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Post by RKC on Nov 13, 2008 11:57:59 GMT 12
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Post by RKC on Nov 13, 2008 11:58:37 GMT 12
From: RKCNZ Sent: 12/06/2008 5:21 p.m. G'day Sam (kevlarsam ), Welcome to the Gold Dredging Forum. Interesting Hot Water System! Did you make it yourself? Is that a self-cleaning filter you have on it? images.trademe.co.nz/photoserver/71/69519271_full.jpg Regards, Rob (RKC) |
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Post by RKC on Nov 13, 2008 11:59:34 GMT 12
From: kevlarsam Sent: 13/06/2008 1:32 a.m.
Hi Rob,
Yes I made it and it is a heavy sucker as well. There is just on 30m of copper pipe wound in it and no exhaust touches copper.
The first heat exchanger on the old dredge I had cooked me really badly, mainly because it was old and I didn't have any safety measures in place to avoid getting cooked alive. Thanks to mining with a buddy I got out ok.
Nothing quite like learning the hard way.
Now I have a surge tank that takes out all the air that may be pushed in through possible cavitation in the pumps or working in turbulent water resulting in bubbles getting into the line.
I found that with bubbles in the line it can heat up a lot and turn to steam, it was the steam that cooked me. So now not only do I have a filter to clean the water, a surge tank to take out bubbles but also a mixer with a wax thermostat and I can dial up the temperature, having boiling water and cold water meeting the mixer, sending the water down to me at 42 - 45 degrees, so by the time it gets to me down a 15 meter hose it has cooled down to 39 - 40 degrees depending on the setting and how cold the water is.
I am never getting cooked again by my own gear.
I have adjusted it for the new 8 inch dredge so that it pumps more hot water and added another filter because of not liking the little bits getting inside the second wet suit.
I never let hot water go directly onto my skin and I wear a 2.5mm 3/4 wet suit under my 7mm dive suit and have enough hot water and pressure for it to be pushed right to my gloves and wet suit socks so that I am even working up a sweat when I used to break the ice on the Taieri river in the winter.
Regards
Sam
021 453 888
kevlarsam.com
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Post by RKC on Nov 13, 2008 12:00:35 GMT 12
From: kevlarsam Sent: 13/06/2008 1:42 a.m.
Hi Rob,
The filter you just unscrew it at the bottom and clean out the disk set at the end of the day by washing it in the river.
It's pretty fine so it is a good idea doing it daily especially if you are doing up to six hours a day. Sometimes I cleaned it out at lunch time as well, depending on how much vegetation is floating/suspended in the river.
Regards
Sam
021 453 888
kevlarsam.com
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Post by RKC on Nov 13, 2008 12:02:08 GMT 12
From: RKCNZ Sent: 13/06/2008 1:07 p.m. G'day Sam (kevlarsam ), I like the idea of mixing cold water with hot water to get a temperature that suits! The most frustrating problem I've encountered with the Hot Water Systems (HWS) I've used is that I've not had a sufficient ' volume' of heated water going into the wet suit. Mixing cold and hot water should be a simple way to increase the volume of water as well as providing a means of adjusting the water temperature to suit the temperature of the environment. If there is one piece of dredging equipment thats needed by Kiwi dredgers its a well made HWS that actually works. Maybe someone should start selling HWSs on Trademe. img.photobucket.com/albums/v172/Coochee/P1010011.jpg?t=1213310473img.photobucket.com/albums/v172/Coochee/P1010010-1.jpg?t=1213310432 Regards, Rob (RKC) |
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Post by RKC on Nov 13, 2008 12:02:51 GMT 12
From: Dredgeotago1 Sent: 15/06/2008 8:11 p.m.
Hi there Sam & Rob,
I'm trying to get my head around this HWS. I see the pressure hose from the pump to the surge tank. But what happens from there?
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Post by RKC on Nov 13, 2008 12:03:58 GMT 12
From: kevlarsam Sent: 16/06/2008 12:10 a.m.
Hi well his is the order that I work it for the 6 inch dredge:
Hose attached to pump
Filter
Surge Tank
T Section
One goes to the heat exchanger
The other goes to the mixer
After going through the heat exchanger it is then in a specialty hot water hose and that then meets the mixer. It is a specialty hot water hose so that it doesn't kink or melt.
It is one of those mixers that they use on the hot water systems you have in your house.
I went and got one with a re-setting thermostat that works quite quickly and this means that if there is an issue I only have a short wait until it has re-set it's self again
The mixer is designed to only send cold water to you if something goes wrong.
On the 8 inch dredge I am having an independent pump pushing the water to me rather than using the water coming from one of the dredge pumps to ensure a regular flow.
It isn't nice having to slow one or both of the motors because of a block up and because of the water slowing down it then stays longer in the exchanger and gets hotter. As a result when you crank it up again, sometimes the thermostat will trip and you get cold water because the water in the exchanger got to hot (because of slowing the engine down pumping the water through the exchanger) and some of it may have turned to steam. Great safety thing this thermostat but it can be a pain in the ass if it trips and then you have to wait for it to re-set so having a consistent flow of water is the best.
My Plumber also recommended to put a flow regulator each side of the mixer, then you will get even more pressure because the mixer isn't then having to do what the regulators are doing.
Because I am using a separate pump for the exchanger I make sure that the fuel in it's tank will last longer than the fuel in the dredge so that I can have a shower if I am quick enough. You are better not getting to carried away and to leave 5-10 min fuel in the tank/s then you can have a real nice shower and be ready for the walk out,
Yes I am getting soft in my old age, and if the boss is staying at camp she appreciates you coming back with some yellow stuff and smelling nice lol.
Regards
Sam
021 453 888
kevlarsam.com
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Post by RKC on Nov 13, 2008 12:05:33 GMT 12
From: RKCNZ Sent: 16/06/2008 6:15 p.m. G’day Sam (kevlarsam ) I’ve been looking closely at the photos on the Trademe add to work out exactly how your HWS functions … when I realized ‘not’ all of the parts of the HWS are shown. Do you have any photos you can post of the complete HWS? For anyone contemplating building a HWS I would suggest first reading the article by Dave McCracken at www.goldgold.com/stories/coldwaterdredging.htmwhich gives an excellent overview of HWSs. And then there is the thread on this forum groups.msn.com/golddredgingforum/general.msnw?action=get_message&mview=0&ID_Message=168&LastModified=4675663964916106208where I’ve attempted to mention all I could think of about building a HWS. It would be great if I could later add a post to this thread about mixing hot an cold water, along with some of the other innovative features you are trying. And for anyone who wants to experiment further with HWSs it might be worth going through applicable patents. www.google.com/patents?id=PKQcAAAAEBAJ&dq=5100261 I doubt its "bubbles" in the line that turns to steam (its the first I've heard of anything such as this) ... its usually small pieces of vegetation reducing or blocking the flow that will cause a blast of steam. A filter on the water line from the pump will usually catch any vegetation ... maybe your filter is not working as well as you think. I've found simple inline filters work very well and will only require cleaning once a day, or twice a day at the most. HWSs are an extremely important tool for Kiwi dredgers and is therefore an issue well worth examining further. Regards, Rob (RKC) |
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Post by RKC on Nov 13, 2008 12:06:54 GMT 12
From: kevlarsam Sent: 16/06/2008 9:14 p.m.
Hi Rob,
I guess I am paranoid about steam, it was the old system I had that cooked me, it was built like an industrial boiler where there was three compartments to a section of pipe.
I will see if I can draw it and load it up here soon.
1st section where the exhaust entered the pipe from the motor and met a coper ceiling with about 12 sections of coper pipe welded in place, the exhaust traveled through the sections of pipe about 15cm long and through to a similar chamber as the entrance one was at the top before it exhausted to the outside world.
There was a entrance at the bottom of the middle chamber on one side of it and an exit at the top on the other side of the center chamber where the water entered the area where the thin coper pipes were joining the top and bottom chambers. The water entered at the bottom and came out at the top hot and then traveled down to you.
Therefore the water circulated around the outside of the small sections of pipe heating up. This worked really well for years and years, I just happened to get it at the end of it's life.
It was in this center chamber that one of the small pipes came off at the top and exhaust was forced into the water chamber in the center section reducing the volume of water, turning it to steam in a hurry and sending it down to me.
So as a result I have done all I could think of to reduce the possibility of air getting in the water and it turning to steam, I don't care how small the risk of it not being bubbles in the water that may turn to steam, because I had 1st 2nd and 3rd degree burns all over the left side of my back from my neck to my waste to under my arm and onto my chest.
There were three places where people could see shoulder blade through the cooked holes.
Within 5 min of getting my wet suit off, all the hair from under my arm and on the left side of my chest fell off like a scolded pig. By the time I got to the Outram Doctor 2 hours later the blisters were as big as coffee cups and about 5-8mm thick sagging in fluid covering the whole left side of my back.
Quite an adventure :-)
Sam
kevlarsam.com
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Post by RKC on Nov 13, 2008 13:41:39 GMT 12
From: RKCNZ Sent: 17/06/2008 1:24 p.m. G’day Sam (kevlarsam), That’s the worst burn story I’ve ever heard! It would be enough to put most people off dredging altogether … let alone ‘just’ becoming “paranoid about steam”. I’m starting to get an idea of what your HWSs involve. And it seems to me that to get the volume of water, its been necessary for you to make a HWS thats much, much larger than conventional dredge HWSs! I can see why you have needed to make the HWS for your new 8” dredge a stand-alone HWS. I can see some advantages in a stand-alone HWS, but there are also significant disadvantages. Conventional HWS that have been in use by gold dredgers for many years now, work quiet well except that, in my opinion, they don’t supply enough of a volume of water flow sufficient to … well, to quote Dave McCracken, “If you do not have plenty of hot water for all of the divers working on a system, then you will most likely end up pumping cooler water into each diver's suit-which can be worse than having a wetsuit with no hot water system. You can never have too much hot water -- because you do not necessarily have to use it all”. And if there is not a sufficient volume of hot water being pumped out to the divers suit, the water will not circulate through the suit to heat the divers entire upper body. If you are getting hot water only in the small of the back it will not be enough to keep a gold diver warm during the winter months when there will be ice on the side of the stream. Also, the hot water won't get as far as the hands and feet (where its needed most). I was thinking last night about how it might be possibly to get an increase in the volume of hot water and it occurred to me that, on dredges with two motors, it may be possible that two HWSs could be employed to feed heater water directly into one (larger) hose, supplying one diver. Something similar was used some years ago on a dredge in New Zealand that ran two HWSs (Water jacket HWSs) on a large motor (which had two exhaust outlets) with two HWSs employed … however one HWS fed into the other HWS and the water volume was not actually increased img.photobucket.com/albums/v172/Coochee/Eductor%20dredges%20and%20equipment/website_005.jpg?t=1213655305. It did work reasonably well for dredging during the spring months when the water was cold, but would probably not have been suitable for mid winter when the water would be near freezing. On one of the early 8” Precision dredges that I saw operating in Australia in the 80s, all they did was to have a wound length of copper tube around the outside of the exhaust from the VW motor, without even a covering to enclose the copper tube (a good example of the KISS principal at work). And they said it worked extremely well. It seems obvious to me that the larger the motor, the much easier it is to get a HWS to work well. www.youtube.com/watch?v=Md-x5S4mFNk Regards, Rob(RKC) |
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Post by RKC on Nov 13, 2008 13:51:09 GMT 12
From: lloyd Sent: 17/06/2008 2:30 p.m.
G'day Sam,
Had much the same experience. I thought I was dead in the last few seconds. I had to gather myself and concentrate to get the hose out of my wet suit. Took me 12 hours to walk out of the scrub. Then got a lift to the bush nurse who patched me up. Next day saw me traveling to the main hospital who then sent me to Melbourne as the burns where too extensive for them to cope with. The next month was spent getting skin grafts which can be pretty painful in itself, as you well know.
In saying all that. I went back to using hot water as its not practical in cold conditions to work without it. "Man, was it hard to put that hose back in" I used exactly the same system of heat exchange afterward but with much better safety systems to avoid it ever happening again and if it ever did, no hoses where clamped after the heat exchange and I simply used a piece of copper pipe to join the hose coming from the heat exchange to the slim hose that went into my wet suit. Easily removed.
My filter was self cleaning which is the most important thing. The heat exchange itself was just refrigerator copper pipe made into a coil and placed inside a modified muffler with both ends poking out of the walls of the muffler. The key is to wrap the coil as tight as possible and get at least 30 ft in there so you can have as much water flow going through it. That saves you having to dial the tap down to get enough heat, If this system does wear out inside you simply get water in your muffler system and you then end up with cold water and possibly your motor starts to run like ****.
The danger in this system is the water flow stopping or reducing enough that the water can get super heated, so you need to think of all possible scenario's for this to occur and make sure it can't occur. The second thing is then to make sure that if for some reason it does, you can disconnect immediately. In my panic, (not hard when out of the blue, someone is blasting you with a shotgun) I couldn't find the hose, it was wrapped around me and entering through the back of my wet suit. The other thing was that I wasn't aware that it could happen, I was self taught, young, and I'd just bought the dredge off someone else. The guy had fitted the tap before the filter so it must have picked something op out of the river which blocked in the tap.
If I feel the water getting even slightly warm these days my hand goes straight to the hose that sticks out of the bottom of my wet suit jacket and it slips off easily. DO NOT use airline fittings or anything else fancy. Six inches of copper pipe with the ends smooth is perfect. Only use non kinking hose and tape it to your airline.
The filter I use is simplicity itself. A hard rubber grommet that has a bulbous fine stainless steel mesh. I'm pretty sure they are the ones people use in the taps when connecting up a washing machine. You can buy them at any hardware store. I simply insert it into the 1" brass hose fitting thats tapped into the top of your dredge pump. Make sure its tight and protrudes to the inside of the pump. In 6 years I've never had it block and I've never had to clean it either. I do check it every so often though.
I'm only guessing Sam, but I'd say, whatever **** itself in your system blocked the water flow so whatever water was in the system could super heat. I just can't see how air might have been the cause. I haven't seen the system though.
I don't have any problems using hot water these days and I hope this might give some people some insight into the dangers and what to be aware of.
One more thing, Chill blains. Last year I got some fairly uncomfortable chill blains in my fingers. One finger was numb for 3 months. Be careful to not let your hands get cold before you get in the water. Not easy I know. After getting chill blains I was careful to never let my hands get cold before I plugged into the hot water. I'd plug in and enter the water slowly letting the water fill the wet suit and only get completely submerged after it had filled my arms and gloves.
And Rob. I never had any trouble with not having enough hot water. and my system was only fractionally bigger than the standard Honda exhaust.
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