Section 6 Engine seatings

6.1.1 Main engines and thrust bearings are to be effectively secured to the hull structure by seatings of adequate scantlings to resist the various gravitational, thrust, torque, dynamic and vibratory forces which may be imposed on them.

6.1.2 For initial guidance, recommended scantlings for engine seatings are given in Pt 3, Ch 7, 6.2 Seats for engines 6.2.1.

6.1.3 In the case of higher power engines or turbine installations the seatings should generally be integral with the double bottom structure. The tank top plating in way of the engine foundation plate or the turbine gear case and the thrust bearing should be substantially increased in thickness, see Figure 7.6.1 Engine seatings, Type 1.

6.1.4 If the main machinery is supported on seatings of Type 2 as shown in Figure 7.6.1 Engine seatings, these are to be so designed that they distribute the forces from the engine as uniformly as possible into the supporting structure. Longitudinal members supporting the seating are to be arranged in line with girders in the double bottom, and adequate transverse stiffening is to be arranged in line with floors, see Figure 7.6.1 Engine seatings, Type 2.

6.1.5 In ships having open floors in the machinery space the seatings are generally to be arranged above the level of the top of floors and securely bracketed to them, see Figure 7.6.1 Engine seatings, Type 3.

6.2.1 In determining the scantlings of seats for engines, consideration is to be given to the general rigidity of the engine itself and to its design characteristics in regard to out of balance forces. As a general guide to designers, recommended scantlings are given in Table 7.6.1 Seats for engines - Recommended scantlings.

Note See Pt 3, Ch 7, 4.2 Single bottom structure 4.2.3

Figure 7.6.1 Engine seatings

Table 7.6.1 Seats for engines - Recommended scantlings

Symbols	Item	Scantlings of one seat
L as defined in Pt 3, Ch 1, 6.1 Principal particulars f = engine factor = t = minimum thickness of top plate, in mm	Top plate
t 1, t 2 = main engine girder thicknesses, in mm t 3 = floor plate thickness under seating, in mm, see also Figure 7.6.1 Engine seatings A = area of top plate for one side of seat, in cm2		Minimum thickness: (a) Where two girders fitted (b) Where one girder fitted
	Girders (both inside and above double bottom where fitted)	Number:
where = effective length of engine foundation plate, in metres, required for bolting the engine to the seating. = The thrust and gearcase seating is to be considered as a separate item P = power of one engine at maximum service speed, in kW (bhp)		Generally two but a single girder can be accepted where all the following apply: (a) f < 1,84 (b) P < 5900 kW (c) L < 100 m
R = rev/min of engine at maximum service speed		Total thickness: (a) Where two girders are fitted (b) Where one girder is fitted
	Floors (between girders or under seat where a single girder is fitted)	Thickness:

6.3.1 Seats are to be so designed as to provide effective support for the turbines and ensure their proper alignment with the gearing, and (where applicable) allow for thermal expansion of the casings. In general, the seats are not to be arranged in way of breaks or recesses in the double bottom.

6.4.1 Boiler bearers are to be of substantial construction and efficiently supported by transverse and horizontal brackets. These should generally be arranged in line with plate floors and girders in a double bottom or with suitable deep beams or transverses and girders at boiler flats. Suitable allowance is to be made in the design of the supporting structure for the variation in loading due to thermal expansion effects, see also Pt 5, Ch 14, 2 Fuel oil - General requirements.

6.5.1 Auxiliary machinery is to be secured on seatings, of adequate scantlings, so arranged as to distribute the loadings evenly into the supporting structure.