Question

IN A LARGE GATE VALVE USED IN A HIGH PRESSURE WATER LINE. THE GATE WEIGHS 1500 lb. AND FRICTION FORCE DUE TO WATER PRESSURE, RESISTING OPENING IS 500 lb THE VALVE STEM IS NON-ROTATING AND IS RAISED BY A ROTATING WHEEL WITH INTERNAL THREADS ACTING AS A ROTATING NUT ON THE VALVE STEM. THE WHEEL PRESSES AGAINST A SUPPORTING COLLAR OF 5/8 in. INSIDE DIAMETER AND 3-in OUTSIDE DIAMETER THE VALVE STEM IS FITTED WITH 3 SQUARE THREADS CSWGLE THREADED) PER INCH. ASSUMING THE COPACENT OF FRICTION POR THE COLLAR 0.25 AND FOR THE THREADS O.O. DETERMINE A.) THE TORQUE THAT MUST BE APPLIED TO WHEEL TO RAISE THE VALVE GATE B.) THE EFFICENCY OF THE SCREW AND COLLAR MECHANISM. C) THE MAX. SHEAR STRESS IN THE BODY OF THE SCREW.

Inside diameter is 1 5/8 inches

Answer 1

Giren, Gate weight (w) = 1500lb. friction force desisting = soolt astem collar collar VW Inner diameki- 15/8 inch 30 = 12 inch outer diameter & 3 inch coefficient of friction between wheel & collar = 0.25 threads = 0.10 To poore find A) Torque required to raise the valve 3 or of the screw and collar mechanism c) Max shear stress in screw body

Screw has 3 thread inch pitch = / because for threads tinch of height is raised Screw can pass through collar, So moccimum diameter or nominal diameter of solar to screw is inner diameter of collar Inner dia of i.e 13 inch. collery 1 Torque required to rate the value Mean diameter = Nominal - pitch diameter mecane 1.242 inch Torque required Trotal = T collart Tscrew Tscrew & W x Dm x tan (a+d) w is the load o is the friction angle & is the he

a= tan ((1/3) a inch Tx 1.292 inch x = 0.081939) * = tan (0.1) -0,099660 Pfoten Tsew=(1500+500) X 1.292 x tan(a+b) - 3000x1 29L,tan(% o¢1939 40 sed) o = 237.239 lb-inch. Trollar = been wx Mx (Dout + Dinner) = 1500x 0.25% (3+13( T collar = 8671875 lb-inch i Torque required = 937.239+8671875 Torque required = 1104.4265 lb-inch/ 2) efficiency of screw 2= work output . wook input Wx lead 2 IT Torque required

1500 217 2:104.6265 n = 0.07205 -> 11 = 7,005%. very less efficiency is due to coller maximum shear stress If we think the screw as a twinks rod with diameter, Don (maximus diandienos 161 167 1104.4265 2= TT03 x 1.292² 12 = 2608.07 Hapsil Shear Steens Zmaz = 2608.07 est