4
Valtek ShearStream SB Ball Valves VLENDS4152-00-A4 05/15
PVST
Partial Valve Stroke Test.
SFF
Safe Failure Fraction - fraction of the overall random failure rate of a device that results in
either a safe failure or a detected dangerous failure
SIF
Safety Instrumented Function - safety function with a specified SIL which is necessary to
achieve functional safety. Typically a set of equipment intended to reduce the risk due to a
specified hazard (a safety loop).
SIL
Safety Integrity Level - discrete level (one out of four) for specifying the safety integrity
requirements of the safety instrumented functions to be allocated to the safety instrumented
systems. SIL 4 has the highest level of safety integrity; SIL 1 has the lowest.
SIS
Safety Instrumented System - instrumented system used to implement on or more safety
instrumented functions. An SIS is composed of any combination of sensor(s), logic
solver(s), and final element(s).
1.4
Product Support & Service
Please refer to the contact information on the back cover of this document.
1.5
Related Documents
Hardware documents:
VLENTB4152, Shearstream SB Ball Valve Datasheet
Fi41.51, Maintenance and installation instructions
Guidelines/References:
FMEDA report NAF – 14/05-134 R003
1.6
Reference standards
IEC 61508-2: 2010, Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems
IEC 60654-1:1993-02, second edition, Industrial-process measurement and control equipment – Operating conditions –
Part 1: Climatic condition.
2
Shearstream SB Ball Valve Description
The Shearstream SB Ball Valve series consists of a single piece body housing and a V-port ball sector. The ball sector has
top and bottom bearings for low operating torque, so that low-torque actuators can be used. The standard Stellite seat
can easily be converted to PTFE after turning the ball sector by 180 degrees, without the need to dismantle the valve
The Shearstream SB Ball Valve is supplied as standard in stainless steel and is also available in other materials, such as,
CG8M, Titanium, etc. The valves are available in sizes from DN25 to DN500 (1 inch to 20 inch) in PN10 to PN40 and ANSI
pressure classes 150-300. Flanged versions are available over the full size range and wafer versions up to DN 200.
3
Designing a SIF Using the Shearstream Sb Ball Valve
3.1
Safety Function
The safety function for the valve and the additional components in the subsystem is to move the valve to the safe position
(which can be either open or closed as required by the application) within the specified safety time when the system is
tripped.
3.2
Environmental limits
The designer of the SIF must check that the product is rated for use within the expected environmental limits, maximum
working pressure and temperature. Refer to the Shearstream SB Ball Valve datasheet for this information.
