Factory acceptance tests


Factory acceptance tests

Commissioning is the process of getting the installed equip­ment to work properly and fulfill its functions. It is done in steps, starting at the manufacturer's workshop where the essential equipment is tested before it is transported to the shipyard. These tests at the makers are called Factory Acceptance Tests (FAT) and certify that the equip­ment performs properly, when leaving the workshop. Essential equipment includes generators, motors, switch­boards and control gear assem­blies, transformers, alarm and monitoring systems.

   1. R otating machines

Generators and motors, usually identified as rotating electrical equipment, have to be subjected to a heat run test, to demonstrate that the rotating equipment can perform its duty within the temper­ature limits of the materials used. Heat run tests can be performed under actual conditions, under load with the same characteristics and cooling conditions as the expected load in service. It is often simulat­ed by a no-load test and a short­circuit test. The sum of the rise in temperature represents the actual temperature rise.

It is often limited to the electrical windings of a machine, but should also include mechanical parts such as bearings. In addition, megger tests, insula­tion resistance tests and high volt­age tests as well as overspeed tests at 120% for two minutes, are carried out. If possible, load steps and other dynamic tests are run. If dynamic tests cannot be carried out in the workshop, they must be done during the harbour accept­ance tests (HAT) or during sea tri­als.

   2.  Cables

Cables used onboard of ships must be type-approved, meaning that they have been subjected to a se­ries of tests together with an ap­proved quality assurance system of the manufacturer. These cables are listed in the type- approved equipment of the various classification societies. In general, these cables are spe­cially designed and are suitable for conditions with respect to vibration. Thus, stranded conductors, fire retardant and low smoke and low halogen insulation.

   3. Switch and control gear

Very few have type approval, but most switch gear and control gear assemblies have been built from type approved parts. All main and emergency switchboards must be factory tested to verify operational and insulation quality by Megger and high voltage tests.

The tests consist of checks of inter­locks, synchronisation, autostart and autoclose of generators and circuit breakers, sequential restart, load shedding, depending upon the ship's specification.

   4.  Circuit breakers

Circuit breakers have to be ad­justed and tested by the manu­facturers. Certificates of required settings and test results must be submitted and verified. Name­plates must be fitted adjacent to the circuit breakers in the switch­board referring to the adjusted set­tings to enable replacement.

Factory acceptance tests

Cables temporarily disconnected for testing purposes

      High voltage connection box:

  1. Terminal LI
  2. Terminal L2
  3. Terminal L3
  4. Conductors LI
  5. Conductors L2
  6. Conductors L3
  7. Earth conductor
  8. Starpoint  

   5. Starting devices

Large starting devices (>100kW) must be tested at the manufactur­er's workshop as far as practicable. The tests are more or less identical to the tests of switchboards.

   6. Converting equipment

Large converting equipment (> lOOkW) must be tested at the manufacturer's workshop. For rotating converting equipment, the same tests are applicable as for rotating machines.

For static converting equipment, built from type-approved parts, functional tests have to be done simulating the performance of the converter and checking tempera­ture rises of the approved parts in the assembly. This can be done during a full load test with the same cooling arrangements as in the ship's design standards.

This usually means cooling air of 45°C, cooling water, if direct sea­water is used, of 32°C, but mostly freshwater through a heat exchang­er of 37°C, or air, cooled by either sea or fresh water with maximum temperatures of 37 and 42°C re­spectively, allowing a temperature difference over the water/air heat exchanger of 5°C. Sometimes, if a chilled water sys­tem is installed, chilled water with a temperature of 6°C is used.

   7.  Transformers

Large transformers (> 125 kVA or lOOkW) with a power factor of 0.8 have to be tested at the manufac­turer's workshop. The test must in­clude a megger test, a high voltage test and a megger test again, as well as a heat-run determining the temperature rise of the windings at full load conditions.

Similar to rotating machines, often the test is done by a combination of a no-load test and a short-circuit test which gives a good idea of the temperature rise at actual load.

   8.  Automatic control systems

Large control systems, or better complicated control systems, have to be tested at the manufacturer's. This means building up the various components, such as equipment, control-stations and work-stations and connecting these, making it a complete system. It is more effi­cient to test a complicated system at the manufacturer's, as all control locations are close together and the changes of control positions are more easy to test. Transfer of con­trol from one location to another shall be bumpless and accepted by the other location. This to avoid un­acceptable surprises.

Failure of a power supply shall not cause change in control result or alarms only,

   9.  Alarm and monitoring systems

Alarm and monitoring systems must also be tested at the manu­facturer's. These include simulation of alarms, checking of group alarms at the bridge, and of engineer's alarms.

Duty selection, safety timer for not accepting alarms, safety timer for one person on watch, automatic change over from unmanned to manned operation when accepting an alarm in the engine room, at the same time starting the safety timer to protect the engineer attending an alarm. Graphics and trending must also be checked during this factory acceptance test.

Also system failures have to be tested. Thus, main power failure with alarm only, back-up power failure, communication failure of distributed systems and cable fail­ures. Printed circuit board card (PCB) failures must be restricted to that part only. Alarms have to in­dicate the location of the fault.

   10. Dynamic positioning systems

Dynamic positioning systems vary from simple computer assisted sys­tems with Notation AM, via redun­dant systems Notation AA, to fully redundant systems Notation AAA. For the more complicated systems, a failure mode and effect analysis (FMEA) has to be made, identify­ing the consequences of all pos­sible failures. This is the basis for the test procedures. The functional tests are more difficult to simulate. As most of the systems have to be adjusted to the characteristics of the ship, especially for the first ship of a series, these are usually done during sea trials.

   11. Systems in general

It should be clear that all factory acceptance tests have one common purpose: that is to confirm the suit­ability of equipment to be installed onboard. Every step in the FAT testing pro­gramme has one major purpose. This is to ensure performance dur­ing the harbour acceptance tests (HAT) and of course, during the fi­nal acceptance test, the sea trials. Consequently, the above testing must be executed with all new and essential equipment or systems working.

   12.  EMC/THD tests

All navigation and nautical equip­ment has been tested for electro­magnetic compatibility during the type approval procedure. Interfer­ence between components should not exist as long as all equipment is installed in the original housing and in accordance with the instructions of the manufacturer.

When in the open deck area other sensitive equipment is installed, such as a frequency converter op­erated deck crane, controlled from a control cabin with many windows in view of the radar antenna beam, also this control cabin has to be tested for EMC.

Measuring the Total Harmonic Distortion (THD) for different op­erational conditions is particularly advised when large Variable Fre­quency Drives are installed. These measurements are sometimes also required by Class.

   13. Step loads

After testing of the individual die­sel generators for proper operation the sets are tested in parallel op­eration. With 3 sets, first 1 and 2 in parallel, thereafter 2 and 3 and finally 1 and 3. When current and kW loadsharing is in order the en­gines and generators have to be subjected to step loads.

A step load is a suddenly applied load on the generator, to check the performance of the generator AVR as well as the diesel governor. Usual steps are from 25 to 50 % and 50 to 100 %, whereby the minimum voltage and the minimum frequency during the process have to be checked.

Another test of the diesel and genera­tor performance is the switching off of a certain load whereby the overvoltage and maximum frequency of the sets are checked during the process. This is usually done in parallel, operat­ing by switching off circuit breakers.

   14. Example of EMC interference

EMC interference problems are some­times hard to trace like in this example of an Offshore Construction Vessel. When the ship got operational it ap­peared that the crane would not work although this had been succesfully tested during harbour trials. It took a long time to find the reason for this failure of the crane but in the end it appeared that the beam from the radar disturbed the crane controls. By screening some cables in the con­trol cabin of the crane the problem was solved.

The test matrix for commissioning should include verification of this sort of interferences.

Factory acceptance tests 

Back to the list