Bosch Rexroth 4WRPD Operating Instructions Manual page 16

16/48 Safety instructions
Bosch Rexroth AG, 4WRPD(H), 4WRPQ(H), 4WRPF(H), 4WRLD, 4WRLF, 4WRLQ, 5WRPF10, 5WRPQ10; RE 29391-B/05.2021
If this reaction on the signal change does not occur in time, the higher-level control
system must immediately initiate the emergency shut-down of the system.
An application with two valves including two-channel control and monitoring (DC
99 %) fulfills the necessary requirements to achieve a PL e, cat. 4 according to
EN 13849-1.
With the exception of "enable" and "enable acknowledgement", all other signals
do not form part of the safety function and must therefore not be used for safety-
relevant functions.
Despite all measures taken in terms of plausibility check and monitoring, the use
of the valve involves a certain residual risk, which must not be neglected. It must
in any case be evaluated by the machine integrator depending on the individual
application. For appropriate evaluation, Bosch Rexroth provides the safety
parameters of the valve on Multi-Ethernet basis according to EN 13849-1. See
chapter 2.7.4 "MTTFd, DC, CCF".
2.7.2 Limits of the safety-related parts
Assessment of the valve on Multi-Ethernet basis according to ISO 13849-2:
• A valve on Multi-Ethernet basis is suitable for channel shut-off according to
EN 13849-1. An appropriate control system must be provided which ensures
plausibility checks between the direction-dependent enable input of the valve
and the direction-dependent "enable acknowledgement" signal issued by the
valve (see chapter 2.7.1).
• Potential failures or unidentified error states of the valve on Multi-Ethernet basis
always require application-dependent and suitable system-related measures
according to EN 13849-1 (see chapter 2.7.1).
• A valve on Multi-Ethernet basis is not suitable as shut-off element according to
category 1 if merely the enable is used without a cyclic evaluation of the enable
acknowledgement. The requirements for the cyclic evaluation must be observed
depending on the specific application.
2.7.3 Residual risks/error states
The following residual risks or error states may occur and must be taken into
account on the system side by providing appropriate measures:
• Complete failure of the electronics of the valve
• Faulty output of operating states
• Failure of the enable inputs or enable acknowledgement outputs
• Delayed reaction to signal changes
• Uncontrolled movement of the valve spool (may lead to uncontrolled movement
of the cylinder, for example)
• Undefined behavior of the electronics of the valve on Multi-Ethernet basis if
signals "enable P-A" or "enable P-B" are provided in the overlap area (5...15 V
according to IEC 61131-2:2008, type 1)
• Difficult level recognition of enable acknowledgement and thus no activation of
the safety function if the enable acknowledgement outputs are not connected to
current sinking inputs according to IEC 61131-2:2008 (types 1, 2 or 3).
• Fuse protection in the case of short-circuits in the electronics of the valve on
Multi-Ethernet basis by means of appropriate protection and design of the supply
line (fuse protection against currents > 4 A).
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