Ex d Barrier Gland Termination and Fit off
AS/NZS 60079.14 is the standard that the specifies the installation requirements for Ex d barrier glands. AS/NZS 60079.14 provides details on the following installation requirements for Ex d Barrier glands:
- The use of sealing washers,
- The use of suitable greases,
- Thread engagement,
- Tightness of tapered threads,
- The use of adapters,
- Requirements for glands to only be able to be dismantled by a tool after installation,
- Cable routing to prevent excess tension on the seal around the cable,
- Coldflow characteristics
Management of Screened Cable Drain Wires
One common item that often requires specific guidance and clarification is the management of the drain wires on screened cables when an Ex d barrier gland is used as the cable entry device. Historically in Australia the uncertainty around the correct management of drain wires when using barrier glands has led to large and costly reworks on a number of packages.
Concerns are regularly raised about the possibility of any coverings used on the drain wire to insulate it, also acting as a gas migration or flame propagation pathway. The result is that many installers and inspectors have then made their own conclusions about how to manage a drain wire, the practices range from:
- Any covering on the drain wire must stop before entering the resin,
- Heat shrink can be taken 2mm into the resin to ensure 20mm of continuous coverage to the cable break out,
- Heat shrink in the resin or putty isn’t an issue as long as the heat shrink is tight fitting on the drain wire,
The reality is that the different drain wire management techniques are not taken from prescriptive parts of standards, rather they are derived and interpreted from a range of assumptions and interpretations. This leads to inconsistencies and errors. This is where the gland manufacturer comes into play, as stated previously both AS/3000 and AS/NZS 60079.14 require hazardous area electrical equipment to be fit off as per the manufacturer’s instructions.
For this reason, if the gland manufacturer’s instructions do not provide clear and specific details on the management of drain wires in Ex d barrier glands additional clarification from a technical representative from the gland manufacturer must be sought prior to installation.
Lithium Oil and Gas has over the years reached out to technical representatives of many major gland manufactures and they have all been willing to provide clear documented instructions on the correct way to terminate drain wires on their barrier glands without invalidating the certification of the gland.
Key Points to Remember
AS/NZS 60079.14 provides details on many installation requirements for Ex d barrier glands that must be followed,