Sumitomo QT Series - Control of Hydraulic Fluid; Control of Fluid Temperature

HMP-0567E Rev.7 (16/19)
In general, a filter inspection should be conducted every one to three months.
If a suction filter with a clogging indicator is used, be sure to clean or replace the filter element
within the period in which the indicator is yellow.
Startup after a filter inspection should be performed in accordance with the instructions given in
Section 4.4.
2) Control of hydraulic fluid
Deterioration/contamination of hydraulic fluid occurs due to accumulation of dirt which has passed
through the filter, sludge produced from deteriorated hydraulic fluid, and entry of external water
into the hydraulic circuit, etc.
Contamination of the hydraulic fluid varies depending on the hydraulic system and/or the
surrounding environment, but it is recommended to inspect during the period shown in Table-5.3.1.
3) Control of fluid temperature
It is necessary to control the hydraulic fluid temperature (in the tank) such that the hydraulic fluid
viscosity is within the specified range.
Care needs to be taken if the atmospheric temperature is high, since a rapid increase in hydraulic
fluid temperature may occur due to deteriorated performance of the cooling tower.
Table-5.3.1: Items for Inspection, Intervals between Inspection, and Acceptance Criteria
Item
Method
Interval
Acceptance criteria
Remarks
A) Fluid
temperature
Thermometer
Continuous
monitoring
Fluid temperature at
which the fluid viscosity is
200 mm2/s (60ºC or less
for ISO VG 46 hydraulic
fluid)
Note: When used at a
pressure of 6.9 MPa
Shortage of cooling
water
Deteriorated cooler
performance
Valve sticking, etc.
B) Hydraulic
fluid
1) Degree of
contamination
2) Viscosity
3) Deterioration
4) Moisture
content
Analysis
3 to 4 months
6 months
6 months
3 to 4 months
ISO Code 22/20/17 or
lower
As stipulated in the
control standard of
the hydraulic fluid
manufacturer
If substantial
contamination or
discoloration is visible,
replacement is
required.