Miner was repairing a discharge on a Tanker (semi-truck unit), and was using a ""Cheater Bar"" (steel pipe) to realign pipe to attach the lock clamp, when the miner felt a pain occurring in the middle section of his stomach region. Injury evaluated medically as a mild/mod. ""Umbilical Hernia"" w/o obstruction. Miner placed on lifting restrictions. Miner allowed to drive.