steam trap1 ppt

STEAM TRAPS 1

By

M.M.Sorour

Mechanical TrapsMechanical Traps

� Mechanical traps use the difference in

density between condensate and live

steam to produce a change in the

position of a float or bucket.

� This movement causes a valve to open

or close.

ball float

float and lever

inverted bucket

open bucket

float and thermostatic

traps.

Mechanical Traps

11-- Ball float trapsBall float traps

� Ball float traps rely on the movement of a spherical ball to open and close the outlet opening in the trap body.

� When no condensate is present, the ball covers the outlet opening, thereby keeping air and steam from escaping.

� As condensate accumulates inside the trap, the ball floats and uncovers the outlet opening.

� This movement allows the condensate to flow continuously from the trap.

� Ball float traps cannot vent air automatically on start up.

11-- Ball float trapsBall float traps

2- Free float traps (low pressure)

�� 11-- At startAt start--up, the bimetal up, the bimetal

strip extends forward to strip extends forward to

prevent the float from prevent the float from

seating on the orifice, seating on the orifice,

allowing air and cold allowing air and cold

condensate to be condensate to be

discharged rapidly.discharged rapidly.

Free float traps (low pressure)

22-- As condensate flows into the trap, the float As condensate flows into the trap, the float

rises due to buoyancy, allowing the rises due to buoyancy, allowing the

condensate to pass through the valve orifice condensate to pass through the valve orifice

to the outlet of the trap.to the outlet of the trap.

The temperature of hot condensate will The temperature of hot condensate will

cause the bimetal to retract, completing the cause the bimetal to retract, completing the

air venting process and allowing the float to air venting process and allowing the float to

seat as the condensate load decreases.seat as the condensate load decreases.

Condensate, however, will continue to be Condensate, however, will continue to be

discharged as long as condensation occurs.discharged as long as condensation occurs.


�� 33-- During normal During normal operation. anoperation. an increase increase

in the condensation rate causes the in the condensation rate causes the

condensate level in the trap to rise. The condensate level in the trap to rise. The

float therefore, rises and modulates on float therefore, rises and modulates on

the up of the orifice, varying the degree the up of the orifice, varying the degree

of opening in accordance with the of opening in accordance with the

amount of condensate entering the trap.amount of condensate entering the trap.

�� In this manner, condensate discharge is In this manner, condensate discharge is

performed continuously while performed continuously while

maintaining a water seal over the orifice maintaining a water seal over the orifice

to prevent steam loss.to prevent steam loss.


44-- Under noUnder no--load conditions the load conditions the

float seats on the orifice, float seats on the orifice,

supported by the two machined supported by the two machined

guides, to provide sealguides, to provide seal--tight tight

shutshut--off. off.

A water seal is maintained above A water seal is maintained above

the orifice at all times.the orifice at all times.

Free Float medium and high pressure

�� When trap is cool, the XWhen trap is cool, the X--element contracts and valve element contracts and valve port (A) opens wide, port (A) opens wide, continuously discharging continuously discharging initial air. initial air.

�� As cold condensate enters As cold condensate enters the trap, the float rises to the trap, the float rises to allow discharge of allow discharge of condensate from valve port condensate from valve port (B) and both air and (B) and both air and condensate from valve port condensate from valve port (A).(A).


�� Once all initial air and cold Once all initial air and cold

condensate have been condensate have been

discharged. hot condensate discharged. hot condensate

heats the Xheats the X----element and closes element and closes

valve port (A) before steam can valve port (A) before steam can

escapeescape. .

�� Condensate which Condensate which

simultaneously enters the trap simultaneously enters the trap

continues to be discharged continues to be discharged

through valve port (B).through valve port (B).


�� 33-- Air or retained condensate Air or retained condensate

entering the trap drop the entering the trap drop the

temperature and contract the Xtemperature and contract the X--

element. element.

�� Valve port (A) Instantaneously Valve port (A) Instantaneously

opens to discharge both air and opens to discharge both air and

condensate. condensate.

�� When higher temperature When higher temperature

condensate follows. the Xcondensate follows. the X--

element expands and closes element expands and closes

valve port.valve port.


�� 44-- When condensate flow to When condensate flow to

the trap ceases, the float the trap ceases, the float

closes valve port (B) which Is closes valve port (B) which Is

always sealed below the always sealed below the

water level. water level.

�� The upper section fills with The upper section fills with

steam, closing valve port (A).steam, closing valve port (A).

�� The trap is then completely The trap is then completely

sealed. preventing any steam sealed. preventing any steam

leakage.leakage.

2. Float and lever traps2. Float and lever traps

� Float and lever traps are similar in operation to ball float traps except the ball is connected to a lever.

� When the ball floats upward due to accumulation of condensate inside the trap body, the attached lever movesand causes a valve to open.

� This action allows condensate to continuously flow from the trap.

� If the condensate load decreases and steam reaches the trap, downward ball movement causes the valve to close, thereby keeping steam from escaping.

Fig. 11.3.1 Float trap with air cock

Float and lever trapsFloat and lever traps

2. Float and lever traps

� Float and lever traps cannot vent air automatically on start up.

� Unless some means is provided for releasing air from the system, condensate will be prevented from flowing into the trap “ air-bound”.

� A manual Air cock is sometimes provided on the top of trap but such a device has the disadvantage of requiring manual operation each time that steam is turned on.

Fig. 11.3.1 Float trap with air cock

Float and lever traps

� The valve must be small or the float will not

have a sufficient buoyancy force to open it.

� The buoyancy relative to the valve area fixes

the maximum pressure at which the trap can

work, and the valve area and the pressure

drop across the valve fixes the maximum

discharge capacity.

Float and lever traps

� If the area of the valve 1cm2 , pressure inside the trap 8kg/cm2. The float would have to exert a buoyancy force of 8 kg on the valve.

� Float lever has a leverage between float and pinof 8 so the buoyancy force required by the float is 1kg.

� 1 m3 of water weight 1000kg

� 0.001 m3 displacement will exert a buoyancy force of 1 kg ( a float of 15cm will give 0.0017m3)

The Lever Float Relay Traps

The Lever Float Relay Traps

� This Trap is suitable for handling large

amounts of condensate at high pressure.

� The float of only sufficient force to open a

small valve which impulse steam

pressure to open the main water valve.

3. Inverted bucket traps

This trap operates on the principal of an inverted water glass (the component referred to as the bucket).


� It is very common type of mechanical steam traps.

� Inverted bucket traps are somewhat more complicated than float and lever traps.

(i) the bucket

hangs down,

pulling the valve

off its seat.

� Condensate flows

under the bottom

of the bucket

filling the body

and flowing away

through the

outlet.


� (ii) the arrival of

steam causes the

bucket to become

buoyant, it then rises

and shuts the outlet.


� (iii) the trap remains shut until the steam in the bucket has condensed or bubbled through the vent hole to the top of the trap body.

� It will then sink, pulling the main valve off its seat. Accumulated condensate is released and the cycle is repeated.


Inverted bucket trapsInverted bucket traps

For horizontal installation For Vertical Installation

Configuration of an inverted bucket steam trap (horizontal installation).

� The inverted bucket trap relies on fluid density differences to actuate its valve.

� Therefore, it cannot distinguish between air and steam and must purge air (and some steam) through a small hole.

� Thus, the top of the bucket has a small hole to allow non-condensable gases to escape.

� The hole must be relatively small to avoid excessive steam loss.

Mechanical Steam TrapsInverted bucket

�� The The airair entrapped in the inverted bucket entrapped in the inverted bucket

provides provides buoyancybuoyancy keeping the inverted keeping the inverted

bucket in its raised position. bucket in its raised position.

�� Recognition of this deficiency with inverted Recognition of this deficiency with inverted

bucket traps or other simple mechanical bucket traps or other simple mechanical

traps led to the development of float and traps led to the development of float and

thermostatic traps. thermostatic traps.


�� On startOn start--up, the initial surge of up, the initial surge of condensate, which precedes the condensate, which precedes the flow of steam, will provide the flow of steam, will provide the liquid prime needed to make the liquid prime needed to make the Inverted Bucket trap work.Inverted Bucket trap work.

�� That prime is what seals the That prime is what seals the bottom open portion of the bucket. bottom open portion of the bucket.

�� Without it, steam would enter the Without it, steam would enter the bucket through the dip tube flow bucket through the dip tube flow out the bottom of the inverted out the bottom of the inverted bucket and pass through the bucket and pass through the outlet. outlet.


� This trap is specified based on the differential pressurebetween the inlet and outlet pressures of the trap.

� With the length of the valve lever fixed the differential pressure is used to determine the weight of the bucket.

� The result allows the bucket to lift and reset the valve after dumping its condensate.

� The calculated weight of the bucket also allows the bucket to drop against the upstream pressure when it's full of condensate.

MECHANICAL STEAM TRAPSInverted Bucket Type

�� Open bucket traps consist of an upright bucket Open bucket traps consist of an upright bucket that is attached to a valve.that is attached to a valve.

�� At start up, At start up, the bucket rests on the bottom of the the bucket rests on the bottom of the trap bodytrap body. .

�� In this position, the valve is wide open. In this position, the valve is wide open.

MECHANICAL STEAM TRAPS

Open bucket traps-4

44-- Open bucket Open bucket trapstraps

�� As condensate accumulates in the trap body on the As condensate accumulates in the trap body on the outside of the bucketoutside of the bucket, the bucket , the bucket floats upwardfloats upward, , which causes which causes the valve to closethe valve to close..

�� When sufficient condensate accumulates outside When sufficient condensate accumulates outside the bucket, it spills over the top and fills the inside the bucket, it spills over the top and fills the inside of the bucket. of the bucket.

�� At this time, the bucket sinks, which causes the At this time, the bucket sinks, which causes the valve to open.valve to open.

�� Similar to inverted bucket traps, Similar to inverted bucket traps, open bucket traps open bucket traps have intermittent discharge. have intermittent discharge.

MECHANICAL STEAM TRAPS4- Open bucket traps

• Attached to the bottom of the bucket A is a spindle B which carries the valve C.

• The spindle and valve are inside a tube D which is open at the bottom.

• At the top end of the tube is the valve seat E.

• When condensate enters at F it fills the body of the trap outside the bucket.

•The bucket floats and the valve is pushed up on its seat. More condensate spills over into the bucket and so on

5- Float and thermostatic traps (F&T)


� Float and thermostatic traps (F&T) traps

are similar to float and lever traps except

they include a thermostatic element that

allows air to be discharged at start up.

� Thermostatic elements used in these

traps are the same as those used in

thermostatic traps.

� The valve F is wide open when the trap is cold so that the air is readily discharged on start up.

� As soon as steam reaches the trap, the element E , expands and pushes the valve F into the seat G so that no steam is able to escape.


Float and thermostatic traps (F&T)

Float Traps versus Bucket Traps

� In both the float and bucket traps two forces are used ; the buoyancy of the buoyant member and the weight of the buoyant member.

� In the float traps it is the buoyancy that opens the valve and the weight that closes it.

� In the bucket traps it is the weight that opens the valve and the buoyancy that closes it.

steam trap1 ppt

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