Under normal circumstances, the bearing needs to be cooled when the temperature of the conveying medium ( ) of the pump.

In the refining chemical plant, ( ) regulating valves do not need to be further explosion-proof treatment.

In refining and chemical units, ( ) regulating valves need to be treated for explosion protection.

Electric regulating valves operate mainly according to ( ) size changes.

( ) The regulating valve mainly operates according to the change of current magnitude.

The following conditions that will not cause the machine pump to reverse are ( ).

The following conditions that will cause the machine pump to reverse are ( ).

Since the FM pump starts at a slow speed, it should be properly ( ) prevented from reversing before switching.

Since the FM pump starts at a slower speed, care should be taken ( ) to prevent reversal before switching.

Petrochemical industry on packing seal leakage: Light oil should not exceed ( ).

Petrochemical industry requirements for leakage of mechanical seals: Heavy oils cannot exceed ( ).

Petrochemical industry requirements for leakage of mechanical seals: Light oils cannot exceed ( ).

Petrochemical industry requirements for leakage of packing seals: Heavy oils cannot exceed ( ).

The machine pump preheating operation is correct ( ).

Machine pump preheating operation wrong is ( ).