Shut down valve
Encyclopedia
A shut down valve is an actuated
valve
designed to stop the flow of a hazarous fluid upon the detection of a dangerous event. This provides protection against possible harm to people, equipment or the environment.
Shutdown valves form part of a Safety instrumented system
. The process of providing automated safety protection upon the detection of a hazardous event is called Functional Safety
Shutdown valves are primarily associated with the petroleum industry
although other industries may also require this type of protection system
s are used as shut-down valves (SDV's). Use of metal
seated ball valves leads to overall lower costs when taking into account lost production and inventory
, and valve repair costs resulting from the use of soft seated ball valves which have a lower initial cost.
Straight-through flow valves, such as rotary-shaft ball valves, are typically high-recovery valves. High recovery valves are valves that lose little energy due to little flow turbulence
. Flow paths are straight through. Rotary control valves, butterfly valve
and ball valves are good example
type. Typical examples of these are:
In addition to the fluid type actuators also vary in the manner in which the energy is stored to operate the valve on demand as follows
The type of actuation required depends upon the application, site facilities and also the physical space available although the majority of actuators used for shutdown valves are of the spring return type due to the fail safe nature of spring return systems
(SIL). In order to adhere to this level of performance it is necessary to test the valve. There are 2 types of testing methods available being
Actuator
An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...
designed to stop the flow of a hazarous fluid upon the detection of a dangerous event. This provides protection against possible harm to people, equipment or the environment.
Shutdown valves form part of a Safety instrumented system
Safety instrumented system
A Safety Instrumented System is a form of process control usually implemented in industrial processes, such as those of a factory or an oil refinery. The SIS performs specified functions to achieve or maintain a safe state of the process when unacceptable or dangerous process conditions are detected...
. The process of providing automated safety protection upon the detection of a hazardous event is called Functional Safety
Functional Safety
Functional Safety is the part of the overall safety of a system or piece of equipment that depends on the system or equipment operating correctly in response to its inputs, including the safe management of likely operator errors, hardware failures and environmental changes.- Objective of Functional...
Shutdown valves are primarily associated with the petroleum industry
Petroleum industry
The petroleum industry includes the global processes of exploration, extraction, refining, transporting , and marketing petroleum products. The largest volume products of the industry are fuel oil and gasoline...
although other industries may also require this type of protection system
Types of valve
Metal seated ball valveBall valve
A ball valve is a valve with a spherical disc, the part of the valve which controls the flow through it. The sphere has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends...
s are used as shut-down valves (SDV's). Use of metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
seated ball valves leads to overall lower costs when taking into account lost production and inventory
Inventory
Inventory means a list compiled for some formal purpose, such as the details of an estate going to probate, or the contents of a house let furnished. This remains the prime meaning in British English...
, and valve repair costs resulting from the use of soft seated ball valves which have a lower initial cost.
Straight-through flow valves, such as rotary-shaft ball valves, are typically high-recovery valves. High recovery valves are valves that lose little energy due to little flow turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
. Flow paths are straight through. Rotary control valves, butterfly valve
Butterfly valve
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve...
and ball valves are good example
Types of actuation
As shutdown valves are form part of a SIS it is necessary to operate the valve by means of an actuator. These actuators are normally fail safe fluid powerFluid power
Fluid power is the use of fluids under pressure to generate, control, and transmit power. Fluid power is subdivided into hydraulics using a liquid such as mineral oil or water, and pneumatics using a gas such as air or other gases...
type. Typical examples of these are:
- Pneumatic cylinderPneumatic cylinderPneumatic cylinders are mechanical devices which utilize the power of compressed gas to produce a force in a reciprocating linear motion....
- Hydraulic cylinderHydraulic cylinderA Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...
- Electro-hydraulic actuator
In addition to the fluid type actuators also vary in the manner in which the energy is stored to operate the valve on demand as follows
- single-acting cylinderSingle-acting cylinderA single-acting cylinder in a reciprocating engine is a cylinder in which the working fluid acts on one side of the piston only. This is in contrast to a double-acting cylinder, in which the working fluid acts alternately in both directions...
- Or spring return where the energy is stored by means of a compressed spring - double-acting cylinderDouble-acting cylinderA double-acting cylinder in a reciprocating engine is a cylinder in which the working fluid acts alternately on both sides of the piston. This is in contrast to a single-acting cylinder, in which the working fluid acts in one direction only....
- Energy is stored using a volume of compressed fluid
The type of actuation required depends upon the application, site facilities and also the physical space available although the majority of actuators used for shutdown valves are of the spring return type due to the fail safe nature of spring return systems
Measuring performance
For shutdown valves used in safety instrumented systems it is essential to know that the valve is capable of providing the required level of safety performance and that the valve will operate on demand. The required level of performance is dicated by the Safety integrity levelSafety Integrity Level
Safety Integrity Level is defined as a relative level of risk-reduction provided by a safety function, or to specify a target level of risk reduction. In simple terms, SIL is a measurement of performance required for a Safety Instrumented Function ....
(SIL). In order to adhere to this level of performance it is necessary to test the valve. There are 2 types of testing methods available being
- Proof test - A manual test that that allows the operator to determine whether the valve is in the "as good as new" condition by testing for all possible failure modes and requires a plant shutdown
- Diagnostic Teset - An automated on-line test that will detect a percentage of the possible failrue modes of the shudown valve. An example of this for a shutdown valve would be a partial stroke testPartial stroke testing' is a technique used in a safety instrumented system to allow the user to test a percentage of the possible failure modes of a shut down valve without the need to physically close the valve.-Standards:...
See also
- Buckling Pin ESV
- DynaTorque D-Stop Partial Stroke Test Device
- Rotork Smart Valve Monitor
- ActuatorActuatorAn actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
- Pipeline transportPipeline transportPipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....
- PipingPipingWithin industry, piping is a system of pipes used to convey fluids from one location to another. The engineering discipline of piping design studies the efficient transport of fluid....
- Unit operationUnit operationIn chemical engineering and related fields, a unit operation is a basic step in a process.Unit operation involves bringing a physical change such as separation, crystallization, evaporation, filtration etc.. For example in milk processing, homogenization, pasteurization, chilling, and packaging are...
- valves