Should graduate students who are graders help undergraduate students with homework? In my department, we hire graduate TAs as both graders and teaching assistants. The teaching assistants are assigned to lead discussion sections that meet twice per week. The graders are assigned to grade all of the homework and exams.

The department requests that both TAs and graders spend three hours in the academic skills center. During these three hours, students can basically ask the grader/TA whatever they want.

My current assignment is an upper division undergraduate course. Many of the students aren't prepared for the course difficulty (ten hour homework assignments, projects, and exams). Inside the academic skills center, I am asked frequently about how to do homework problems when I am not a TA.

How should I handle this situation? Am I responsible for helping students do every single individual homework problem before the assignment is due? I thought that a grader would solely be responsible for grading homework. I spent a nontrivial amount of time helping students do their own homework. 

Should graders have some sort of protection from these scenarios? I don't know why an undergraduate student would ask the grader grading their homework for help.
This is really a question for the professor(s) in charge of the course. You can and should get specific direction from them. 

However, just for background and context. A lone professor in a smaller class will find him/herself in this situation frequently. It is unlikely that it is wise to not answer at all, but also unwise to give such specific hints that student learning ceases and the student just follows directions. 

But it may take some experience to be able to balance the needs (and also to keep the prof happy). In general, you can think about the question you were asked, and before answering it, ask yourself whether the student has an unmet need that generates that question. Do they have a misconception? Have they missed an important reading? Something. I suspect that it is generally fair to address those needs rather than "helping" them with the specific assignment. Even giving them an easier task that might help them understand where they are and why they are having problems might be suitable. 

The base line is, don't get in the way of their learning just to help them complete a specific task. 

But you might check even this advice with the prof. You might also cause more specific training to be provided to you are your fellow graders/TAs.