液压管道冲洗规范(力士乐内部资料

FLUSHING HYDRAULIC SYSTEM FLUSHING HYDRAULIC SYSTEM
During the assembly and installation of extensive hydraulic system with many pipe runs ,it is easy possible for dirt and other contamination to find their way into the pipes and other items of equipment. Therefore , it is necessary with such system to flush out all the contamination ,so that it cannot have an adverse effect on the operation and life of the equipment.
Flushing involves circulating hydraulic fluid through the system at high speed. The fast-flowing fluid carries the particles of dirt along with it to where they can eventually be removed in a separate filter circuit.
The duration and intensity of flushing depend on the cleanliness of system required.
1. Preparing the System for Flushing
Any part of the system that could be damaged by the flushing must either be replaced by suitable device or be by-passed using pipes or hoses. If necessary , isolate certain units of the system and flush them individually.
Venting valves must be provided at high points in the pipework system in order to be certain that the pipes and equipment are completely full of fluid.
Drains must be provided at low points an in dead legs so that any dirty fluid can be drained off.
2. Flushing Unit
Flushing unit comprises pumps , heater, filters , tank and the necessary connections. The pumps must be fitted with adjustable pressure relief valves which must be set to a pressure which ensure that the full volumetric flow of the pumps is being passed through the parts being flushed. The capacity of the tank should be at least three times the pump delivery per minute. It should also be at least equal in capacity to the capacity of the installation being flushed.
3. Flushing Velocity and Temperature
Flushing Velocity and temperature should be as high as possible for the quick and effective flushing of the hydraulic system.
Practical experience has shown that the temperature should be higher than the operating temperature if possible. In the case od mineral oils 60 ℃is recommended. The flow velocity should be at least twice that during normal operation of the installation and the flow should be in turbulent range at all points.
The minimun volumetric flow of fluid through a pipe necessary to achieve turbulent flow conditions is defined as :
V ×d
Re = ------------- ≥4000
γ
Q ≥0.9 ×γ×d
Where Re = Reynold ‘s number
V = Flow velocity
Q = V olumetric flow in L / min
d = Insid
e diameter o
f pipe in mm
γ= Viscosity in mm2 / s
4. Flushing Fluid
The type of flushing fluid used must be compatible with the fluid eventually to be used in the system and with the materials used in the system ,especially the seals . Although the same fluid to be used subsequently can be used for flushing , a lower viscosity flushing fluid with no expensive additives can flush a system more quickly and more cheaply.
5. The Flushing Procedure
The flushing fluid should be introduced into the tank of the flushing unit through a filter.
Then heat the fluid to the required temperture and start the flushing pump . Ensure that the hydraulic system is properly vented .
While flushing is in progress keep a close watch on the clogging indicators of the filters . so that the elements can be changed or cleaned at the right time .
It is advisable to reverse the direction of flow after about an hour of flushing . Flushing should be continued untill the filter blockage indicators have been showing nothing for more than an hour . The flow should be reversed again . Take fluid sample from the system and see whether the required cleanliness of fluid has been achieved.
Make sure that all circuits comprising the hydraulic system are flushed .
When flushing is complete ensure that residual fluid is removed from any dead legs .
Obviously ,any by-passes and other auxiliary devices that have been fitted solely for the purposes of flushing must ben removed again afterwards. So that the hydraulic system is then restored to its fully functioning state .
If the system is not to be filled with fluid for some time before the final commissioning is undertaken it might be necessary to flush the system through with an anti-corrosion fluid .。