Transport for Brisbane Observations 2019

[TLK]

So why the need to withdraw the older ones early when they still have a good 6-8yrs of service left?

[Merc1107]

Aside from the fact BT enjoy boasting about the nation's youngest fleet of buses, and so replace buses at a younger age than most areas, the CNG tanks in gas buses only have a finite lifespan before they MUST be replaced. This may not be practical if the buses aren't expected to remain in service long enough to justify the cost (CNG cylinders are expensive due to the pressures they must withstand).

The life of the tank is determined by its manufacturer, who stamp an expiry date on the CNG cylinders; past that date the tank is legally unserviceable. The manufacturer determines the expiration date - some tanks remain serviceable for over 20 years (e.g. up to 30yrs is possible/permissible in the USA), others don't, presumably due to how they're constructed.
I'm not sure what (if any) domestic legislation might affect how long a CNG cylinder may be used for.

[BT Enthusiast]

Anyways MAN 18310 buses are not compliment with the new CNG bus standards, so BT may have wanted to remove them earlier...

[Merc1107]

Anyways MAN 18310 buses are not compliment with the new CNG bus standards, so BT may have wanted to remove them earlier...

What standards are they? Doesn't seem to be affecting Perth's withdrawal rate of similarly-aged units.

[BT Enthusiast]

I'm not sure, but they do have a sign stating 'Non Compliance' with the CNG standard. Although I don't think this is affecting their withdrawal

[TLK]

So would the Scanias being withdrawn early (mainly in regards to the younger ones) be because of the CNG compliance? Or something completely different?

[Merc1107]

A Brisbanite would have to answer that question; but I doubt a CNG bus that presumably could've remained serviceable for near-on 20yrs would be withdrawn just halfway through its life without a very good reason.