GuaRdboX
–
SIL
1
Eisenbau s.r.l. a socio unico
Via T.A:Edison, 16 20090 Cusago (MI) Italy
Phone: +390293562116 Fax: +390293567735
Guardbox production unit: Via XXIV Maggio, 13
25017 – Sedena di Lonato (BS)
Phone: +390309131240 Fax: +390309130946
www.eisenbau.it
www.guardbox-ex.com
Safety Manual for limit switch boxes series GP, GI and GD
SIL-SM-GBX_EN
rev.2
Table of Contents
0
Introduction ...............................................................................................................................................................................1
1
Functional specification .................................................................................................................................................1
2
Configuration of the product................................................................................................................................. 2
3
Constraints of use ............................................................................................................................................................ 6
4
Failure modes and estimated failure rates .............................................................................................8
5
Periodic tests .......................................................................................................................................................................... 9
6
Periodic maintenance ....................................................................................................................................................... 9
7
Hardware fault tolerance ...................................................................................................................................... 9
8
Classification.......................................................................................................................................................................... 9
9
Mean repair time ................................................................................................................................................................... 9
10
Systematic Capability ................................................................................................................................................ 9
11
Troubleshooting ............................................................................................................................................................ 10
12
Certificate of conformity ....................................................................................................................................... 11
0
Introduction
Purpose of this Safety Manual, written in compliance with IEC 61508-2, Annex D, is to give all the necessary information to
the system integrator for a correct use of the product in Safety Instrumented Systems for SIL classified applications.
This Safety manual is related to limit switch boxes series GI, GD and GP and in particular to the models containing the types
of contacts indicated in the table shown on the product Conformity Certificate.
1
Functional specification
Guardbox Limit switch boxes are electromechanical devices ideal for monitoring the remote operation of industrial valves in
plants, designed and manufactured for demanding applications in extreme environments and where there are requested high
standards for safety and reliability products. The Guardbox devices are used to control the position of the valve and provide
high accuracy electrical feedback signal of valve status to plant control systems. Guardbox limit switch boxes are built to be
installed on valves or actuators which drive the process valves from closed to open position (Normal acting) or from open to
closed position (Reverse acting).
Normal acting
is considered full CW when the process valve is closed and CCW when the
process valve is open.
Reverse acting
is full CW when the process valve is open and CCW when the process valve is
closed. The Figure 1 below shows a valve on which other parts are mounted via bracket and coupling elements to provide
the desired valve control function such as the actuator, the electrical solenoid and the limit switch box in its different contact
configurations. The Limit switch box when used with Safety Function shall give an electrical signal when:
a)
the actuator starts to drive the emergency valve to its safe position, or
b)
the actuator reaches the safe position
The choice of the Safety Function is responsibility of the system integrator.
note !:
In both cases, the Safety Function shall correspond to the situation in which the switches pass from
“operating
position
” to “released position”, i.e., the Limit Switch Box, when used with Safety Function, shall work in “De-Energize-To-
Trip
” mode, and shall be configured in that way to perform the Safety Function.
The above Safety Function is realized when the cam arrives on the activation point of the sensor causing the contact
switching.
To guarantee the
“De-Energize-To-Trip” operation, the customer connection shall be made on the NO contact/s.
The Limit Switch Box is intended to be a part of a Safety Instrumented System as defined per IEC 61508 and the achieved
SIL of the designed function must be verified by the system integrator.
