Lesson 3. Diesel Engine Repairs

MARINE DIESEL ENGINE REPAIRS

During operation of the diesel engine deterioration of its parts takes place. This process is influenced by various factors such as friction, vibration, high temperature, chemical composition and the mechanical properties of the materials, and the engine load. Besides engine details are affected by corrosion which is the result of chemical and electrochemical effects of the environment.

The extent of detail wear is assessed with the help of durability.

Ships undergo preventive, scheduled maintenance (routine and overhaul) and unplanned repairs (corrective and emergency). Depending on the amount of the repairs diesel engines and other machinery are disassembled completely or partially. All disassembled engine components and parts are thoroughly cleaned, degreased and washed with petrol or with soda ash solution in specialized chambers of washing plants. Aqueous soap solution is added to soda solution for degreasing.

Scale is removed from the surfaces of the engine parts and they also are cleaned from corrosion with the help of special scrapers and wire brushes. Acids and alkalis are used for removing corrosion as well.

While disassembling, cleaning and washing the engine parts their defects are detected. These can be cracks, scorching, deflexion, breakage, galling and wiping, wear. Circular and taper deviations, disalignment of parallel sides are also determined.

The location and size of the internal detail defects can be detected by various failure detection methods: chalk kerosene tests, radiography, gamma flaw detection, soniscope tests, magnetic detector tests etc.

Bedplate defects are corrected in such way: the cracks are plastered up, seam sealing is checked, stud thread is corrected, upper surface is treated, main bearing seatings are bored and central space is painted with moisture-resisting and oil-resistant paint.

Crankcase defects correction includes corrosion removal, building up of main bearing saddles, plastering up the cracks, restoration of stud threads and boring of bearing seatings.

Main cylinder head defects are scorching, corrosion and cracks. After repairs cylinder heads undergo a hydraulic-pressure test.

Characteristic piston defects are deterioration of piston ring daps, wear of gudgeon pin ports, ellipticity and taper deviations of piston head and piston skirt, scorching and cracks. Main repair operation is replacing of piston rings.

Main defects of connecting rod are the bearing wear in connecting rod heads and damage of connecting-rod bolts. Connecting rods can also suffer from cracks, deflexions and torsional deflexions. Defective connecting rods should be replaced.

Batteries need to be kept topped up, charged and clean. If a battery becomes fully discharged and is then recharged it suffers from internal damage. A battery standing idle will slowly discharge itself, so it should be periodically recharged. Once a battery refuses to hold its charge it must be replaced.

I. Answer the questions.

1. What factors influence the details wear?

2. What is corrosion?

3. What are the main types of repairs?

4. What is used to wash the engine parts?

5. How is corrosion removed?

6. What are the main external defects?

7. How can be internal defects detected?

8. What kind of paint is used when painting the bedplate internal space?

9. What test do cylinder heads undergo after the repairs?

10. When is the battery to be replaced?

II. Complete the sentences.

1. Main cylinder head defects (…).

2. The extent of detail wear (…).

3. Connecting rods can also suffer (…).

4. During operation of the diesel engine (…).

5. Depending on the amount of the repairs (…).

III. Find in the text the English equivalents for the following words and word combinations.

різні фактори, хімічний склад, вплив навколишнього середовища, ретельно очищаються, спеціалізовані камери, розчин мила, розташування і розмір, внутрішні дефекти