Hydraulic Flushing (Flushing of Hydraulic Systems)
Hydraulic Flushing (Flushing of Hydraulic Systems)
Hydraulic Flushing (Flushing of Hydraulic Systems)
Hydraulic flushing is a process that involves using pressurized water to clean out debris and buildup from pipes and other plumbing systems. This is often done to improve the performance and efficiency of the plumbing, as well as to prevent clogs and other problems. The process typically involves using a specialized hydraulic flushing machine to force water through the plumbing at high pressures, which can effectively remove any buildup or debris that may be present. Hydraulic flushing is a common maintenance practice in many different industries, including buildings and facilities management, water treatment, and more.
What is Flushing Pickling?
It is extremely important to carry out pickling and flushing processes for the long-term operation of fluid systems without problems. Cleaning of piping circuits is very important in fluid systems. In poorly cleaned dirty circuits, the particles in the pipe circuits are carried by hydraulic oil during the operation of the system, causing jams, blockages and abrasions in the pump, valves and other elements. In order to prevent the above-mentioned problems caused by pollution in the systems and to increase the performance of the systems to the maximum level, the newly drawn pipe circuits should be subjected to pickling and flushing processes before the system is commissioned. If new piping circuits are to be drawn into the existing system, pickling and flushing should be performed for these new circuits as well. By carrying out the pickling and cleaning processes, the particles of a certain size and amount in the circuits are removed from the pipes.
The above-mentioned pollutants can enter the systems in different ways;
During assembly,
Welding burrs, liquid sealants, soil, sand, etc.
Contamination in the system,
Inadequate selection of the filtration system, bacteria, fungi, etc.
Pollution from the external environment,
During oil filling, maintenance, etc.
In order for hydraulic systems to be long-lasting and to perform their functions correctly, the cleaning class of the system must be appropriate. To achieve this, the system must be flushed. The rules to be followed in the washing process and the realization of this in practice determine the success of the washing.
Rules to be followed when washing hydraulic systems:
1- The viscosity of the fluid used in washing should be as low as possible. Preferably wash vis. < 32 cst. Compatible with the fluid to be used after washing
should be.
2- Before washing, the fluid to be used and the cleaning class of the tank should be filtered and cleaned up to the cleaning class to be reached.
3- Flushing should only be applied to pipelines. Other equipment should be disabled by by-pass lines.
4- A turbulent flow is required for washing to occur. This means that the Reynolds number must be greater than 4000.
Q Flow L./min.
ν viscosity cst
dpipe Pipe Inner Diameter mm
5- The temperature of the fluid during washing should be 50 C on average.
6- The flow size of the filter to be used during washing is determined according to the largest flow in the washing. In general, the pump flow rate that should be used for washing in Iron and Steel applications is 600 Lt/min. The nominal size of the filter is 1300 Lt. or higher should be selected. 20, 10, 5 or 3 micron absolute ( βx≥ 200) filter elements are used respectively according to the cleaning class to be achieved. In order to use the filter elements with all their performance, it should have a 6 bar check valve.
7- Unless otherwise stated, it is aimed to reach the 18/16/13 cleaning class according to ISO 4406 (1999).
8- It is not easy to determine the washing time. Because the washing time varies depending on the size of the system, the installation and the cleanliness of the pipes used. During the washing, the cleaning classes should be checked, and after noticing that there is no change, the washing should be continued for about three more hours, and the process should be continued by using a more sensitive filter element. When the desired cleaning class is reached, the process should not be completed and washing should be continued for at least three more hours.
9- The cleaning class reached at the end of the washing process must be checked with pollution measuring devices and documented in writing.
Cleaning (Flushing) System:
Flushing is done after pickling. In this process, the pipes are connected to each other and the hydraulic oil used in the system is circulated through the pipes in a way that causes friction and cleaning is performed. The friction of the oil in the pipe occurs when the oil flow turns from laminar flow to turbulent flow. Flow variation depends on oil viscosity, pipe diameter and Reynolds number. When the Reynolds number is 2320 or more, the flow becomes turbulent. The flow rate varies in direct proportion to the Reynolds number. In hydraulic systems, flushing is very important since the most important factor in the smooth operation of the system is the cleanliness of the system. Considering that the smallest particle that the best eye can see is 40 microns, we cannot see the particles that will cause malfunction with the naked eye. A high percentage of particles may leak into the system through improperly installed oil tank vent filters, pistons and other seals. Oil comes into contact with all system components and should be perceived as important, just like blood in the human body. As a result, maintaining optimal machine components and oil performance is vital.
How often do hydraulic systems need to be flushed?
When overhaul or hydraulic system modification is done. In the detection of a faulty hydraulic part. (pump, valve, cylinder, etc.) Counting the particles in the oil is made in six-month periods and is done according to the result.
The flushing process is done in two stages.
Stage 1 is done by adapting a unit of the required size to the system from outside.
The second stage is done by using the pump and tank in the system.
First cleaning operation
Pipes are connected to each other and installed as a closed circuit outside, or they are assembled so that they will work in the system. By using a temporary pump and tank, a circuit is created that will circulate. Cleaning fluid (hydraulic oil) during flushing; The system pump is installed as a closed circuit in such a way that it will not pass over the cylinders and valves and will be bypassed. If there are pipes of different sizes in the system, pipes with similar diameters can be grouped and cleaned separately.
ISO-NAS-SAE Benchmark
ISO NAS SAE Required fiber filter (micron)
14/12/09 3 4 3
15/13/10 4 5 3-6
16/14/11 5 6 6
17/15/12 6 7 6-10
18/16/13 7 8 10-15
19/17/14 8 9 10-15-20
20/18/15 9 10 15-20
21/19/16 10 11 15-20-25
22/20/17 11 12 20-25
23/21/18 12 13 25
Filter Production Standards
ISO 3968 Differential pressure-flow characteristic ISO 2942 Bubble point test
NFPA T3.10.17 ISO 10771 Compressive fatigue test ISO 2941 Slump pressure value verification test
ISO 16889 Multipass, yield test ISO 2943 Compatibility with different liquids
ISO 3723 Final load verification test ISO 23181 Flow fatigue test in high viscosity liquids
ISO 3968 Differential pressure, flow and bypass valve test ISO 4405 Pollution test by gravimetric method
ISO 4021 Test with working system sample ISO 4406 e NAS 1638 Solid particle classification standards
Particle analysis with ISO 4407 Microscope
Cleaning Classes of Hydraulic Equipment
Component ISO Class NAS
Servo valves 16/14/11 5
Proportional valves 17/15/12 6
Valves, piston pumps and motors 18/16/13 7
Direction and pressure control valves 18/16/13 7
Gear pumps and motors 19/17/14 8
Flow control valves and cylinders 20/18/15 9
New unused oil 20/18/15 9
NOTE; 70-80% of malfunctions in hydraulic systems and 90% of ball bearing malfunctions are caused by dirty hydraulic oils.