curve there would also be less need for internal structure, so it might also be cheaper and lighter to make.

 

[parlee]

The problem you have is the sheets need welding on both side as the flexing of the sheets from the water moving around will crack the welds in no time.
The only way i can see round it using the design you've got is to fully weld it to the angle frame.
Have you got any baffles welded into it, or is it just the angle supports?

sir, thanks to your reply, you mean that we should weld the sheets by overlapping them? so as to have welds on both sides? what does baffles mean?

 

[parlee]

Do you have any photos to show the cracking?

If they are fatigue cracks it would suggest there is movement in the structure. A flat panel might move in and out as you fill/empty the tank, or drive around corners. Most water tanks have a curved shape for this reason. If you used thicker steel rolled into a curve there would also be less need for internal structure, so it might also be cheaper and lighter to make.

i'll try taking photos of some cracks.. the cracks happened on the welds. thanks for your suggestion sir on the curved shape., i'll try proposing this to my group, but would making the tank rectangular and strong still be possible?

 

[^neo^]

Baffles are basically plates welded inside the large tank to slow down the movement of water. When you brake hard when driving, or go round a corner too quickly, the water will all 'rush' to that side. The idea of the baffles is to slow it down.

Look like this:

As Malcolm says, a curved tank would be better, can you not find an old fuel tanker and cut it down?

 

[parlee]

Baffles are basically plates welded inside the large tank to slow down the movement of water. When you brake hard when driving, or go round a corner too quickly, the water will all 'rush' to that side. The idea of the baffles is to slow it down.

Look like this:

ah , yes, we have those, you can see on the unfinished pics. we have maybe about 8 baffles each with about 2x2 ft holes, alternating between them.

 

[Delgado]

Essentially, as has been said, you're building a water tanker not a fire truck, so the best (cheapest and easiest) way to do this would be to find a scrap tanker and simply remove the tank (obviously making any necessary repairs).

If you want to build your tank this way, (and I have never seen a fire truck with a square tank that large, even the fire brigades high volume pumping units are only half that size) you need to make the tank smaller than the width of the truck (so that it fits inside), then bolt it to the chassis and reinforce it on the outside with angle/channel straps (bolted together would be better, then it could be removed for repairs). Then box the whole thing in to make it look nice, leaving plenty of space for pipes, hoses , pump etc....... Make sure that you put an open (without valve) overflow pipe in the top of the tank, so that you are not pressurising it. Also, try to make each side of the tank from a single sheet of SS, because any joins (except in the corners) are just asking for trouble (although it will obviously limit the size of the tank, but you could always just make more than one).

I know a guy who owns several fire engines and water tankers, I will try and get some photos for you, so that you can just copy the designs.

Just as a side note, you are never going to need that much water to put out any fire, if you can't put it out with half that amount of water, then you will never put it out. your best bet would be just to let it burn and wet down the surrounding area to stop it speading (that's what the fire brigade here would do)

Nice fotos, by the way!

Hope this helps!!

 

[Morris]

It looks like the tank is solid mounted to the chassis. Ladder type lorry chassis flex a hell of a lot! The tank has become a torsional box member. It really needs to be de-coupled from the truck chassis to help it survive for long.

 

[parlee]

It looks like the tank is solid mounted to the chassis. Ladder type lorry chassis flex a hell of a lot! The tank has become a torsional box member. It really needs to be de-coupled from the truck chassis to help it survive for long.

thanks morris, what can you suggest for de-coupling it?

 

[rtbcomp]

To go off at a tangent slightly.....

Would it be easier to use a dozen plastic 1000 ltres IBCs, connected by pipes? You would then only have to fabricate a frame to hold them and the bulkhead problem would be eliminated.

Google IBC - they come in all shapes and variants!

 

[pedrobedro]

IBCs are a good idea, a place I worked used to have glue delivered in them and they already had a frame you could bolt down or clamp together with interconnecting pipes.

 

[Tino]

Stick, tig and mig are all suitable processes. I think Malcolm is right the problem is the shape but if that is how it has to be you could try to reduce the flex by welding some bracing from corner to corner like this

and I would use longer stitch welds rather than all the little spots, something like weld 2 inch miss 2inch

 

[parlee]

Essentially, as has been said, you're building a water tanker not a fire truck, so the best (cheapest and easiest) way to do this would be to find a scrap tanker and simply remove the tank (obviously making any necessary repairs).

If you want to build your tank this way, (and I have never seen a fire truck with a square tank that large, even the fire brigades high volume pumping units are only half that size) you need to make the tank smaller than the width of the truck (so that it fits inside), then bolt it to the chassis and reinforce it on the outside with angle/channel straps (bolted together would be better, then it could be removed for repairs). Then box the whole thing in to make it look nice, leaving plenty of space for pipes, hoses , pump etc....... Make sure that you put an open (without valve) overflow pipe in the top of the tank, so that you are not pressurising it. Also, try to make each side of the tank from a single sheet of SS, because any joins (except in the corners) are just asking for trouble (although it will obviously limit the size of the tank, but you could always just make more than one).

I know a guy who owns several fire engines and water tankers, I will try and get some photos for you, so that you can just copy the designs.

Just as a side note, you are never going to need that much water to put out any fire, if you can't put it out with half that amount of water, then you will never put it out. your best bet would be just to let it burn and wet down the surrounding area to stop it speading (that's what the fire brigade here would do)

Nice fotos, by the way!

Hope this helps!!

thanks delgado, our firetrucks here in the philippines are mostly tankers, we need lots of water to bring in to the fire scene because our fire hydrants here are not reliable, sometimes there is water, sometimes there aren't., most houses here are made of light materials and sit close by to each other on a big area, fire spreads out easily, so controlling these fires are difficult, needing lots of water. thanks for your suggestions and we'll wait for your pictures of fire engines and tankers. thanks again

 

[parlee]

To go off at a tangent slightly.....

Would it be easier to use a dozen plastic 1000 ltres IBCs, connected by pipes? You would then only have to fabricate a frame to hold them and the bulkhead problem would be eliminated.

Google IBC - they come in all shapes and variants!

thanks sir, we've already searched IBC's and its also a good idea. i will also recommend this to my group. i just have to find a local supplier.

 

[Iain Westland]

by decoupling he just meant that the tank is fixed to to chassis in a removable method really, so the frame can flex separate to the chassis. as for the holes in your baffles, smallest you can get away with the better, and more smaller holes than one large one, similar to a Helmholtz resonator used in audio baffles.

Yours is a very tricky situation, Here we have water on tap as it were, the tankers only need enough to make a decent start while somebody sets up a refill, for you its all or nothing so you have much greater needs.

Could you not 'borrow' a petrol/derv tanker, purge it and fit your pumps ladders etc around that?

Hats off to you sir!! nothing but respect for those who 'Go in while every body else is trying to leave'

Iain

 

[parlee]

by decoupling he just meant that the tank is fixed to to chassis in a removable method really, so the frame can flex separate to the chassis. as for the holes in your baffles, smallest you can get away with the better, and more smaller holes than one large one, similar to a Helmholtz resonator used in audio baffles.

Yours is a very tricky situation, Here we have water on tap as it were, the tankers only need enough to make a decent start while somebody sets up a refill, for you its all or nothing so you have much greater needs.

Could you not 'borrow' a petrol/derv tanker, purge it and fit your pumps ladders etc around that?

Hats off to you sir!! nothing but respect for those who 'Go in while every body else is trying to leave'

Iain

thanks a lot Iain, our fabrication of firetrucks here in our place is difficult, we can get second hand fire trucks from japan or korea, but it is expensive. what volunteer fire brigades do, by working on a small budget, is make our own. what we do is find a used engine from japan that came from a firetruck, fit it in our own used 10 wheeler truck, connect the fire pump and fabricate the tank, that way, we save more money.