All machines of shini's equip with versatile protecting system so as to ensure safe operation. This problem was caused by unstable pressure of cooling water which fluctuate at 2bar. Because all of STM of shini's equip with pressure protector at inlet of cooling water whose setting point is 2bar, when pressure of cooling water deviates down to be less than this value, STM will stop work automatically, so cutomer should ensure the minimum pressure of cooling water being more than 2 bar.