Which Condensate Drain Is Best For Your Compressed Air System?

In a perfect world, your air compressor’s intake would be free of dirt, oil, and water. Proper maintenance (i.e., periodic cleaning and/or changing) of the intake filter will keep most of the dirt out. Oil and water vapor will pass right through…but that’s not the end of the world (however imperfect it may be); they’re easy to take care of later in the process.

Once these vapors have been compressed (along with all that air that was drawn in), it’ll go into the receiver (usually via an aftercooler in industrial compressors) where it cools down, and that vapor condenses. If it’s left alone, a couple of things can happen:

  • Standing water in the bottom of a steel tank will cause corrosion. This can be carried into your compressed air distribution system. Over time, it will also rust through the reservoir. You don’t want either of these things to happen.
  • Eventually, it’ll take up enough space that your reservoir’s capacity will effectively shrink. That can cause your compressor to cycle rapidly. You don’t want that either.

Even the smallest of compressors will have manual drain valves on the bottoms of their reservoirs. Users will simply blow down the gallon or so tank every so often and go about their business. The small amount of electrical power that the compressor will use to recharge those tanks makes this a perfectly acceptable practice.

In the perfect world I mentioned above, the large reservoirs on industrial air compressors could be drained of condensate in the same manner. There are a few challenges to periodic manual draining:

  • You could do it on a schedule, but varying levels of humidity mean different accumulation rates of condensation. Weekly blowdowns might be OK in the winter, but you may need to do it daily in the summer. And a couple days a week in the spring or fall. It can be a real chore to keep track of all of that.
  • A practiced operator may develop the skill to shut the valve immediately upon the last drop of condensate passing. More often than not, though, you’re going to lose some compressed air doing it manually.
  • File this under “don’t try this at home (or anywhere, really)” – an unfortunately all-too-common practice is to just leave a manual drain cracked open. It works, but it wastes compressed air. On purpose. There’s too much accidental waste to give this any further discussion. Just don’t do it.
  • Plain old forgetfulness, someone going on vacation, or even leaving the company could result in someone else noticing the compressor is frequently cycling (because the reservoir is filling with water…see above), and realizing nobody’s drained the tank in a while.

Again, these manual drains are quite common, especially in smaller air compressor systems…and so are the above challenges. I may or may not have personal experience with an incident similar to that last one. Good news is, there are automated products designed to prevent this from happening to you:

  • Timer drains are popular and inexpensive. They operate just as advertised: a programmable timer opens and closes the drain valve just like you tell it to. They don’t do anything at all to address the first two challenges above: they might blow down for longer than needed (and waste compressed air) or not long enough (and allow water to build up in the reservoir.) They come in two primary configurations:
    • Solenoid Valve: the timer energizes the valve’s coil to open the valve, and a spring shuts it when the timer runs out. Strainers will prevent blockage, and will need periodic maintenance.
    • Ball Valve: the timer operates an electric actuator to open & close the valve. The full port opening of the ball valve means a strainer is usually not necessary, so these are less maintenance intensive.
  • Demand (AKA “no waste” or “zero loss”) drains are actuated by the condensate level in the reservoir. They don’t discharge any of the reservoir’s compressed air, because they close before the last bit of water exits. There are a few common options to choose from:
    • Mechanical float drains can be internal or external…the latter is more common for use with air compressor reservoirs; the former is fairly standard with point-of-use filters (more on that later). When the liquid level rises, the float opens the drain; when liquid level drops, the float closes the drain…easy as that. They CAN be susceptible to clogging with debris, but many have screens to prevent or limit that.
    • Electronic types use a magnetic reed switch or capacitance device to sense the condensate level…so they require electric power.
    • These cost more than the timer types, though, and they’ve got a number of moving parts, so they can find themselves in need of repair. Inexpensive and user-friendly rebuild kits are oftentimes available, and many of these come with alarms to let you know when to use that rebuild kit.

Whether you have a manual, timer, or demand drain, keep in mind that some moisture can still be carried over, and rust/scale can still form in pipelines. Good engineering practice calls for point-of-use filtration, like EXAIR’s Automatic Drain Filter Separators and Oil Removal Filters. If you’d like to talk more about getting the most out of your compressed air system, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Intermediate Storage Tanks & How To Size Them

When evaluating processes that utilize compressed air and adhering to the Six Steps to Compressed Air Optimization, intermediate storage proves to be a critical role coming in at step number five. Intermediate storage tanks may already be in place within your facility and often times can be implemented as modifications to aid existing lines that are struggling to maintain proper availability of compressed air to keep the line at peak performance.

EXAIR Receiver Tank in 60 Gallon Capacity

When determining whether or not a production line or point of use compressed air operation would benefit from a receiver tank/intermediate storage we would want to evaluate whether the demand for compressed air is intermittent.  Think of a receiver tank as a capacitor in an electrical circuit or a surge tank in a water piping system.  These both store up energy or water respectively to deliver to during a short high demand period then slowly charge back up from the main system and prepare for the next high demand.   If you look from the supply point it will see a very flattened demand curve, if you look from the application side it still shows a wave of peak use to no use.

Intermittent Applications are prime for rapid on/off of compressed air.

One of the key factors in intermediate storage of compressed air is to appropriately size the tank for the supply side of the system as well as the demand of the application.  The good news is there are equations for this.  To determine the capacity, use the equation shown below which is slightly different from sizing your main compressed air storage tank.  The formulate shown below is an example.

Where:

V – Volume of receiver tank (ft3 / cubic feet)

T – Time interval (minutes)

C – Air demand for system (cubic feet per minute)

Cap – Supply value of inlet pipe (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P1 – Header Pressure (PSIG)

P2 – Regulated Pressure (PSIG)

One of the main factors when sizing point of use intermediate storage is, they are being supplied air by smaller branch lines which cannot carry large capacities of air.  That limits your Cap value. The only way to decrease the V solution is to increase your Cap. The other key point is to ensure that all restrictions feeding into the tank and from the tank to your point of use are minimized in order to maintain peak performance.

If there are intermittent applications that are struggling to keep up with the production demands within your system, please reach out and speak with an Application Engineer.  We are always here to help and we may even be able to help you lower the demand needed by utilizing an engineered point of use compressed air solution.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

How to Size a Receiver Tank and Improve your Compressed Air System

Receiver Tank: Model 9500-60

My colleague, Lee Evans, wrote a blog about calculating the size of primary receiver tanks within a compressed air system.  (You can read it here: Receiver Tank Principle and Calculations).  I would like to expand a bit more about secondary receiver tanks.  They can be strategically placed throughout the plant to improve your compressed air system.  The primary receiver tanks help to protect the supply side when demands are high, and the secondary receiver tanks help systems on the demand side to optimize performance.

Circuit Board

I like to compare the pneumatic system to an electrical system.  The receiver tanks are like capacitors.  They store energy produced by an air compressor like a capacitor stores energy from an electrical source.  If you have ever seen an electrical circuit board, you notice many capacitors with different sizes throughout the circuit board (reference photo above).  The reason is to have a ready source of energy to increase efficiency and speed for the ebbs and flows of electrical signals.  The same can be said for the secondary receiver tanks in a pneumatic system.

To tie this to a compressed air system, if you have an area that requires a high volume of compressed air intermittently, a secondary receiver tank would benefit this system.  There are valves, cylinders, actuators, and pneumatic controls which turn on and off.  And in most situations, very quickly.  To maximize speed and efficiency, it is important to have a ready source of air nearby to supply the necessary amount quickly.

For calculating a minimum volume size for your secondary receiver tank, we can use Equation 1 below.  It is the same as sizing a primary receiver tank, but the scalars are slightly different.  The secondary receivers are located to run a certain machine or area.  The supply line to this tank will typically come from a header pipe that supplies the entire facility.  Generally, it is smaller in diameter; so, we have to look at the air supply that it can feed into the tank.  For example, a 1” NPT Schedule 40 Pipe at 100 PSIG can supply a maximum of 150 SCFM of air flow.  This value is used for Cap below.  C is the largest air demand for the machine or targeted area that will be using the tank.  If the C value is less than the Cap value, then a secondary tank is not needed.  If the Cap is below the C value, then we can calculate the smallest volume that would be needed.  The other value is the minimum tank pressure.  In most cases, a regulator is used to set the air pressure for the machine or area.  If the specification is 80 PSIG, then you would use this value as P2.  P1 is the header pressure that will be coming into the secondary tank.  With this collection of information, you can use Equation 1 to calculate the minimum tank volume.  So, any larger volume would fit the requirement as a secondary receiver tank.

Secondary Receiver tank capacity formula (Equation 1)

V = T * (C – Cap) * (Pa) / (P1-P2)

Where:

V – Volume of receiver tank (cubic feet)

T – Time interval (minutes)

C – Air demand for system (cubic feet per minute)

Cap – Supply value of inlet pipe (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P1 – Header Pressure (PSIG)

P2 – Regulated Pressure (PSIG)

If you find that your pneumatic devices are lacking in performance because the air pressure seems to drop during operation, you may need to add a secondary receiver to that system.  For any intermittent design, the tank can store that energy like a capacitor to optimize the performance.  EXAIR stocks 60 Gallon tanks, model 9500-60 to add to those specific locations, If you have any questions about using a receiver tank in your application, primary or secondary, you can contact an EXAIR Application Engineer.  We can restore that efficiency and speed back into your application.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

Photo: Circuit Board courtesy from T_Tide under Pixabay License

Ionizing Point Best Thing for Static on Trim Scrap in Cyclone Separator

This application came in from our distributor (AYRFUL) in Argentina. They had a customer who is recycling film scraps. The scrap material is conveyed into a cyclone separator. The problem is that the scrap becomes charged with static as a result of the motions and interactions within the conveying pipe. This results in the scrap sticking to itself and to the parts of the cyclone separator inside. The problem is so bad that it becomes almost impossible to separate the material when it comes time to clear it out of the cyclone separator once clogged.

After discussing the challenges the customer faced in trying to keep their cyclone up and running, we decided to recommend that the customer utilize 4 pieces of EXAIR’s Model 7199 Ionizing Point and 1 piece of Model 7941 (4 outlet Power Supply) to neutralize the static within the cyclone.

The ionizing Points would be attached by means of inserting through the wall of the inlet pipe of the cyclone separator.

Ion Point

cyclone

The existing blower moving air into the cyclone separator will do the job of carrying the positive and negative ions into the cyclone separator and keep it and the contents at a neutral state.

If you have a similar problem, contact us to discuss the application. We would be glad to help with our full range of static eliminators to address your application issues.

Neal Raker, Application Engineer
nealraker@exair.com