View Full Version : Sihi Vacuum pump with no vacuum
I changed out my 10 hp single stage vacuum pump with a 15 hp two stage pump. I have the service liquid at the shaft like the old one and I get almost no vacuum, only 5 inches. The single stage has two inlets for the water and the two stage has one on the drive end. The motor is drawing only half the amps so the pump is not drawing the power it is rated at.
Has anyone come across this problem before?
Homestead Maple
10-20-2010, 09:50 PM
Check this thread. It may have an answer for you.
http://mapletrader.com/community/showthread.php?t=8789&highlight=no+vacuum
Thanks for the link. I looked it over and I am still confused, I have my two stage pump hooked up the same way as the single stage was. I will have to check that I have the water level at the shaft level. The single stage would draw it's own service water without pumps or valves. The two stage is drawing water but I think it is not enough.
maplecrest
10-21-2010, 07:17 AM
plumb a 5/16 inch line into the intake side of the head
802maple
10-21-2010, 05:06 PM
Jeff you beat me to it. It is not important to have the water at the shaft level at all, but on the intake side of the pump there is a 1/4 inch plug.
Thread a nipple in the place where the plug is and then put a piece of 5/16 tubing from there to the water source. Prime the pump and you should be good to go. Let us know how it works.
I usually run the water 18inches below the shaft using this setup and I have been told by Donald Lapierre that it will create more vacuum this way.
Would that water supply for the 5/16" line be the same water 18 inches below the pump?
802maple
10-22-2010, 06:38 AM
Yes, it would still come from there. I have set some up that are getting a constant supply of cold water from a spring and others from a huge permeate tank.
Jerry
Buffalo Creek Sugar Camp
10-22-2010, 07:13 AM
Is there a lot to gain when going to a two-stage pump versus a single stage? Do they produce more cfm's to help compensate for leaks at higher vacuum levels, and do they compensate enough to justify the cost?
The 10 hp single stage cfm's really start to drop off at 20 inches. I could run 23 inches no problem with 10,000 taps and a tight system, but after going to 15,000 taps it did not have the cfm's and I could only get to 20 inches. The 15 hp has almost twice the cfm's and the curve is flat to 27 inches and a small drop to 28
The pump is also all stainless so it will not rust together on the inside during the off season if you forget to oil it. I am running it with a "Written Pole" motor made by Percise Power. The pump and motor is over 21 grand so I hope it does the job up to 20,000 taps. The motor spins at 1800 rpms so the pump may put out an extra 10 percent.
With the 5/16" line hooked to the intake I can get to 20" with the valves closed on the extractor. Not much cfm's, it I crack a valve on a sap line the vacuum drops down to 15"
I still think it is a water problem, I am going to try a larger water line next. I have a one inch diameter now. The single stage had one on each end and this pump has only one on the intake end. The single stage needs 5 gallons a minute and the two stage needs 10 gallons a minute through one hose not two.
802maple
10-22-2010, 08:12 PM
Is there anyway that you can get another 5/16 line into the suction. I find that it works better feeding the pump thru that way instead of thru the base. Another line like that should feed your pump with that much water as you have come from 5inches to 20 with that 1 line.
There are more fittings to add more and I can reduce the resistance in the main intake. Thanks for the advice, glad I am doing this now and not in the spring.
802maple
10-23-2010, 06:24 AM
You should have waited until spring, then it would have made sugaring just that much more exciting. hahaha Good luck
Now I can put more water in to the point of overloading the motor but still will not go over 20 inches and no volume.
Thad Blaisdell
10-23-2010, 01:02 PM
This may sound stupid ..... but is the motor wired correctly? It may be something as simple as that.
It is wired correct and the computer indicates that it is turning 1800 rpms. I don't think turning it 50 rpms faster would hurt anything other than require 10 percent more torque.
What model Sihi is it? Was it new? Does it have four flanges with a cross pipe connected to two of the flanges?
Buffalo Creek Sugar Camp
10-23-2010, 05:56 PM
Did you make sure the rotation is correct?
It is a new LPH 55312 with four flanges and cross pipe and it is turning the correct direction. In the morning I will check the volume of water coming out the exhaust and see how close to 10 gallons a minute it is.
These pumps are not very sensitive to service liquid gpm, something else must be wrong.
Make sure the cross pipe is on the correct two flanges so your inlet is on the larger first stage of the pump.
Make sure there isnt a seal/packing leaking. Block off inlet and outlet and pressurize to a few psi (< 5 psi ) to check casing and seals for big leaks. Sometimes you can have a huge leak and not hear it over the sound of the pump.
That is a good idea, I will check for leaks. Everything else is hooked up like it should be, the cross over tube will only go one way because of the bolt alignment since it is not at 45 degrees. But I am going to take it off for a look. Pipes on the correct ends and all the arrows pointing the right way. Correct rotation and up to speed. Check valve is the correct way.
Parker
10-26-2010, 06:06 PM
You get pump working? What was the problem?
I got it running and it was several things. Too much water so I put a valve in the water line to adjust. One sap line was not closed all the way letting air in. Vacuum gauge was a little off so I replaced it. The pump had a loose 1/4 plug and I think it was letting air in and messing with the liquid ring, just a guess. And the two stage pump does not pump good until you get over 20 inches, I expected to see much more at the low end. It pumps the most cfms at 27 inches. Like starting out in your car in high gear.
So it is working good now but the motor is rated at 58 amps and I am at about 56 amps once I am up to vacuum, before that it goes over the limit a little. I wish there was a little reserve power and don't like being that high but maybe it is ok.
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