Air entrapment and gas bubbles are some of the most common causes of poor fluid performance and parts failure in modern fluid management. In the first of this two-part blog series Loris Medart, SR-TEK founder and a fluid dispensing engineer of more than 20 years’ experience, discusses four of the eight most common causes of gas entrapment and how it can be avoided or managed out of the production process.
- Excess fluid
Fluids change over time and the shifting chemical composition can itself cause air bubbles to form. Production managers using too much fluid will often find that its properties have changed significantly after just a few short days, with production processes having to be altered to suit and then re-altered to accommodate a fresh batch of fluid – whereupon the process starts all over again. Best practice is to use just the amount of fluid needed for a single production day. This de-risks the likelihood of air bubbles and also reduces lost production time by preventing the need to continually adapt processes to the changing properties of the fluid.
2. Size matters
One of the issues many production managers encounter, particularly those using legacy equipment, is the sheer size and capacity of vessels. This can often leave operatives having to manage four or even nine times the amount of air to fluid needed in a five or 10 litre tank. A smaller one or two litre vessel adapted to the daily volume usage minimises the likelihood of air bubble contamination inside the fluid
3. Under Pressure
Pressure requirements change over time in-line with the amount of fluid used. The pressure set by the operator at the start of production with a full tank to deliver a certain size deposit, will have changed significantly halfway through the production period. As the volume of fluid goes down, the volume of air grows with operators increasing the air pressure inside the vessel to compensate the flow rate and achieve the desired deposit size. A sudden burst of air entering the pressurised tank at force, however, can penetrate the liquid causing air bubbles. The absolute best way of addressing this is to make use of an automated system that gradually adjusts the pressure in-line with the volume of fluid used – ensuring consistent flow rates and deposits throughout production. If for any reason this cannot be done, however, a simple and effective way of reducing (but not eliminating) the formation of air bubbles is to install an elbow fitting to deflect the air jet onto the side of the fluid container.
4. Managing the levels
Another common cause of air bubbles is too little fluid in the pressure tank. On automated or fast-moving production lines, the level of fluid can inadvertently drop below the dip tube. Air then enters the dip tube travelling through the feed line to the dispensing/spraying head. Using a level sensor will prevent the system from getting to this point avoiding a full production reset. Other methods include assessing levels by eye, something that has been made a lot easier following the commercial availability of transparent pressure vessels, or weight monitoring.
Want to find out more? Check out the second blog in this series How the correct set up can reduce bubbles in the manufacturing process.