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Acid Neutralizing

Acid neutralizing is a big problem with vacuum pumps.  We see a lot of pumps and talk to a lot of people with problems in this area. Many acids can be pumped because they go into a gas phase (become a vapor) when hit with a high vacuum.  Often the customer wants the acid out of the product they are pulling a vacuum on but they do not realize this acid then goes somewhere.  A lot of times it goes into the vacuum pump.   This main issue can be dealt with a couple of different ways.  

First and foremost we want to stop the acid from moving into the pump if at all possible.  For this we generally use a trap.

What's going on here?

The customer needs to detail the chemicals or contaminants in the system that will be pumped or that have a "low vapor pressure".  A list should be made of the items to be placed under vacuum and the vapor pressure of each item detailed on a sheet.  Understanding at what pressure an item comes across can make understanding quantitatively (actual amount) the amount of each chemical item present.  You can even get an idea of pump down time based on sample size once this is known.  Use of a good vacuum gauge depending on chemicals pumped can greatly assist in this effort and help create the detail.  The pump will pump a given chemical at a specific vapor pressure until it is removed from the sample by turning it into a gas.  After the first item is turned into a gas and pumped then the evacuation process moves onto the next item on the list with the next lower vapor pressure.  Timing this whole sequence can be rather enlightening and also helps us review our basic physical chemistry skills.  Remember PV=nRT?  Well this is what is happening here.  Just as a real simple example say we had a milliliter of nice fresh Pepsi-cola.  Hit it with a vacuum and first all the CO2 will be pumped (removes the fizz) then we would pump the water out of the sample and be left with only sugar, caramel color (assuming we stopped after the water) and whatever other secret ingredients might be in there with a vapor pressure point greater than water.

Get back to the point.

Ok, understanding vapor pressure points and all and knowing that we can pump acids and understanding these are bad for your pump what the heck do we do now?  Stop these bad actors from getting in the pump.  Generally we "trap" them.  This can happen typically using a cold trap.  This cold trap deal is addressed in more detail elsewhere.  We can also to a degree, neutralize them by moving them through a trap with a "base" product in the trap.  Back to chemistry class again ACID+BASE= Salt + Water.  I know I have overly simplified this for many of you, but it works in principle.  Our VIT traps have an option for a Acid Neut Element.  This element employs KOH or Potassium Hydroxide in the element.  This product is highly basic.  As the acid vapors hit the element the convert to the acid salt and water.  This is not perfect again but at least it helps in stopping the bad actors from just marching into the pump.  The trap is a help and really should be used after a decent cold trap. The trap has a blue indicator as part of it's makeup to tell when it has been used up and should be replaced.

Some customers state that the pump runs, but if they shut it down with acid rich oil then it locks up or is tough to get going again.  If your system is contaminated, keep the pump running until you can change the oil.  HyVac pumps are designed to run for extended periods of time days, weeks, months on end (although not with contaminated oil).  But if your pump has been used for a nasty process valve it off and keep it running and arrange to change the oil as soon as possible.

Change the OIL OFTEN.  Unfortunately you have a tough system and are going to have to watch you oil quality on a regular basis.  Nothing really substitutes for this task.   Sorry, but it is part of your process that must be dealt with.  If you do not want to maintain it, understandable, get someone to do it for you or you will be sending your expensive vacuum pump to us for expensive repairs.  We really don't mind this, it helps us stay in business, but we are trying to help you save some money, downtime and aggravation here. 

see also cold traps, changing the oil and water in the pump.

11/27/2005 ęCopyright HyVac Products, Inc. All Right Reserved
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