When you are having a stove installed into an existing fireplace we will nearly always recommend that you have the chimney lined as part of the job. Stoves become so much easier, and cheaper to operate when they are connected to a lined chimney; the liner basically serves as an insulated passage, quickly drawing the flue gases away from the stove. This movement of air keeps the fuel burning efficiently and cleanly - which is just what you, and the stove, want.
Of course in some cases there really isn't any choice. If the chimney walls are cracked, or crumbling, it would have to be lined to prevent flue gases, smoke etc leaking through the walls and into other rooms in the house.
The most common type of liner is one made of flexible stainless steel - either 316 or 904 grade. The 316 is normally sufficient for most installations, although it does have a shorter life expectancy than the more resilient 904 grade. If, however, customers are having a boiler stove installed, or if they think they are likely to 'slumber' a stove (ie. burn at a low temperature for a considerable period of time), particularly when using a smokeless ovoid, we would always recommend they choose the 904 grade, or even consider a different liner system all together.
Boiler stoves, by the nature of their use, are often 'slumbered'; this can cause a build up of un-burnt fuel deposits coating the inside of the liner, which can, over time, eat into the stainless steel. The more resilient the liner is to begin with therefore, the longer it will last.
Likewise, the chemicals in some smokeless ovoids can over time cause a liner to suffer from 'acid erosion'. In fact some liner manufacturers state that their guarantee will become void if petrochemical fuels are burnt on the stove.
All these factors needs to be taken into consideration before final decisions are made on the type and nature of chimney lining. We can guide you through these, and other issues, advising where appropriate.