Hemodialysis is a complicated process that takes the blood from an individual, runs it through a machine that has a series of filters, and then reintroduces the blood back into the person being dialyzed. The maintenance and cleaning of these machines is a daily process, sometimes they are cleaned several times a day depending upon the number of people that used the machine.
HIV infection is due to a virus. Experts claim that the virus is very labile outside of the human body, the claim is that the virus can not survive outside of the human host.
Infection with one of the hepatitis viruses (there are many) has similar claims, that the virus can't live outside of the body for any appreciable amount of time. Other author's make the claim that the hepatitis virus can live for months on inanimate objects (like HD machines). It is a well known fact that many patients undergoing hemodialysis contract the Hepatitis B virus (HBV). In spite of rigorous cleaning of the machines.
I can not cite a single case of HIV infection contracted from HD. Realize that opinions differ on exactly how we can get the HIV virus. For example, some authors state that the virus can not be transmitted in tears, others wholeheartedly disagree with this statement.