Section 5 Securing of machinery

5.1 Fastenings

5.1.1 Bedplates, thrust seatings and other fastenings are to be of robust construction. The machinery is to be securely fixed to the craft's structure, such that the arrangement is sufficient to restrain the dynamic forces arising from vertical and horizontal acceleration appropriate to the intended service.

5.2 Collision load

5.2.1 Unless an accurate analysis of the collision load is submitted and found acceptable by LR, the collision load is to be determined from:

where the load P _coll is taken as the lesser of:

P _coll	=
P _coll	=

where

C _H	=	a factor given in Table 1.5.1 Factor C _H
C _L	=
D	=	craft depth, in metres, from the underside of keel amidships to the top of effective hull girder
E	=	0,5 Δ V ² kNm
H _T	=	minimum height, in metres, from tunnel or wet-deck bottom to the top of effective hull girder for catamarans and surface effect ships
	=	D for air cushion vehicles
L _WL	=	craft waterline length, in metres
M	=	1,3 for high tensile steel
	=	1,0 for aluminium alloy
	=	0,95 for mild steel
	=	0,8 for fibre reinforced plastics
T	=	buoyancy tank clearance to skirt tip, in metres, (negative) for ACVs
	=	lifted clearance from keel to water surface, in metres, (negative) for hydrofoils
	=	craft draught to the underside of keel amidships, in metres, for all other craft
V	=	operational speed of craft, in m/s
g	=	gravitational acceleration = 9,806 m/s²
Δ	=	craft displacement, to be taken as the mean of the lightweight and maximum operational weight, in tonnes

Table 1.5.1 Factor C _H

Factor C _H	Catamarans, SES	Mono-hulls, H'foils	ACVs
C _H
where
f = 0 for	T + 2 < D - H _T	T + 2 < D	-
f = 1 for	D > T + 2 ≥ D - H _T	T + 2 ≥ D	H _T > 2
f = 2 for	T + 2 ≥ DM	-	H _T ≤ 2

5.3 Resilient mounts

5.3.1 The dynamic angles of inclination in Table 1.4.1 Inclinations may be exceeded in certain circumstances dependent upon ship type and operation. The Shipbuilder is, therefore, to ensure that the vibration levels of flexible pipe connections, shaft couplings and mounts remain within the limits specified by the component manufacturer for the following conditions:

Maximum dynamic inclinations to be expected during service;
Start-stop operation; and
The natural frequencies of the system.

Due account is to be taken of any creep that may be inherent in the mount.

5.3.2 For equipment of installed power greater than 375 kW, see Pt 16, Ch 2, 1.6 Definitions 1.6.10(b), a calculation report is to be submitted to demonstrate that the requirements of Pt 9, Ch 1, 5.3 Resilient mounts 5.3.2 are met. The calculation report is to include as a minimum:

A plan showing the arrangement of the machinery including mounts, exhaust bellows, and flexible couplings and pipe connections, as applicable; and
Maximum allowable loads and deflections and any appropriate type approval documentation for each flexible element (resilient mounts, exhaust gas bellows, flexible couplings and any other applicable flexible pipe connections) for the conditions identified in Pt 9, Ch 1, 5.3 Resilient mounts 5.3.2; and
Calculations including natural frequencies and maximum expected loads and deflections of each flexible element (resilient mounts, exhaust gas bellows, flexible couplings and any other applicable flexible pipe connections) for the conditions identified in Pt 9, Ch 1, 5.3 Resilient mounts 5.3.2.

5.3.3 Chocks are to be fitted, together with positive means to ensure that manufacturers’ limits for lateral or vertical motion are not exceeded. Where resilient mounts are approved for collision loading, see Pt 9, Ch 1, 5.2 Collision load, then the extent of any additional chocking that may be required will be specially considered. Suitable means are to be provided to accommodate the propeller thrust.

5.3.4 Mounts are to be shielded from the possible detrimental effects of oil and, where appropriate, paint and other contaminants.

5.3.5 Shafting, piping connections and electrical cable connections are to be provided with sufficient flexibility to accommodate expected movements. Particular attention should be paid to exhaust bellows and the effectiveness of flexible couplings.

5.4 Resin chocks

5.4.1 Synthetic resin compounds used as materials for chocks under machinery components for which alignment is critical, e.g. main engine, gearbox and auxiliary installations where the engine and generator do not share a common baseplate, are to be of a type approved by LR.

5.4.2 The resin chock materials referred to in Pt 9, Ch 1, 5.4 Resin chocks 5.4.1 are to be tested in accordance with Ch 14, 2.11 Machinery chocking compounds (resin chocks) of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.

5.4.3 Materials for chocks are to be approved for the maximum service temperature that the chock will experience.