Yes that is the correct way to spell "ordnance" but I wasn't sure if the "Ordiance Steel Works" was a mis-spelling by the writer (Grace) or if that's was the official company name spelling???.......most likely a mis-spelling
1901 Of Cyclops Works, Saville Street, Saville Street East and Carlisle Street East and Ordinance Steel Works, Grimesthorpe; and Yorkshire Iron and Steel works, Penistone and Derwent blast furnaces, iron and steel works, Workington; Solway Iron Works, Maryport and Old and New Oaks collieries, Barnsley were boiler and ship plate manufacturers