The horse head was not fully secured to the walking beam because the safety bar was incorrectly installed and did not pass through all required slots. Verification of the horse head installation relied on assumption and visual confirmation was inadequate to identify the unsafe condition. The hazard associated with horse head installation and potential structural failure was not adequately identified in the risk assessment and work planning process. Personnel were working within the potential dropped-object and line-of-fire zone during commissioning activities. Communication between work groups was ineffective, and personnel were not alerted before movement of the beam pump system was initiated. Management of Change was not applied when a different beam pump design was introduced, and the change-related risks were not adequately assessed.