The process of removing contamination that is either inherent during the assembly of a new hydraulic system or generated internally after a significant failure in an existing system is commonly referred to as flushing.

This particular type of flushing typically involves the use of a specialized rig designed specifically for this task. While the hydraulic oil intended for the system can serve as the flushing fluid, it’s common to opt for an alternative fluid with lower viscosity and devoid of costly additives.

To ensure optimal results, the Car Lift Repair Tampa Florida flushing procedure necessitates flow in both directions, with the flushing fluid heated to approximately 60°C (140°F) and exhibiting turbulent flow. While turbulent flows are typically undesirable in operational hydraulic systems, they are advantageous during flushing as they aid in dislodging and expelling contaminants.

The flow rate required to achieve turbulent flow conditions depends on the internal diameter of the conduit (such as pipes, tubes, or hoses) being flushed and the viscosity of the flushing fluid. 

Q > 0.19 x v x d


Q = flow rate required for turbulent flow conditions in liters per minute.

v = kinematic viscosity of the flushing fluid at the flushing temperature, measured in centistokes.

d = internal diameter of the conduit in millimeters.

This necessity for turbulent flow implies that the flushing rig must be capable of generating flow rates higher than those typically encountered in the hydraulic system being flushed, even surpassing the capacities of its installed pumps.

Water hammer refers to the phenomenon that arises when there is a sudden change in the velocity of fluid flowing through a pipe. This abrupt alteration in fluid velocity generates a pressure wave that travels along the pipe. Under specific circumstances, this pressure wave can produce a loud banging noise, akin to the sound of striking a pipe with a hammer, hence the term. Predictably, common indications of this issue include excessive noise levels, vibration, and even pipe damage.

When a moving column of fluid encounters a solid boundary, such as when a directional control valve abruptly closes, its velocity diminishes to zero, causing the fluid column to deform within the pipe’s rigid cross-sectional area. This deformation absorbs the kinetic energy associated with the fluid’s motion, akin to a car colliding with a concrete wall. However, unlike a car, the fluid is nearly incompressible, resulting in minimal deformation and the accumulation of energy within the Car Lift Repair Tampa Florida fluid, similar to compressing a spring. The mathematical expression for the magnitude of the ensuing pressure increase resulting from the release of this stored energy is:

Pr = P + u p c


P represents the initial pressure,

u and p denote the initial fluid velocity and density respectively, and

c signifies the speed of sound through the fluid.

To mitigate the symptoms of water hammer, accumulators and other damping devices are occasionally installed. However, the crux lies in the pressure rise equation mentioned above, where fluid velocity stands as the sole variable that can be adjusted to tackle the root cause. In essence, reducing the velocity of the fluid column upon impact with the solid boundary diminishes the subsequent pressure rise. Drawing a parallel to a traffic collision, the slower the vehicle’s speed upon impact with the wall, the lesser the resulting damage.

In Car Lift Repair Tampa Florida hydraulic systems, the simplest approach to achieve this, theoretically, is by increasing the diameter of the pipe, which lowers the fluid velocity for a given flow rate. Alternatively, controlling the deceleration of the fluid column by optimizing valve switching time to a point where the pump’s pressure compensator and/or the system relief valve react swiftly enough to curtail flow rate through the pipe, consequently reducing fluid velocity, offers another solution.

The Car Lift Repair Tampa Florida hydraulic hose fabrication process, particularly the cutting phase, introduces contaminants into the system. These contaminants include metal particles from the hose’s wire reinforcement and cutting blade, as well as polymer dust from the hose’s outer cover and inner tube.

Various Car Lift Repair Tampa Florida techniques can reduce the amount of contamination during cutting, such as using a wet cutting blade instead of a dry one, blowing clean air through the hose during cutting, or employing a vacuum extraction device. However, these latter methods are impractical for cutting long lengths of hose or in mobile hydraulic hose-van scenarios.

Therefore, the primary focus should be on effectively removing cutting residue and any other contamination present in hydraulic hoses before installation. The most efficient method for achieving this is by using a foam cleaning projectile blown through the hose.

Car Lift Repair Tampa Florida Manufacturers of these cleaning systems claim that cleanliness levels as high as ISO 4406 15/13/10 are attainable. However, actual results depend on various factors, including using a projectile of the correct diameter for the hose, whether the projectile is dry or wetted with solvent, and the number of shots fired. Generally, more shots result in cleaner hose assemblies. Additionally, if cleaning a new hose assembly, it’s essential to perform the projectile cleaning before crimping the ends.

While most hydraulic hose fabricators use cleaning projectiles, the thoroughness of their cleaning practices varies. Therefore, if you require hydraulic hose assemblies to meet specific cleanliness standards, it’s crucial to specify and insist upon them. An anecdote from one of our Car Lift Repair Tampa Florida members illustrates this point:

“I was replacing hydraulic hoses on a Komatsu 300 HD for a customer who noticed me washing out a hose before installation. He asked, ‘Don’t they clean them when they make them?’ I assured him they did, but I like to double-check. I cleaned a new hose with solvent, and when I emptied the contents onto paper towels, his reaction was shocking!”

Ensuring cleanliness standards isn’t the only requirement; proper handling during delivery is also crucial. A few years ago, while at a customer’s premises, their hydraulic hose supplier delivered a batch of hose assemblies without protective caps to prevent contaminant ingress. Despite this obvious oversight, the customer accepted the delivery. Such negligence should not be tolerated from any hydraulic hose fabricator.