System getting heated with integrator=sd

GROMACS version: 2018.4
GROMACS modification: No
I am trying to equilibrate Icosane (C20H42) in octanol using mdp file (mdp_prod.mdp), I have done short NVT (mdp_nvt.mdp) and NPT (mdp_npt.mdp) simulations. My system is blowing up. I noticed sudden temperature increase in the system, may be due to friction, I am using integrator = sd. I am using gromos54a7 force field. I have to use this system further for free energy calculations. mdp files are created using templet given at free energy tutorial given by Justin (Free Energy Calculations)
please help.
mdp files:
mdp_npt.mdp (1.8 KB)
mdp_nvt.mdp (1.8 KB)
mdp_prod.mdp (1.8 KB)

temperature plot: