3.3 Batch and continuous lubricating systems For removing soluble sludge, a system combining the batch and continuous systems Is effective The used oil drains to a tank. where it is allowed to rest for about ten days The oil cools and any sludge settles. The oil is then drawn off, run through the purifier, and pumped to the clean oil tank3.3 Batch and continuous lubricating systems • For removing solub1e sludge, a system combining the batch and continuous systems is effective. • The used oil drains to a tank, where it is allowed to rest for about ten days. • The oil cools and any s1udge settles. The oil is then drawn off, run through the purifier, and pumped to the clean oil tank