Section
3 Construction and design
3.1 General
3.1.3 The
welding details and welding procedures are to be approved. All welded
joints within the pressure boundary of a rudder actuator or connecting
parts transmitting mechanical loads are to be full penetration type
or of equivalent strength.
3.1.4 The
construction is to be such as to minimise local concentrations of
stress.
3.1.6 For
the rudder actuator, the permissible primary general membrane stress
is not to exceed the lower of the following values:
where
σB
|
= |
specified
minimum tensile strength of material at ambient temperature |
σy
|
= |
specified
minimum yield stress or 0,2 per cent proof stress of the material,
at ambient temperature |
A and B are given by the following
Table:
|
Wrought steel
|
Cast steel
|
Nodular cast iron
|
A
|
3,5
|
4
|
5
|
B
|
1,7
|
2
|
3
|
3.2 Components
3.2.1 Special
consideration is to be given to the suitability of any essential component
which is not duplicated. Any such essential component shall, where
appropriate, utilise anti-friction bearings such as ball bearings,
roller bearings or sleeve bearings which shall be permanently lubricated
or provided with lubrication fittings.
3.2.2 All
steering gear components transmitting mechanical forces to the rudder
stock, which are not protected against overload by structural rudder
stops or mechanical buffers, are to have a strength at least equivalent
to that of the rudder stock in way of the tiller.
3.2.3 Actuator
oil seals between non-moving parts, forming part of the external pressure
boundary, are to be of the metal upon metal type or of an equivalent
type.
3.2.4 Actuator
oil seals between moving parts, forming part of the external pressure
boundary, are to be duplicated, so that the failure of one seal does
not render the actuator inoperative. Alternative arrangements providing
equivalent protection against leakage may be accepted.
3.2.6 Hydraulic
power operated steering gear are to be provided with the following
:
-
Arrangements
to maintain the cleanliness of the hydraulic fluid taking into consideration
the type and design of the hydraulic system;
-
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 is to 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
provided with a contents gauge.
3.3 Valve and relief valve arrangements
3.3.1 For
vessels with non-duplicated actuators, isolating valves are to be
fitted at the connection of pipes to the actuator, and are to be directly
fitted on the actuator.
3.3.2 Arrangements
for bleeding air from the hydraulic system are to be provided, where
necessary.
3.3.3 Relief
valves are to 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 settings of the relief valves
is not to exceed the design pressure. The valves are to be of adequate
size and so arranged as to avoid an undue rise in pressure above the
design pressure.
3.3.4 Relief
valves for protecting any part of the hydraulic system which can be
isolated, as required by Pt 5, Ch 19, 3.3 Valve and relief valve arrangements 3.3.3 are
to comply with the following:
-
The setting pressure
is not to be less than 1,25 times the maximum working pressure.
-
the minimum discharge
capacity of the relief valve(s) is not to be less than 110 per cent
of the total capacity of the pumps which can deliver through it (them).
Under such conditions the rise in pressure is not to exceed
10 per cent of the setting pressure. In this regard, due consideration
is to be given to extreme foreseen ambient conditions in respect of
oil viscosity.
3.4 Flexible hoses
3.4.1 Hose
assemblies approved by Clasifications Register (hereinafter referred to as
'LR') may be installed between two points where flexibility is required
but are not to be subjected to torsional deflection (twisting) under
normal operating conditions. In general, the hose should be limited
to the length necessary to provide for flexibility and for proper
operation of machinery, see also
Pt 5, Ch 12, 7 Flexible hoses.
3.4.2 Hoses
should be high pressure hydraulic hoses according to recognised Standards
and suitable for the fluids, pressures, temperatures and ambient conditions
in question.
3.4.3 Burst
pressure of hoses is to be not less than four times the design pressure.
|
Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime
and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective
officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications
Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance
on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant
Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is
exclusively on the terms and conditions set out in that contract.
|
![](LR-FooterLogo.png) |
|