Measured values for task 2
Project 09: Throttle valve, adjustable
Project 0:
Throttle valve, adjustable Bosch Rexroth AG I RE 00845/04.07
Project 09: Throttle valve, adjustable
Project/trainer information
In hydraulic systems the piston velocity of a hydraulic cylinder or the revving speed of a hydraulic motor should often be adjustable. The flow provided by the hydraulic pump can be controlled with the help of flow control valves. Flow control valves are classified in:
Throttle - fine throttle/orifice and flow control valve.
In the following Project 09 knowledge is to be imparted with regard to the operating principle and the use of throttle valves. The task of a throttle valves is to offer a flow resistance by chang-ing the flow cross-section. As a result of the pressure drop, ∆p across the throttlchang-ing point, the flow and consequently the speed of the actuator changes.
In the project order the trainee is to work out and document the characteristic curve of a throttle.
By changing the throttle settings, he/she is to understand that:
• the differential pressure ∆p rises while the flow increases and the throttling cross-section remains constant,
• the differntial pressure ∆p rises in proportion to the reduction in the throttling cross-section while the flow remains constant,
• the flow is independent of the pressure level when the pressure differential ∆p is con-stant.
The control set up on the training system allows the trainee to measure various differential pres-sures across the throttle valve at certain flows. A load can be simulated by installing a pressure relief valve in the return line of the 4/3 directional valve.
Notes on detailed technical information about the throttle valve:
• The Hydraulic Trainer Volume 1/Bosch Rexroth AG Basic principles and components, Chapter 13
• Technical data sheet RE 27219 Throttle valve type MG
09
Project definition
In the plant of the customer, a conveyor belt, on which unchanged loads are transported, is powered by a hydraulic motor. The drive speed of the hydraulic motor is to be adjustable in both directions of travel.
In order that the customer can understand the proposed solution, he requires technical docu-mentation.
As an option, he wants to know whether the drive speed changes when loads of different weights are transported.
Fig. 09.1 Practical example: Conveyor belt for transporting printed-circuit boards
Project tasks
• Independent understanding of the task and its putting into practice using hydraulic control technology
• Planning and organizing the customer requirement (core qualification)
• Analyzing the technical data sheet of a throttle valve (specialist qualification)
• Handling of hydraulic components in line with functional needs
09
Project 0:
Throttle valve, adjustable Bosch Rexroth AG I RE 00845/04.07
Project steps
• Informing: Accepting and understanding the order, among others, through discussions with the customer.
• Planning: Planning and organizing the execution of the customer order; among oth-ers, through the selection of hydraulic components from the data sheet collection (RE 27219 Throttle check valve).
• Deciding: Preparation of a schematic diagram sketch and selection of components.
• Executing: Set-up of the hydraulic control on the training system. Working out and documenting the system parameters requred by the customer.
• Checking: Are all customer requirements met?
• Evaluating: Are there further possibilities of meeting the customer requirement or simpler ways of project execution?
Notes
09
Hydraulic circuit diagram
Fig. 09.2 Hydraulic circuit diagram: Throttle valve, adjustable
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Item 1.0
Item 1.2 Item 1.1
Item 1.3
Item 0.3 Item 0.2
Item 0.1
Optional
Load pressure
Measuring glass
Power unit limit
Item 1.5
Item 1.4
5 Project 0:
Throttle valve, adjustable Bosch Rexroth AG I RE 00845/04.07
Electrical circuit diagram
Fig. 09.3 Wiring diagram for hydraulic circuit diagram Fig. 09.2
09
Stop
Rotation Rotation -Hydraulic motor-Control 4/3 directional valve
Component selection with parts list
Item Qty Component designation Type designation Symbol
1.0 1 Fixed displacement motor with external leakage line and two
directions of rotation DM 2.N
1.1 1
4/3 directional valve with direct actuation by two solenoids, spring centering of the central position and central position P, T, A, B
DW 13E
1.2/1.4 2 Direct operated pressure relief valve, the cracking pressure can be
adjusted by means of a spring DD 1.1
1.3 1 Throttle valve, adjustable DF 1.2
2 Distributor plate with four ports DZ 4.1
0.1 - 0.3 4 Pressure gauge with hose and quick release coupling without check valve
DZ 1.4
3 Hose with quick release coupling
with check valve DZ 25
Hose VSK 1
1 Stopwatch
1 Flowmeter DFF 1
Table 09.1 Parts list for hydraulic circuit diagram Fig. 09.2
09
7 Project 0:
Throttle valve, adjustable Bosch Rexroth AG I RE 00845/04.07
Component arrangement
Fig. 09.4 Recommended component arrangement with component designation for parts list 09.1 and hydraulic circuit diagram Fig. 09.2
Notes
Note:
The designations of components in the parts list and the component arrangement are Rexroth-specific designations. Also the grid arrangement is Rexroth-Rexroth-specific and adapted for use on the training system.
D Note:
09
In the case of connection elements marked with “D”, the components can be connected directly with each other.
Connection block Measuring glass
Set up the control as described below:
1. Mount the components required according to Table 09.1 in a clearly arranged form on the training system according to the prepared circuit diagram.
Connect the hydraulic control according to hydraulic circuit diagram Fig. 09.2 by means of hoses.
For connections, to which pressure gauges with minimess line DZ .4 are to be connected, use hydraulic hoses DZ 25. Hand-tighten the pressure gauge measuring lines at the relevant minimess connection of the hydraulic hose.
The correct and proper fit of the component connections with hoses can be checked by slightly turning the hoses.
Make sure that pipes or hoses are connected to all connections - in this case also to minimess lines, or that the connections are plugged by means of plug screws or protective caps. Leakage oil may drip through open connections and cause a slipping risk.
Before commissioning the hydraulic control, i.e. before switching the hydrau-lic pump on, check, whether all pressure control valves are set to minimum pressure (spring unloaded) and all throttle valves are open.
Wire the electrical control according to wiring diagram Fig. 09.3.
2. Switch the hydraulic pump on and inspect the set up control for leakage. No pressure gauge may indicate a pressure.
3. Set the system pressure on pressure relief valve Item . to 50 bar plus one turn.
4. By actuating push-button S solenoid Yb of 4/3 directional valve Item . is energized, the hydraulic motor Item .0 rotates.
Throttling process :
5. Close throttle valve Item .. Then open the throttle valve by � turn of the adjustment knob.
Marking with a point for the precise adjustment (st position).
Execution of the order Safety notes
To ensure the operability of plant and machinery, and consequently to allow the recognition of potential risks, safety regulations must be observed before and during the execution of the order. Relevant sources of regulations are given in the introduction of the present manual.
If work on electrohydraulic components is carried out improperly, risks of injury and a safety risk can arise during operation of the system, including danger to life.
Before starting work on the training system, check that the electrical ON/
OFF switch on the hydraulic power unit is pressed in, i.e. that the system is switched off. Check on the system pressure gauge that the system is depressurized.
Hydraulic systems can store pressure energy when at rest. It can cause injury when the system is opened.
Warning
Caution
Warning
Caution
09
Project 0:
Throttle valve, adjustable Bosch Rexroth AG I RE 00845/04.07
While directional valve Yb is operated, the load pressure can be adjusted to 0 bar on pressure relief valve Item .4, which is installed in the return line of the 4/3 directional valve, and the pressure value read off from pressure gauge M.
6. The flow measurement can be taken with the help of a measuring glass in liters/time or optionally using flowmeter Item .5. Measure the pressure differential ∆p across throttle valve Item . using pressure gauges M and M and enter the values in Table 09.2.
7. While the throttle position remains unchanged (st position) increase the load pressure to 5 bar, 0 bar, 5 bar, 40 bar and 4 bar.
Throttling process :
8. Throttle valve Item ., � turn opened (nd position).
Follow the instructions in points 6 to 8 and enter the values in Table 09.2.
Throttling process :
9. Throttle valve Item ., 1� turns opened (rd position).
Follow the instructions in points 6 and 7 and enter the measurement result in Table 09.2.
After having completed practical work on the training system, switch the hydraulic pump off! Open the throttle valve and set the pressure relief valves to minimum pressure. No pressure gauge may indicate a pressure!
10. Optional: Carry the measured values over in a Diagram 09.1.
Caution
Measured values
Table 09.2 Measurement results from execution of the order
Throttle
Evaluating the work results with regard to the customer requirement
• The customer requirement can be met by means of a throttle valve.
• As the flow increases the differential pressure ∆p rises when the throttling cross-section remains constant.
• At a constant flow the differential pressure becomes greater, the smaller the throttling cross-section is.
• At a constant differential pressure, the flow is independent of the pressure level.
• As an optional extra, the customer wishes to implement a velocity adjustment feature for various weights. Since the throttle operates in dependence upon loads, the velocity of the conveyor belt becomes smaller as the load increases (greater weight).
Diagram 09.1 Diagram with measured values
1 2 3 4 5 6 7
0 0 5 10 15 20 25 30
The values were measured at an oil temperature of approx. 20 °C.
The values measured by the trainees can deviate by 10 %.
1st position 2nd position 3rd position
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Flow qV in l/min
Differential pressure ∆p in bar
Project 0:
Throttle check valve Bosch Rexroth AG I RE 00845/04.07