Go ahead… give your TO-15 canisters a rough cleaning… I do!

Recently, I have been playing around with our TO-Clean Canister Cleaning System. Awesome unit, which I plan to blog on more in the future! In any event, the TO-Clean comes standard with a single Edwards RV8 Two Stage Rotary Vane Pump. Single was italicized, because our competitor’s canister cleaning system requires a 2-Stage Diaphragm Pump and a Molecular Drag Pump. One more pump, means one more thing to possibly break down, and I cannot imagine a Molecular Drag Pump is cheap to repair or replace. I know I can have an Edwards rough pump brought back from death for ~$500. In any event, I digress…So the RV8 rough pump works wonders at pulling twelve 6 L canisters down to 50 mtorr of vacuum. No complaints whatsoever… however I always want more!!! In fact, I will not be worried about having too much vacuum until I see the sides of my canisters dimple in. So when I recently had the power cut to my instrument bench to add more juice for my Markes CIA Advantage (keep your eye out for more blogs on that in the future too), I decided to play around with an old Edwards RV18 I found in the lab and get a littler rougher with my canisters. And the following two findings came from this:

1. As you can see from the table below, the RV18’s relatively larger displacement and pump speed did correspond to a “real world” difference in pump down time. Depending on the number of cleaning cycles (I have seen laboratories with as few as 1 and others with 15), soak durations, and desired pressures… a 10 minute savings (each cycle that is) may add up to a fair amount of time savings over the full cleaning process. Something you may find worth the extra $1,700 to upgrade to an RV18.

 Pump Comparison Table

2. Several experienced chromatographers (not here at Restek of course) were misled by how much oil needs to be in the rough pump. I polled 3 chromatographers, each with 20+ years of experience, on how much they fill their rough pumps up. All three answered about halfway. Makes sense… right?

See the Edwards rough pumps have a max and min fill line. Intuition tells us we do not want to be at the max or the min, so we go for the middle. However, if you read the owner’s manual, it clearly states fill to the max. Makes sense too… right? It makes sense to fill your rough pump to the max for the following two reasons, as they relate to the purpose of the rough pump oil:

a. The oil acts as a sink for any contaminants in your vapor stream you are vacuuming. The more oil you have, the less frequently you have to change out your oil.

b. The oil dissipates the heat generated by the rough pump. The more oil, the more efficient you are dissipating the heat, the longer your pump lasts… in theory.

So go ahead and top off your rough pump with some fresh oil and get rough with those TO-15 canisters. One last piece of advice; do not overfill your oil. The max line is there for a reason; and trust me, it gets messy if you do. Oh… if you do not already have a TO-Clean, time to get out of the dark ages!

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