EPO 125 Marine Engineering - Valves, Strainers, Piping, and Fittings

Vocabulary flashcards covering marine engineering valves, strainers, filters, piping standards, and fittings from EPO 125 lecture notes and USCG exam review.

Accumulator

A hydraulic system component that enables the pump to be temporarily shut down while still providing an instantaneous source of hydraulic force.

Phosgene Gas

A toxic chemical gas formed when chlorinated fluorocarbon refrigerants decompose in the presence of an open flame or hot surfaces.

Double Mechanical Seal

A pump shaft seal arrangement effectively used for pumps handling toxic or highly flammable liquids that cannot be permitted to escape into the atmosphere.

Duct Keel

An internal passage of watertight construction fitted along the centerline between double bottoms to carry piping throughout the length of a vessel.

Deadband

The change in speed required before a speed control governor will initiate corrective action as the load changes.

Compound Gauge

A direct-reading pressure gauge capable of measuring and displaying both positive and negative pressures.

Critical Speed

The operational speed at which excessive engine vibration is created.

Check Valve

A valve designed to limit fluid flow to one direction only, preventing backflow in systems such as bilges.

Swing Check Valve

A common type of check valve that uses a hinged disc to permit flow in one direction and swing closed against backflow.

Lift Check Valve

A check valve where the disc lifts upward off its seat by fluid pressure, often containing a spring-loaded closure for horizontal or vertical mounting.

Globe Valve

A valve used to start, stop, and throttle flow by moving a disc linearly against a seat via a threaded stem, creating a flow direction change and pressure drop.

Gate Valve

A valve that uses a wedge-shaped gate moving perpendicular to fluid flow to start or stop flow without changing flow direction; it must not be used for throttling.

Butterfly Valve

A compact quarter-turn valve restricted to low-pressure and low-temperature fluids that seals via a disc rotating on a hinge against a resilient lining.

Stop-Check Valve

A hybrid valve combining characteristics of a globe valve and a lift-check valve; when raised, it acts as a check valve, and when screwed down, it stops flow entirely.

Pinch Valve

A valve equipped with a flexible rubber lining that prevents corrosive fluids (such as brine or bleach-treated ballast water) from contacting metal valve parts.

Stuffing Box Packing

Soft packing rings placed inside a stuffing box and compressed around a valve stem by a gland and packing nuts to seal fluid where the stem exits the body.

Pressure Relief Valve

An automatic valve used primarily in liquid systems that opens gradually and proportionally to overpressure, often simmering and returning fluid to the low-pressure side.

Safety Valve

An automatic pressure relief device designed for compressible fluids (steam/air) that uses a huddling chamber to pop fully open rapidly once set pressure is reached.

Direct Acting Pressure Reducing Valve

An automatic valve that uses spring pressure balanced against downstream fluid pressure on a diaphragm or bellows to maintain a steady reduced outlet pressure.

Thermostatic Mixing Valve (TMV)

A self-sensing control valve containing a sealed wax pellet that expands and contracts with temperature changes to automatically regulate coolant flow.

Micron

A unit of length equal to one millionth of a meter ($10^{-6}\,m$ or $0.000039\,\text{inches}$), used to measure particle size and filter filtration ratings.

Strainer

A reusable mechanical filtration device containing perforated metal or wire mesh, used to remove coarse particles from fluid lines.

Filter

A non-reusable, consumable filtration component possessing a small micron rating designed to capture fine contaminants.

Absorbent Filtration

A filtration method ("think sponge") where solid, liquid, or gaseous particles permeate uniformly throughout the entire volume of a porous medium.

Adsorbent Filtration

A filtration method where target contaminants adhere directly to the solid outer surface or pores of materials such as activated carbon, clay, or silica gel.

Simplex Strainer

A single-basket strainer assembly that requires fluid flow through the line to be stopped whenever the strainer basket needs cleaning.

Duplex Strainer

A dual-basket strainer system featuring an internal diverter valve, allowing fluid flow to continue through one chamber while the other basket is cleaned.

Nominal Pipe Size (NPS)

A standard pipe sizing designation where the outside diameter remains constant for a given size up to 12 inches, while the inside diameter varies with wall schedule.

Pipe Schedule

A designation number (such as Schedule 40 or Schedule 80) that specifies the wall thickness of a pipe.

Class Rating

A pressure-temperature rating category (such as Class 150 or Class 300) assigned to threaded pipe fittings.

NPT (National Pipe Taper)

The American standard for tapered pipe threads, featuring a $60^\circ$ thread angle with flattened peaks and valleys that forms a seal via mechanical wedging.

BSPT (British Standard Pipe Taper)

The British standard for tapered pipe threads, featuring a $55^\circ$ thread angle with rounded peaks and valleys.

Teflon Tape (PTFE Tape)

A thin PTFE film wrapped around male pipe threads to fill clearances, prevent spiral leak paths, and provide thread lubrication.

Pipe Dope

A paste or liquid thread sealant compound used on larger, high-pressure, or high-stress pipe connections to fill thread voids.

Flare Connection

A metal-to-metal tubing connection used for gas and high-pressure lines where a flared tube end is clamped securely against a fitting seat.

Compression Connection

A tubing joint using a ferrule and nut compressed onto the tube body, commonly used for lower-pressure water and compressed air lines.

Banjo Fitting

A fluid connector consisting of a perforated hollow bolt and copper crush washers, commonly used on engine fuel lines.