A marine engineering graduate at Georgian College – Published Feb 5, 2020 Where a ship’s machinery space is not right aft, an enclosed area or tunnel is provided to lead the shafting to the after peak bulkhead. The tunnel must be watertight to ensure integrity should the shaft seal cease to operate correctly.

1. The forward end of the tunnel is fitted with a sliding watertight door to seal off the tunnel if necessary.
2. The structure is made to be capable of withstanding the water pressure should the tunnel become open to the sea.
3. The scantlings are equivalent to those of a watertight bulkhead.
4. The width of the tunnel is decided by access and maintenance consideration and will be reduced to the minimum necessary.

A raised floor is usually fitted, and pipework is run along beneath it. The shaft bearing positioned at intervals along the tunnel is carried on stools or seats. These stools are welded to the tank top and tunnel structure to form a rigid platform. Shaft tunnels must be hose tested on completion to ensure their water tightness.

How do you open a watertight shaft tunnel?

Shaft Tunnel – Ship Construction When the ship’s machinery is not located fully aft it is necessary to enclose the propeller shaft or shafts in a watertight tunnel between the of the machinery space and the aft peak bulkhead. This protects the shaft from the cargo and provides a watertight compartment which will contain any flooding resulting from damage to the watertight gland at the aft peak bulkhead.

1. The tunnel should be large enought to permit access for inspection and repair of the shafting.
2. A sliding which may be opened from either side is provided at the forward end in the machinery space bulkhead.
3. Two means of escape from the shaft tunnel must be provided, and as a rule there is a ladder in a watertight trunk leading to an escape hatch on the deck above the waterline, at the aft end of the shaft tunnel.

Where the ship narrows at its after end the aftermost hold may be completely plated over at the level of the shaft tunnel to form a tunnel flat, as the narrow stowage space either side of the conventional shaft tunnel could not be utilized. The additional space under this tunnel flat is often used to stow the spare tail shaft.

• Shaft tunnels also provide a convenient means of carrying piping aft, which is then accessible and protected from cargo damage.
• Construction of the shaft tunnel The thickness of the tunnel plating is determined in the same manner as that for the,
• Where the top of the tunnel is well rounded the thickness of the top plating may be reduced, but where the top is flat it is increased.

under hatchways the top plating must be increased in thickness unless it is covered by wood of a specified thickness. Vertical stiffeners supporting the tunnel plating have similar scantlings to the watertight bulkhead stiffeners, and their lower end is welded to the tank top (see Figure 18.5).

On completion the shaft tunnel structure is subject to a hose test. At intervals along the length of the shaft, stools are built which support the shaft bearings. A walkway is installed on one side of the shaft to permit inspection, and as a result, in a single screw ship the shaft tunnel will be offset from the ship’s centre line.

This walkway is formed by gratings laid on angle bearers supported by struts, etc., any piping is then led along underneath the walkway. Continue reading here: Was this article helpful? : Shaft Tunnel – Ship Construction

What are tunnel shafts?

FAQs – What are tunnel shafts? Tunnel shafts are vertical passages that connect the ground surface to the tunnel roof. Shafts have many advantages and are used in constructing tunnels. When the position and course of the tunnel are correctly aligned and accordingly set out on the surface, shafts are sunk at defined points on the tunnel line to aid tunneling operations.

What are the types of tunnel shafts? The types of tunnel shafts based on their shape are 1. Inclined Shaft 2. Vertical Shaft 2. Circular Shaft What are the advantages of a tunnel shaft? 1. They greatly expedite the work by adding two faces per shaft for driving.2. They afford outlets for excavated material and means of access into the tunnel for building materials.3.

They could be used as pumping shafts in case of a large influx of water.4. They help correct alignment and help carry the center line into the tunnel properly.5. In long tunnels, they afford ventilation and are helpful for exhausting smoke and foul air out of the tunnel.6.

What is section 23 of the US Code for tunnel construction?

Section 23—Tunnel and Shaft Construction October 2009 23-17 When sinking shafts more than 75 feet (22.86 meters) deep, keep the guide rails or cables as close as possible to the bottom of the shaft. Maintain rail guides within one rail length of the bottom. Provide a safe means of access from the bottom landing to the bottom of the shaft.

Why are propeller shafts enclosed in a watertight tunnel?

Shaft Tunnel – Ship Construction When the ship’s machinery is not located fully aft it is necessary to enclose the propeller shaft or shafts in a watertight tunnel between the of the machinery space and the aft peak bulkhead. This protects the shaft from the cargo and provides a watertight compartment which will contain any flooding resulting from damage to the watertight gland at the aft peak bulkhead.

1. The tunnel should be large enought to permit access for inspection and repair of the shafting.
2. A sliding which may be opened from either side is provided at the forward end in the machinery space bulkhead.
3. Two means of escape from the shaft tunnel must be provided, and as a rule there is a ladder in a watertight trunk leading to an escape hatch on the deck above the waterline, at the aft end of the shaft tunnel.

Where the ship narrows at its after end the aftermost hold may be completely plated over at the level of the shaft tunnel to form a tunnel flat, as the narrow stowage space either side of the conventional shaft tunnel could not be utilized. The additional space under this tunnel flat is often used to stow the spare tail shaft.

Shaft tunnels also provide a convenient means of carrying piping aft, which is then accessible and protected from cargo damage. construction of the shaft tunnel The thickness of the tunnel plating is determined in the same manner as that for the, Where the top of the tunnel is well rounded the thickness of the top plating may be reduced, but where the top is flat it is increased.

under hatchways the top plating must be increased in thickness unless it is covered by wood of a specified thickness. Vertical stiffeners supporting the tunnel plating have similar scantlings to the watertight bulkhead stiffeners, and their lower end is welded to the tank top (see Figure 18.5).

On completion the shaft tunnel structure is subject to a hose test. At intervals along the length of the shaft, stools are built which support the shaft bearings. A walkway is installed on one side of the shaft to permit inspection, and as a result, in a single screw ship the shaft tunnel will be offset from the ship’s centre line.

This walkway is formed by gratings laid on angle bearers supported by struts, etc., any piping is then led along underneath the walkway. Continue reading here: Was this article helpful? : Shaft Tunnel – Ship Construction