Steam Traps & Strainers Flashcards

Flashcards on Steam Traps and Strainers based on lecture notes.

Steam Trap

A mechanical device used for removing condensate from steam piping. It's an automatic valve that allows condensate to pass through but closes in the presence of live steam, also removes air and non-condensable gases.

Purpose of a Steam Trap

To prevent water from being carried into equipment and machinery, causing damage, and to prevent water hammer, which can damage pipes and cause personal injury.

Steam Trap Installation Locations

1. Ends of main steam header or lines. 2. After steam radiators in heating systems. 3. Specified spacing in long steam piping. 4. Low points in steam piping. 5. Before restrictions in steam lines. 6. After process equipment using steam for heating.

Classes of Steam Traps

1. Mechanical. 2. Thermostatic. 3. Thermodynamic.

Mechanical Traps

Remove condensate based on the mechanical properties of steam vs. condensate, using a bucket or float that rises and falls with condensate level. Examples: Ball-float, Inverted-bucket, Upright-bucket traps.

Thermostatic Traps

Remove condensate based on the temperature difference of steam vs. the liquid phase. The valve is driven by expansion/contraction of an element exposed to heat. Examples: Bellows and Bimetallic traps.

Thermodynamic Traps

Operate on the dynamic principles of steam vs. condensate and Bernoulli’s principle. Condensate released through an orifice increases speed and causes a pressure drop to flash steam to close a valve. Examples: Disc, Impulse, Labyrinth, and Orifice traps.

Ball Float Trap

Contains a thermostatic bellows or element and a steel ball float connected to a discharge valve by linkage. Condensate makes the float rise, opening the valve for drainage.

Bucket Trap

Steam and condensate enter then strike the deflector and are directed downwards into the body of the trap. As condensate collects, the empty bucket floats and swings upward on its pin, forcing the valve against its seat and closing the entrance to the outlet.

Inverted Bucket Steam Trap

Contains an upside-down steel cup (bucket) attached to a linkage that opens/closes a discharge valve as the cup rises/falls inside the trap. Condensate enters through a standpipe inside the cup.

Air Vent Hole (Inverted Bucket Trap)

A small hole drilled through the top of the bucket to allow air and noncondensable gases to pass through, preventing improper trap function and corrosion.

Bellows Type Thermostatic Steam Trap

Contains a temperature-operated device (corrugated bellows) that controls a small discharge valve. The bellows contain a fluid with a specific boiling temperature.

Bimetallic Type Trap

Consists of bimetallic bars (invar steel and brass) that expand differently with temperature changes, causing the bars to bend or warp and close/open the outlet port of the valve.

Thermodynamic Disc Type Trap

Simple design with only one moving part, operating on the principles of flashing condensate and pressure changes. Doesn't require pilot steam.

Thermodynamic Impulse Type Steam Trap

The amount of water flowing through the trap depends entirely on the temperature of the condensate and the flashing of hot water under pressure. However it cannot provide a tight shut off and will always pass some live steam.

Steam Trap Failure (Open Position)

Live steam blows through the trap, wasting steam energy and potentially causing water hammer.

Steam Trap Failure (Closed Position)

Steam piping and equipment become waterlogged, resulting in lost efficiency, water hammer, or freezing.

Steam Trap Testing Methods

1. Temperature difference across the trap. 2. Sound. 3. Temperature crayons. 4. Flow indicators. 5. Trap test valves. 6. Knowledge of equipment.

Steam Trap Malfunctions

1. Clogged orifice. 2. Water hammer damage. 3. Freezing and cracking. 4. Clogged air vent.

Strainer

A device which provides a means of mechanically removing solids from a flowing fluid by utilizing a perforated, mesh or wedge wire straining element.

Strainer Purpose

To prevent grit, scale, dirt, and other foreign matter from obstructing pump suction valves, throttle valves, or other machinery parts.

Types of Strainers

Y-Strainer, Simplex Strainer, Duplex Strainer, Geometric Strainer, Plate or Expanded Cross Section Strainers, Metal-Edged Filter, Automatic Self-Cleaning Strainers, Magnetic Strainer or Filter

Y-Strainer

Commonly used in pressurized lines (gas or liquid) where small amounts of solid particulate are expected and clean-out will be infrequent. Can also be used in suction or vacuum conditions.

Simplex Strainer

Used where flow can be interrupted for basket cleaning, providing inexpensive protection to pumps, meters, and valves. Designed for easy maintenance and large capacity straining.

Duplex Strainer

For applications where continuous operation is required. Examples: fuel oil strainers, lubricating lines, cooling towers, chemical operations, and industrial water intake lines.

Geometric Strainers

Inexpensive strainers installed between flanges in a pipe line. Have a lower net open area than basket strainers. Structural strength can be difficult to achieve and are now often left in the line during operation.

Plate or Expanded Cross Section Strainers

Used where short face-to-face dimensions are essential. Offer only low net open areas, resulting in higher pressure drops.

Wash-down Strainer

Fitted with side inlets for high-velocity liquid, creating turbulence to back-flush the strainer basket and evacuate debris through a drain valve.

Automatic Self-Cleaning Strainer

A unit which goes through a complete cleaning cycle, using some of the fluid flowing through the strainer to flush out collected debris.

Knife Edge or Scraper Strainer

For systems requiring continuous operation with large quantities of extraneous matter. Has a blade or brush-type rotor and can be equipped for automatic blowdown.

Magnetic Strainers

Standard strainer fitted with magnets to create a magnetic field, attracting fine ferrous particles that could damage downstream equipment. Some use electromagnets for enhanced filtration.

Corrosion Resistance (Strainers)

An important consideration when selecting strainer materials and coatings, taking into account the type of fluid, pressure and temperature conditions, adjacent piping, and desired service life.

Oil Strainer Gages

Fuel oil and forced lubrication strainers should be fitted with a gage and a 3-way valve to show gage connections on each side of the strainer to measure the cleanliness.

When to Clean Strainers

Bilge suction strainers should be cleaned frequently each day, fuel oil strainers about once a day, and forced lubrication strainers should be cleaned once a day and if the pressure difference is greater than 10 psi.

Filtration

Is a process used to remove suspended solids from a solution. Filter passage must be small enough to catch the suspended solids but large enough that the system can operate at normal pressure and flow

Filters

Filters usually employ some form of “sock” or cartridge that has the ability to remove small particles down to the size of fine sand, or even microbials.

Cartridge Filters

Cylinders constructed of pleated paper, synthetic fibers, or fiber yarn wound around a perforated metal core. Relatively inexpensive.

Micron

an abbreviated term for micrometer, or a millionth of a meter.