talk about steering gear system

1-    steering gear system, telemotor, electro hydraulic, electric , ram type, vane type Steering gear with 4 ram, floating lever - Hunting gear arrangement with heleshaw pump(Constant speed unidirectional rotary variable stroke positive displacement)

You can read about common problems of steering gear system at  the following link
(Select the whole link address with right clip and  open link in new window)

https://www.marineinsight.com/tech/common-problems-steering-gear-system-of-ships/

Safety devices for steering gear system

1-hunting gear, 2-buffer spring, 3-angle adjusting stop, 4-double shock valve, 5-relief valve, 6-tank level alarm( oil leak alarm), 7-overload alarm, 8-electrical failure, 9-hydraulic lock, 10- filter clog ,11- phase failure alarm, 8-servo loop alarm at electro hydraulic system( in case of different between rudder angle command & actual rudder angle)

Steering clear (four ram types)

The tiller is fixed to the rudder stock and the hydraulic rams operate it by means of swivel blocks carried in forks of the ram.

          The swivel blocks are designed to convert linear movement of the rams to the rotary movement to the tiller arms and the rudder stock.

          Each pair of rams is bolted together, the joint end being bored vertically and bushed to form top and bottom bearings for the reunion arms on the swivel block.

          Hydraulic pressure is supplied by the motor driven, constant speed, variable stroke delivery pumps. Amount and direction of oil flow is controlled by the movement of the pump control rod, which is linked to the floating lever.

          Hand operated by pass valve combined with spring loaded double shock valves are fitted across the hydraulic circuits.

          Shocks vales are set to lift at a pressure of 100 bar and are intend to allow the rudder to give way when it is subjected to a severe shock from a heavy sea or other causes.

The linkage through the floating lever of telemotor, pump control rod and rudder stock forms the hunting gear.

        The pump delivers oil, only when the steering wheel is moved. The hunting gear returns the pump control rod to mid position as soon as the rudder received the position relative to the wheel and remains there the wheel move again.

          The telemotor moves the end of the floating rod A to A1 and the pump control rod moves B to B1. Pumping of the hydraulic oil causes movement of the tiller arm, through rams and the end of rod C moves to C1. These movements cause the pump control to pull back to the neutral position B.

          If the rudder is rotate by the heavy sea through lifting of the shock valves, the hunting gear is moves by the tiller. This put the pump to work and the rudder will be restored to its previous position.

Follow up & non follow up - The control system described up to this point are all associated with "Follow up" or "Hunting Gear" systems, wherein the amount of rudder angle depends upon the amount of hand-wheel movement. In "Non-follow up" system, the steering gear will move as long as the control is held in an actuating position, and will only stop when it is moved back to an "Off" position or until the steering gear has reached the hard-over position. Thus, the amount of rudder movement depends upon how long the control is held over and this system is therefore sometimes called "time dependent steering". The control on the bridge is by means of a lever, which is spring loaded to a central "off" position and when held to one side, will give rudder movement towards port and to the other side towards starboard. The lever operates a switch, which energizes one of two solenoids, depending upon the direction of movement required.

These solenoids operate a pilot valve, which causes the main control valve to move, so as to divert oil pressure from a continuously running fixed delivery pump to the steering gear in order to give the desired direction of rudder movement. When the switch is released,  springs to the central position, the control valve moves to a position, where it bypasses the pump delivery, and the steering gear stops. At the same time, the control valve seals off the pipes to the steering gear stops. At the same time, the control valve seals off the pipes to the main cylinders so as to hold the rudder. Since the rudder moves as long as the control lever is held over by the helmsman, and stops moving as soon as the lever is released to spring to the "off" position, the helmsman acts as the hunting gear, stopping rudder movement as soon as it has reached the desired angle as signaled by the rudder indicator. Therefore the rudder indicator becomes an essential link in the steering gear system & together with helmsman completes the control loop.

credit to marine electrical technology by Elstan A Fernandez


How to operate if one ram and cylinder fail

~   (1) For cylinders 1 and 2 operational, with valves B, C and F open, A, D and E closed  (2) For Cylinder 3 and 4 are operational, with valves A, D and E open B, C and F Closed I.e. isolating 2 rams (not diagonally)

~   Use only one pump at any time,

~   Ship’s speed should be reduced to 70% of normal, if large rudder angles are expected e.g. in heavy weather or enclosed waters etc.

~   Preferably watches should be kept in steering compartment

~   Locking arrangement should be ensured on all valves, which have been altered

~   Informed Bridge on limitations of steering system.

Fail safe steering gear system for UMS

~   There are basically two pairs of rams, which can be operated by two independent Steering motors. In case of single failure, the leaking circuit has to be detected and isolated, in order to restore steering.

~   In case of oil leakage in either of the steering circuits (Single Failure), there will first be an indication (low level alarm), then the isolating valve will operate, and if the level falls further (Low-Low level), the second motor will start with its isolating valve already operated, and the first motor will stop. One Steering motor can isolate only one pair of rams, hence if the fault is in the other pair, the second Steering motor needs to be started. This is an essential requirement in Tankers above 10,000 GRT

The telemotor system consists of the transmitter (in wheelhouse) and the receiver (in steering gear room), which are connected with two solid drawn copper pipes. The transmitter consists of movable single acting bronze rams in two cylinders. The upper ends of the rams are extended to form racks. They are engaged with the steering wheel through gearing.

        The receiver consists of stationary two fixed rams and one movable cylinder along the rams. Each outer end of ram short pipe is lead to circuit valve and it is connected to bottom of transmitter cylinder.

          Any fluid displaced in the transmitter cylinder by the ram is forced through pipe and circuit valve to the receiver cylinder.

          Movement of cylinder must against the spring force, which brings back to mid position when wheel is put back into mid position.

        One end of the receiver cylinder is connected to the floating lever and the movement is transmitted through the cross head. A replenishing tank is above the highest part of cylinder to prevent air into system.

Air in the system

          Air being compressible gives incorrect balance between units, time lags and abnormal operation, which can be dangerous.

          Air in the system is indicated by defective steering, excessive movement of steering wheel before telemotor move.

          No initial pressure and wheel slack on turning, jerky operation and perhaps jumping at the pressure gauges.

Rectify

          Air can be purged out from air vents valves. If there is considerable air inside the system, the system oils should be totally emptied and recharged completely.

Emergency steering gear

          In the case of telemotor failure, by switching the change over pin, emergency steering can be carried out by isolating the receiver cylinder.

          And direct controlling the connecting rod of the main steering power unit's pump lever. The emergency rudder angle indicator and communication system to bridge being provided at the emergency station.      

Washing Out and Charging Procedure

          The charging and the replenishing tanks must be carefully washed out before charging the system. In order to clear the pipes of all dirt and grit, the followings must be carried out.

          Disconnect pipes B and C at the transmitter end and connect these two ends to a wash out piece. Then disconnect pipes A and C at receiver end. Fill the charging tank with fresh oil and pump until a quantity of oil has passes through pipe A. Connect pipe A to receiver. Open all charging and circuit valves. Insert end of pipe C into a bucket and continue pumping.

          To ensure the pump does not draw air the charging tank should be recharged at intervals. Pumping must be continued until the oil discharged through pipe C is free from dirts.

          The pipe now being cleaned, connect pipe C to the receiver. Disconnect wash out piece and pipes B and C connect back to the transmitter.

          Put the steering wheel into the mid position and open safety by-pass valve by means of lever. These valves can be opened when the wheel is in mid position and the wheel will be locked in this position while these valves are opening.

          Open valve J and pump the charging pump until oil rise in the replenishing tank to the working level. Close valve J and release air at the air cocks on the transmitter. Then release air at air cocks on the receiver. Continue pumping until for each stroke of the pump a rush of oil comes from the return pipe D. Close the charging valves, open valve J and release the safety by-pass lever.

Tests required before departure

o      Steering gear should be checked at least one hour prior to departure.

o      Duty Officer and senior Duty Engineer carryout test together

o      Telemotor transmitter oil level to be checked.

o      Oil level of the actuating system tank should be checked and replenished if necessary.

o      Rudder carrier bearing and bottom sea gland checked and greased

o      All links on steering gear checked to be in order

o      First one pump is started from the bridge and the Wheel is turned from port to starboard to check telemotor response

o      Next with both the officers in steering flat, the wheel is turned from hard-a-port to hard-a-starboard and running condition checked

o      Checked if the Bridge helm angle indicator and local mechanical indicator correspond correctly to each other for all position

o      The first pump is shut off and the second pump started and check likewise

o      Then both pumps started in parallel and check likewise again

o      Check load carrying and running of the gear.

Before Arrival Port

o     One hour before picking-up Pilot, ME speed reduced and engine manoeuvring, astern running, and all steering gear actuation checked

o     Both pumps are started and movements on either side checked

o     Bridge angle indicator and local indicator checked for correct matching response on either side.

Hydraulic pump -Hele-Shaw Pump, Swashplate Pump, Vane Pump

Piston Pump. On an inline piston pump, the drive shaft and the cylinder block are on the same centerline 

CREDIT TO BASIC OF HYDRAULIC 

Reciprocation of the pistons occurs when the pistons run against a swash plate as the cylinder block rotates. The drive shaft turns the cylinder block, which carries the pistons around the shaft. The piston shoes slide against the swash plate and are held against it by the shoeretainer plate. The angle of the swash plate causes the cylinders to reciprocate in their bores. When a piston begins to retract, the opening on the end of the bore slides over the inlet slot in the valve plate and oil is drawn into the bore through less than onehalf a revolution of the cylinder block. A solid area is created in the valve plate, and the piston retracts. As the piston begins to extend the opening, the cylinder barrel moves over the inlet port and oil is forced through the outlet port.

a- The major components of a piston pump consist of a housing, a bearingsupported drive shaft, a rotating group, a shaft seal, and a valve plate. The valve plate contains the inlet and outlet ports and functions as the back cover. The rotating group includes a cylinder block, which is splined to the drive shaft; a splined spherical washer; a cylinderblock spring; nine pistons with shoes; a swash plate; and a shoeretainer plate. When this group is assembled, the cylinderblock spring forces the cylinder block against the valve plate and the spherical washer against the shoe retainer plate. The nine piston shoes are held positively against the swash plate, ensuring that the pistons reciprocate as the cylinder turns. In fixeddisplacement pumps, the swash plate is stationary.

b. Displacement (outflow) from the piston pump depends on the number of pistons, their bore, and their stroke. The swash plate's angle determines the stroke; therefore, the stroke can be changed by altering the angle

CREDIT TO BASIC OF HYDRAULIC 

Constant speed unidirectional rotary variable stroke positive displacement

The pump consists of central valve arrangement by ports for the supply and delivery of oils. The pistons are fitted in the radial cylinders and fasten to slippers by a gudgeon pin.

The slipper fit into a track in the circular floating ring. When the floating ring is concentric with the valve the pistons have no relative reciprocating movement in the cylinders.

As a result no oil is deliver and although the pump rotating. If the floating ring is pulled to right, the relative reciprocating motion of pistons in the cylinders occur.

The lower piston will move inwards and discharge fluid out through the lower port. As it continues passed the horizontal position, the piston will move outwards and draw fluid in from the upper port.

Once past the horizontal position on the opposite side, it begins to discharge the fluid. If the circular floating ring is pushed to left side, then the suction and discharge ports will be reversed.

To prevent reversal of pump

Two nos. of positive displacement pumps are fitted in the system and only one is operating, reverse operation of other is prevented by non- reverse locking gear.

It consists of a number of steel pawls are mounted on the coupling and stationary steel ratchet is fixed to the motor supporting structure.

At rest the pawls engage into the ratchet, the other pump running the sense of rotation in reverse order it will not be able to turn.

When the pump starts the reverse sense of rotation pawls fly outwards due to centrifugal force and can rotate freely.

rotary vane type steering gear

          It consists of a rotor with vanes which can move in stator casing. A rotor is securely keyed to the tapered rudder stock. The stator is solidly attached to the ship's structure. The sealing strips are fitted on the moving face of the rotary and fixed vane

          Chambers are formed between the rotating vanes and fixed vane of the stator casing. These cambers are alternately connected to the suction and delivery from the hydraulic pump.

          Its supply hydraulic fluid to all chambers on the left and drawing fluid from all chamber on the right the rudder can be turned anti clockwise and clockwise movement the circuit is reversed.

Hydraulic pumps are controlled by telemotor unit through floating lever type hunting gear arrangement to ensure the rudder can stop when steering gear wheel standstill.

          A relief valve is fitted in the system to prevent over pressure and allow for shock loading of rudder. The whole weight of gear is taken up by rudder carrier bearing. Two anchor bolts held in fixed anchor brackets with rubber shock absorbing sleeves prevent the rotation movement.

          Vanes are made of spheroid graphite cast iron; the rotor and stator are cast steel. Synthetic rubber backs steel sealing strips.

Advantages over Ram Type

(1)     Smaller space required

(2)     Low installation cost

(3)     Low in weight

(4)     Smaller power required, for the same load, because it can transmit pure torque to the rudder stock.

Disadvantages

(1)     Synthetic rubber backed steel sealing strips at vane tips are not strong enough for large ship gears.

(2)     Can be used for rudder stock ratings of about 1700 KNm and less (torque generated by two ram is 120 to 650 KNm and for four ram 250 to 10,000 KNm)

ROTARY   VANE   VERSUS  RAM   TYPE

	RAM  TYPE	ROTARY  VANE  TYPE
1	Torque about 1,000 KNm in 4 ram type and 650 KNm in two ram type	More adaptable to increase of Torque produces about 3,000 KNm
2	Withstand Maximum pressure about 170 Bar	Limited pressure about 90 Bar
3	Having efficient sealing	Sealing difficulties
4	More Robust	More careful attention required for Rudder support and shock loading owing to its very close and direct connection between Rudder and Actuator.
5	Suitable for all sizes and types of ships	Suitable for small and medium sizes excluding larger vessels.
6		Saving in cost, weight, space and maintenance
7	Limited rudder angles up to 35' each side only	Wider working Rudder angles, giving 70° to 80°.

How to lubricate upper and lower radial bearing and a thrust bearing of rotary vane steering gear

PORSGRUNN ROTARY VANE STEERING GEAR.

Function rudder fall off.

The rotary vane steering gear is working like a type of hydraulic motor with limited movement.

In the housing we have two stoppers limiting the movement, where normal movement

is 2 x 37 or 2 x 65

We have an upper and lower radial bearing and a thrust bearing, all lubricated through the system oil. Oil for lubricating of the bearings will during running have a flow from pressure side to low pressure side in the actuator. This condition will result in an internal liquid by pass.

With steering control in NFU-mode, i.e. emergency steering, and no order given the rudder will fall off to the side with lowest pressure.

With the steering control in F.U.-mode the falling off will be taken care of by the autopilot system. The dead band of the follow up system should normally be 0.5 to 1.0 degree.

The mech. limit switches should be adjusted to 1 degree below max. possible rudder

angle. The electronic limitation should be adjusted to 1 degree below adjustment of the mech. limit switches and allow a dead band like 0,5 degree.

The time registration for rudder falling off depends on actual rudder force, rudder angle, speed of vessel, and will always be different for each steering gear actuator and also type of vessel.

Due to the design of our sealing system our experience is that the rudder falling off time will be reduced after a time is service, however an internal liquid by pass will always be present in order to lubricate and wash the bearings. In that way the lubrication oil for the bearings is changed continuos.

RUDDER ACTUATOR MAIN COMPONENTS:

Type of rotor : Cast in one piece w/two vanes

Material - rotor : Nodular cast iron:

Material – housing/cover/stoppers : Nodular cast iron:

Material - linings and rudder bearing : JM1-15 Johnson Metall

Cu 85%, Sn 4-6%, Pb 4-6%, Zn 4-6%

Material sealings : Unpressurized sealing rudderstock / steering gear:Box sealing

Sealing rotor / cover:Spring loaded cast iron sealing ring.

Sealing in vanes and stoppers: founded iron GG-25 w/tensioned springs.

DESCRIPTION OF STEERING GEAR FUNCTION AND DESIGN.

STANDARD TYPE

The Porsgrunn rotary vane steering gear actuator is provided with two vanes.

It is a keyless conical connection between rudder stock and rotor, and the oil injection method is used for the fit. Rudder stock nut with pull up piston on top of the stock.

The actuator is provided with internal mechanical stoppers to limit the max. rudder angle.

Built into the lower section is a fixed bronze radial bearing and a floating rudder carrier of the same material.

The upper part has a fixed radial bronze bearing. The bearings are lubricated by the steering gear system oil.

The loads/forces from rudder/rudder stock are taken by the upper and lower radial bearings and the rudder carrier. The torque is transferred to the hull via staybolts (fitbolts) in the stoppers.

Valve-block with pilotvalve (type On / Off) and shut off valves (fast acting) are mounted direct on the housing or on the cover. Relief valves are incorporated in the control valves for the protection of the pumps.

There are at least two off power units.

One common “leak” tank, open to air, is mounted at the top of the actuator,with pipelines to the Pump tanks.

Mechanical rudder indicator, rudder angle transmitter, feed backs and rudder angle limit

switches are mounted on the expansion tank.

The “leak” tank is permanently connected to a storage oil tank.

One or two relief valves are mounted direct on the housing or on the cover in order to protect the actuator.

One common level switch is mounted on the “leak” tank and one in each of the pump tanks.

Steering gear room: Electric starters with instruments, start-stop switch. Device for Remote/Local steering control. Local steering control of NFU mode or directly on the magnetic valves.

E.C.R.:Panels with run indications and alarm indications for el. failure, hydraulic lock and low oil levels.

W.H.: Panels with start-stop-standby functions.

Run indications, steering control ready, remote and local indication, alarm indications for el.failure, hydraulic lock, filter clogged, and oil low levels.

2. FUNCTION

Start-Stop/Stand by:Start/stop may be operated from two places:

Wheel house - Steering gear room.

The start/stop - operation is normally a manual operation.

"Start/Stop" by means of "Pulse switch" and "Step relay". The "Step relay" can also be manually operated, (inside starters).The two hydraulic power units may be operated separate or together.

Auto-start based on following and stand by mode.

a. At electrical failure.

b. At oil leakage.

c. At hydraulic lock

Only alarm as follows.

Phase alarm. Pump stopped.

Low level in “leak” tank, (run or not run).

Filter clogged.

Steering control: If steering control is transferred to "Local". This mode will either not allow "stand by" of the next pump. The indication lamp "Local" on bridge will light.

"Stand by" in one power unit will always be set automatically when the other one is started manually.

"Stand by" in one power unit will always be set automatically when one power unit is stopped in a normal way.

"Stand by" can also be set and reset manually by the push button "Stand by".

Power unit in operation can not be in "Stand by".

Power unit out of order due to a failure can not be in "Stand by".

A. ELECTRICAL FUNCTION FAILURE.

The following will be monitored for electrical failure:

1. Overloaded alarm

2. Phase alarm

3. Steering control alarm

4. Power

5- Phase alarm and Power have same nature in the system and therefore have common alarm.

By all alarms we have flash-light and pulsating sound signal until acknowledge.

B. OIL LEAKAGE

Common oil level switch in “leak” tank. This tank is common for both power units.

One level switch in each pump tank. Alarm on low level.

B1. FILTER CLOGGED

Each pump tank have built in a return filter with a pressure drop measuring indicator. The task

of the indicator is to monitor the filter condition and will be activated before the filter is in by

pass.

C. HYDRAULIC LOCK
You can watch at the following link the explanation about hydraulic lock
https://www.youtube.com/watch?v=uCnpCBcG7vc

The function is monitoring the valve block function, based on steering control signal from

wheel house and the response from the main directional spool.

Alarms:

All common alarms are based on N.C. contacts. Alarm will occur when we have a break in the circuit.

When an alarm occur, the specific alarm lamp start flashing and the buzzer is activated, until

acknowledge. Then we have a fixed light and no sound as long as the alarm condition remain.

If a new alarm occur, the procedure starts again.

If the power unit has been stopped before acknowledge, the flashing alarm and sound will be there until acknowledge. If the condition for the alarm disappear before acknowledge, the flashing alarm and sound will be there until acknowledge, but there will be no fixed light after acknowledge. All alarms are delayed for 2 till 5 sec., filter clogged is delayed 5 min. at start of pump, thereafter 10 sec. All alarms activate one common output. Pot-free.

The system is based on "Single failure" criteria.

Autostart:One power unit has to be in operation. The other power unit to be in "Stand by". If not in "Stan-by" we will only have alarm.

Autostart can not occur if both pumps are stopped, (alongside).Lamp test:Only on panels. Acknowledge: Only on W.H. panel.

credit to PORSGRUNN ROTARY VANE STEERING GEAR MANUAL

Chambers are formed between the sealing bars on rotor and the stopper bars in stator casing. These chambers will vary in size as the rotor move and can be pressurized since spring back sealing bar.

Chambers are alternatively connected to the suction and delivery pipe from hydraulic pumps so that low and high pressure compartments are created which produced the rudder actuating torque.

Steering gear oil

1-low pour point(-50’C), 2-low viscosity (redwood 30 secs at 60’C), 3-High flash point(150’C) closed,4-non corrosive, 5-non sludge forming 6-non freezing, 7-good lubricating properties with high V.I(110) 

credit to PORSGRUNN ROTARY VANE STEERING GEAR MANUAL 

Regulation 29 - Steering gear

1. Unless expressly provided otherwise, every ship shall be provided with a main steering gear and an auxiliary steering gear to the satisfaction of the Administration. The main steering gear and the auxiliary steering gear shall be so arranged that the failure of one of them will not render the other one inoperative.

2.1. All the steering gear components and the rudder stock shall be of sound and reliable construction to the satisfaction of the Administration. Special consideration shall be given to the suitability of any essential component which is not duplicated. Any such essential component shall, where appropriate, utilize antifriction bearings such as ball-bearings, roller-bearings or sleeve-bearings which shall be permanently lubricated or provided with lubrication fittings.

2.2. The design pressure for calculations to determine the scantlings of piping and other steering gear components subjected to internal hydraulic pressure shall be at least 1.25 times the maximum working pressure to be expected under the operational conditions specified in paragraph 3.2, taking into account any pressure which may exist in the low-pressure side of the system. At the discretion of the Administration, fatigue criteria shall be applied for the design of piping and components, taking into account pulsating pressures due to dynamic loads.

2.3. Relief valves shall be fitted to any part of the hydraulic system which can be isolated and in which pressure can be generated from the power source or from external forces. The setting of the relief valves shall not exceed the design pressure. The valves shall be of adequate size and so arranged as to avoid an undue rise in pressure above the design pressure.

3. The main steering gear and rudder stock shall be:

.1. of adequate strength and capable of steering the ship at maximum ahead service speed which shall be demonstrated;

.2. capable of putting the rudder over from 35° on one side to 35° on the other side with the ship at its deepest seagoing draught and running ahead at maximum ahead service speed and, under the same conditions, from 35° on either side to 30° on the other side in not more than 28 s; Where it is impractical to demonstrate compliance with this requirement during sea trails with the ship at its deepest seagoing draught and running ahead at the speed corresponding to the number of max continuous revolution of the main engine and max design pitch, ships regardless of date of construction may demonstrate compliance with this requirement by one of the following methods:

1-during sea trails the ship is at even keel and the rudder fully submerged whilst running ahead at the speed corresponding to the number of max continuous rev of the main engine and max design pitch: or

2-where full rudder immersion during sea trails cannot be achieved, an appropriate ahead speed shall be calculated using the submerged rudder blade area in the proposed sea trail loading condition. The calculated ahead speed shall result in a force and torque applied to the main steering gear which is at least as great as if it was being tested with the ship at its deepest seagoing draught and running ahead at the speed corresponding to the number of maax continuous rev of the main engine and max design pitch: or

3-the rudder force and torque at the sea trial loading condition have been reliably predicted and extrapolated to the full load condition. The speed of the ship shall correspond to the number of max continuous rev of the main engine and max design pitch of the propeller.

.3. operated by power where necessary to meet the requirements of paragraph 3.2 and in any case when the Administration requires a rudder stock of over 120 mm diameter in way of the tiller, excluding strengthening for navigation in ice; and

.4. so designed that they will not be damaged at maximum astern speed; however, this design requirement need not be proved by trials at maximum astern speed and maximum rudder angle.

4. The auxiliary steering gear shall be:

.1. of adequate strength and capable of steering the ship at navigable speed and of being brought speedily into action in an emergency;

.2. capable of putting the rudder over from 15° on one side to 15° on the other side in not more than 60 s with the ship at its deepest seagoing draught and running ahead at one half of the maximum ahead service speed or 7 knots, whichever is the greater; and

.3. operated by power where necessary to meet the requirements of paragraph 4.2 and in any case when the Administration requires a rudder stock of over 230 mm diameter in way of the tiller, excluding strengthening for navigation in ice.

5. Main and auxiliary steering gear power units shall be:

.1. arranged to restart automatically when power is restored after a power failure; and

.2. capable of being brought into operation from a position on the navigation bridge. In the event of a power failure to any one of the steering gear power units, an audible and visual alarm shall be given on the navigation bridge.

6.1. Where the main steering gear comprises two or more identical power units, an auxiliary steering gear need not be fitted, provided that:

.1. in a passenger ship, the main steering gear is capable of operating the rudder as required by paragraph 3.2 while any one of the power units is out of operation;

.2. in a cargo ship, the main steering gear is capable of operating the rudder as required by paragraph 3.2 while operating with all power units;

.3. the main steering gear is so arranged that after a single failure in its piping system or in one of the power units the defect can be isolated so that steering capability can be maintained or speedily regained.

6.2. The Administration may, until 1 September 1986, accept the fitting of a steering gear which has a proven record of reliability but does not comply with the requirements of paragraph 6.1.3 for a hydraulic system.

6.3. Steering gears, other than of the hydraulic type, shall achieve standards equivalent to the requirements of this paragraph to the satisfaction of the Administration.

7. Steering gear control shall be provided:

.1. for the main steering gear, both on the navigation bridge and in the steering gear compartment;

.2. where the main steering gear is arranged in accordance with paragraph 6, by two independent control systems, both operable from the navigation bridge. This does not require duplication of the steering wheel or steering lever. Where the control system consists of a hydraulic telemotor, a second independent system need not be fitted, except in a tanker, chemical tanker or gas carrier of 10,000 tons gross tonnage and upwards;

.3. for the auxiliary steering gear, in the steering gear compartment and, if power-operated, it shall also be operable from the navigation bridge and shall be independent of the control system for the main steering gear.

8. Any main and auxiliary steering gear control system operable from the navigation bridge shall comply with the following:

.1. if electric, it shall be served by its own separate circuit supplied from a steering gear power circuit from a point within the steering gear compartment, or directly from switchboard busbars supplying that steering gear power circuit at a point on the switchboard adjacent to the supply to the steering gear power circuit;

.2. means shall be provided in the steering gear compartment for disconnecting any control system operable from the navigation bridge from the steering gear it serves;

.3. the system shall be capable of being brought into operation from a position on the navigation bridge;

.4. in the event of a failure of electrical power supply to the control system, an audible and visual alarm shall be given on the navigation bridge; and

.5. short circuit protection only shall be provided for steering gear control supply circuits.

9. The electrical power circuits and the steering gear control systems with their associated components, cables and pipes required by this regulation and by regulation 30 shall be separated as far as is practicable throughout their length.

10. A means of communication shall be provided between the navigation bridge and the steering gear compartment.

11. The angular position of the rudder shall:

.1. if the main steering gear is power-operated, be indicated on the navigation bridge. The rudder angle indication shall be independent of the steering gear control system;

.2. be recognizable in the steering gear compartment.

12. Hydraulic power-operated steering gear shall be provided with the following:

.1. arrangements to maintain the cleanliness of the hydraulic fluid taking into consideration the type and design of the hydraulic system;

.2. a low-level alarm for each hydraulic fluid reservoir to give the earliest practicable indication of hydraulic fluid leakage. Audible and visual alarms shall be given on the navigation bridge and in the machinery space where they can be readily observed; and

.3. a fixed storage tank having sufficient capacity to recharge at least one power actuating system including the reservoir, where the main steering gear is required to be power-operated. The storage tank shall be permanently connected by piping in such a manner that the hydraulic systems can be readily recharged from a position within the steering gear compartment and shall be provided with a contents gauge.

13. The steering gear compartments shall be:

.1. readily accessible and, as far as practicable, separated from machinery spaces; and

.2. provided with suitable arrangements to ensure working access to steering gear machinery and controls. These arrangements shall include handrails and gratings or other nonslip surfaces to ensure suitable working conditions in the event of hydraulic fluid leakage.

14. Where the rudder stock is required to be over 230 mm diameter in way of the tiller, excluding strengthening for navigation in ice, an alternative power supply, sufficient at least to supply the steering gear power unit which complies with the requirements of paragraph 4.2 and also its associated control system and the rudder angle indicator, shall be provided automatically, within 45 s, either from the emergency source of electrical power or from an independent source of power located in the steering gear compartment. This independent source of power shall be used only for this purpose. In every ship of 10,000 gross tonnage and upwards, the alternative power supply shall have a capacity for at least 30 min of continuous operation and in any other ship for at least 10 min.

15. In every tanker, chemical tanker or gas carrier of 10,000 gross tonnage and upwards and in every other ship of 70,000 gross tonnage and upwards, the main steering gear shall comprise two or more identical power units complying with the provisions of paragraph 6.

16. Every tanker, chemical tanker or gas carrier of 10,000 gross tonnage and upwards shall, subject to paragraph 17, comply with the following:

.1. the main steering gear shall be so arranged that in the event of loss of steering capability due to a single failure in any part of one of the power actuating systems of the main steering gear, excluding the tiller, quadrant or components serving the same purpose, or seizure of the rudder actuators, steering capability shall be regained in not more than 45 s after the loss of one power actuating system;

.2. the main steering gear shall comprise either:

.2.1. two independent and separate power actuating systems, each capable of meeting the requirements of paragraph 3.2; or

.2.2. at least two identical power actuating systems which, acting simultaneously in normal operation, shall be capable of meeting the requirements of paragraph 3.2. Where necessary to comply with this requirement, interconnection of hydraulic power actuating systems shall be provided. Loss of hydraulic fluid from one system shall be capable of being detected and the defective system automatically isolated so that the other actuating system or systems shall remain fully operational;

.3. steering gears other than of the hydraulic type shall achieve equivalent standards.

17. For tankers, chemical tankers or gas carriers of 10,000 gross tonnage and upwards, but of less than 100,000 tonnes deadweight, solutions other than those set out in paragraph 16, which need not apply the single failure criterion to the rudder actuator or actuators, may be permitted provided that an equivalent safety standard is achieved and that:

.1. following loss of steering capability due to a single failure of any part of the piping system or in one of the power units, steering capability shall be regained within 45 s; and

.2. two independent steering gear control systems shall be provided each of which can be operated from the navigation bridge. This does not require duplication of the steering wheel or steering lever;

.3. if the steering gear control system in operation fails, the second system shall be capable of being brought into immediate operation from the navigation bridge; and

.4. each steering gear control system, if electric, shall be served by its own separate circuit supplied from the steering gear power circuit or directly from switchboard busbars supplying that steering gear power circuit at a point on the switchboard adjacent to the supply to the steering gear power circuit.

20. In addition to the requirements of paragraph 19, in every tanker, chemical tanker or gas carrier of 40,000 gross tonnage and upwards, constructed before 1 September 1984, the steering gear shall, not later than 1 September 1988, be so arranged that, in the event of a single failure of the piping or of one of the power units, steering capability can be maintained or the rudder movement can be limited so that steering capability can be speedily regained. This shall be achieved by:

.1. an independent means of restraining the rudder; or

.2. fast-acting valves which may be manually operated to isolate the actuator or actuators from the external hydraulic piping together with a means of directly refilling the actuators by a fixed independent power-operated pump and piping system; or

.3. an arrangement such that, where hydraulic power systems are interconnected, loss of hydraulic fluid from one system shall be detected and the defective system isolated either automatically or from the navigation bridge so that the other system remains fully operational.

credit to marine electrical technology by Elstan A Fernandez

Electro-hydraulic Control--Turning a wheel causes change a value at potmeter that attached to steering wheel. Pot meter fitted at steering wheel give signal to B channel (terminal 1 & 11) and Pot meter fitted at rudder stock give rudder angle feedback signal to A channel (terminal 1 & 2) of 2286A.  2286 A CPU will detect and calculate the error between B channel (terminal 1 & 11) & A channel ( terminal 1 & 2). After calculated error, CPU will send correcting signal by activating relay 1 or relay 2 correspondingly. Activating action of relay 1 or relay 2 will drive the DCV of hydraulic pump to receive port or stb movement of ram.  local (manual) control of the steering gear was achieved by electrically operate local control switch at steering gear room.

Two-ram Electrically-controlled, Hydraulically-operated Steering System

Adventage of electrically control hydraulically operate steering gear - Compatibility with complex control systems, Less running hours for pumps, Increased reliability,  Easy and quick changeover to a standby hydraulic system,  Local control from the unit itself in case of an emergency.

Electro-hydraulic Steering Gear is of the "Rapson Slide Type" construction and consists mainly of tiller, ram and ram pin, hydraulic cylinder, axial piston pump, valves and pipings.

The hydraulic pump is of fixed displacement type (used by fixing the stroke of variable-displacement type) and delivers the rated volume of oil in the rated direction. This direction of oil is controlled by the solenoid valve or ·sol-hyd. valve according to the order angle from the steering stand on the bridge and the oil acts on the ram. The ram thrust produced by the pressure oil is transmitted to the tiller arm through the ram pin and roller bearings and converted to the torque of the tiller keyed to the rudder is moved.

The actual angle is feed-backed to the steering stand through the repeater back unit and the ram stops since the valve is shifted to neutral position when order and actual angles are completely coincident.

pls check at following link about 4 ram hydraulic steering gear 
https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwi7oaCVhO7iAhVCnI8KHUxQBPMQjRx6BAgBEAU&url=https%3A%2F%2Fforshipbuilding.com%2Fship-machine%2Fsteering-gear%2F&psig=AOvVaw1iOtkb7KN6oVIkuwMmauYX&ust=1560775533651124

Thus ARST series (valve control) steering gear is so arranged that order and actual angles are compared and the solenoid valve is directly controlled by its deviation signal, consequently the rudder can be moved in high responsibility.

One or two sets of the hydraulic pump and electric motor are provided and have enough capacity to operate the rudder within the time required by the classification society.

For the specifications of the steering gear, refer to the particulars of the separate

volume.

Tiller

The tiller made of cast steel, designed and manufactured according to the requirements of classification society is fixed to the rudder stock with the key. On the fork typed openings of the tiller, the hardened steel plates are bolted and they contact directly with the roller bearing of the ram. According as the ram is converted to the circular motion of the tiller.

Ram and Hydraulic Cylinder

1) The ram is made of carbon steel for mechanical structural use, and the hydraulic cylinder of nodular carbon steel. (2) The ram pin is incorporated into the center of the ram whose surface has been finished with high accuracy, and the rotatory roller bearings are fitted into the upper and lower parts of the ram pin and contact directly with the fork typed openings of the tiller arm. The ram thrust is transmitted to the tiller through the ram pin. Therefore, the ram pin is subjected to a strong force, but this can be dealt with by employing the material of high tensile strength. The oilless metal is fitted in the bore of the roller bearing and minimize the rotational friction between the ram pin and the roller bearing. And also lubrication with oil on the bearing is unnecessary. (3) Two hydraulic cylinders that move the one set of ram are securely installed on the bed plate of the hull. A pair of opposed hydraulic cylinders is connected with the ram guide bar. The hydraulic pump unit and the electric motor are installed on the hydraulic cylinders.

Inside of the each hydraulic cylinder, neck bushing is provided, supports the ram and withstands the perpendicular component force of the ram. Five V-packings are also provided inside of the each hydraulic cylinder for preventing oil leakage. The packings are tightened by the adapters and the packing gland, and have superior sealing effect. The rudder movement is indicated by the rudder angle indicator plate fitted between opposed hydraulic cylinders.

The max. turning angle is restricted by the mechanical stopper at the bottom of hydraulic cylinder.

Oil tank :

The oil tank is made of cast iron and mounted on the hydraulic cylinder. Inside of the tank, the hydraulic pimp and pipes are installed, and outside of the tank, valve unit is mounted. The oil filler, filter, oil lever gauge, thermometer, drain plug etc. are also provided on the tank.

The maximum tilting angle is fixed by the pump fixing plate on the pump

Valve unit:

Valve unit consists of the oil-hyd valve, the brake valve having safety valve and check valve, the air vent valve etc. and these valves are assembled on a common manifold which is mounted out side of the oil tank

1) Solenoid Valve or Sol-Hyd Valve

Receiving the steering order (electric rudder command signal) from the steering stand on the bridge, this valve controls the direction of oil delivered from the pump, When the steering order is not given, this valve is in neutral position and blocks the pressured oil from the hydraulic cylinders, consequently the rudder is stopped. At the failure of control source of steering stand, the steering can be carried out by pushing manually the push rods of solenoid valve in the steering gear room (local steering) subjected that the hydraulic pump, the electric motor and valves are in sound conditions.

(2) Brake Valve

Brake valve consists of the safety valve and the check valve

Safety valve: This valve releases an abnormal high pressure produced in the hydraulic system by any reason and protects the system.

This valve is adjusted at the pressure of 1.25 times max. working pressure (design pressure)

Check valve : These valves have the functions of not only controlling the direction of oil from/to the safety valve but also replenishing oil from the oil tank to prevent the cylinder from sucking the air due to the rudder force at ship's anchoring.

(3) Check Valve

This valve is provided to control the direction of oil from the pump to safety valve and protect the pump when the delivered pressure is risen abnormally by any reason. Also this valve has a function to produce the pilot pressure applied to the sol-hyd valve.

Cylinder Stop Valve :

The steering gear has two pumps and duplicate piping systems against one set of actuator 1 ram 2 cylinders).

Although all cylinder stop valves are opened normally, In case of single failure of the pump pipings, steering can be continued by closing the valves according to the instruction plate. Also the rudder can be fixed by closing this valves at ship's anchoring in long period (In this case, don't fail to open the stop valves before starting the pump).

Hydraulic Pump :

This steering gear adopts the hydraulic pump of which tilting stroke is fixed although followings are general instructions for standard pump.

 Construction and Name of Parts :

The hydraulic pump is of a variable displacement axial piston type, compact and light, and shows high volumetric and mechanical efficiencies without influenced by pressure range.

The pump is installed top of the oil tank by means of the bolted bed and direct-coupled through the flexible coupling to the electric motor outside of the oil tank.

The pump consists mainly of the cylinder fitted in the cylinder casing. the seven piston sub being in reciprocating motion in seven bores of the cylinder, the driving shaft sub-group which transmits power to the pump, the bearings which support the driving shaft, the bearing casing the front cover in which oil seal is provided, the valve cover sub-group.

The cylinder is guided by the center rod and rotated on the valve plate fitted on the valve cover. As contact surfaces of the cylinder and the valve plate are of the spherical construction, self-centering can be obtained when the cylinder is rotated. The driving shaft is supported by the bearing casing through the roller bearing and tapered roller bearing. The cylinder casing is supported by the two needle roller bearings. The cylinder casing together with the cylinder, therefore, can be tilted around the axis of the needle roller bearings by moving the pi of the' cylinder casing by means of pump control gear (link mechanism). Rotating motion of the driving shaft actuated by and electric motor is transmitted to the cylinder through the connecting rod, the cylinder is accordingly rotated around its center in the synchronous speed of the driving shaft. In the case the cylinder is located in the oblique position against the driving shaft centre, the piston reciprocates in the cylinder bore relatively to the cylinder. The valve plate having a suction and a delivery port to change over oil with the reciprocating motion of the piston is provided between the cylinder and the valve cover. The valve plate and the cylinder are in optimum hydraulic balance during pump running. Oil to be delivered from and sucked in the pump cylinder passes through the passages in the valve cover, the cylinder casing and the pipe flange, then it is transferred to the pipe outside of the pump. Suction valve unit serves for replenishing oil automatically from the oil tank during pump running.

Air Release in Hydraulic System:

It is not enough to fill the. hydraulic system with working oil at preparation (When the pump is started, its abnormal noises prove that a great amount of air is still left in the system).

To expel air in the system, operate the steering gear slowly to "Port" and "Starboard" sides alternately (up to near 30 degrees in both directions) and open the air vent valve on the upper part of the hydraulic cylinder of the pressure side (ram-drawing side) .

Keep on doing this work until the intermittent movement of the ram is finished and smooth movement begins.

In this case the hydraulic pump will be started one by one. Care should be taken to the oil level of oil tank and replenish the working oil if necessary.

Note : 1. Don't open the air vent valve on the cylinder into which ram is pressed. If it will be opened, the air that has tried to expel will be sucked much. 2. Before expelling the air, don't run the hydraulic pump for hours.

The air releasing methods are different according to the type of steering gear. So expel the air after confirming the type of hydraulic pump in particulars.

1) In case of steering gear provided with the sol-hyd valve - Before moving the ram by local steering, fill the oil and expel the air In the hydraulic system between pump and sol-hyd valve in the following procedure.Caution : 1. Aboves should be carried out at the installation of steering gear and after re-assembling of hydraulic pump and sol-valve. 2. Aboves will be unnecessary at periodical air release.Remove the air vent plug and the air vent valve on the manifold for No. 1 valve unit.

2) Rotate the hydraulic pump about ten to twenty turns by hand to fill with working oil and then screw the plug (keep on opening the air vent valve).

3) Start the No. 1 pump unit and expel the air. After confirming that ram can be moved by pushing the push rod of solenoid valve, close the air vent valve.

4) Apply the same manner to No. 2 pump unit. - Operating the steering gear by local steering, expel the air in the hydraulic system by opening the air vent valve on the upper part of cylinder as mentioned in general instructions.

Adjusting Test of Safety Valve:

The safety valve limits the max. pressure of the hydraulic system and releases abnormal high pressure produced in the hydraulic system to protect the system to protect the system against abnormal load acting on the rudder. The adjusting pressure has been set at the adjusting pressure shown in particulars before delivery from our works. Re-adjustment is not required

accordingly. However, it is necessary to confirm the operation on board together with the

pressure test of the hydraulic pipes, gaskets etc. whose procedures are as follows:

1) Preparation :

The safety valve test will be carried out by local steering. Depending on the safety valve subject to confirmation, the hydraulic pump and the stop valve shall be operated as shown in hyd circuit.

(2) Safety Valve Operation:

Start the electric motor and hydraulic pump and operate the steering gear.- When the rudder angle is over 35 degrees, move the rudder slowly.

Since the ram reaches the stopper at the bottom of the cylinder, the pressure will rise.

Under this condition, confirm the adjusting pressure of the safety valve by observing the movement of the pointer of the pressure gauge. (The adjusting pressure is marked with red on the dial plate of the pressure gauge.)

- The operation of the safety valve shall not exceed 30 seconds at a time because the electric motor may cause burning. (3) Adjustment of Safety Valve: If the adjusting pressure of the safety valve is differed form the designed one, adjust it in the following manner ;

- Remove the safety valve cap nut and loosen the lock nut.

- Adjust the pressure by turning the adjusting screw. Pressure will rise if screw is turned to right and pressure will drop if turned to left.

- After the adjustment, fix the lock nut and put the cap nut as original. When confirming the safety valve, check for oil leakage and abnormality in each part of the steering gear.

After the test is over, put the stop valve to the original condition.

Electronic Steering Control

credit to marine electrical technology by Elstan A Fernandez

This method may use a microprocessor-based circuit to receive the helm order and the rudder position feedback and compare them. Some other cases an operational amplifier could also be used instead. Cumbersome mechanical linkages and differential controls are replaced by quick-response electronic servo control valves on the hydraulic pump, which receive the order from the microprocessor and stroke the pump in the direction and the degree requested.

The variant of this is a system where the electronic signals from the controller and the feedback device are compared, amplified by the power amplifier whose output controls solenoids within the electro-hydraulic unit. The electro hydraulic unit serves as an interface between the computing circuit and the hydraulically-operated rams. It directs the hydraulic pressure to the cylinders.

Electronic steering gear – manual mode

The follow-up element, which, is either a potentiometer or a rotary transformer, is moved in direct proportion to the motion of the rudder-stock or simpler said, the ram itself. It provides the negative feedback signal to the control circuit to de-stroke the pump and stop the rudder at the ordered angle or, in the other case, to nullify the output of the operational amplifier which in turn forces the output of the power amplifier to zero. This brings the solenoid valve to the neutral position. The blind-ports are then aligned with the hydraulic lines leading to the rams; this action results in holding the rudder in the desired position by trapping the hydraulic fluid within the cylinders.

credit to marine electrical technology by Elstan A Fernandez

Auto pilot mode

An error in the feedback system caused by a new helm or autopilot order as above mode or by motion of the rudder due to external dynamic forces reactivates the control system; other signals that influence the control of the rudder are:

# The ship's speed;

# The turning radius (may be set manually also);

# The set course;

# The rate of change o f course;

# The present position of the rudder itself

Rudder Position Indicator

Rudder position indicators are meant to continuously transmit the actual position of the rudder to control consoles on the bridge, the engine control room and possibly the engine room and steering flat too.

The Precision Potentiometer and Stepper Motor Type (Type A070)

This equipment is available in different sizes and styles according to the various requirements on a ship and can be installed in all types of vessels. The system in mention consists of a power supply unit, a transmitter mechanically

coupled to the rudder shaft by a lever-drive or flange coupling, and one or more receivers(indication instruments).

Operating Principle

The changing of the rudder: position is registered by a precision potentiometer in conductive plastic, installed in a watertight aluminium casing. The output current loop (4 – 20 mA) is driven by precision operational amplifiers. Thus, the influence of wire resistance and voltage fluctuation is eliminated. The receiver electronically controls a high-resolution stepper motor, which enables the pointer to settle within 0.5° of the rudder position.