Locked Open / Locked Closed ValvesToolbox talk 6: Supervisor’s instructions

ASSET INTEGRITY

MAJOR HAZARDS AWARENESS

This toolbox talk is designed to:

• Help your team understand the significance of a locked valve and why it is locked

• Inform your team of the importance of following procedure when changing the position of a locked valve

• Identify likely areas where locked valves might be encountered on a facility

Carry out this toolbox talk before commencing a new task/job involving a change in status of a Locked Open or Locked Closed valve.

It is best to complete this talk in small groups – maximum ten people. Additional information and training may be required at the discretion of local management.

1) Give a copy of the Group Sheet to your group.

2) Using the flow chart given below discuss the process that must be followed to change (and reinstate) the status of a locked open / locked closed valve. Ask the Group to identify who is the responsible person for each of the stages in the process by marking or colouring the boxes as applicable.

3) Ask the Group to study the diagrams on the Group Sheet showing the various classifications of LO/LC valve types. Ask the Group to identify the hazard that might arise if they move the valve from its status designated in the LO/LC Register without applying suitable controls or mitigation.

4) Use the diagrams on the Group Sheet to discuss the mitigations/controls that should be put in place prior to moving the position of the LO/LC valves in each case.

5) At the end of the Toolbox Talk, provide the Group with their own copy of the Supervisors Sheet for them to keep as a reference; ‘Know the Process, Know the controls’.

6) Ask what the team should do if they become aware of any improperly locked valves or broken locks (first step would be to report them to their supervisor).

No

No

YesYes

Start

Key

Request approval to change valve status

Con�rm classi�cation

Approve de-isolation

Authorise and sign LOLC register and issue keys

Identify Mitigation and controls needed

Sign LOLC register activities complete -valve returned to normal status

Apply Mitigation and Controls

Apply Isolation TAG to valve

Move valveUpdate tags with status change

Remote PA con�rms to Authorising Authority Valve returned to normal position and tags updated

Update tags with status change

Complete Task

Performing Authority

AuthorisingPerson

Return valve to normal position

Part of IsolationCerti�cate

Part of IsolationCerti�cate

Remote PA con�rms to Authorising Authority controls in place

LO/LC valves – Flow chart of approval process

AnswersToolbox talk 6: Supervisor’s instructions

PSV

LO

LO

LC

LC

LO

Flare/Vent

Blow down valve NC

LO

Vent/ �are/ LP system

LO

PCV

LP system/drains

LCV

Atmospheric Vent LO Spec

Break

Spec Break

Spec Break

LO

Vent/ �are/ LP system

LC LP system/drains

Atmospheric Vent

LC

LO

Source ofpressure/�uids

Type A 5 Manual isolation from vent, atmosphere or drains

4

?

? ? ?Type A 1 & 2 Single PSV with Isolation Valves

Type A 3 Blow down valve with Isolation Valve(s)

Type A 4 Pressure/ Level Control Valve with Isolation Valve(s) and atmospheric vent

1 2 3

MAJOR HAZARDS AWARENESS

Hazard: There is a risk of loss of containment if an over pressure event occurs and the PSV is isolated from the system under pressure.

Mitigation: The system being protected should be isolated and depressured before changing from LO to LC.

Hazard: If the BDV is isolated when the system is pressurised it will not be possible to depressurise the system in an emergency. This could lead to overpressure and loss of containment in a fire event.

Mitigation: The system being protected should be isolated and depressurised before changing from LO to LC.

Hazard: If the PCV/LCV is isolated when the system is pressurised there is a risk of loss of containment if an over pressure / overfill event occurs.

Mitigation: The system being protected should be isolated and depressured before changing from LO to LC.

Hazard: If a LC manual valve is opened when the system is pressurised there is a risk of loss of containment and uncontrolled discharge of gas, hydrocarbons or toxic fluids.

Mitigation: The system to be depressurised / drained should be isolated from the pressure source before changing from LC to LO.

Hazard: If manual valves are closed safety critical devices will not function.

Mitigation: Over-ride process to be used with risk assessment. The downstream primary SCE to be fully functional keeping at least 1 barrier in place.

Hazard: If purge valves are closed there is a risk that air will enter the vent allowing an explosive atmosphere to develop inside the vent system with a risk of internal explosion. If the pilot gas valves are closed there is a risk of flare flame-out resulting in (potentially toxic) process streams being vented to atmosphere.

Mitigation: If no pilot gas; facility shutdown or alternative flare ignition method in place. If no purge gas; facility shutdown if no alternative purge system available.

LT

LO

Corrosion monitoring

Air/Hydraulics

Fiscal/critical metering &,

Analysers

HIPS / ESDTrip functiontransmitter

LoLo/ Hi HiPressure trips

PT LO

ESDV

LO

LO

LO

LO

LO

LoLo/ Hi Hi Level trips

LO

Type B Control of Safety Critical Instruments and High Integrity Protection Devices (HIPS)

5

?

Purge Gassupply intovent/ areheader

Vent/Flare HeaderPilot gas supply

LO LO

To Vent/Flare StackTo Flare Pilot

Vent/Flare KO Drum

Type C 1 Protection against ingress of air/ gas into a system/ Equipment / flare purge systems

6

?

MAJOR HAZARDS AWARENESS

Plant/ Equipment

ESD LC

LC

LC LC

LC

Off Spec �uid

Spec Break

High H2S Stream

Nace piping

Non-Nace piping

LC

LCV/ PCV

LC

LO

LO

LT Spec

LT Spec HT Spec

HT Spec LC

Spec Break

LC

Spec Break

Spec Break

Chemical Storage

LO

LO

LO

FT PT

LO LO

Type D 1, 2 Protection of Downstream Facilities against adverse conditions

Type E 1, 2 Isolation valves preventing off spec fluids reaching downstream facilities

Type D 3, 4, 6 Protection of downstream facilities against adverse conditions

Type E 3 Protection of Downstream Facilities Protected by Chemical Injection

8

11

9

12

Air or Inert Purge gas

Pressurised instrument cabinet

LO

PSV PSV

LO LO

LO LC INTERLOCK

Type C 2 Protection against ingress of gas into a Pressurised instrument cabinets

Type D 5 Protection against adverse downstream conditions – dual PSVs

7

10

?

?

?

?

?

?

Hazard: If purge valves are closed and flammable gas enters the cabinet there is a risk of an internal explosion in the cabinet.

Mitigation: Gas checks negative, power isolated, Facility should be shutdown if no alternative purge system is available and the instrument cabinet is in a classified area.

Hazard: Loss of control of volumes/pressure can occur when by-passes/ start up lines are left open.

Mitigation: Adherence to procedure and isolation standards. (does not apply to automatic start up facilities and by passes controlled by PLC).

Hazard: Open by passes have the potential to increase flow / pressure on downstream equipment and lead to loss of containment. Exposure of downstream systems to temperature extremes may cause low temperature embrittlement, or weakened material due to high temperatures.

Mitigation: Correct engineering design. Specified Safe Operating Envelope limits. Compliance with procedures. Valves should only be opened when temperatures have normalised.

Hazard: There is a risk of loss of containment if an over pressure event occurs and both PSVs are isolated from the system under pressure.

Mitigation: Interlock procedure used to ensure one PSV is on line at all times.

Hazard: Open valves would allow high H2S stream to enter a non-Nace spec piping/ equipment with potential for failure of equipment. Open valves would allow off-spec fluid to mix with on-spec fluids with potential for scale formation, napthenates or off-spec product. Mitigation: There are no circumstances where high H2S should be allowed to enter non-Nace facilities. Specified Safe Operating Envelope limits should be applied. Off-spec fluid should only be allowed to mix with on-spec fluids where appropriate procedures and mitigations are in place.

Hazard: Loss of protective chemicals (e.g. corrosion inhibitor) can lead to adverse downstream conditions and a risk of loss of integrity.

Mitigation: Adherence to procedure and isolation standards. Apply Management of Change (MOC) procedures if changes required.

AnswersToolbox talk 6: Supervisor’s instructions