Welford was an engineer aboard the deep space mining vessel DSMO Marion. He was serving on the ship above LV-178 in 2159 when the miners on the planet below stumbled upon a large number of Xenomorphs deep underground in the mines. The incident eventually led to the destruction of the Marion and the loss of all but one of its crew.
Welford was killed when the Marion crew were forced to confront several Xenomorphs on the docked shuttle Samson in order to retake the vessel for their own needs.
As well as being an engineer aboard the Marion, Welford also occupied himself with developing new technologies to allow the miners on the planet below to more easily recover the trimonite they were excavating. One concept he was investigating was the use of powerful hydrofluoric acid to dissolve the sands and shales in which the small deposits of trimonite ore were found, leaving the trimonite itself unaffected due to its resistance. To this end, Welford constructed several spray guns to deliver the acid, but safety concerns meant they had yet to be put into practice. The survivors of the Marion would later arm themselves with the spray guns against the Xenomorphs.
During the disaster
Following the disastrous collision between the Delilah and the Marion, Welford accompanied Hoop and Sneddon to the Marion's docking bay area to survey the damage. While there, they depressurized the airlock in docking bay four, where the Samson had docked, in an attempt to contain the Xenomorphs on board, before also sealing and deactivating several bulkheads leading into the bay, placing further obstacles in the creatures' path should they escape the shuttle. Later, Welford assisted Hoop and Powell on a space walk to cut free wreckage from the Delilah that was still attached to the Marion's hull and could potentially have caused further damage. Welford and Powell also set up cameras to monitor the Samson and give the crew an early warning should the Xenomorphs on board try to escape.
Eleven weeks after the accident, when Ellen Ripley arrived on the Marion, the surviving crew realized they needed to use the Samson to retrieve a replacement fuel cell for the Narcissus from the mine on LV-178. Armed with only mining tools and some netting, they had no choice but to open the Samson and confront the four Xenomorphs within. Although the creatures were initially contained in the net, they broke free almost immediately, and Welford was killed when the severed netting whipped into him, the steel cables slicing through his head. His body was subsequently expelled into space when acid blood breached the Marion's hull and caused explosive decompression.