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Xylem Bell & Gossett Hoffman Speciality Series, Инженерный справочник данных

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modulate over a wide range of conditions, pro-
viding a drainage rate equal to the system
load. The Float and Thermostatic Trap also
has a separate thermostatic vent to provide
quick passage of air during start-up or during
a change of condition. The bucket trap will
completely drain the condensate but operates
in cycles between full open and close. The
bucket trap has a slower air venting rate
unless fitted with a separate thermostatic ele-
ment. Return line sizing can be minimized
using the Float and Thermostatic Trap due to
its modulating feature which provides a con-
tinual flow equal to the condensing rate.

General practice in sizing traps is to allow a
safety factor in the selection. During start-up
when the heat exchanger shell is cold, the
steam piping is cold and the fluid to be heat-
ed may be at less than design temperature.
All these conditions will cause a higher steam
condensing rate. Float and Thermostatic Trap
safety factors are normally 1.5 to 2.5 times
rated load. Bucket Trap safety factors are nor-
mally 2 to 4 times rated load .

Guidelines for selecting traps for heat
exchangers using modulating steam tempera-
ture regulators are as follows:

—Select capacity based on maximum con-
densing load at minimum differential pressure
that can occur. The heat exchanger manufac-
turer can provide this information.

—No lifts should be installed in the return line
piping. The trap must drain into an atmo-
spheric gravity return line.

—Install a vacuum breaker to prevent induced
vacuum in the heat exchanger from causing a
reverse in differential pressure across the
trap.

—Install the trap as far below the heat
exchanger as possible to develop a static
pressure to the trap inlet. The minimum
should be 15 inches.

—Select a trap that provides complete
drainage of condensate. Avoid use of temper-
ature controlled traps.

—Allow an adequate safety factor for start-up
conditions.

25

TEMPERATURE

REGULATING VALVE

GLOBE

VALVE

GATE

VALVE

FLOAT AND

THERMOSTATIC

TRAP

FLOAT AND

THERMOSTATIC

TRAP

PRESSURE

GAUGE

HOT

WATER

THERMOMETER

VACUUM

BREAKER

CONDENSATE

RETURN

Y STRAINER

GATE

VALVE

15" MINUMUM

RECOMMENDED

HEAT EXCHANGER

COLD

WATER

GATE

VALVE

Y STRAINER

GATE

VALVE

CONDENSATE

RETURN

PRESSURE

GAUGE

Y STRAINER

CONNECTION TO

HEAT EXCHANGER

Typical Heat Exchanger Installation

Float & Thermostatic Traps assure complete condensate drainage
at saturation temperature. They also modulate to handle varying
condensate loads associated with temperature regulators. The
thermostatic element provides rapid air venting during start-up.

Содержание Bell & Gossett Hoffman Speciality Series

Страница 1: ...Hoffman Specialty Steam Traps HS 203C ENGINEERING DATA MANUAL Application Selection Installation Piping Diagrams...

Страница 2: ...ng Pressure Limits 17 Installation and Calculating Differential Pressure 18 Drip Traps for Distribution Pipes 20 Chapter 3 Selecting Traps for Heat Exchangers 24 Lock out Traps for Start up Loads 27 D...

Страница 3: ...charge To assure condensate drainage there must be a positive differential pressure across the trap under all load conditions Water Hammer When a trap drains high temperature conden sate into a wet re...

Страница 4: ...ntages Completely drains condensate at satura tion temperature Modulates to handle light or heavy loads continuous discharge equal to condensing load Large ports handle high capacities Separate thermo...

Страница 5: ...hon type or tilting kettles 6 INLET OUTLET COVER BODY V BUCKET A STEAM BUBBLES THROUGH WATER INLET OUTLET COVER BODY V BUCKET A STEAM BUBBLES THROUGH WATER INLET OUTLET COVER BODY V BUCKET A BUCKET TR...

Страница 6: ...inexpensive Fast response to changing conditions Fail open models Disadvantages Water hammer can damage bellows Superheat can damage bellows if it exceeds trap temperature rating Pressure limit of 125...

Страница 7: ...re maximum tem perature is required Outdoor applications including drips on steam mains Drying tables Tire mold press and vulcanizing equipment Dry kilns Pressing machines Rugged applications superhea...

Страница 8: ...hitting the disc Operating As the condensate nears saturation tempera ture greater amounts of flash steam will appear Some of the flash steam escapes to the area above the disc causing the pressure ab...

Страница 9: ...sed only as a guide 10 Chapter 1 Condensate must be completely removed at saturation condition to prevent water hammer Type of Steam Trap Required Based on System Conditions Modulating load wide range...

Страница 10: ...p 3 Apply Safety Factor A SFA Recommended 1 Float Thermostatic Trap 1 5 to 2 5 2 Bucket Trap 2 to 4 3 Thermostatic 2 to 4 4 Disc Traps 1 to 1 2 See specific applications B The SFA Will Depend On Degre...

Страница 11: ...cury 13 6 inches water column Size condensate receivers for 1 min net storage capacity based on return rate Size condensate pumps at 2 to 3 times condensate return rate W x Sh x T2 T1 L x T Helpful Hi...

Страница 12: ...of objects as opposed to latent heat In the sat uration tables it is the Btu remaining in the condensate at saturation temperature Latent Heat The amount of heat expressed in Btu required to change 1...

Страница 13: ...5 353 3 21 324 1193 867 130 355 3 12 327 1194 867 135 358 3 02 329 1194 864 140 361 2 92 332 1195 862 145 363 2 84 335 1196 860 Specfic Heat Content Latent Pressure Saturated Volume Btu per Ib Heat of...

Страница 14: ...600 Pipe Size PRESSURE PSI GAUGE Inches 5 10 15 30 50 75 100 125 200 250 1 2 30 40 45 60 90 120 150 180 270 330 3 4 55 70 80 110 160 220 280 340 510 620 1 90 110 125 180 270 390 460 560 840 1020 11 4...

Страница 15: ...the flash loss and required heating of make up water to replace the flash loss The amount of make up water and water cost can also be determined using this form How to Calculate Your Own Flash Steam...

Страница 16: ...al operating pressure is higher than the seat rating the differential pressure across the seat will prevent the trap from opening Thus the trap must be selected for the maximum differential pressure t...

Страница 17: ...e of the trap required Piping Details A dirt pocket should be provided ahead of the steam trap to collect scale and dirt A shut off valve should be provided ahead of the trap to permit service Straine...

Страница 18: ...ressure in the return line minus static head in the discharge piping Trap capacities should be calculated at the minimum differential pressure to assure com plete condensate drainage Lifts in the retu...

Страница 19: ...ators The size and type of drip traps used will depend on the method used in heating the steam mains to final pressure and tempera ture The two methods commonly used are automatic start up and supervi...

Страница 20: ...x T1 T2 x 114 L W Weight of pipe see table below for weight per ft T1 Steam temperature at saturation T2 Initial pipe temperature at ambient L Latent heat of steam at final operating pressure 114 Spec...

Страница 21: ...a gravity return line this would be 30 psi Step 4 Select the trap Based on the previous description of traps if the trap from a steam header is not subject to freezing conditions the normal selection...

Страница 22: ...o allow conden sate to flow back into main When the branch line is over 10 ft pitch the branch line toward the control valve and install a steam trap The steam trap should be as close to the control v...

Страница 23: ...ing rate at design pressure is not the only load the trap must handle The condens ing load of a heat exchanger designed for 15 psi may in fact be in excess of 90 at 0 psig When the heat exchanger is s...

Страница 24: ...ws Select capacity based on maximum con densing load at minimum differential pressure that can occur The heat exchanger manufac turer can provide this information No lifts should be installed in the r...

Страница 25: ...bottom outlet for the condensate drainage When a modulating steam regulator is used on the steam to water heat exchanger the vacuum breaker will allow air to enter to pre vent an induced vacuum from h...

Страница 26: ...ground steam lines during start up The low pressure trap con nected to an open drain or sump drains con densate during start up When the steam line pressure exceeds the trap rating it will close and r...

Страница 27: ...ted to the overhead return line with a check valve to prevent backflow The second trap may be a low pressure trap When condensate backs up 4 inches it will drain into the second trap which will drain...

Страница 28: ...ized one pipe size smaller than the trap inlet but never less than 1 2 pipe size The coils in Figures 2 3 and 4 are of the con tinuous type Coils are often multi circuited A safety factor of 4 is need...

Страница 29: ...y The excellent air handling capability of Thermostatic Traps makes them suitable for trapping applications where quick air removal is required For example batch processes resulting in on off operatio...

Страница 30: ...heat load is required Small low pressure unit heaters up to 15 psi often use Thermostatic Traps Large unit heaters or those operating at higher pressure may use F T as first choice and Bucket Traps a...

Страница 31: ...elation to other types of traps This makes them attractive for heating systems where many large numbers of traps are required Trap Damage from Water Hammer When automatic temperature controlled sup pl...

Страница 32: ...NPULL SUPPLY MAIN NO PRESSURE WET RETURN REDUCING ELL NOT LESS THAN 24 WATERLINE OF BOILER SUPPLY VALVE WITH CHAINPULL TRAP FULL SIZE OF TAPPING DRY RETURN MAIN MINIMUM COOLING LEG 5 0 LONG SUPPLY VAL...

Страница 33: ...CKET SUPPLY LINE STRAINER UNIT HEATER MINIMUM COOLING LEG 5 0 LONG SAME SIZE AS TRAP TRAP TRAP SUPPLY MAIN GATE VALVE GRAVITY VACUUM DRY RETURN MAIN FULL SIZE OF TAPPING Low pressure closed gravity sy...

Страница 34: ...UNION PITCH DOWN PITCH DOWN PITCH DOWN Distance from center of radiator tapping to face of sill must be given Straight extended stem on supply valve TRAP DIRT POCKET TRAP GATE VALVE DIRT POCKET DIRT...

Страница 35: ...ALVE TRAP MINIMUM COOLING LEG 5 0 LONG RISER PITCH DOWN FROM HERE PACKLESS RADIATOR VALVE AIR VALVE SUPPLY MAIN PITCH DOWN FROM HERE PACKLESS RADIATOR VALVE AIR VALVE Upfeed connection to radiator Rad...

Страница 36: ...LEAST 24 DIRT POCKET AT LEAST 18 ABOVE W L WET RETURN AT LEAST 12 One pipe steam systems convector connections Venting concealed radiator of header type air vent tapping in top Dripping end of one pi...

Страница 37: ...n at 45 Expansion joint made up of pipe for risers Drop riser branch taken from top of main at 45 Drop riser taken from bottom of main Riser branch taken from bottom of main and dripped into wet retur...

Страница 38: ...xi mum heat transfer They are inexpensive and the Hoffman 650 Series allow com plete replacement of the seat and disc without removing the trap body from the line 3 Thermostatic Traps open in response...

Страница 39: ...Friction Factor where flow of condensate does not inhibit the flow of steam Basic Chart for Weight Flow Rate and Velocity of Steam in Schedule 40 Pipe Based on Saturation Pressure of 0 PSIG Figure 10...

Страница 40: ...le size 41 Velocity Multiplier Chart Figure 10 continued Reprinted by permission from ASHRAE 1972 Handbook of Fundamentals Example of Use of Basic and Velocity Multiplier Charts Given a Weight Flow Ra...

Страница 41: ...0 a a 8 228 600 a a Condensate that collects ahead of a steam trap is approximately at saturation temperature and corresponds to the operating pressure As the condensate normally above 212 F drains in...

Страница 42: ...to test operation You will be looking for two phase flow in the discharge line Two phase flow has steam in the discharge line and will be over 212 F along the piping Flash steam normally con denses i...

Страница 43: ...osion Must distinguish between live steam flash steam Crushed ball failure mode is closed 44 THERMOSTATIC TRAP IS TRAP CYCLING TIGHT CLOSURE BETWEEN CYCLES GOOD TRAP REPLACE OR REPAIR IS RUSHING STEAM...

Страница 44: ...AP CAN CYCLES BE HEARD SHUT TIGHT BETWEEN DISCHARGES GOOD TRAP IS RUSHING STEAM HEARD OR SEEN NO YES YES NO CONTINUOUS DISCHARGE LOAD APPROACHING TRAP CAPACITY NO IS RUSHING STEAM SEEN OR HEARD YES GO...

Страница 45: ...re The weight of a column of air one square inch in cross section and extending from the earth to the upper level of the blanket of air surrounding the earth This air exerts a pressure of 14 7 pounds...

Страница 46: ...ater with steam without mixing the two It may be used for supplying hot water for domestic purposes or for a hot water heating system Cooling Leg A length of uninsulated pipe through which the condens...

Страница 47: ...vectors base boards finned tubing coils embedded in floor wall or ceiling or any device which transmits the heat from the heating system to the room and its occupants Horsepower A unit to indicate the...

Страница 48: ...n EDR By definition that amount of heating surface which will give off 240 Btu per hour when filled with a heating medium at 215 F and surrounded by air at 70 F The equivalent square foot of heating s...

Страница 49: ...ar atmo spheric pressure and returns the condensation to the boiler or receiver by gravity Velocity Pressure The pressure used to create the velocity of flow in a pipe It is expressed as a unit pressu...

Страница 50: ...to meet our world s water needs Developing new technologies that will improve the way water is used conserved and re used in the future is central to our work We move treat analyze and return water t...

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