1) Tests and trials are carried out on board ships, during production process with following objectives.
- The equipment provided are tested to confirm that their capacities are meeting specification requirements and class requirements.
- The quality of work meets the required standards so that the safety of the vessel is assured and the scantlings provided can withstand the stresses developed during operation of the vessel.
- The vessel meets the performance required by owners with regard to speed, dead weight etc.
2) During the production process, the following important tests are carried out to check the quality of work and performance of equipment.
2.1) STEEL WORK:
- The quality and integrity of welding joints are tested by taking X-Rays etc and also by doing hose tests.
- The tanks are tested by hydrostatic tests, by maintaining water head pressure and leakages are checked.
- Dimensions of various structures are checked to see that they are within tolerance limits of quality standards of the yard.
2.2) PIPING WORK:
- The piping spools for each system are tested in the shop for 1.5 times the working pressure of the system.
- After the erection of the system on board, the total system is tested for leakages at the working pressure.
2.3.1) MAIN ENGINE: DOCK TRIALS
After the erection on board, the shafting system is coupled to the Main Engine. To check that the alignment is properly done and there are no leakages from systems connected to the main engine. Dock Trials (also called quay trials, jetty trials) are conducted at the jetty at a very low R.P.M. (about 2% rated r.p.m); by tying the ship with ropes to dock/jetty. The test is done for about 2 hours and the engine is also run in the astern direction. The temperature/pressure of all systems are checked for leakages crank web deflections are taken to check the alignment of the crankshaft.
2.3.2) D.A. SETS & LOAD TESTS:
- Each D.A. Set is tested for checking its full rated capacity as per specification requirements. The D.A. Set is run at 25%, 50%, 75%, 100% & 110% of rated capacity and at each load, the important parameters (Temp/Pr. of all systems, voltage, frequency, KW) are recorded.
- Paralleling operation of two generators (with different combinations) is observed and sharing of load (equally) is checked.
2.3.3) AIR COMPRESSORS & AIR RECEIVERS:
- Filling time of air bottles with air compressor is recorded (as per rules it shall be 1 hr).
- From each air bottle number of starts of the main engine is recorded (by starting the engine in both ahead and astern directions alternatively). The number of starts shall be 12 for the reversible engine.
2.3.4) BALLAST PUMPS:
The time required for filling and emptying the tanks are recorded to check the capacity of pumps.
2.3.5) VENTILATION SYSTEM:
At each ventilation terminal, the velocity is recorded with velometer and the discharge rate is calculated by multiplying with the area of the terminal. The total discharge from the terminals connected to fan unit shall give the capacity of the fan.
2.3.6) OTHER SYSTEMS N BOARD:
Other systems on board are tested by running the system and observing their performance.
3) OUTFIT ITEMS:
- Deck cranes are tested to their full capacities.
- Lifeboat davits are tested by lowering and heaving.
4) Propellers, Shafting & Rudder:
- Boring & sighting of stern-tube and fitting of stern-tube bushes is done in presence of surveyors/owners for establishing sighting line (shafting centre line).
- Fitting of Propeller: Push up/hub & Nut pressures recorded for the key-less propeller. Tightening of nut and locking of the nut is observed.
- Establishing rudder centerline, boring and fitting of the rudder is observed and recorded.
5) SEA TRIALS:
After all, systems are erected on board and the vessel is almost ready for delivery, sea trials are conducted for the vessel for testing all systems in voyage condition of the vessel.
6.1) REFRIGERATION SYSTEM IS CHECKED FOR:
- Leakages in pipelines (gas leakage)
- The capacity of the plant for maintaining the temperatures in meat room (-18 degree celsius) Fish room (-18 degree celsius) vegetable 7 dairy room (2 to 4-degree celsius).
- The effectiveness of insulation of refrigerated chambers.
- On and off of the compressors depending on the temperature of chambers.
6.2) AIR CONDITIONING SYSTEM IS CHECKED FOR:
- Leakages in pipelines (gas leakage)
- The capacity of the plant in maintaining the temperature in accommodation spaces.
- Running time ( in 24 hours duration) of plant
- On/Off controls of compressors depending on temperature.