Vacuum Pump FAQ’s Courtesy of J/B® Industries
Vacuum Pump FAQ’s Courtesy of J/B® Industries
1. My vacuum pump runs, but I cannot get a vacuum.
Either the coupler between the shaft of the pump and the shaft of the motor is either broken or slipping. Make sure the set screws are tight on the flats of the two shafts.
2. Why is it so important to change the oil often in my vacuum pump?
The proper oil in a vacuum pump acts as a blotter and absorbs all of the moisture and non-condensables. As the oil becomes saturated with these contaminants, the efficiency of the pump is dramatically reduced. Maintaining clean oil in the pump ensures that the pump will operate at peak efficiency.
3. Can I use any oil in my vacuum pump?
No. JB Black Gold oil is extremely pure and non-detergent. Black Gold is hydro processed which means it goes through a series of catalytic steps rendering the oil extremely refined, more viscous, and more stable. The result is a clear mineral oil that will alert you to contamination sooner as it becomes cloudy or milky.
4. Why is it important to change my oil when the pump is hot?
As the pump cools, the moisture and contaminates start to separate in the pump and when drained, the contaminants cling to the walls of the pump. When you refill the pump with new oil, those contaminants will mix in with the new oil as the pump warms up resulting in the new oil quickly becoming contaminated.
5. If I am always pulling a vacuum on clean, dry systems, is there a way to check my oil in the pump to see if it is contaminated and not have to change it so frequently?
It is recommended that a micron gauge be attached directly to the pump and it should pull to 50 microns or lower if the oil is clean. If the micron gauge will not pull to 50 microns, it is an indication that the oil is becoming contaminnated and should be changed.
6. Other than pulling air out of the system, how does my vacuum pump get rid of the moisture in the system?
Most two stage vacuum pumps will go low enough in vacuum and reduce the atmospheric pressure within the system, thus allowing boiling of the moisture at a lower temperature. Once the moisture is in a vapor form, it is readily removed by the pump.
7. What is a gas ballast and how do I use it?
On the initial pull of vacuum on a system, the gas ballast is open allowing the initial volume of air in the system to bypass the oil so as to not contaminate the oil immediately. When the pump starts to quiet down, close the gas ballast and the pump will start reducing atmospheric pressure in the system to boil the moisture and non-condensables.
8. What is a blank-off valve?
The blank-off valve acts no different than a water valve. Open it, and with the pump running you will get your desired vacuum. Close it, and with the pump running there is no vacuum.
9. If I use a larger CFM pump, will I be able to pull a vacuum on a system faster?
In most cases NO. Using a vacuum pump on air conditioning systems from 1 ton to 10 tons, you will not see the difference between a 3 CFM pump and a 10 CFM pump. For example, if you put a pump on a system and you notice within 2 minutes the pump quiets down and you cannot really feel any air leaving the exhaust. This means that there is no more CFM left in the system and you are now working with molecules. Thus, at this point if you replaced a 3 CFM pump with a 10 CFM pump, there is no change in vacuum or time.
10. What is a micron?
There are 25,400 microns in an inch. Therefore with a compound gauge reading 0 inches to 30 inches, there are 762,000 microns.
11. I have been using my low side gauge to pull a vacuum, is this wrong?
YES. The low side gauge knows only atmospheric pressure and cannot sense moisture or non-condensables. A micron gauge is a heat sensing device that not only reads atmospheric pressure, but also measures the gases created by the vacuum pump as it boils the moisture. For example, if you were to pull a vacuum on an enclosed bottle of water, the low side gauge when pulling a vacuum will read a perfect vacuum. Using a micron gauge, it will immediately tell you with a high reading the you have a problem in you system.
12. I have been pulling a vacuum on my system using a micron gauge and cannot get it down to a low reading.
See FAQ #1. Another possibility is that some oil may have entered the micron gauge and is giving false readings. The remedy is to pour regular rubbing alcohol into the connector on the micron gauge, shake, and pour out (do not use a q-tip, rag, or any other material- use the liquid alcohol only). Do this about three times, then try to pull a vacuum with the gauge.
13. I am able to pull a vacuum on my system, but when I blank-off, the micron gauge rises rapidly.
Unless you are using JB`s DV-29, copper tubing, or flexible metal hoses, it is not recommended to use your existing manifold and hoses for blanking-off a system to check for leaks. Hoses work very well under high pressure. Vacuum is very critical in leaks, more so than pressure. All charging hoses, including the black hoses ¼”or 3/8″ permeate. Where the crimp is on the brass to the hose also has possible leak issues, and the gasket at the coupler is a major leak offender. The vacuum industry uses o-rings on most couplers. When you screw down on a gasket, it goes into many contortions and will not seal. When using an o-ring, you screw down on it to get a metal to metal seat and the o-ring lies around the lip of the flare giving it a positive seal.
14. Can I mount my micron gauge onto the vacuum pump?
It is not recommended to do so as you are reading what the pump is doing and not what the pump is doing to the system (see DV-29). It is suggested that you tee off on the suction side of the system and mount the gauge there.
15. How low of a vacuum should we pull on a system?
JB recommends that a system be pulled to at least 250 microns and held at least five minutes. On any polyester oils in a system, it is recommended to pull a much lower vacuum as moisture is very difficult to remove even with heat and vacuum.
16. Why does the micron gauge slowly fall back and then start to hold after pulling a vacuum and blanking-off?
The reason for this is there is equalization within the system. If you pull a vacuum lower, it will then fall back at a shorter range and hold.
June 22, 2009 at 3:28 am
8. What is a blank-off valve?
The blank-off valve acts no different than a water valve. Open it, and with the pump running you will get your desired vacuum. Close it, and with the pump running there is no vacuum.
This one made me laugh, so I copied the question and the answer! I’m having a little fun here so roll with me on this…
“The blank-off valve acts no different than a water valve.” Except it’s vacuum proof, has nothing to do with water and is mounted on my vacuum pump!
“Open it, and with the pump running you will get your desired vacuum. ” FINALLY, the Silver Bullet for pulling a vacuum! All I had to do was open the valve and I magically achieved my desired vacuum! Yea, Boss, I pulled a vacuum, I mean I opened the magic valve on the side right there…
“Close it, and with the pump running there is no vacuum.” When you close it and”…there is no vacuum…”you got problems Brutha!
Okay, seriously. The blank off valve is nothing more than a vacuum proof ball valve located on the pump to isolate the PUMP from the SYSTEM and CONNECTING HOSES. Nothing more, nothing less. However, I recommend NOT using the built in valve when performing your drop tests as this will not isolate your hoses (potential leaks) from your Micron Gauge. Instead use core removers and isolate the hoses and the pump there (right at the schrader valves), of course you need your Micron Gauge hooked up there as well.
The blank off valve will keep oil from running out of the inlet ports in the even of a tip over, however it will not stop it from coming out of the exhaust port!
June 22, 2009 at 3:04 am
5. If I am always pulling a vacuum on clean, dry systems, is there a way to check my oil in the pump to see if it is contaminated and not have to change it so frequently?
NO! Change the oil before each evacuation and on a large evac job watch the oil for contamination! CHANGE THE OIL, you are charging the customer for it anyway so give them what they pay for.
June 22, 2009 at 3:01 am
3. Can I use any oil in my vacuum pump?
I can’t blame J/B for plugging their product, and it is very good vacuum oil; but the fact is, if you buy a high quality vacuum oil it will work fine in any pump.
However, it MUST be HIGH VACUUM OIL, don’t try to put 10W-40 in your vacuum pump, it ain’t gonna work!
June 22, 2009 at 2:57 am
2. Why is it so important to change the oil often in my vacuum pump?
The FAQ answered this one with a rather large brush stroke, while it is all true, there is more to it than what is stated.
1) The vacuum oil is the SEAL for the HIGH VACUUM you are trying to pull. High Vacuum oil is very refined to reach a very low vapor pressure; in fact it must have a LOWER vapor pressure than the vacuum level you are trying to achieve.
2) System contaminates, namely moisture, that are removed from the system will condense in the oil. This condensed moisture vapor (water), will effectively raise the vapor pressure of the oil thereby causing the the seal to be less effective. The pump will be less efficient, true, but it is mitigated by a poor seal, not a bad pump.
So, the better the seal (nice clean oil) the lower the vacuum can be achieved (and faster). Use clean oil every time, it’s the best way.
June 22, 2009 at 2:46 am
1. My vacuum pump runs, but I cannot get a vacuum.
The FAQ automatically assumes the pump is the culprit, so eliminate the pump.
1) Make sure you have clean oil in the pump
2)Make sure the gas ballast is closed
3)Remove all hoses and place your Micron gauge directly on the inlet of the pump, close (cap) all other inlets, if any.
4) Turn on the pump. You should see the Microns start to fall very rapidly and end up somewhere in the 50-20 Micron range (depending on pump model).
If you can’t get down to the rated Micron level, THEN make the checks (and repairs) to the pump as described above.
If you CAN get to the rated Micron level there is nothing wrong with your pump and you need to be looking for a massive leak or lots of moisture in the system.
Never assume anything, it will always kick your ass (it’s a Universal Law)!
June 16, 2009 at 11:18 am
Perhaps you’d care to elaborate? : )
June 15, 2009 at 8:27 pm
So much is left unsaid…