Refrigeration principles and systems

46 CFR §12.505

Examination requirements. (a) Before an applicant is issued an endorsement as QMED in the rating of oiler, fireman/watertender, junior engineer, pumpman/machinist, or electrician/refrigerating engineer, he or she must prove, to the satisfaction of the Coast Guard, by oral or other means of examination, his or her knowledge of the subjects listed in paragraph (c) of this section. (b) The examination, whether administered orally or by other means, must be conducted only in the English language. (c) Table 1 to § 12.505(c) provides a list of subjects required. Table 1 to § 12.505()—Examination Subjects for QMED Ratings Subjects | Pumpman/machinist | Fireman/watertender | Oiler | Electrician/refrigerating engineer | Juniorengineer General subjects: | | | | | Auxiliary machinery | X |…

NAVEDTRA 14075 §6-1

The vapor-compression refrigeration cycle Refrigeration moves heat from a cold space to a warmer one, against its natural direction, by repeatedly evaporating and condensing a refrigerant in a closed cycle. It works because a liquid absorbs a large amount of heat (its latent heat) when it boils, and gives that heat up again when it condenses; by controlling the pressure, the refrigerant can be made to boil at a low temperature in the space being cooled and to condense at a higher temperature where the heat is rejected. The vapor-compression cycle has four essential components connected in a loop: the compressor, the condenser, the metering (expansion) device, and the evaporator. Following the refrigerant around the loop: low-pressure liquid refrigerant boils in the evaporator (the cooling…

NAVEDTRA 14075 Ch. 6 — Refrigeration and Air Conditioning

As an EN1 or ENC you have already learned the principles of refrigeration and air conditioning, and the components and accessories that make up the system. You have learned how to start, operate, and secure refrigeration plants. In addition, you have performed routine maintenance jobs such as trouble shooting, and servicing the system, and used correct procedure’s for leak detecting, and changing the lubricating oil in refrigeration compressors. As you advance in rate, you will be expected to have a greater knowledge of the construction and operating principles of refrigerating equipment. You will be required to perform more complicated maintenance jobs, to make repairs as required, and to determine the causes of inefficient plant operation and accomplish the necessary corrective procedure…

NAVEDTRA 14075 Ch. 9 — Engine Maintenance ¶13

8-8. What method should you use to remove 8-13. A refrigeration unit is working under a foreign deposits from the tubes of a normal heat load and has a sufficient refrigerant condenser? charge of refrigerant. The water side of the condenser should be cleaned if the 1. Lance with water only operating difference between the 2. Lance with air only temperature corresponding to the 3. Both 1 and 2 above condensing pressure and the temperature 4. Wash with acid solution of the outlet circulating water increases above the temperature obtained when the 8-9. On an air-cooled condenser, the exterior unit was in good condition by how many surfaces of the tubes and fins are dirty degrees? and restricting air circulation. What should be used to clean these surfaces? 1. 5°F to 10°F 2. 10°F to 20°F 1. Je…

NAVEDTRA 14075 Ch. 9 — Engine Maintenance ¶14

8-27. During plant operation, which of the following symptoms will indicate a clogged R-12 liquid line strainer? 1. The temperature of the tubing on the outlet side of the strainer is much warmer than the tubing on the inlet side 2. The temperature of the tubing on the inlet side of the strainer is much warmer than the tubing on the outlet side 3. The pressure on the outlet side of the strainer tubing is much higher than on the inlet side 4. The pressure on both the inlet and outlet sides of the strainer tubing are the same 8-28. Which action should you take prior to tightening the cap on a liquid line strainer that has been cleaned? 1. Test the strainer for leaks 2. Open the strainer outlet valve 3. Purge the air out of the strainer 4. Replace the strainer screen spring 8-29. Which of the…

NAVEDTRA 14104 Ch. 10 — Fundamentals of Refrigeration

Refrigeration is a general term. It describes the process of removing heat from spaces, objects, or materials and maintaining them at a temperature below that of the surrounding atmosphere. To produce a refrigeration effect, the material to be cooled needs only to be exposed to a colder object or environment. The heat will flow in its NATURAL direction-that is, from the warmer material to the colder material. Refrigeration, then, usually means an artificial way of lowering the temperature. Mechanical refrigeration is a mechanical system or apparatus that transfers heat from one substance to another. It is easy to understand refrigeration if you know the relationships among temperature, pressure, and volume, and how pressure affects liquids and gases. Refer back to chapter 2 for a review.