People have the tendency to cope with major setbacks by quickly shifting into what is known as a "comfort zone". This is an area in our mind and sometimes within our bodies where we run to and try to make ourselves feel better. It is also a familiar zone, where nothing new can happen to further shift our life.
In Silas's case, he went straight to the loom. He had been comforting himself with work ever since the incident at Lantern Yard and his subsequent entrance to Raveloe. Since he was a weaver by vocation, his mind would concentrate on nothing but his loom. He would consistently go back to his loom because this is what he knew, and the anchor of his life. It is what gave him the balance to move forward, or to simply sit and mourn.
Remember that Silas's character was very unique in that he awarded confidence, loyalty and appreciation to the things with which he felt most related to: It happened with his brown pot, and now it is happening with his loom. These comforting mechanisms allow him to cope and grief as best as he can.