What is the ruling on unintentionally damaging something at work and recording it as used to prevent harm to colleagues, and is expiation due upon me?

If something is damaged due to negligence or transgression, you are liable for compensation. If you fear harming your colleagues by informing the management, you can provide a replacement or refund its value to your employer. If you are unable to do so, then increase your good deeds, seek Allah's forgiveness, and turn to Him to relieve you of this burden on the Day of Judgment. As Al-Ghazali said, if a sin involves money, it must be returned if possible. If you are unable, then seek forgiveness from the person concerned. If that is impossible due to their absence or death, then give charity on their behalf. Otherwise, you must increase your good deeds and humbly implore Allah to make them pleased with you on the Day of Judgment.