We are looking at taking a sleeper train from Xi'an to Jinan K912/K913. Is this a clean safe train?

We are 2 business travelers from America. We are looking at taking a sleeper train from Xi'an to Jinan train # K912/K913. In Jinan we will likely switch to a high speed train to Qingdao. Do you know what style train this is? Is it clean and safe? How old is it? We want to experience a soft sleeper train but we also smoke so it looks like the high speed sleepers are out. Is there a website that reviews the different train numbers? That would be really helpful.