When do I use coiled versus straight tubing on a Single Line system?

Unist sells many different variations of single line systems with many different nozzle types. Single line systems mix air and fluid at the pump outlet and then carry this mixture through the tubing all the way to the nozzle tip. This is in contrast to our coaxial tubing which carries the air and oil separately until they are mixed at or near the nozzle tip.

Single line systems are typically found on saw blade and guide lube systems as well as mini-piggy systems. When ordering these systems, the option exists for either straight or coiled tubing to connect the pump to the nozzle. Operationally, when the systems are running, there should be little to no difference between the two. Both are constructed from 1/8” OD nylon tubing. 

The coiled tubing can be advantageous in that it can stretch and retract to a relatively compact size. A 30” coiled tube will retract to approximately two feet long when it is at rest. Another advantage of coiled tubing is that it can help even out the distribution of the fluid in the tube while the system is off. As the system is operating the entire length of the tube will be full of oil and air mixed together. The air is used to atomize and propel the oil up to and through the nozzle. When the system is at rest the air in the line will bleed out through the nozzle, but there will still be fluid that will settle out in the tube. With coiled tubing, as long as the length of tubing is somewhat horizontal, the fluid will tend to settle out in the low parts in each coil along the entire length of the tube. Usually, you will end up with the fluid relatively evenly distributed along the length of the tube. This can help avoid a large shot of fluid when the system is started back up from having all of the fluid come to rest in a single low spot and being propelled to the nozzle at once.

There are instances where coiled tubing may not be feasible or easy to apply. If tubing from the pump to the nozzle must be routed through a machine for instance, then straight tubing will likely have to be used. The straight tubing can be much more convenient for routing through tight quarters and along specific paths. Straight tubing can also be much easier to route when there needs to be a long distance between the pump and the nozzle. Care should be taken to try to avoid having the tubing running all “downhill” or “uphill” through its routing to help avoid all of the fluid coming to rest in one spot and the aforementioned large shot of fluid when the system is started back up from rest.