Is it permissible to shorten the prayer for an engineer working on a project 230 km away from his place of residence for a period ranging between 3 and 9 months?

It is sunnah for you to shorten the four-rak'ah prayers (qasr) and combine the prayers that share a time (jama') when you travel to your workplace after passing all the houses of your village. The ruling of qasr ends when you return to the beginning of these houses, or by intending to reside in another place for four days or more. If you stay at your workplace for three to nine months, you are not entitled to shorten or combine prayers. However, if you reside for less than four days, you are still permitted to shorten and combine prayers.