▁fed ▁to ▁the ▁LP ▁super he ater , ▁and ▁then ▁the ▁LP ▁cyl inder . ▁The ▁LP ▁exhaust ▁fed ▁the ▁bl ast pipe ▁in ▁the ▁smoke box . ▁The ▁H P ▁exhaust ▁cond ensed ▁in ▁the ▁LP ▁bo iler ▁he ating ▁tub es ▁was ▁p ump ed ▁back ▁to ▁the ▁H P ▁steam ▁generator . ▁It ▁was ▁a ▁complex ▁system . ▁ ▁Example ▁The ▁only ▁locomot ive ▁built ▁using ▁this ▁system ▁was ▁the ▁German ▁DR G ▁H ▁ 0 2 ▁ 1 0 0 1 ▁of ▁ 1 9 3 0 . ▁It ▁was ▁not ▁a ▁success , ▁being ▁hop eless ly ▁un re li able . ▁ ▁The ▁straightforward ▁approach ▁ ▁Fire - t ube ▁bo iler ▁The ▁Bald win ▁ 6 0 0 0 0 ▁prototype ▁worked ▁at ▁a ▁mod est ▁ ▁and ▁did ▁not ▁use ▁either ▁of ▁the ▁complex ▁systems ▁described ▁above . ▁It ▁had ▁a ▁relatively ▁conventional ▁wat ert ube ▁fire box ▁and ▁a ▁fire t ube ▁bo iler . ▁Nevertheless , ▁high ▁maintenance ▁costs ▁and ▁poor ▁reli ability ▁more ▁than ▁cancel led ▁the ▁fuel ▁econom ies ▁promised ▁by ▁high - press ure ▁and ▁comp ounding , ▁and ▁the ▁design ▁was ▁not ▁repeated . ▁Other ▁relatively ▁conventional ▁high - press ure ▁locomot ives ▁were ▁built ▁in ▁the ▁USA , ▁including ▁the ▁remarkable ▁triple - exp ansion ▁L ▁F ▁L ore e ▁locomot ive ▁of ▁ 1 9 3 3 . ▁None ▁was ▁successful . ▁ ▁Water - t ube ▁bo iler ▁In ▁Great ▁Britain , ▁the ▁L NER ▁Class