In the blast furnace casing is a hole via which a lance probe can be driven horizontally into and out of the furnace. The hole is aligned with an outer, water cooled tube, which is provided with a valve so gas cannot escape from the furnace. A set of rolls is used to straighten lance when the latter is driven by a trolley towards hole via a gas seal. A rotary saw is pref. located near valve, so a lance which has become bent in the furnace can be cut to simplify its extn. The front end of the lance pref. forms a cavity via which a sample of solid material can be obtd. from the charge in the furnace. For example, when a tubular lance with length 14 m is used for a furnace with internal vol. 5000 cu.m.
