RE-A 91610/12.2015,
Bosch Rexroth Corp.
Axial piston variable motor | A6VM series 71
Hydraulic fluids
5
Hydraulic fluids
The variable motor A6VM is designed for operation with
mineral oil HLP according to DIN 51524.
Application instructions and requirements for hydraulic
fluids should be taken from the following data sheets
before the start of project planning:
▶ 90220: Hydraulic fluids based on mineral oils and
related hydrocarbons
▶ 90221: Environmentally acceptable hydraulic fluids
▶ 90222: Fire-resistant, water-free hydraulic fluids
(HFDR/HFDU)
▶ 90223: Fire-resistan, water-containing hydraulic fluids
(HFAE, HFAS, HFB, HFC)
Details regarding the selection of hydraulic fluid
The hydraulic fluid should be selected such that the operat-
ing viscosity in the operating temperature range is within
the optimum range (
ν
opt
see selection diagram).
Note
At no point of the component may the temperature be higher
than 240 °F (115 °C). The temperature difference specified
in the table is to be taken into account when determining the
viscosity in the bearing.
If the above conditions cannot be maintained due to extreme
operating parameters, we recommend flushing the case at port
U or using a flushing and boost pressure valve (see page 63).
Viscosity and temperature of hydraulic fluids
Viscosity
Temperature
Comment
Cold start
ν
max
≤ 7400 SUS
(1600 mm
2
/s)
θ
St
≥ −40 °F (−40 °C)
t
≤ 3 min,
n
≤ 1000
rpm, without load
p
≤ 725 psi (
p
≤ 50 bar)
Permissible temperature difference
ΔT
≤ 45 °F (25 K)
between axial piston unit and hydraulic fluid in the system
Warm-up phase
ν
<
7400 to 1850 SUS
(1600 to 400 mm
2
/s)
θ
= −40 °F to −13 °F
(−40 °C to −25 °C)
at
p
≤ 0.7 ×
p
nom
,
n
≤ 0.5 ×
n
nom
and
t
≤ 15 min
Continuous
operation
ν =
1850 to 47 SUS
(400 to 10 mm
2
/s)
This corresponds, for example on the VG 46, to a temperature range
of +41 °F to + 185 °F (+5 °C to +85 °C)(see selection diagram)
θ
= −13 °F to +217 °F
(−25 °C to +103 °C)
measured at port T
Note the permissible temperature range of the shaft seal
(
ΔT
= approx. 22 °F (12 K) between the bearing/shaft seal and port T)
ν
opt
= 167 to 81 SUS
(36 to 16 mm
2
/s)
Range of optimum operating viscosity and efficiency
Short-term
operation
ν
min
≥ 49 SUS
(7 mm
2
/s)
t
< 3 min,
p
< 0.3 ×
p
nom
▼ Selection diagram
60
200
300
100
500
1000
2000
3000
5000
7000
VG 22VG 32VG 46VG 68VG 100
80
150
(7)
(10)
(40)
(60)
(20)
(100)
(200)
(400)
(600)
(1000)
(1600)
(16)
(36)
−40
−13
120
0
20 40 60 80
160
195
240
(−40) (−25) (−10) (0) (10)
(30)
(50)
(70)
(90)
(115)
50
70
Range of optimum operating viscosity
ν
opt
Optimum efficiency
Maximum permissible viscosity for cold start
Minimum permissible viscosity
for short-term operation
Temperature
θ
[°F (°C)]
Viscosity
ν
[SUS (mm
2
/s)]
Continuous oper
ation
Warm-up phase
Minimum permissible temperature for cold start
