Hello Tarun, 

As you have mentioned your category rank around 20k,  sorry but there are no chances in NIT hamirpur for any branch. 

NIT Hamirpur closes its allotment at an SC rank of around 8k to 9k.

It will be good if you try for some other government colleges of your state. Also, there are some well established private colleges too which take admissions on basis of your JEE score. 

Hope this will help. 

All the best for future.