PLANT ISOLATION – DESIGN

Design – This article highlight areas where design has been found to be inadequate when the isolating  plant

Consequences of poor design result in:

1. Human error with the potential for injury, plant damage and catastrophic failure.
2. Extra workload for the plant owner to create isolation plans and coordinate plant shutdowns.
3. Affect productivity via unnecessary down time

Common issues are detailed as follows:

• Isolation devices are not easily accessible.
• HAZAN and review studies have not considered access to isolation points and devices.
• Isolation devices are not able to be secured in an isolated or de-isolated position .
• Piping & Instrumentation Diagrams (P&ID)  and Single Line Diagrams(SLD)  do not use software with the ability to embed and extract isolation device and Plant ID and GPS metadata into and from the drawings
• In Field isolation devices are do not have a combined Alphanumeric and QR Code/Bar Code/NFC  ID label attached to the device.
• Devices ID tags are not easily identifiable and do not have robust physical tag attached to the isolation device which can be easily cleaned  or replaced in the field to show the electronic Code and Alphanumeric ID.
• Isolation devices do not have GPS coordinates embedded as extra metadata in the P&ID and SLD when the plant has been commissioned.
• Isolation device data stored in CAD drawings cannot be associated with the plant SCADA process flow display.
• The QR/Bar/NFC ID tag is not durable and cannot be read via a mobile device such as a field table or phone.
• The Alphanumeric and QR/Bar/NFC Code ID labels for isolation devices are not  embedded in the P&ID and SLD as extractable metadata.
• A task isolation plan for each item of energised  equipment – such as a pump or thickener rake, is not provided as extractable metadata on P&IDs and SLDs and are not integrated to form the Plant Isolation Database.
• Isolation plan database records not provided as part of the project deliverable , such as the name of the plant, name and ID of each isolation device and the order of isolation and de-isolation.
• OEM manual requirements for equipment isolation are not linked to the P&ID and SLD.
• Equipment requiring confined space entry does not have a  minimum of a double block and bleed arrangement on pipelines entering and exiting the confined space.
• HAZOPs fail to  identify and prevent the potential for reverse flow in pipelines, launders and valves.
• HAZOP fails to determine the potential for chemical reactions that may cause emissions of toxic gasses in cells or present flammable and low oxygen hazards in confined spaces.
• The design does not incorporate proof testing ‘ Test for dead” to demonstrate that the mechanical and electrical isolations are effective , such as phase lights and pipeline bleed valves to test for fluid leakage around or through valves.
• Air/Electrically operated valves (Flow control , Dart Valves etc) are not able to be isolated on the input and exit sides to allow physical internal inspection of the valve and housing for condition and wear.
• The air pressure energy source to the valve actuator cannot be mechanically isolated and stored residual air pressure cannot be bled to atmosphere. These valves cannot be physically blocked into position to ensure the valve cannot move during the inspection such as inserting a lockable pin to prevent movement of the valve as part of the mechanical isolations.
• Does not consider equipment which has stored gravitational energy must be blocked to prevent movement – such as thickener rakes, conveyor counterweights and conveyor belts. The design fails to note these requirements and refer to the OEM manuals.
• Notes on equipment which has stored pressure are omitted on the P&ID and are not incorporated into the equipment isolation plan , such as hydraulic accumulators.  
• There is no valve naming convention applied to P&IDs or  recorded in the isolation system database for the plant.
• There is no electrical circuit breaker ID naming convention which can be applied a to SLDs and recorded in the isolation system database for the plant.

Craig Power   FIE Aust CPEng (Risk Engineering),NER.

25/04/2025

Managing Director – iSOL8 Pty Ltd

craig.power@isol8.systems