Valve World Americas October 2024 | Page 9

By addressing these top-level considerations , an industrial plant can ensure a safe , compliant , and efficient isolation process .

In industrial settings , isolation levels typically refer to the degree to which equipment , systems , or processes are separated and protected to ensure safety and operational integrity . Different industries might have specific terminologies and standards , but the general levels of isolation include :

1 . Primary Isolation

• Definition : The initial and most immediate form of isolation , typically involving the first barrier or control measure to prevent the flow of hazardous energy or materials .

• Examples : o Valves : Closing a valve to stop the flow of fluids or gases . o Circuit Breakers : Turning off a circuit breaker to cut electrical power .

• Usage : Common in routine maintenance or minor repairs where quick isolation is necessary .

2 . Secondary Isolation

• Definition : Additional isolation measures that provide a second layer of protection , often used in conjunction with primary isolation to enhance safety .

• Examples : o Blanking or Blinding : Physically inserting a blank or blind into a pipeline to ensure no flow . o Double Block and Bleed : Using two isolation valves with a bleed valve in between to ensure complete isolation .

• Usage : Used for more critical maintenance tasks , or when working with hazardous materials where redundancy is important .

3 . Tertiary Isolation

• Definition : Further isolation measures that provide an additional safety layer , often including redundant systems and safety devices .

• Examples : o Isolation of backup systems : Ensuring that even secondary systems are also isolated . o Enhanced containment : Using additional physical barriers or containment areas .

• Usage : Employed in high-risk operations or environments where utmost safety is required , such as chemical plants or nuclear facilities .

4 . Physical Isolation

• Definition : Complete physical separation of equipment or systems , often involving disassembly or removal of components .

• Examples : o Removal of piping sections . o Disconnection of equipment .

• Usage : Utilized during major overhauls , significant repairs , or when equipment needs to be completely taken out of service .

5 . Administrative Isolation

• Definition : Procedural and organizational measures to ensure isolation , often involving documentation , permits , and communication protocols .

• Examples : o Permit-to-Work Systems : Requiring formal permits for isolation tasks .

o Lockout / Tagout ( LOTO ): Ensuring that equipment cannot be re-energized or operated until the work is complete .

• Usage : Essential for managing human factors , ensuring procedural compliance , and maintaining safety culture .

6 . Electronic / Remote Isolation

• Definition : Use of electronic systems to isolate equipment remotely , often involving automated controls and monitoring systems .

• Examples : o SCADA Systems : Supervisory

Control and Data Acquisition systems that allow remote isolation . o Remote Actuated Valves : Valves that can be controlled from a distance via electronic systems .

• Usage : Increasingly common in modern industrial plants for convenience and enhanced control , particularly in large or hazardous environments .

7 . Emergency Isolation

• Definition : Rapid isolation measures designed to be activated in case of an emergency to quickly contain hazards .

• Examples : o Emergency Shutdown Systems

( ESD ): Systems designed to automatically or manually shut down processes in an emergency . o Fire Suppression Systems : Systems that isolate and contain fires or other hazards .

• Usage : Critical in situations where immediate action is required to prevent escalation of an incident .

Each level of isolation serves a specific purpose and is often used in combination to provide a comprehensive safety and control strategy in industrial operations . The appropriate level of isolation depends on the specific risks , operational requirements , and regulatory standards of the industry .

DBB Vs DIB

Originally , double block and bleed was conceived of as pressure responsive valves with a bleed valve in between .

DBB and DIB Valve Types :

Slab gate Yes Yes No

Expanding gate Floating ball No No No

Dual-plate check No No No Swing check No No No Expanding plug Yes Yes Yes Butterfly No No No Triple offset No No No

Our modern conception was transformed by the introduction of the trunnion ball valve .

When dealing with a typical trunnion mounted ball valve design , you can apply two features on seating arrangements :

Self-relieving seat : A valve seat designed to relieve pressure in the valve cavity . Depending on valve type , the pressure may be relieved to the pressure source , or the low-pressure side . Note : In a ball valve this is called a Single Piston Effect ( SPE ) seat .

Non-relieving seat : A valve seat designed to hold pressure in the valve cavity . In this instance an alternative means of pressure relief is required .

Note : In a ball valve this is called a Double Piston Effect ( DPE ) seat .

Double Block and Bleed ( DBB ): A single Valve with two seating surfaces that , in the closed position , provides seal against pressure from both ends of the valve , with a means of venting / bleeding the cavity between the seating surfaces .

Note : This valve does not provide positive double isolation if only one side is under pressure .

Does DBB Provide Isolation : Not Always ! A valve with two SPE seats is considered a block and bleed valve , but if pressure rises in the body cavity the fluid will relieve through the seat with the least resistance , which is the low-pressure side .

Double Isolation and Bleed ( DIB ): A single Valve with two seating surfaces , each in the closed position , provides a seal against pressure from a single source , with a means of venting / bleeding the cavity between the seating surfaces .

Note : This feature can be provided in one direction or in both directions

DIB1 : A DIB valve that has two non-relieving ( DPE ) seats . An external body relief is required in liquid service which is subject to thermal expansion . This valve provides DIB in either one or two directions , depending on the external relief configuration .

DIB2 : A DIB valve with one non-relieving ( DPE ) and one self-relieving ( SPE ) seat . This valve only provides DIB in one direction ( the side with the non-relieving seat is DIB protected )

The Alberta OHS ( occupation health and safety ) regulation calls for section 215.5 “ Isolation requirements for piping or a pipeline ” as below :

215.5 ( 1 ) To isolate piping or a pipeline containing a substance under pressure , an employer must ensure the use of ( a ) a system of blanking or blinding , or ( b ) a double block and bleed isolation system providing ( i ) 2 blocking seals on either side of the isolation point , and ( ii ) an operable bleed-off between the

2 seals .

215.5 ( 2 ) An employer must ensure that piping or a pipeline that is blanked or blinded is clearly marked to indicate that a blank or blind is installed .

215.5 ( 3 ) An employer must ensure that , if valves or similar blocking seals with a bleed-off valve between them are used to isolate piping or a pipeline , the bleedoff valve is secured in the “ OPEN ” position , and the valves or similar blocking seals in the flow lines are functional and secured in the “ CLOSED ” position .

215.5 ( 4 ) An employer must ensure that the device used to secure the valves or seals referred to in subsection ( 3 ) is ( a ) a positive mechanical means of keep ing the valves or seals in the required position , and

www . valve-world-americas . net • October 2024 | Valve World Americas 9