A locomotive boiler with a wide firebox may have arch tubes or thermic syphons. A large boiler with a Belpaire firebox and long combustion chamber was fitted. A mechanical stoker is a device which feeds coal into the firebox of a boiler. The stays support and separate the outer boiler and inner firebox. The new boiler will be of traditional construction with a copper firebox. The new boiler would be of traditional construction with a copper firebox. Many use solid diffuser plates between the firebox and grill to provide even temperature distributions. Lead fusible plugs may be present in the crown of the boiler's firebox. There were three instances of firebox crown collapse, resulting in boiler explosions. In the case of a firebox explosion, these typically occur after a burner flameout. It was superheated, with a Belpaire firebox, Walschaerts valve gear and plate frame. Four syphons were fitted, three in the firebox proper and one in the combustion chamber. The engine was fitted with a large Wootten firebox. It also enabled the incorporation of a wide firebox for burning poor-quality coal. Conversion was done by relocating the frame stretcher immediately in front of the firebox.