Hydraulic Control Systems-GB

HYDRAULIC CONTROL SYSTEMS

CONTENTS HYDRAULIC PRINCIPLES

1

CONTROL VALVE V50

2

CONTROL VALVE V90 and 91M

3

CONTROL VALVE V80

4

LOAD CONTROL VALVES

5

ADDITIONAL VALVES

6

SPOOL POSITIONERS

7

SLEWING MOTORS

8

CYLINDERS

9

HYDRAULIC DIAGRAMS

10

COUPLINGS and FITTINGS

11

Contents

HYDRAULIC CONTROL SYSTEMS

Section 1 Hydraulic principles Contents Safety regulations ........................................................3 Hydraulic principles .....................................................4 Energy transfer by oil .........................................................4 Transmission of force.........................................................4 Pressure ............................................................................5 Force..................................................................................5 Pressure x cylinder area = Force.......................................6 Force = Pressure x cylinder area.......................................6 Displacement .....................................................................7 Flow ...................................................................................7 Speed ................................................................................8 Work...................................................................................9 Power.................................................................................9 Power (cont.) ................................................................... 11 Power (cont.) ...................................................................12 Power (cont.) ...................................................................13 Hydraulic system..............................................................13 Check valve .....................................................................14 Hydraulic system (cont.) ..................................................14 Hydraulic system (cont.) ..................................................15 Single-acting cylinder, idling ............................................16 Single-acting cylinder, lifting ............................................17 Single-acting cylinder, lowering .......................................18 Single-acting cylinder, overload .......................................19 Double-acting cylinder, idling ...........................................20 Double-acting cylinder, lifting ...........................................21 Double-acting cylinder, lowering ......................................22 Double-acting cylinder, overload......................................23

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The manufacturer accepts no liability for any consequences resulting from inappropriate, negligent, or incorrect operation of the equipment or from misuse of the equipment. Every effort has been made to ensure the accuracy the contents of this Manual, however the manufactures, publishers and author accept no liability for any loss, damage or injury caused by any errors in or omissions from the imformation contained within this document. The contents of this Manual are believed to be correct at the time of printing. In the interests of a commitment to a policy of continuous development and improvement , the manufacturer reserves the right to change the specification of the products or their performance or the contents of this Manual, without notice. All rights reserved. No part of this Manual may be stored, reproduced or transmitted in any form or by any means, electronically or mechanically including photocopying, recording or by any information retrieval system, without permission in writing from the publisher. Copyright © October 2002

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Safety regulations Read this for your safety

The HIAB Cargo Handling Equipment can be hazardous if it is not operated correctly. Make sure you read and understand the general safety information given in this chapter. The equipment must be operated in accordance with the instructions given in the relevant Operator’s Manual. Using the equipment in any other way or for any other purpose is prohibited. Warnings, cautions, notes and tips are given in this manual. Their meanings are as follows:

WARNING A Warning is given where wrong action could result in death or injury to the operator and nearby personnel. Warnings must always be adhered to, and given precedence over written and verbal instructions as well as Cautions. CAUTION A Caution is given where wrong action could result in damage to the equipment. Cautions must always be adhered to, and given precedence over Notes, and written and verbal instructions. NOTE! A note emphasises an important piece of information or an instruction. Warnings and Cautions that apply to the general operation of the HIAB Cargo Handling Equipment are given in the relevant Operators Manual. TIP! Tip to make work easy to carry out.

Excluded personnel

Untrained personnel must not operate or carry out repairs to the Cargo Handling Equipment.

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Hydraulic principles Energy transfer by oil The advantage of using oil to transmit force is in its unlimited mobility. These qualities are shown in fig.1. 1. 2. 3. 4.

It can easily change form. It can be divided up to enable it to work in several places at once. It can be moved quickly from one point to another. It will work in any direction or angle. fig.1

H001-7

Transmission of force In simplified form as in figs.1&2 the transmission of force is achieved by putting the oil under pressure so that the work, such as lifting a load is carried out. The load is moved when the pressure created by the force acting on the left-hand piston is higher than the pressure generated by the load on the righthand piston. If the same force is applied to a smaller piston the pressure created will be higher and a bigger load can be moved using the same force.

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fig.2

H002-7

fig.3

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Pressure Pressure is the load per unit of surface.

P=

F A

It follows that a small diameter piston produces a higher pressure compared to one with a large diameter when subjected to the same load. The example in fig.4 shows pistons having an area of 500 mm2 and 5000 mm2. When subjected to a force of 100 N a pressure of 0.2 and 0.02 Mpa respectively will be generated.

fig.4

H004-7

fig.5

H005-7

Force Inversely, pressure against a surface will produce a force. F= p x A Assuming as in (fig.4) a force of 100 N on the small piston, thereby producing a pressure of 0.2 Mpa and letting this pressure act on the larger piston having a surface 10 times larger, a force of 1000 N is produced, this corresponds to a weight of 100 kgs. (fig.5) This demonstrates the force is in direct proportion to the pressure and the area.

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fig.6

H006-7

Pressure x cylinder area = Force If this theory is applied to a practical crane application fig.6 it can be seen that a certain oil pressure can lift or, stop and hold a load.

fig.7

H007-7

Force = Pressure x cylinder area The force exerted by a crane inner boom (fig.7) depends on oil pressure and piston area. Nothing else. For example increasing a trucks engine speed will not affect the pressure in the cylinder.

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fig.8

H008-7

Displacement Displacement is the same thing as swept volume. The swept volume is calculated by multiplying the piston area by the stroke. (fig.8) In a hydraulic pump the displacement is taken to be the swept volume per revolution, which is the volume of oil that the pump moves in one revolution of the shaft.

fig.9

H009-7

Flow Flow is the volume passing per unit time. (fig.9) If the displacement is two litres per stroke, and the pump does 10 strokes per min, the flow will be 2 x 10 = 20 Litres/min. A hydraulic pump with a displacement of 53 cm3 per rev, and running at 1000 rpm, delivers 53,000 cm3 per min or 53 litres/min.

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fig.10

H010-7

Speed At a given flow to a cylinder we get a particular speed. The speed will be inversely proportional to the piston area. (fig.10)

Speed=

flow area

If we open the throttle of a truck and increase engine/pump speed, the flow will increase and we achieve more speed.

fig.11

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Work The work of a crane requires the lifting of a wieght over a certain distance (s =distance). To achieve this it is necessary to lift with a certain force (f = force) using these factors we use the formula, Work = force x distance (fig. 11). As shown in fig.7 hydraulic force is equal to pressure x area, F = p x A. Combining these two formulas results in W = p x A x s. It is also known that displacement is equal to area x distance D = A x s. This leads to the conclusion that work is equal displacement x pressure. W = D x p. From this it can be seen that the factors that do the work are the displacement of the pump and the working pressure. The speed that results will depend on how fast we pump, as speed is dependent on the flow.

fig.12

H012-7

Power A job can be done quickly or slowly. If done quickly, more power is required as shown in fig.12.

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fig.13

fig.14

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Power (cont.) Here follows a more complete definition: Power (P) is most simply defined as work (W) per unit time (t).

P=

Since work (W) is force (F) times distance (s) we get, after combining the formulas, the expression

P=

Everyone knows that speed (v) is distance (s) divided by time (t), i.e.

V=

We are familiar with kilometres per hour. If we substitute v for s/t we get the formula: power (P) is equal to force (F) times speed (v)

W t Fxs t s t

P= F x V

Assume that the horse lifts a weight of 75 kg through a height of 1 metre in a time of 1 second. The horse will then be lifting with a force of 75 kgf, which is equivalent to 736 N, and a speed of 1 m/s. If we substitute these figures in the formula we find that the power developed by the horse was 736 watts, or, if we employ an older unit, 1 horse-power (hp). If the weight weighed 100 kg we see at once that at the same speed the horse will develop a power of 1,000 watts (W) or 1 kilowatt (kW). Doubling this speed to 2 rn/s would raise the power to 2 kW. Power is thus dependent on time.

The power formula for a crane is p = Qxp 60 Flow is given in litres/mm, pressure in MPa. Power is received in kW.

fig.15

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fig.16

H016-7

Power (cont.) A derivation of the formula leads to the following: The crane is lifting with a force F and a speed V. We already know these three formulas: Power is equal to force times speed. P= F x V power will vary with the speed (RPM). Force is equal to pressure times area. Speed is equal to flow divided by area.

Thus power is dependent on time. This means that the

F= p x A v=

Q A

In order to arrive at a power formula that will apply in hydraulics we combine these three expressions. The result is

P=

pxAxQ A

Cancelling out A leaves us with the basic formula:

P=Qxp

Power is equal to flow times pressure. Using the standard units of these formulas, flow is measured in cubic metres per second. In our pump world, however, we are concerned with cubic decimetres, which is the same thing as litres, and with minutes. To be able to calculate, we must first convert to the right units. A cubic metre is the same as a thousand cubic decimeters.

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Power (cont.) A second is the same as one-sixtieth of a minute. If we substitute accordingly in the basic formula, we get a thousand above the line and sixty below it.

P=

1000 x Q x p 60

watt

“Kilo” means a thousand, so that the final formula will be:

P=

Qxp kW (kilowatt) 60

The pressure p is calculated in MPa. We see, then, that the power increases if the flow increases. The flow is directly dependent on the speed and the displacement. The power also increases if the pressure increases.

Hydraulic system A hydraulic system, as used on a loader crane, is built up by: A pump (A) to move the oil into the cylinder (B), which moves the boom. A tank (C) to store the oil. (D) and (E) are check valves, which stop oil flow in one direction and allow free flow in the opposite direction. (Fig 17).

fig.17

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Hydraulic system (cont.) When filling the pump with oil from the oil tank, the check valve under the tank opens and lets the oil pass. The check valve on the cylinder side is closed because of lower pressure on the pump side.

H018-7

fig. 18

Check valve In the left-hand picture (fig.19), the balltype check valve opens when the oil below the ball (1) is sufficient under pressured to depress the spring (2). The ball is lifted from its seat (3) allows the oil to pass. In the right hand picture, the oil pressure above the ball has decreased and the ball has been pushed back to its starting position (4) by the spring and the oil pressure below the ball. The connection is closed.

fig.19

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Hydraulic system (cont.) When exerting a downward movement on the pump (fig.20), the oil pressure in the hydraulic circuit line increases. The check valve (2) will close and prevent the oil returning to the tank. The check valve (3) will be opened by the increased pressure above the ball and allow oil to flow to the cylinder. The increased oil volume in the cylinder will make the piston move and the loader crane boom will be pushed upwards.

H020-7

fig.20

In fig.21, the area of the pump piston is 1 cm2 and the one of the cylinder piston is 50 cm2. When moving the pump piston down 5 cm (fig.22), an oil volume of 5 cm3 will be forced over to the cylinder piston. Since the cylinder piston has an area of 50 cm2, the volume of 5 cm3 can only raise this piston by 1 mm..

fig.21

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fig.22

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Single-acting cylinder, idling

H023-7

fig.23

In order to make the oil circulate in the hydraulic system and to direct it to the functions to move, some more components have to be added to the system. (fig.23) (F) is a pump giving a continuous flow of oil. (E) is a relief valve, which will open, if the oil pressure exceeds the pre-set value, and allow excess oil to return to the tank. (G) is a control valve which starts, stops and directs the oil flow in the system. In this picture, the valve spool allows the oil to go back to the tank. It is said to be in neutral position. Fig.24 shows how the previous figure looks in a hydraulic diagram. The 3-position valve is in neutral position. Oil at a low pressure is circulated through the control valve and back to tank without pressure.

fig.24

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Single-acting cylinder, lifting

H025-7 fig.25 In this position, the valve spool closes the return line to the tank and opens the line to the underside of the cylinder piston. The oil will press the piston upwards and thus obtain a movement from the cylinder. Fig.26 shows that the valve spool has been moved to the right, making it possible for pressurised oil to flow from the pump up to the cylinder. The tank port is closed.

fig.26

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Single-acting cylinder, lowering

fig.27

H027-7

With the valve slide in this position, the oil is pressed out of the cylinder by the weight of the boom and the load. The oil is directed back to the tank.(fig.27) Fig.28 shows that the valve spool has been moved to the left making it possible for oil to return from cylinder to tank. You will note that also the pump flow is directed to the tank port inside the valve.

fig.28

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Single-acting cylinder, overload

H029-7

fig.29

The weight of the boom and the load is so big that the pressure created in the hydraulic line exceeds the preset value of the relief valve. The relief valve will then open and allow the oil to escape to the tank instead of creating excessive pressure in the system (fig.29) Fig.30 shows the valve spool is moved to lift position but the load is too high. Oil from the pump is instead directed through the main relief valve to the left.

fig.30

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Double-acting cylinder, idling

fig.31

H031-7

We have switched to a double-acting cylinder and increased the number of valve ports to 4. The valve is in neutral position and the pump circulates oil through the valve. Fig.31 shows in more detail how the pump port is connected to the return port in neutral position. The cylinder ports are closed. To the left in fig.32 a cross-section of a real control valve is shown. The top part contains relief valves not shown in the diagram.

fig.32

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Double-acting cylinder, lifting

H033-7

fig.33

Pulling the valve spool connects the pump channel with the cylinder channel. Pressurised oil (red) is pumped to the cylinder bottom part. Simultaneously, the spool has opened the passage between return line and tank line making it possible for return oil (blue) to re-circulate in the system (fig.33). This is the same process in the hydraulic diagram (fig.34). The spool has been moved to the left and oil flows crosswise up to the cylinder and out.

fig.34

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Double-acting cylinder, lowering

fig.35

H035-7

Here (fig.35) the valve spool is moved in the opposite direction opening channels for lowering the load. In contrast to the single-acting cylinder, where load and dead weight pressed the piston back, here return movement is effected by pressurised oil. The greatest advantage is the pulling force in the return movement. The hydraulic diagram (fig.36) shows the spool moved to the right, giving straight channels from pump to the cylinder top part and return from the cylinder bottom to tank. The advantage of a pulling cylinder is significant.

fig.36

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Double-acting cylinder, overload

fig.37

H037-7

Shown here (fig.37) is an overload situation where pump pressure is not capable of lifting the load. The main relief valve E opens and pump oil circulates directly to the tank. The same situation is shown in the diagram (fig.38) The control valve is actuated to lift the load, however, due to high resistance the main relief valve opens and allows the oil directly to the tank.

fig.38

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Section 2 Control valve V50 Contents Control Valve V50 .....................................................................2

Description ............................................................................................2 Connections ..........................................................................................2 Pressure gauge connection ..................................................................2 Sections ................................................................................................2 Manufacturer’s sign...............................................................................2 Casting marks .......................................................................................2 Technical data .......................................................................................2

Valve variants ...........................................................................3 Valve variants ...........................................................................4 Dump valve (open) ...................................................................6

Description ............................................................................................6 Function ................................................................................................6

Dump valve (closed, work position) .......................................9

Description ............................................................................................9 Function ................................................................................................9

Inner boom function, all CE-cranes ......................................10

Descriptio ............................................................................................10 Function ..............................................................................................10

Slew function, small CE-cranes ............................................11

Description ..........................................................................................11 Function ..............................................................................................11

Slew function, small CE-cranes (overload)..........................12

Description ..........................................................................................12 Function ..............................................................................................12

Slew function (large CE-cranes) ...........................................13

Description ..........................................................................................13 Function ..............................................................................................13

Inner boom function (small Non-CE-cranes) .......................14

Description ..........................................................................................14 Function ..............................................................................................14

Slew function (large Non-CE-cranes) ...................................15 Slew function small Non-CE-cranes .....................................15

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Control Valve V50

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HYDRAULIC CONTROL SYSTEMS Control valve V50

fig.1

H001-6

Description

Valve 50 (fig.1) is a further development of valve 40 for open center systems. The main differences include: built-in dump valve, stronger housing, spools with improved operational properties on all functions. There are 4 main varieties of valve 50. .Connections The valve has 3 alternative input pressure connections (3/4”) and 2 alternative tank connections (1” and 3/4”).

Pressure gauge connection

The front pressure connection is in most cases fitted with a nipple for gauge connection.

Sections

At present the valve is only available with 6 sections.

Manufacturer’s sign

The manufacturer’s sign shows valve number and data. Following “Type” the code for week of manufacture is stated. In this case 7 for 1997 and 39 for week number.

Casting marks

The valve casting has markings for B-side, P-connections, T-connections, and section numbers. G means gray iron, SG means nodular iron.

Technical data

Max pressure gray iron 27 Mpa Max pressure nodular iron 35 Mpa Max return pressure 2,5 Mpa Nominal pump flow 35, 50, and 70 l/min Pressure drop P3–T 2 in dump position