In previous blogs, we talked about the types of shipyards and the different works carried out on ships according to the Class Company and the type of vessel. But whether in new constructions or at the end of repair periods, sea trials are always carried out.
But what are the sea trials of a boat?
These are the tests carried out on equipment and systems after the ship has been manufactured following its purpose or after a maintenance period in the shipyard. The shipyards and the Class Company carry out different tests before the vessel is delivered to the shipping companies or owners for the purposes for which they were designed. These tests are to certify and review the different equipment of the boat in different conditions and speeds of the vessel in the open sea.
The tests that are usually carried out are:
- Power measurements to the propulsion shaft with torque meters and ship speed.
- Consumption and temperature tests according to the driving regime in main and auxiliary propulsion machinery.
- Vibrations of the main machine and auxiliary equipment.
- Measurement of reactions in axle and horn line bearings.
- Measurement of torsional, lateral, and axial vibrations.
- Electrical Magnitudes according to the electrical balance for navigation.
- Maneuverability Tests: Evolution Circle, Zig Zag, Crash-Stop, and Man Overboard.
- Noise and vibration measurements by Class Society standards.
- Acoustic insulation test by international regulations (MLC) for habitability.
- Condition and reaction of the structure to different types of sea.
These are the most common tests and trials carried out on ships, without forgetting that depending on the type of vessel, other types of more specific tests are carried out following the design or work to be carried out.
A) Power measurements to the propulsion shaft with torsiometers and vessel speed: The torsiometer is an indirect system through which we identify the adequate power being delivered to the propulsion shaft of the vessel.
When the ship has more than one propulsion machine, one unit is placed on each propulsion shaft. The concept of the torsiometer is based on the mechanical torsion effected by a moment or force on the ship’s propulsion shaft. The engine torque is the moment of force a machine exerts on the transmission shaft, in this case, the propeller shaft. Thus, the engine torque or torque is applied to the drive shaft, along the shaft an angle Ï´ called the torsion angle is experienced. This torsion angle is the result of the resistant torque of the system to the propulsion machine, that is, the propeller with the entire line of shafts and bearings.
B) Consumption and temperature tests according to the driving regime in main and auxiliary propulsion machinery: At different driving regimes in the propulsion machine or load in the auxiliary engines, data on all machine temperatures are taken. Pressures, revolutions, ambient temperatures in the engine room or auxiliary room, sea conditions, time, and reading of the fuel consumption mass meters. These conditions are maintained for several hours, and all data are taken in no more than one hour. After several hours, the power of the propulsion machine or the load of the online generator is gradually increased, and all the values previously taken are noted. These data are taken and loaded into a spreadsheet that, at the end of the sea trial, shows the consumption and running curves according to the different speeds of the propulsion machine or the load of the online generator. This is done until it reaches its maximum power. This maximum power is tested to know the response of the vessel, the propulsion machine, and the auxiliary electrical generation equipment in cases of emergency or that warrant the use of 100% of its design power.
In the following blogs, we will explain the other tests in detail.
At SOUTHERN OCEAN MARINE ENGINEERING SOLUTIONS, we are specialists in organizing for shipowners and owners the different tests to be carried out in sea trials and issuing the corresponding reports.
Do not hesitate to contact us.
