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Marine Auxiliary Machinery Chapter 9 Lesson 6 Deck Machinery Cargo Access By Professor Zhao Zai Li 05.2006.

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Presentation on theme: "Marine Auxiliary Machinery Chapter 9 Lesson 6 Deck Machinery Cargo Access By Professor Zhao Zai Li 05.2006."— Presentation transcript:

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2 Marine Auxiliary Machinery Chapter 9 Lesson 6 Deck Machinery Cargo Access By Professor Zhao Zai Li

3 CARGO ACCESS (1)  Although not strictly a ‘machinery’ item, the mechanical complexity of present-day cargo hatch covers-whose periodic maintenance may fall in the domain of the ship’s Engineering Department-warrants some mention in this chapter.  Many types of mechanically operated hatch covers can now be found at sea. The principle ones are listed in Table 9.1.

4 Table 12.1 Types of mechanically operated hatch covers

5 CARGO ACCESS (2)  The most common type of hatch cover is the ‘single pull’.  The complete cover consists of a number of transverse panels which span the hatchway and are linked together by chains.  In the closed position, the panel sides sit firmly on a horizontal steel bar attached to the top of the hatch coaming.  Just inside the side plates is a rubber gasket housed in a channel on the under-side of the hatch cover and which rests on a steel compression bar to form a weathertight seal (Figure 9.13).

6 CARGO ACCESS (3)  When closed the covers are held onto the seals by a series of peripheral cleats. Rollers are arranged on the sides of the covers to facilitate opening/closing.  The opening arrangements are shown in Figure 9.14.

7 Figure 9.13 Detail of single-pull cover showing scaling arrangement and jacking system

8 Figure 9.14 Single pull cover showing fitting and opening arrangements

9 CARGO ACCESS (4)  To open a single pull cover the securing cleats are first freed and each panel is raised off its compression bars by hydraulic jacks.  The cover wheels, which are arranged on eccentrics, are rotated through 180º and locked into position.  The jacks are then removed and the cover can be pulled backwards or forwards as required.  Instead of the opening/closing arrangements shown in Figure 9.14 the hatch may be fitted with a fixed chain drive on the periphery of the hatch, complete with its own electric or hydraulic motor.

10 Folding covers  These may be wire operated or hydraulically operated.  A multipanel end-folding hydraulic cover is shown in Figure 9.15, while Figure 9.16 shows an interesting hydraulic hinge arrangement.  Known as the Navire Hydratorque hinge it incorporates a pair of helixes attached to two pistons.  When hydraulic pressure is applied between the two pistons it forces them apart thus rotating the helixes.  Pressure applied to the outside of the pistons creates a torque in the opposite direction.

11 Figure 9.15 A multi-panel folding hydraulic cover for weather deck use

12 Figure 9.16 The Navire Hydratorque rotary actuator and hinge

13 Maintenance (1)  Hatch cover equipment has to exit in a very hostile environment.  The Importance of regular maintenance cannot be over- emphasised.  Drive boxes and electrical enclosures should be checked regularly for water-tightness.  Drive chains, trolleys and adjusting devices such as peripheral and cross-joint cleats should be cleaned and greased regularly.  Seals, compression bars and coamings should be inspected and cleaned at each port. Drain channels should be cleared regularly.

14 Maintenance (2)  On the subject of seals and cleats it is important not to over tighten cleats.  The seal should be compressed but not beyond the elastic limit of the gasket material.  Standard rubber gaskets can be expected to last from four to five years of normal service.

15 Maintenance (3)  In freezing conditions special grease or commercial glycerine should be spread over the surface of all gaskets to prevent them from sticking to their compression bars.  Quick-acting cleats axe fitted with thick neoprene washers arranged to exert the correct degree of compression.  After a time these lose their elasticity and the cleat must be adjusted or replaced.

16 Hydraulic systems  The most important thing about any hydraulic system is to make sure that the hydraulic oil remains clean (regular inspection of filters).  Any protective boots fitted over rams be periodicaly examined as also should flexible hoses.  Hydraulic hoses should have their date of manufacture printed on them and can be expected to have a life of about five years .


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