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Author Topic: Boiler Feed Pump Questions  (Read 10401 times)

derekwarner

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Boiler Feed Pump Questions
« on: September 22, 2013, 06:58:15 am »

 In preparation for the need of boiler feed water [and the new boiler certification rules] I have sourced two identical 6 bore x 5 stroke piston pumps with 4.0 diameter shaft eccentric drives

The initial plan was to have the auxiliary pump electrically driven @ 70 RPM & the primary pump driven from the main engine 4.0 diameter shaft conveniently located between two plummer blocks on the stdb side with  the pump under the engine
A new pump drive eccentric strap & the lubrication hole @ 90 degrees will be required but shouldn’t be a problem
The planned main engine speed is in the order of 130 RPM, so this will create the need for a bypass valve & this is where I am baulked

So a question for ooyah/2 or JerryC…………in the setup of the bypass needle valve
·         Do you simply bench test the engine watching the boiler water level  whilst steaming & adjust the bypass needle valve occasionally to obtain some sort of balance?
·         Or is the same test & adjustment made with the engine underload in water?
·         I have read in the Wear thread on how pleased Jerry was with the makeup water balance, although no real explanation was made in achieving & maintaining the balance
·         I have spoken with our local model steam train guys, but naturally understand they use they bypass valve in a totally different manner

Because of sailing in salty/brackish water, I will need an onboard water supply, however will need to discharge clear makeup water overboard as I cannot pressurise the makeup water tank
Naturally any comment greatly appreciated


Derek
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Derek Warner

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mrsgoggins

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Re: Boiler Feed Pump Questions
« Reply #1 on: September 22, 2013, 06:05:20 pm »

You will not pressurize the feed water tank, simply fit it with a breather.
Have you considered electronic control of boiler level? It's fairly cheap and simple and in my experience very reliable. Using a bypass valve means that your pump is absorbing power all the time rather than just when it is needed.
I like your workmanship.


Keith
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Jerry C

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Re: Boiler Feed Pump Questions
« Reply #2 on: September 22, 2013, 06:47:32 pm »

Hi Derek, ref bypass valve and level control. I only open my bypass valve at the start of a run in order to prove it's pumping. I then close it. If I see the level rise above the middle of the glass I allow pressure to rise towards maximum. This reduces the efficiency of the pump (I think) and the level falls. If I see the level fall I run the engine over speed and the pressure falls so the pump works better and the level rises. If I forget about it and just run it as I wish the level in general looks after itself. It just seems to be a perfect match for the engine. I once went for seven weekends without having to intervene. As I'm drawing water from the lake and the lake is perfectly clean I don't have a problem with dirty valves. Last week I did 7 miles on a dirty canal and did get trouble. I'm planning to include some form of filtration this winter. I don't understand about you pressurising your feed tank though. If you can't get it in you won't get it out. It must be vented somehow. If your bypass is open there is virtually no load on the pump.
It looks really nice, I love the lagging but I would also lag the flanges ( a bit like a poodle cut) so you can access them if needed.
Jerry.

hammer

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Re: Boiler Feed Pump Questions
« Reply #3 on: September 22, 2013, 08:07:15 pm »

Derek. Will the hand pump used for the initial fill be one of the 2 methods required ? the engine driven pump the other??? :embarrassed:  Geoff
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derekwarner

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Re: Boiler Feed Pump Questions
« Reply #4 on: September 23, 2013, 06:08:45 am »

Thanks for the responses
Geoff....no, the initial fill will be manually via the boiler top port, subsequent filling or topping up is planned via the steam drive [main] or auxiliary [electric] driven pump
JerryC....I think I had misunderstood the concept you use....... :embarrassed: ...from your latest posting it is similar to the model steam train engine boiler feed/ bypass system....may I ask the bore & stroke of the ooyah/2 [George] ...designed & built pump?
Keith.... I have  a fellow member Southstyne2 a few kilometres from me.........he has designed & built a fully functioning boiler level water control level system & I have witnessed that it works perfectly  :-))
In fairness, I must learn to walk before I can run...so will wait until the primary & auxiliary pumps are running under manual control.........Derek
 
 
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southsteyne2

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Re: Boiler Feed Pump Questions
« Reply #5 on: September 23, 2013, 12:13:31 pm »

Hi Derek thanks for the mention in your post but must confess the electronic control board was developed as far as I know by Malcolm Beak and is available on the Paddleducks forum ,the problem I had with it was in the sensor shorting out after a few runs, Could also be a fault in my workmanship ,however I experimented with my own design of sensor (see attachment and so far this one has been very successful  :-))
Cheers
John
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derekwarner

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Re: Boiler Feed Pump Questions
« Reply #6 on: September 24, 2013, 12:04:28 pm »

 %) ...I think member Southsteyne2 is being a little modest here  O0 .......Derek
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southsteyne2

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Re: Boiler Feed Pump Questions
« Reply #7 on: September 26, 2013, 01:46:28 pm »

Hi Guys just got my first boiler certificate so its full steam ahead, to my mind this is the real joy of steam getting out on the water( see pic ) South Steyne full throttle
Cheers all
John
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Landlocked

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Re: Boiler Feed Pump Questions
« Reply #8 on: September 27, 2013, 10:40:00 pm »

Looks great!   :-)) :-))


Landlocked!
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derekwarner

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Re: Boiler Feed Pump Questions
« Reply #9 on: September 28, 2013, 12:20:01 am »

Couldn't agree more ...she looks great O0
Looking at your image..... %)  she must be returning to Circular Quay.......as according to my understanding, the aft funnel is for the boiler & the fwd funnel is a dummy water tank above the engine
So she always sailed backwards going to Manly & to Broken Bay {-) ............is this correct or inline with your research John?
Derek
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southsteyne2

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Re: Boiler Feed Pump Questions
« Reply #10 on: September 28, 2013, 02:17:10 am »

You are spot on Derek the the burner smoke rather than steam should be emmitting from the front funnel.
Back to the make up pump it is trial and error preferably on water as speed and load varies so to my mind the boiler probe and electronics is the best way,the downside is the need to install an electric geared pump and battery in my case I have a hand pump hooked up to a geared 100-1 12 volt motor pumps 60 strokes per min which is more than enough to maintain water level as the motor only cuts in when needed which I think is better than a engine driven pump and bypass having said this I must respect those with open boats who may prefer the more traditional eccentric pump and bypass which I agree would look more in line with
full size practice .

I would also like to know where to find the new boiler code source that states 2 pumps must be employed as having mine recently tested there was no mention of this.
Cheers :-))
John
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Landlocked

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Re: Boiler Feed Pump Questions
« Reply #11 on: September 28, 2013, 02:48:00 am »

John,


I'm coming to similar conclusions with my Sabino build.  I'm having trouble finding the sweet spot on my bypass valve.  My system will be well buried inside the superstructure so doing a glance check on level as she steams by such as the launch folks can do won't work. 


I bought a BF Industries Water Level Detection System which has a probe and modified servo electric pump.


My thoughts though are to keep my shaft driven pump and have the level probe system control a 90 degree throw bypass valve.   I don't have a good spot to mount an electric pump and my TVR1A seem to be putting out power to spare.


Thought?


Ken/Landlocked
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derekwarner

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Re: Boiler Feed Pump Questions
« Reply #12 on: September 28, 2013, 04:21:40 am »

southsteyne2..........the text I referred to [about independent or a twin boiler water makeup facility] was I thought from the Northern Association of Model Engineers [NAME].........however I cannot locate the same on their WEB site
In the short term I plan to go down the path of twin electric makeup water pumps.......until I can resolve a better understanding
I have added a 4.0 mm diameter shaft [316 stainless ZZ bearing] plummer block on each pump output shaft for improved rigidity  & take the off axis load off the epicyclic gearbox's
Did you have the St George boiler inspector vet your system?......Derek
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southsteyne2

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Re: Boiler Feed Pump Questions
« Reply #13 on: September 28, 2013, 11:48:51 am »

Derek like the pumps were did you come by them in OZ ? be nice to see the plant working when finished,not sure what you mean by vet the system, test was pump up to twice working pressure ,hold for 20 min then a steam test everything went fine
Cheers
John
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southsteyne2

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Re: Boiler Feed Pump Questions
« Reply #14 on: September 28, 2013, 12:06:04 pm »

John there is no sweet spot on a model boiler that will drive you bonkers trying to find it in a boat as it fluctuates depending on throttle and level of gas in the bottle or canister also ambient temperature and sailing conditions ive even tried to adjust the gas output ,no luck there so full gas and the safety valve blows after stopping the boat for a couple minutes but it's just water so no real problem this is the reason I like the probe as it will cut in and start the pump immediately as I need all the power from the engine and not wasting it pumping most of the time for no reason so all you need to worry about is enough water on board
John
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derekwarner

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Re: Boiler Feed Pump Questions
« Reply #15 on: September 28, 2013, 10:23:47 pm »

[font=]John....here is the link for the eccentric drive water pumps........I substituted an Australian sourced 6 to 18 volt geared motor from Jaycar  [70 RPM on 12 V]........the original geared motor as supplied as very noisy..... so for my second assembly I purchased just the pump & the motor mounting bracket[/font]
[font=]http://www.ebay.com.au/itm/161094300712[/font]
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TAG

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Re: Boiler Feed Pump Questions
« Reply #16 on: September 29, 2013, 03:15:42 pm »

Hi
I have been following this discussion with interest and agree with mrsgoggins that the best solution is to use electronic control of the boiler water level. I have written a number of articles in Model Engineer magazine which appear in Volume 195, No 4261 Vol 198, No 4290 Vol 210, No 4451 which might be helpful. I have also posted a number of items on this site on the matter which unfortunately have appeared to have disappeared in the "great crash" sometime ago together my de-motion to 'shipmate'. A quick summary of my design is an electrode in the boiler energised by an AC signal which detects low water level and is processed/time delayed/and gives two outputs. One output is an on/off signal which can drive an electrically driven feedwater pump (provided by a high current Mosfet). The other can drive a servo to operate a bypass valve for an engine driven pump, this output is servo reversible. There are two optional "add ons" which can give alarms 'feedwater tank low' and 'pump excessive running'. The former is implicit in the latter. Anyone interested in further discussion please PM me.
On another subject has Bill Ford restarted manufacturing his water level unit again? Last time I emailed him he had stopped manufacture as it was uneconomic.
On the subject of feedwater requirements for model boat boilers my understanding from reading "The Examination & Testing of Miniature Steam Boilers (Revised Edition 2012)" also known as   "The Green Book" section 11 is that, for boilers under 10 bar litres AND a volume of under 2 litres two independent feeds are not required. This section is quite detailed and needs to be read from the book!
Tim   
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oiler

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Re: Boiler Feed Pump Questions
« Reply #17 on: September 29, 2013, 08:00:31 pm »

I used a water sensor mated with a alarm relay so the pump only kicks on for 7 seconds at a time but it's adjustable with a pot.

http://www.youtube.com/watch?v=GnR6F5sHy_M

I have about 8 hours of run time on the ship with no problems so far
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derekwarner

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Re: Boiler Feed Pump Questions
« Reply #18 on: September 29, 2013, 09:34:43 pm »

Thanks TAG...section 11.5 & 11.6 of  "The Green Book" clarifies the situation ....Derek
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xrad

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Re: Boiler Feed Pump Questions
« Reply #19 on: December 31, 2013, 09:25:21 pm »

Oiler: can you post source for alarm relay? Thanks
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southsteyne2

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Re: Boiler Feed Pump Questions
« Reply #20 on: January 01, 2014, 12:10:12 am »

Derek I have done a bit more research and the south steyne aft funnel was the water tank so I have repositioned the exhaust ,here's a clip of her in service http://www.youtube.com/watch?v=mB7g99Sk4gY

cheers
John
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southsteyne2

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Re: Boiler Feed Pump Questions
« Reply #22 on: January 08, 2014, 10:37:17 pm »

Thanks for that I will buy the ebay one will do the job :-))
Cheers
John
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xrad

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Re: Boiler Feed Pump Questions
« Reply #23 on: January 08, 2014, 11:19:50 pm »

Thanks for reply! What type of sensor is required for water board? Ground and boiler probe? or active sensor?
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dlyyld

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Re: Boiler Feed Pump Questions
« Reply #24 on: January 09, 2014, 02:03:51 am »


Hi Derek,
It looks very good, nice work.
Jin
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