The phrase "an hour to replace" is correct and usable in written English.
It can be used when discussing the time required to substitute or change something, often in a context related to repairs or maintenance.
Example: "The technician estimated that it would take an hour to replace the faulty part in the machine."
Alternatives: "one hour for replacement" or "an hour for the swap".
The race continued, although it was slowed for nearly an hour to replace the guardrail at the impact site.
In the darkness, working under the lamps on their helmets, Peake and Kopra had half an hour to replace the failed unit with a new one before the sun rose and sent high voltage electricity surging through the fresh box of electronics.
It took a surgeon at the Wills Eye Institute in Philadelphia about an hour to replace one lens with the implant, called CentraSight, from VisionCare Ophthalmic Technologies Inc. (Because the implant causes loss of peripheral vision in the eye it's placed, there's only one implant, allowing the patient to retain peripheral vision in the other eye).
Farmers, which signed on for one year with an option, jumped in at the 11th hour to replace Buick, which had sponsored the tournament since 1992.
In 1922, Rebecca L. Felton of Georgia served a mere 24 hours to replace a dead member, and from then on, women accounted for just one or two members — at times none at all — until 1993.
Rick Mastracchio and Mike Hopkins completed a spacewalk of 7.5 hours to replace the faulty ammonia pump.
Most surgeons take one to two hours to replace a knee, but this doctor routinely completes the procedure in 20 minutes.
A team of doctors at Memorial Sloan-Kettering Cancer Center in Manhattan needed 10 hours to replace 20 years of plates and screws and staples.
The tubes lasted for about 50,000 to 100,000 X rays and took about four hours to replace.
The report has promoted renewed calls for the minimum wage of £5.93 an hour to be replaced by a national "living wage" of £7.50 per hour.
Stuart McCall had to do something if the Fir Park men were to leapfrog Aberdeen in the table, and with a quarter of an hour to go he gambled - replacing centre-back Stephen McManus with James McFadden.
