steam traps ok

8/13/2019 STEAM TRAPS OK

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STEAM TRAPS 1

By

M.M.Sorour


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What is a steam trap?

Steam traps are automatic valves thatrelease condensed steam (condensate)

from a steam space while preventing theloss of live steam.

They also remove air and non-condensablefrom the steam space.


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Why recover condensate?

Efficient utilization of energy.

Economy of use of steam.


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Why recover condensate?Why recover condensate?

Heat contentHeat content

Less fuelcombustion

and emissions

Less fuelcombustion

and emissions

chemicalschemicals

scale/corrosion inhibitordsscale/corrosion inhibitords

oxygen removedoxygen removed

Treated waterTreated water


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Steam Circuitwith a multiple set of steam traps


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A trap consists of:

A vessel in which the condensate accumulates,

An orifice through which the condensate isdischarged,

A valve to close the orifice port,

Mechanisms to operate the valve,

Inlet and outlet openings for the entrance anddischarge of the condensate from the trap vessel

Componentse a steam trap?


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Steam Traps


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Unfortunately, when it comes to steam traps,people often ignore them. This is costing steamusers much more than they realize.

The hard reality of a plant maintaining its boilerand forgetting about the rest of the steam systemcan be a horribly wasteful proposition.

Losses can include not only wasted energy butreplacement of damaged equipment and misuse ofman-hours. It is not uncommon to discover system

losses in the hundreds of thousands of dollars.

Steam Traps


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Fortunately, much of these potential losses can beaverted by a cautious steam management systemthat includes a program for steam trap surveys.

Corrective actions can add substantially to acompanys bottom line as "found money." In somebusiness circles, it has been estimated that $10.00in-house savings is the equivalent $1,000 in sales.

In other words, if a steam system generated$10,000 in savings, it would be the same asachieving $1 million in sales for that company.

Steam Traps


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In order to create savings by producing steamsystem efficiencies, it is important tounderstand the basics of a steam system.

Steam loss can occur in both the supply andreturn side.

Such elements as pipe layout, slope angles,sizing and trap type all contribute to theeffective use of steam.

Steam Traps


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The principal design consideration is tobalance the condensing rate and the

import rate of the control device on theinput side with the exiting condensate.

Steam Traps


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There are many types of steam trapsbecause there are many different types

applications.

Each type of trap has a range ofapplications for which it is best suited.

Types of Steam Traps


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Types of Steam Traps

THERMODYNAMIC

THERMOSTATIC

MECHANICAL


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Dependent operating property

Mechanical TrapsMechanical Traps

Density

Thermostatic TrapsThermostatic Traps

temperature

Thermodynamic TrapsThermodynamic Traps

Kinetic Energy


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Thermostatic Traps

Thermostatic traps useThermostatic traps use temperature differencetemperature difference

to distinguish between condensate and liveto distinguish between condensate and live

steam.steam. This difference is used toThis difference is used to openopen oror close a valveclose a valve..

Under normal operating conditions, theUnder normal operating conditions, the

condensatecondensate must cool below the steammust cool below the steam

temperature before the valve will opentemperature before the valve will open..


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Thermostatic TrapsGeneral Characteristics

They can never discharge condensateThey can never discharge condensateimmediately as they are formed.immediately as they are formed.

They are very small and light.They are very small and light.

They remove the air efficiently.They remove the air efficiently.

They can work at any pressure.They can work at any pressure.

They can work in conditions of movementThey can work in conditions of movementand vibrations.and vibrations.

They are unsuitable for handling very largeThey are unsuitable for handling very largequantities of condensate.quantities of condensate.


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Balanced PressureBalanced Pressure

Expansion TrapExpansion Trap

Metallic Expansion TrapsMetallic Expansion Traps Liquid Expansion TrapsLiquid Expansion Traps

Thermostatic TrapsThermostatic Traps

Bimetallic ExpansionBimetallic Expansion

TrapsTraps


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BalancedPressureExpansionTraps

The trap will open whenever it is in contactwith anything that is cooler than condensateat the pressure at which the plant is working.

It will therefore pass air whenever the air hascooled to below steam temperature.

Balanced pressure traps are very light, smalland cheap.

They are not suitable for handling large quantities.


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Balanced PressureExpansion Traps

The expansion elementconsists of one or morecapsules or bellows.

This element expands andcontracts in response totemperature changes.

An alcohol mixture with a boiling point lower than that of water iscontained inside the element and provides the necessary force tochange the position of the valve. At start up, the bellows trap isopen. This operating condition allows air to escape and providesmaximum condensate removal when the load is the highest.

Bellows traps can fail either open or closed.


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Typical response of a balanced pressure

steam trap Y-Y


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Advantages of the balanced pressureAdvantages of the balanced pressuresteam trap:steam trap:

Small, light and has a large capacity for itssize.

The valve is fully open on start-up, allowing airand other non-condensable gases to bedischarged freely and giving maximumcondensate removal when the load is greatest.

This type of trap is unlikely to freeze whenworking in an exposed position (unless thereis a rise in the condensate pipe after the trap,which would allow water to run back and floodthe trap when the steam is off).


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Advantages of the balanced pressureAdvantages of the balanced pressuresteam trap:steam trap:

The modern balanced pressure trapThe modern balanced pressure trap

automatically adjusts itself to variations ofautomatically adjusts itself to variations of

steam pressure up to its maximumsteam pressure up to its maximum

operating pressure. It will also tolerate upoperating pressure. It will also tolerate up

to 70to 70C of superheat.C of superheat.

Trap maintenance is simple. The capsuleTrap maintenance is simple. The capsule

and valve seat are easily removed, andand valve seat are easily removed, and

replacements can be fitted in a few minutesreplacements can be fitted in a few minutes

without removing the trap from the line.without removing the trap from the line.


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Disadvantages of the balancedDisadvantages of the balancedpressure steam trappressure steam trap

TheThe older styleolder style balanced pressurebalanced pressure

steam traps had bellows which weresteam traps had bellows which were

susceptible to damage bysusceptible to damage bywaterhammer or corrosivewaterhammer or corrosive

condensate.condensate.

WeldedWelded stainless steelstainless steel capsulescapsules

introduced more recently, are betterintroduced more recently, are better

able to tolerate such conditions.able to tolerate such conditions.


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Disadvantages of the balancedDisadvantages of the balancedpressure steam trappressure steam trap

In common with all other thermostaticIn common with all other thermostatictraps, the balanced pressure type does nottraps, the balanced pressure type does notopen until the condensate temperature hasopen until the condensate temperature has

dropped below steam temperature (thedropped below steam temperature (theexact temperature difference beingexact temperature difference beingdetermined by the fluid used to fill thedetermined by the fluid used to fill theelement).element).

This is clearly a disadvantage if the steamThis is clearly a disadvantage if the steamtrap is chosen for an application in whichtrap is chosen for an application in whichwaterlogging of the steam space can not bewaterlogging of the steam space can not betolerated, for example;tolerated, for example; mains drainagemains drainage,,

heat exchangersheat exchangers,, critical tracingcritical tracing..


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Fig.11.2.10Op eration ofabimetelsteamtrap with two leafelement

Simple Bimetallic TrapSimple Bimetallic Trap


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Simple Bimetallic TrapSimple Bimetallic Trap


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Double Ported TrapDouble Ported Trap


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Thermostatic Trap with BimetallicThermostatic Trap with BimetallicPlatesPlates


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ThermostaticThermostatic

Trap withTrap withBimetallic PlatesBimetallic Plates


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Typical response of a single element bimetal steam trapTypical response of a single element bimetal steam trap


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ZTypical response of a two leaf element Z


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Comparing the operating temperatures of single leaf and multiComparing the operating temperatures of single leaf and multi--leaf bimetallic trapsleaf bimetallic traps


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Advantages ofAdvantages ofBimetallic TypeBimetallic Type

Bimetallic traps are usually small in size and yetBimetallic traps are usually small in size and yet

can have a large condensate discharge capacity.can have a large condensate discharge capacity.

The valve is wide open when the trap is cold, givingThe valve is wide open when the trap is cold, givinga good air venting capability and maximuma good air venting capability and maximum

condensate discharge capacity under start upcondensate discharge capacity under start up

conditionsconditions.. Bimetallic traps can be constructed to withstandBimetallic traps can be constructed to withstand

waterwater--hammer, corrosive condensate, high steamhammer, corrosive condensate, high steam

pressures and superheated steam.pressures and superheated steam.


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Advantages ofAdvantages ofBimetallic TypeBimetallic Type

The bimetal elements can work over a wide range ofsteam pressures without any need for a change in thesize of the valve orifice

If the valve is on the downstream side of the seat it willact as a check valve and prevent any reverse flowthrough the trap.

Maintenance of this type of trap presents fewproblems, as the internals can be replaced without thetrap body being removed from the line.


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Disadvantages of theDisadvantages of theBimetallic TypeBimetallic Type

Bimetallic traps do not usually respond quickly tochanges in load or pressure because the bimetal isrelatively slow to react to variations in temperature.

As condensate is discharged below steam temperature,

water-logging of the steam space will occur unless thetrap is fitted to the end of a fairly long cooling leg.

Bimetallic traps are not generally suitable for fitting toprocess plant where immediate condensate removal is

vital if maximum output is to be achieved. If the trap has to discharge against a back pressure,

the condensate must cool down further than normalbefore the valve will open. It may be necessary toadjust the trap to meet this condition.


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Metallic


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Metallic

ExpansionTrap

In this design condensate enters the tube A and flowout past the valve C.

The tube A is made of copper which expands

considerably more than the iron body B. When the tube A expands it closes the opening at C by

moving towards C.

The valve C is pressed towards the tube A by spring E. The two nuts D allow adjustment to be made so that th

valve shuts tight at any desired temperature.


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Liquid Expansion TypeLiquid Expansion Type

Liquid


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LiquidExpansion

Type

Thermal expansion traps contain athermostatic element that is filled with oil.

As the oil heats up and expands, it causes apiston to move and thereby close a valve.

During start up, air and condensate are

expelled from the open valve. When the oil is sufficiently heated by the

steam, the valve closes to keep the steam

from escaping

Liquid


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LiquidExpansion

Type

This trap contains an oil-filled cylinderencasing a sealed bellows with an enclosedpiston driven rod with a valve on one end.

When the temperature of the condensate,flowing through the trap housing, begins torise the oil in the cylinder begins to expand in

response. As the oil expands it drives the rod assembly

toward a valve seat located in the inlet of the

trap body.

Liquid


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LiquidExpansion

Type

As the condensate surrounding the cylindercools down the oil contracts allowing the rodassembly to retract from the valve seat.

Condensate begins to flow until it heatssufficiently to close the valve again.

The Liquid Expansion Trap also has anadjustable nut on one end. This allows the settemperature to be adjusted within the

operating range of the trap.


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Response of a liquid expansion steam trap XResponse of a liquid expansion steam trap X -- XX


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Installation of a liquid expansion TrapInstallation of a liquid expansion Trap

Because of its fixed temperature dischargeBecause of its fixed temperature discharge

characteristic, the liquid expansion trap may becharacteristic, the liquid expansion trap may be

used as aused as a shutdown drain trapshutdown drain trap ..

Here its outlet must always point upwards toHere its outlet must always point upwards toenable continuous immersion of the oil filledenable continuous immersion of the oil filled

element.element.

As the trap can only discharge between 60As the trap can only discharge between 60--100100CCit will only normally open during start upit will only normally open during start up

I ll i f li id i T


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Installation of a liquid expansion TrapInstallation of a liquid expansion Trap

steam traps ok

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