Franz Krull Sk class

{{Short description|Locomotive class manufactured in Estonia}}

{{Infobox locomotive

| powertype = Steam

| name = Franz Krull Sk class

| image = Mõisaküla depoo.jpg

| caption = Sk-154

| designer = A. Borsig works, Berlin, Germany

| builder = AS Franz Krull, Tallinn, Estonia

| builddate = 1931-1940

| totalproduction = 16

| whytetype = 2-8-0

| uicclass = 1′D h2

| gauge = {{track gauge|750mm}} narrow gauge

| leadingdiameter =

| driverdiameter = {{convert|900|mm|ftin|frac=8|abbr=on}}

| length =

| locoweight =

| tenderweight =

| locotenderweight =

| axleload =

| fueltype = Oil shale

| tendertype =

| fuelcap = 8 tons

| watercap = 6 tons

| firearea =

| cylindercount = Two

| cylindersize = {{convert|380|x|450|mm|in|frac=16|abbr=on}}

| boilerpressure = {{convert|13|atm|MPa psi|sigfig=3|abbr=on}}

| tractiveeffort =

| operator = Estonian Railways

| locale =

| powerclass =

| axleloadclass =

| withdrawndate =

| disposition = All scrapped, none preserved

}}

The Franz Krull Sk-class is a class of steam locomotive built by the Franz Krull metal works of Tallinn, Estonia between 1931-1940.{{cite web |title=KITSARÖÖPMELINE AURUVEDUR Sk |url=http://est-train.ertas.eu/kv/sk.php?lng=est |website=est-train.ertas.eu |access-date=19 January 2022}}

The Sk were narrow-gauged and used oil shale as fuel, since it is the primary energy source in Estonia. A total of 16 units were produced, of which none has survived. The last Sk, Sk-156, was scrapped in 1980 in Beloretsk, Russia, where it was actively used until scrapping.