Transducer installation in a blister
In order to install a transducer with a circular housing, one recommended installation method is by means of a blister. The blister must be designed and manufactured by the installation shipyard to fit the transducer, as well as the vessel’s size and hull shape. The transducer may be added to an already existing blister that also holds other flush mounted transducers.
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Illustration:
A Mounting ring
B Clamping ring
C Cable service loop
D Bolt
The best performance is obtained with a blister height of 40 cm or more. A streamlined shape and rounded edges reduce the flow noise. A vertical leading edge or front will guide the aerated water to the sides of the blister.
The orientation of the blister should follow the water flow.
The interior of the blister must be filled with sea water. Use drainage holes in the bottom and an air outlet on the top. The water pressure behind the transducer will then compensate for the outside pressure during vessel movements in rough sea. This is an important security precaution to prevent damage to the transducer.
The transducer cable penetrates the hull using a cable gland. This cable gland consists of a bushing, washers, a rubber gasket and a packing nipple. Leave an adequate loop of the cable over the transducer body inside the blister for easy mounting or removal of the transducer.
Example
Image
A Streamlined blister
B Stiffening rib
C Drainage holes
D Inclination angle
E Mounting ring
F Air outlet
G Cable service loop
H Bushing
I Height: 400 mm (Minimum)
J Rounded corners
Physical location of the blister
The blister is placed on the side of the hull. The distance from the keel is a trade off between a close distance giving a turbulent flow of water in a narrow passage, and a large distance bringing the transducer higher up, and therefore more affected by the vessel roll. Normally a distance of approximately 1 m is a good compromise.
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A Keel
B Transducer blister
C Horizontal distance between the keel and the blister
D Vertical distance between the bottom of the keel and the blister surface
Observe the horizontal and vertical distances between the keel and the transducer blister. (C + D)
On a medium sized vessel, the horizontal distance (C) should be approximately 1 meter.
The vertical distance must in general be as small as possible. This is important to prevent the keel from shadowing the transducer beam in shallow waters.
Using the mounting ring
This large circular is transducer is designed to be mounted using the integrated flange and a mounting ring.The mounting ring is welded to the hole prepared for the transducer. Bolts through the transducer flange into the mounting ring will secure the transducer in place.
Note
Make sure that the "Forward" direction on transducer points in the forward direction of the vessel.
A suitable mounting ring can be provided by Kongsberg Maritime. A drawing is available for local manufacturing. End user manuals and source drawings (normally in AutoCad format) can be downloaded from our website.
Smooth surface is important
Make sure that the surface of the transducer face, as well as the plating and putty around the transducer is as even and smooth as possible.Obstructions on these surfaces will create problems with turbulent flow, and may cause noise.
Mounting screws or bolts must not be extruding from the transducer or the plating immediately around it.
Note
Obstructions on these surfaces will create problems with turbulent flow, and may cause noise.