en l ’an 2000 100 ans d ’expérience sur la vapeur

Armstrong International 100 years of experience in

Steam applications

The purpose of a condensate steam trap.

To obtain a maximum efficiency and productivity from an installations, a steam trap should not only provide the separation of water and steam. A number of criteria, grouped in four categories must be satisfied.

• Operation and output• Energy conservation• Maintenance and life span• Installation/investment

Operating criteria

• Instant condensate evacuation • Adapt to flow variations• Adapt to upstream pressure variations • Functioning in presence of back pressure • Venting of non-condensables on start-up• Venting of non-condensables at steam temperature • Insensitive to climatic changes• Pressure/flow operating range• Follow the saturation curve. • Check valve fonction

Energy conservation criteria

• Tight shut off valve and seat arrangement• No leaks at body joints• Tight shut-off at closure or no delay at closure• Efficient at low flow• Possibility of trap insulation• Sub-cooling energy conservation

Maintenance and life span criteria

• Ability to handle dirt• Resistance to wear• Internal and external corrosion resistance• Resistance to superheat• Water hammer resistance• Resistance to damage from freezing• Easy maintenance • Easy and fast trap testing diagnostic

Assembly and investment Criteria

• Capacity / size ratio

• Price

• Ease of installation

• Application versatility

• Spare parts prices

Steam straps various technology

Type Method of operation Family

Mechanical Density differencial I.B. F.&.T

Temperature Temperature differencial B.M Capsule

Thermodynamics Speed differencial T.D

Venturi Pressure loss Orifice

Inverted bucket steam trap.Principal of operation

(I.B.)

sortie

entrée

Inlet

Outlet

Valve and seat

Bucket

Lever

Inlet Tube

Start up mode

Steam + Air

Condensate

Presence of steam = Steam trap closing

Condensation phase and incoming condensate

Steam trap opening – elimination of condensate

Operational Forces

IB Steam trap Avantages

• No loss of live steam : the steam trap water seal prevent the loss of steam.

• Continuous condensate discharge

• Long life expectancy

• Water hammer resistance

• Remove air and CO2 at saturated steam temperature

IB Steam trap Advantages

• Adapt to upstream pressure variations

• Instant response to condensate load variations

• Not affected by dirt because of its discharge orifice at the top of the trap and the syphon effect when the orifice is completely open

• Fail open steam trap

Important details of conception

The mechanism is free-floating

Valve continues to seat itself deeper with wear, preserving a tight seal.

IB Steam trap inconveniencies

• For all the models , except the models with connector, the IB should be installed only on horizontal or vertical lines.

• Some model have a tendency to pass live steam on superheated steam application, if proper piping installation is not done .

Operation principals of Float & Thermostatic steam trap

FloatWater seal valve

Thermostatic air vent

levier

Start up mode

Presence of steam - Thermostatic air vent closing

F & T steam trap advantages

• Can vent a large quantity of non-condensables because the air vent mechanism is distinct from the steam trap condensate mechanism.

• Continuous condensate discharge without retaining water upstream of the steam trap

• The discharge orifice is surrounded by a water seal, preventing live steam loss.

• Capable of handling large capacity of condensate

F & T steam trap inconveniences

• Because the orifice is at the bottom of the trap and the continuous discharge principle this steam trap is sensitive to dirt.

• When steam is shut off, water stays in the steam trap body becoming sensitive to frost damage.

• Water hammer can damage the float by implosion and destroy the thermostatic element.

• Can’t be used in superheated steam because of thermostatic element limitations.

• Fail close position.

Operation principals of thermodynamics steam traps

Discharge orifice

Disc

Pressure chamber

Seat

Steam

CondensateFlash Steam

The steam penetrates inside the steam trap

The steam occupies the chamber capacity – Steam trap closing

Condensation of steam in the steam trap chamber

The steam trap air binds in presence of non-condensable

Air

This problem appears frequently at start-up.

Operational Forces

Features of a thermodynamic steam trap

• Small, light weight, easy to install.

• One size orifice for all pressure ranges,

• Stock reduction.

• Large capacity in proportion to it’s size.

• It’s one mobile part make it resistant to ‘’water hammer’’.

• Competitive pricing

Inconveniences of the thermodynamic steam trap

• The disc opening cycle depends on the pressure over the disc. The climatic conditions therefore influence the operation of each cycle, by cooling the body of the trap, where a rapid condensation of the steam and a pressure drop occur over the disc.

• Operation cycle, fast at low loads, cause a premature wear and tear.

• The operation cycle speeds up when seat wear appears, this accelerates the wearing process and reduces the service life of the steam trap.

Inconveniences of the thermodynamic steam trap

• Does not close if back pressure reaches 50 % of upstream pressure.

• A steam trap leak could drive other steam traps that are connected to the same line system to leak.

• Does not close if a pressure drops under 5 psi.

• The requirements specified for the surface conditions, makes it very sensitive to dirt.

• No instant reaction to condensate loads variations. Retains the condensate between cycles.

2 main reasons why the TD steam trap wear and tear rapidly

Snap closure of the discagainst the seat at each cycle.

High velocity outlet = prematureerosion of disc and lost, of seat tightness.

Operation principals of thermostatic bellow steam strap

Bellow

Valve

Alcohol

Seat

Operation principal of thermostatic bellow steam strap

Condensatecooling

Steam

Operation principal of thermostatic wafer steam trap

Diaphragm

Distilled water+ alcohol

Wafer steam trap opening curve

Delta T

Pressure (psig)

tem

pera

tue Steam

Water

Saturation curve

Open Steam trap

Close Steam trap

Operational Forces

Advantages of Wafer Steam trap and Bellow Steam strap

• In general sizes are small and light

• Reduces the amount of flash steam

• Allows sensible heat recuperation

• Will adapt to pressure and discharge variations

• At start-up, it will remove the non-condensables

Inconveniences of bellow steam trap

• Sensitive to dirt• Upstream condensate retention (sub cooling)

causes a reduction in Ph which develops corrosion and premature wear

• Sensitive to water hammer• Not adapted for superheated steam• Can fail close

Bimetallic Steam Trap

Bimetallic strips

Inverted valve

Adjusting screw

Valve stem

Air at Start-Up

Condensateat start-up

Steam

Condensate

Flash Steam

Steam+air

Operational Forces

Opening curve of a Bimetallic Steam Trap

Delta T

pressure

tem

pera

ture steam

water

Saturated curved

Close steam trap

Open steam trap

Bimetallic Steam Trap Advantages

• Ability to handle start-up air loads

• Recuperation of sensible heat

• Reduces the amount of flash steam

• Resistance to water hammer

Bimetallic Steam Trap inconveniences

• Sensitive to dirt

• Sensitive to back pressure

• Sensible to upstream pressure variation

• Improper continuous air venting

• Not adapted for process applications

• Valid capacity curves for a given temperature

Selection methodology for condensate steam trap

Steam Main Boiler Header Unit Heather Exchanger Tracing Drum dryer

Q=L.M.Cs.t.60 Q=V..Cs.t Q=<1 kg/h.m r.temps r

Q= Cap. Boiler Q=V..Cs.t Q=L.Ø..35 kg/h.m²0,1 r

Qx1,5 QX2 QX2 QX2 Aucun Q x3 à 5 QX3 QX3Application

Calculation of flow in kg/hSafety margin