Thanks!
Monotube Flash Boiler Design
- Thread starter Toymaker
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K2, you were right about back pressure from steam production impacting the flow rate !! I just needed to get the boiler to over 80% power before the dial pressure guage on the feed pump moved enough to be noticed. Below left is the feed pump guage while the pump is pumping tap water through the boiler with the burner turned off, ie no steam production in the boiler. Below right shows the same guage with the boiler just over 80% power setting, making lots of steam. The right guage shows about 30 to 40 psi back pressure from steam production. That's certainly enough back pressure against the pump to allow me to measure a false, higher flow rate, once the boiler was turned off.
My friend, you need a new gauge. The pressure range you want to measure should fall with the two thirds to one third of the middle of the gauge.
Measuring your back pressure with that gauge is not giving you meaningful data...
Measuring your back pressure with that gauge is not giving you meaningful data...
Fair enough!Sometimes, you use what you got
Edit: What's the availability of stuff like gauges where you are? Can you walk into a hardware store and pick one up or do you need to order it? Genuinely asking.
Thailand has numerous hardware stores, much like the big-box stores found in the US (Home Depot) and carry mostly home-use items. Stores that carry hardware for builders like me, are typically mom-&-pop stores that carry a mixed bag of items,...one store may have what I want, but I need to go to the store, in person, to find out if they actually do have what I'm looking for. Sometimes I get lucky and the store has what I need, but mostly, I end up ordering my parts online.
I'm using the 0 to 1000 psi guage mounted on the feed pump because 1000 psi is the max pressure I intend to never exceed in the boiler, and 400 to 600 psi will be the likely working range. I never intended to use that guage to read pressures as low as 50 psi. The pressure sensors on the boiler input and output have both been plagued with so much noise that pressure readings bounce around +/- 25 psi, rendering them useless to read 30 or 40 psi.
I am looking forward to any revised calcs. considering the estimated 40psi back pressure...
K2
K2
I am looking forward to any revised calcs. considering the estimated 40psi back pressure...
K2
Recent tests have shown that I need a smaller feed pump; 2 LPM at 60 bar (870 psi) should work nicely. Any suggestions on where I can find one?
I finally ran a few tests at max fuel burn and as with all the previous test runs, the boiler output was unrestricted. With the feed pump set to 14% the boiler shoots out slightly wet steam, which tells me that this setting is the max flow rate; measuring the flow rate after the burner was turned off revealed a flow rate of 1.75 LPM. This is very interesting since a previous test run performed at 72% power & feed pump at 13% resulted in a measured flow rate of 2.44 LPM.
What I suspect is happening: it's very difficult to accurately control the rpm of DC motors at very low rpm, and with only 14% power, the feed pump motor is barely turning. The motor needs at least 8% to begin turning. If I close the boiler output valve, with only the feed pump operating (no burner) at 8%, pressure quickly shoots up to 100 to 200 psi as motor rpm quickly drops. To get better motor control, I need a pump which will allow the motor to run at close to 100% rpm at 2 LPM at 60 bar.
Several cordless pressure washers claim to meet my requirements, but,...manufacturers love to over-sell their products,...and I've been disappointed in the past.
Needle valve with a return hose, a stainless hydraulic valve.
If you also get a stainless over pressure valve you can put it and a ball valve with a low psi gauge on and have them connected to a ball valve.
Edit: can you just machine a plate to hold the bearing and swash plate arrangement and put the d
Pump motor on a belt drive jack shaft?
re-edit: many triplex pressure pumps have a bearing on the drive shaft so they can be chain or belt driven. Lacking a wobble plate, the efficiency is high, they run cooler and have a longer oil life as well as bigger oil sumps.
They can be run across a wide range of speeds.
A triplex pump is probably best for you with either one that has the capacity for side thrust allowing a direct pulley install or one that does not and instead has a jack shaft.
They are also better at pulling water from a reservoir, usually, and are far easier to maintain.
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Thank you for that insight.
ajoeiam
Well-Known Member
Keeping the current pump and installing either a by-pass arrangement or a speed reducer (pulley or geared) would most likely work,....but it's not a very elegant solution. Another important consideration to me is keeping the weight down, and using a much smaller, lighter feed pump would be nice. Clearly, the simplest solution for me would be to find a small pump with a DC motor attached that's ready to drop in. The specs for this cordless Pressure Washer are ideal,...but can I trust the specs??
My online go-to places are (in no particular order); eBay, Lazada, & AliExpress.
We could do the math, but I bet the longevity of whatever they stuck in there would be really subpar?
Let me know what you think.
Edit: adding a return line with a servo mounted to a three way valve would give you the option of adding a radiator. Keeping the reservoir in the pumps happy range will be a real consideration. This could give you the ability to digitally increase the pump flow, increase bypass and by doing so, cool the reservoir. And that, to me, would be elegant.
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Esska-tech may have one 60 bar 6.5 lpm
I ran their numbers through the hydraulic power formula to see if their claims made sense. The pump would need a 600 watt motor, which are available and used in some cordless electric drills. The 21 volt 4 Ah battery could easily supply 600 watts for an hour. So the math says their claims are doable.
You are very likely right that longevity will/may be an issue, as will water temperature limitations, as I suspect these pumps will use a lot of plastic parts to keep the price down.
I agree, your solution is elegant,....but it's also more complex and would require tying in the ECU and software to control the servo.
The simplicity of being able to install and use a single, dc motor powered pump has a very strong allure. Sure wish I could get more data on the pump they're using.
I will keep looking for small, well made, industrial use pumps, but failing that, my next choice will be to buy one of those cordless pressure washer pumps and hope for usable quality.
Thanks for the suggestion.
I visited their web site but did not find any hydraulic pumps.
Try pressure test pump E-push 2 ?
K2
K2
This past Dec., when I was still looking for the prefect feed pump, and before I purchased the beast I'm using now, I purchased this Cordless Pressure Washer ; with a price under $30, and a claim of 60 bar and10 LPM, I had to try it. After I had a chance to test it, I found the max flow rate was actually 3 LPM and max pressure was closer to 30 bar (435 psi); well under what I was looking for at the time. Today, my needs have changed; the 3 LPM is a bit high, but acceptable, and 30 bar is close to what I need.
The same company I purchased the first cordless pressure washer from is now selling this slightly more powerful washer for just over $30. They claim 100 Bar and 4.1 LPM; if it meets half of those values it will be a good fit for my needs.
I will try this approach first
The same company I purchased the first cordless pressure washer from is now selling this slightly more powerful washer for just over $30. They claim 100 Bar and 4.1 LPM; if it meets half of those values it will be a good fit for my needs.
I will try this approach first
This past Dec., when I was still looking for the prefect feed pump, and before I purchased the beast I'm using now, I purchased this Cordless Pressure Washer ; with a price under $30, and a claim of 60 bar and10 LPM, I had to try it. After I had a chance to test it, I found the max flow rate was actually 3 LPM and max pressure was closer to 30 bar (435 psi); well under what I was looking for at the time. Today, my needs have changed; the 3 LPM is a bit high, but acceptable, and 30 bar is close to what I need.
The same company I purchased the first cordless pressure washer from is now selling this slightly more powerful washer for just over $30. They claim 100 Bar and 4.1 LPM; if it meets half of those values it will be a good fit for my needs.
I will try this approach first
That's practically zen.
What about also getting the drill style one and reverse engineering it?
