TM 10-6640-233-10 Table 2-12. Operator Preventive Maintenance Checks and Services (cont.) B - Before A - After M - Monthly D - During W - Weekly B D A W M 17 e.   Observe drive belts for Drive belts are loose (cont) cracks, slippage or binding or cracked. caused by excessive loose- ness or tightness of belt. Proper drive belt deflec- tion should be 3/4 inches under moderate thumb pressure. 18 Vacuum System Inspect for leaks, leaky valves, Leaks or defective Piping and or inoperative valves. valves. Valves 19 Water Pump, a.   Check for loose mounting Missing bolts. Valves, and bolts. Piping * b.   Check water piping in Class III leaks mechanical and laboratory detected. compartments for signs of leakage. c.   Make sure tank contains Low water level. sufficient water. d.   Inspect pump and motor Pump or motor over- for unusual noises or heat heats. that could indicate mal- function. e.   Make sure pump does not Shaft seal leaks. leak at shaft seal. f.    Make sure all outlet valves Defective valves. deliver full flow when open and do not leak when closed. 20 Water Tank a.   Check for loose or missing Missing bolts. mounting bolts. b.   Inspect for leaks. Class III leaks detected. INTERVAL ITEM NO. ITEM TO BE INSPECTED Equipment is Not Ready/ Available Procedures Check for and have repaired or adjusted as necessary. 2-22