Answer Happy

Trainer Exercise #14: Meter-In 1. Description: This exercise illustrates control of a cylinder's speed by placing a restriction in its intet flow. This is called a meter-in circuit. A bypass check is required to insure that when the cylinder reverses directions, its outlet flow is not restricted. (Reference Chapter 9 in Bul. 0232-81, Industrial Hydraulic Technology, 2nd Edition.) 11. Loose Components: Hoses and tees III. Procedure: a. REFER TO SAFETY CHECK LIST, PAGE 2. b. Reference schematic on next page. Connect a hose from one of the pressure ports on the connection header (27) to port "P" of directional control valve (14). c. From port "B" of the directional control valve, connect a hose to the rod end port of cylinder (22). From the "A" port of the directional control valve, connect a hose to the inlet port of a flow control valve (23) or to the inlet port of needle valve (2). [If needle valve (20) is used, a tee must be con-nected to both sides of the valve so that a check valve (24) can be connected to effect a meter-in flow condition to the cylinder. d. At the inlet and outlet ports of the flow meter (16) connect a tee. From the outlet of the flow control valve (23) or the needle valve (20), connect a hose to the inlet of the flow meter. From the outlet of the flow meter connect a hose to the base end port of cylinder (22) e. Once the circuit has been checked and upon instruction, back out relief valve (5) completely and have handle for vent valve (4) in the "open" or horizontal position. 1. Start electric motor on power unit and slowly close vent valve (4). g. Deadhead the system and then set pressure to 250 psi (17 bar). [If pressure doesn't go up to 250 psi (17 bar), back out the relief valve to minimum pressure then notify-instructor.] Warning! Exceeding 500 psi (34.5 bar) can cause the electric motor to stall, tripping the circuit breaker. i. The students should complete the exercise questions at the end of this exercise before dis-man- tling the experimental circuit. ii. Retract the cylinder and stop the electric-motor. Dissassemble circuit and return components to their proper storage place.
Exercise #14 Questions 1. Fill in the chart below. What were the results of the timings at the various pressures? Why? Pressure Flow Time Time psi/bar gpm or l/min Extend (sec) Retract (sec) 250/17 1/3.7 9 S 275/19 137 9 SA 300/21 1.1.5 7 4 350/24 1.2 400/28 1.S 500/34.5 1.75 4 2.5 If the needle valve (20) was used in the circuit, why was a check valve (24) required? Is speed control of the cylinder accomplished without the relief valve opening? N 2. 3. 6 S مالیا 3 3
M Exercise #14 Schematic 24 1 gpm (3.75 Ipm) B IHX P T 16 14 23 or 20 and 24 250 psi (17.25 bar) 10