When working on hazardous equipment it is necessary to make sure that everyone is protected from any potential source of energy that could cause harm, such as electricity, heat, toxic chemicals, high pressures etc. In a typical industrial operation, multiple people might be working on the same processing unit or in the same area, and teams might inadvertently try to start up the equipment being worked on, restart the process or run tests. If this takes place while someone else is working on the same piece of equipment there is a chance of an accident.
To prevent accidents all equipment being worked on needs to be isolated from any potential energy source that could cause harm. As part of the preparation of the area for safe work, isolations are put in place and verified by the responsible persons. Maintenance teams then check the isolations before doing any work. Mechanisms need to be in place to make sure that the isolation is not compromised while work is taking place. Physical locks and keys are typically used for this. During work it might also be necessary to test the equipment for which a temporary removal of isolations is required, and this must be strictly controlled.
At the end of the job the locks are removed before the plant or equipment is restarted. These processes are typically controlled using the permit to work (plant clearance) system.
Types of isolations
Isolations can be of many different types, but in almost all situations isolation is required for maintenance work. Positive isolation means that there is a physical barrier between the source of the hazard or energy and the equipment being worked on. This could be locked out electrical switch gear, slip plates in process piping, removal of connecting lines, disconnecting feeders etc. All of these isolations are temporary in nature and to make sure that they are not compromised while work takes place a lock and key is normally used to prevent anyone tampering with the isolation.
These locks are sometimes grouped together for more complex jobs and all the keys put into a single locked box sometimes referred to as a “key safe”. The master key to the key safe is separately held thereby protecting from anyone inadvertently accessing and unlocking one of the locks.
Lock boxes and keysafes
Sometimes two locks are put onto a single isolation point so that two separate people have to physically unlock the isolation. The key to the one lock might then be held by the person in the field working on the equipment.
There could also be locks on local isolators in the field which might need to be removed temporarily to energise the system for testing.
When work takes place in adjacent areas there are sometimes common isolations applicable to several jobs and it is important to ensure that none of the jobs can put the others at risk by removal of any isolation. Sometimes these jobs are organised as master/slave combinations.
One problem with a lock out system is managing the complexity. It is critical to ensure that every possible source of energy is isolated, and in some situations this could involve dozens of isolations in multiple areas of the plant, each of which needs to be recorded and tagged.
Managing isolations using IntelliPERMIT
IntelliPERMIT features a comprehensive isolation management system and solution integrated into the permit to work. Some of the features of IntelliPERMIT’s isolation management include:
- Preconfigured approved isolation lists that embed and enforce isolation procedures
- Isolation procedures that are linked to equipment type, equipment and/or activity
- Prompting with the relevant isolation lists when preparing a permit
- Automatic printing of weatherproof tags used to identify isolations, locks or keysafes.
- Isolations can be verfied and confirmed in the field using mobile devices
- Management of lock boxes and dependencies between master and slave permits with the associated isolation lists
- Extensive isolation cross referencing between permits, master permits, templates and adjacent permits
Used daily in the most demanding environments
There is no environment more demanding in terms of safety than a nuclear power station. IntelliPERMIT software is used to manage isolations for maintenance work at the Koeberg power station near Cape Town in South Africa. The high integrity of the system is relied on to make sure all maintenance work on process equipment and electrical installations conforms to procedures and the requirements of the nuclear regulator.
IntelliPERMIT isolation management is used extensively in energy, process manufacturing and mining sectors. In many situations the isolation management is the main focus of the permit process. The system manages isolations from the simplest to the most complex situations involving master/slave permits, lock boxes and key safes and tagging.
In this overview, we will take a look at some of the principles around managing isolations during maintenance. Isolations are a critical precaution when working on energised plant and equipment.
Is it possible to use IntelliPERMIT in combination with a DCS or PLC to manage isolations using software only? Read more about software assisted isolations.
During maintenance it is important to take every possible precaution to avoid loss or harm. One important precaution is to isolate all the equipment being worked on from uncontrolled energy sources. Positive isolation should be used where possible and controlled by a system of locks managed by the permit to work.