Abstract: At approximately 1:00 p.m. on April 3, 2013, Employee #1, a 25-year-old male with Chevron Refinery was working on the first deck of the FCC unit at Chevron Refinery in El Segundo, California. Employee #1 attempted to manually test the two limit switches located near the stroke limit stop inside the FCC Regent slide valve housing. Employee #1 reached up with his arms from the underside of the Regent slide valve housing to get to the two limit switches located inside the Regent slide valve housing. The underside of the Regent FCC slide valve housing was not guarded. As Employee #1 touched the two limit switches with his left and right hands, the Regent slide valve suddenly moved to shut. Employee #1 could not get his right hand out of the slide valve housing in time before his right hand was pinched between the slide valve stroke limit stop and the slide valve split nut assembly when the slide valve moved to close. The FCC slide valve was pressurized and was not de-energized at the time of the incident. Multiple bones in Employee #1's right hand were broken. The manufacturer of the Regent Slide valve was MEA, model number 2-6.4K-36, serial number 1135/8603. The approximate dimensions of the split nut assembly housing external to the FCC was 8 ft. long, 3 ft. wide and 2 ft. high and stands about 4 ft. off the deck floor. Employee #1 was a full time employee of Chevron. The incident was caused due to the fact that the Regent slide valve was not de-pressurized or blocked out by the employer. Employee #1's contact with the limit switches caused the Regent FCC slide valve to go into a safe mode which in turn caused the slide valve to move. Employee #1's right hand was injured from being pinched between the slide valve split nut assembly and the slide valve stroke limit stop. Chevron Refinery refines crude oil into different petroleum products.