300−P−9050076−E−03/11.2009
CFS
2/11
Contents Page
1 General
description 3
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2 Advantages
3
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3 Application
3
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4 Technical
data
4
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5 Installation/startup
5
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5.1 Installation
information
5
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5.2 Adjustment
information
5
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6 Description
of
function
6
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7Port
designations
8
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8 Circuit
example
8
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9 Standard
design,
sizes
16/20
9
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9.1 Dimensions
9
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9.2 Performance
graphs
10
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9.3 Model
code
key
11
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300−P−9050076−E−03/11.2009
CFS
3/11
1 General description
In accordance with standard EN 474−5 "Safety of earth−
moving machinery − Requirements for hydraulic exca-
vators", the excavator pipe−rupture valve, type CFS (Com-
pact Flow Control and Safety Valve), prevents uncontrolled
lowering of the actuator in the event of a pipe− or hose−rup-
ture. In addition, the CFS valve holds the actuator in its posi-
tion when the main valve is centred. The valve also includes
a secondary pressure relief function, which protects the
actuator against overload.
2 Advantages
The inlet and actuator ports on the CSF excavator pipe−rup-
ture valve are standard SAE flanged ports, and the valve
can therefore be retrofitted to existing equipment without
any difficulty.
Thanks to its load−independent, pilot−operated opening
principle, variations in load pressure − even right up to the
maximum − have no effect on the fine−control characteristics
and the hydraulic performance of the valve. The design of
the valve means that it can be operated by very small lower-
ing pressures.
The CSF is set at the machine in a way that ensures that the
excavator pipe−rupture function has no effect on the hy-
draulic values that have already been set in the machine
(pre−opening principle). This means that excavators with
and without a lifting function can be equipped with the same
basic hydraulic system; the machines’ work cycles remain
unchanged.
The secondary pressure−relief function can handle the full
rated flow. When the main spool valve is a closed−centre
model and a secondary valve is connected in parallel, no
pressure summing occurs. The secondary pressure−relief
valve in the excavator pipe−rupture valve opens at exactly
the opening pressure that has been set. There is no need
for a large−bore, external tank return line.
3 Application
The excavator pipe−rupture valve is used wherever so
required by the standards EN 474, ISO 8643 and DIN
24093 for excavators with a lifting device (e.g. a load
hook on the bucket. The actuators concerned are the lift
cylinder, the stick cylinder and the adjusting cylinder.
It is also possible to envisage machine applications in which
a pipe−rupture on the actuators could produce dangerous
situations e.g. machines for materials handling and demoli-
tion.
Attention: the excavator pipe−rupture valve may
only be used for the purpose for which it has been
designed!
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CFS
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4 Technical data
General characteristics Description, value, unit
Design 2−stage proportionally−controlled seat valve, with initial hydraulic decompression
patented follower principle
Mounting method flange−mounting, SAE 6000 psi
Mounting attitude unrestricted
Flow direction A → B free flow through check valve
B → A controlled flow
Weight/Material 3.6 kg, body material = SG iron GGG40
Surface treatment Valve is zinc plated (Cr6−free, thick−film passivation)
mounting bolts are zinc−flake coated
Hydraulic characteristics Description, value, unit
Nominal sizes 16
20
Nominal flow rate size 16 = 250 l/min
size 20 = 350 l/min
Pilot pressure range opening pressure 4.410 bar
(setting ex−work at 20l/min (B → A) and 100bar load pressure; with this flow
and load pressure the pilot pressure can be adjusted within the range
1116.5bar)
full opening opening pressure + 18 bar + leakage oil pressure
Operating pressure max. 420 bar
Secondary PRV − adjustment range min. 320 420 bar (max. up to 460 bar also possible); settings are sealed
other models − consult Bucher Hydraulics
Ambient temperature range −40 °C +100 °C
Operating fluid mineral oil to DIN 51524 and DIN 51525 (HL/ HLP),
other fluids − consult Bucher Hydraulics
Fluid temperature range −20 °C +90 °C
Viscosity range S minimum 2.8mm
2
/s (cSt)... maximum 1500mm
2
/s (cSt)
S recommended 10mm
2
/s (cSt) 380mm
2
/s (cSt)
Temperature range,
seal material
S Nitrile = −20 °C +90 °C
S Viton = −20 °C +200 °C
S Low (N7T40) = −50 °C +80 °C
Filtration NAS 1638 class 9, ß10 ≥ 75
ISO 4406 class 18/15
(valves do not have any internal filters)
Internal leakage values
(HLP 46 at 40 °C)
A → L = 100cm
3
/min (dynamic)
X → L = 20cm
3
/min (dynamic)
B → A = 0.15cm
3
/min (static)
B → L = 0.15cm
3
/min (static)
300−P−9050076−E−03/11.2009
CFS
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Ports Description, value, unit
SAE to SAE J518 DEC87, ports fitted with a plastic protector
Threads to DIN 3852, Parts 1 and 2, open ports fitted with a plastic protector
Fittings to ISO 8434−1
5 Installation/startup
5.1 Installation information
Attention: only trained and competent personnel
may carry out any work on the excavator pipe−rup-
ture valve!
The valve must not be opened without the manu-
facturer’s express permission!
Mounting bolts can be supplied as an optional extra and are
grade 12.9 to DIN 912, with "Geomet" surface finish.
Protect flange faces from damage and before installing the
valve check that all the seals are present. The mating flange
face must be of the quality specified in the catalogue.
Before initial start−up, bleed all air from the hydraulic system.
Do not use any pipe fittings that have tapered threads.
Attention: before removing or disassembling the
valve, vent all hydraulic pressure from the system
− double check!
Before fitting the valve, remove all plastic protec-
tors and plastic residues.
5.2 Adjustment information
Pilot valve for main function
The pilot valve for the lowering function is factory−set during
testing to the opening pressure stipulated by the customer
and then sealed.
S clockwise → increases the pressure
S counterclockwise → decreases the pressure
The change in pressure is approx. 5.8 bar per turn.
Attention: the adjusting screw can be completely
unscrewed − it has no end−stop!
Important: if the adjustment seal is broken, the
warranty is null and void!
Pilot valve for pressure−relief function
The pilot valve for the pressure−relief function is factory−set
during testing to the pressure stipulated by the customer
and then sealed. The pressure is set with flow Q = approx.
0.75 l/min.
S clockwise → increases the pressure
S counterclockwise → decreases the pressure
The change in pressure is approx. 94 bar per turn.
(with the spring for 320420 bar)
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CFS
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6 Description of function
94278
10311516
X
A
B
Fig. 1
300−4−10012929
1 CV spring
2 Control spring
3 Spring for secondary valve
4 Adjusting screw for pilot valve
5 Poppet for secondary valve
6 Control spool
7 Pilot spool
8 Pilot piston
9 Stroke limiter
10 Adjusting screw for secondary valve
11 Emergency−lowering screw
A Load−control assembly
B Pilot valve for load−control assembly
C Pilot valve for secondary pressure relief
The neutral position (load pressure at B; A and X unpressurised)
In the neutral position, the excavator pipe−rupture valve is
held closed by the spring (1), which acts on the control
spool(6), and also by the load pressure, which acts on the
rear side of the control spool.
The check−valve function (flow A → B)
To raise the actuator, pump pressure is applied via port A to
the valve seat area of the control spool (6) and causes the
control spool to open, pushing against the light spring (1).
The control function (flow B → A)
1. Decompression
The pilot pressure at port X moves the pilot piston (8) in op-
position to the springs (2) and the pilot spool (7) opens at the
set pressure. The load pressure behind the control spool (6)
now decays as it escapes past the pilot spool to port A. The
progressive characteristic of the decompression phase en-
sures that the actuator motion begins smoothly and without
jerks.
300−P−9050076−E−03/11.2009
CFS
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2. Main opening
With further increase in the pilot pressure at X, the pilot spool
opens further and the reduced pressure behind the control
spool falls still more. The load pressure acting on the differ-
ential area of the control spool now pushes the spool off its
valve seat in the opening direction until the pressures of the
oilflows into, and out of, the control spool have changed
enough to produce a situation of force balance.
The pilot pressure acting on the pilot piston therefore con-
trols the open metering area of the control spool, and conse-
quently the flow rate from B → A. The pilot valve is compen-
sated and is unaffected by any back−pressure in port A that
may occur.
The opening point of each excavator pipe−rupture valve is
precisely matched to the particular make/model of exca-
vator and is set to the required value on the test stand with
adjusting screw (4). With the optional stroke limiter (9), the
pilot spool stroke can also be restricted. This in turn in-
fluences the lowering speed.
Function of the secondary pressure−relief valve
The pilot valve for the pressure−relief valve is connected di-
rectly to actuator port B. When the pressure set with spring
(3) is reached, the poppet (5) opens and unloads the rear
side of the control spool (6) to port L. The load pressure, act-
ing on the differential area of the control spool, now pushes
the spool fully open and opens the B−to−A flow path for the
full rated flow. The pilot valve is not connected to the return
line and is therefore unaffected by any back−pressure in port
A that may occur. With a closed−centre directional valve, no
pressure summing occurs with the necessary series−con-
nected downstream pressure−relief valve. The secondary
pressure can be set at any desired level with the adjusting
screw (10).
Attention: when the pilot valve for the secondary
pressure relief function opens, there is a pilot flow
of 9 l/min per valve to port L. The pressure in the
L−line has a 1:1 effect on the setting of the pres-
sure−relief valve. To ensure that the performance
characteristics are not affected, the drain line
should be sized so that the back−pressure never
exceeds 10 bar.
Leakage−oil drain
The leakage oil from both pilot cartridges as well as their
spring chambers is drained to port L. This port should be
drained to tank with the least possible back−pressure. Any
tank preload− or back−pressure in the drain line has a 1:1 ef-
fect on the opening values of both pilot valves.
Emergency−lowering screw BL
An optional emergency−lowering screw (11) can be incorpo-
rated. The actuator is vented to port L through a ø3 connect-
ing drilling that is normally shut off. The screw cannot be
completely unscrewed.
Attention: when emergency lowering has been
completed, the screw must be screwed in again to
reestablish the valve’s function!
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CFS
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7 Port designations
Port Description
B Actuator/load port
A Flow or return port
X Pilot port
L, L1 Drain port
E, E1 Port for balance pipe in parallel−cylinder applications; protected by a ø1 fixed orifice
8 Circuit example
X
L1
L
A
E1 B
E
Ø1
2
1
3
Fig. 2 300−4−10012146
1 Version with optional pressure balance valve,
for parallel−cylinder application
2 Version with optional emergency lowering
3 Version with optional stroke limiter
300−P−9050076−E−03/11.2009
CFS
9/11
9 Standard design, sizes 16/20
9.1 Dimensions
137.5...141
21
40.5
52.5
31 31
31.5
72
85.5
37.5
40.5 40.5
89
4
25.5
54
97
128...131
14
a
b c
88.5
131.5...133
E
E1
A
B
3
B
A
X
EE1
L1
L
E1
E
B
B
A
E1
E
1
4
3
2
10
R
max
10
0.02 / 100 mm
A
4
Fig. 3 300−4−10012889
1 Version with optional balance valve
Fitting, type 8S, for cutting ring to DIN 3861
2 Version with optional emergency lowering
3 Version with optional stroke limiter
4 Serial number
A Required quality of the mating surface
Design Ports Dimensions
A B X, L, L1, E, E1 a b c
CFS 16−A SAE 3/4" 6000psi SAE 3/4" 6000psi G 1/4" M10 15 25
CFS 20−A SAE 1" 6000psi SAE 1" 6000psi G 1/4" M12 16 24
300−P−9050076−E−03/11.2009
CFS
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9.2 Performance graphs
Δp A to B = (Q)
20
15
10
5
0
0 50 100 150 200 250 300 350
Q [l/min]
p [bar]
Δp B to A = (Q)
20
15
10
5
0
0 50 100 150 200 250 300 350
Q [l/min]
p [bar]
Opening curve, Q = (pX) at 33 bar load pressure
pX [bar]
20
14
16
18
12
10
8
6
4
2
0
0 20 100 200 300
Q [l/min]
pX = pilot pressure [bar]
Opening curve, Q = (pX) at 100 bar load pressure
16
14
12
10
8
6
4
2
0
0 20406080100
Q [l/min]
*
**
pX [bar]
pX = pilot pressure [bar]
* = pilot pressure setting ex−works
** = effective opening pressure
Pressure−relief valve, secondary PRV, Q = (Load)
(Example curve)
500
400
*
*
*
*
300
200
100
0
0 50 100 150 200 250 300
Q [l/min]
pB [bar]
* pressure setting
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CFS
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9.3 Model code key
Nominal size
16 = 16
20 = 20
Model series
Series A = A
Application
Earth−moving machines to EN 474, ISO 8643 = E
Design
Standard design = S
Seal material
Temperature range
Nitrile (standard) −20°C to +90°C = N
Nitrile (low temperature) −50°C to +80°C = T
Viton (special fluids) −20°C to +200°C = V
Mounting bolts
Without mounting bolts = O
With mounting bolts, surface−treated t = D
Control spool
100 l/min. = R100
250 l/min. = R250
290 l/min. = R290
Opening−point setting
Pilot pressure ... bar at 20 l/min and 100 bar load pressure
(determined by Bucher Hydraulics in the range 1116.5bar) = ... [bar]
Secondary pressure relief
Pressure relief at port B = SV
Setting of the secondary pressure−relief valve
Pressure setting ... bar at approx. 0.75 l/min = ... [bar]
Ports X, L, E
To DIN 3852 Part 2 (Imperial) = Z
Fittings package for X and L (optional) = V
Optional accessories
Without balance valve (single cylinder)
Balance valve in port E (parallel cylinders), port L open = R
Balance valve in port E1 (parallel cylinders), port L1 open = L
Optional mechanical emergency lowering
Without emergency lowering =
With mechanical emergency lowering = N
Optional stroke limiter
Without stroke limiter =
Adjustable stroke limiter = H
Stroke−limiter setting
Q setting at 33 bar load pressure = ... [l/min]
−− −− −−−CFS − A E − SVS
E 2009 by Bucher Hydraulics AG, CH−6345 Neuheim.
www.bucherhydraulics.cominfo.nh@bucherhydraulics.com
All rights reserved.
Data is provided for the purpose of product description only, and must not be considered as warranted characteristics in the legal sense.
The information does not relieve users from the duty of conducting their own evaluations and tests. Because the products are subject to
continual improvement, we reserve the right to amend the product specifications contained in this catalogue.
