The hydraulic hose fabrication process - or more specifically - the hose cutting process introduces contamination. This comprises metal particles from the hose's wire reinforcement and the cutting blade itself, and polymer dust from the hydraulic hose's out cover and inner tube.
The amount of contamination which enters the hose during cutting can be reduced by employing techniques such as using a wet cutting blade instead of a dry one, blowing clean air through the hose as it is being cut and/or using a vacuum extraction device. The latter two aren't very practical when cutting long lengths of hose from a roll or in a mobile hydraulic hose-van situation.
Therefore the main focus must be on effectively removing this cutting residue - and any other contamination that might be present in a hydraulic hose - prior to its installation. The most efficient and therefore most popular way of doing this is by blowing a foam cleaning projectile through the hose.
The manufacturers of these cleaning systems claim that hose cleanliness levels as good as ISO 4406 15/13/10 are achievable. But like most everything else, the results achieved depend on a number of variables, which include using a projectile of the correct diameter for the hose being cleaned, whether the projectile is used dry or wetted with solvent, and the number of shots fired. Generally, the higher the number of shots, the cleaner the hose assembly. Oh, and if it is a new hose assembly that's being cleaned, the projectile cleaning should be done BEFORE the ends are crimped on.
Almost all hydraulic hose fabricators these days have and use hose cleaning projectiles. But how meticulous they are when doing it is another matter entirely. This means if you want to ensure you take delivery of hydraulic hose assemblies to a certain standard of cleanliness, it's something you must specify and insist upon - as this little story from one of our members illustrates:
"I was changing some hydraulic hoses on a Komatsu 300 HD for a customer and he noticed me washing out a hose before I put it on, so he asked: 'They clean them when they make them don't they?' I said yup, but I like to check. I took the caps off a new hose and washed it with solvent and emptied the contents into some paper towel as he watched. His response was wholly sh-t!"
And it's not just the standard of the cleaning which must be insisted upon. A few years back I was at a customer's premises when their hydraulic hose supplier arrived to deliver a big bunch of hose assemblies. When the pallet came off the truck it was obvious to anyone with eyes that none of the hoses were capped to prevent contaminant ingression. And the customer accepted them. Nuts!
As soon as I saw what was going on, I advised this customer to require all hoses be delivered with caps installed and not to accept them otherwise. This sort of penny foolishness should not be tolerated from any hydraulic hose fabricator.
Bottom line: failing to properly clean a hydraulic hose after fabrication--and capping its ends, can be a costly mistake. And to discover six other costly mistakes you want to be sure to avoid with your hydraulic equipment, get "Six Costly Mistakes Most Hydraulics Users Make... And How You Can Avoid Them!" available for FREE download here.