Large Amount of Air? When inlet to equipment is controlled by a 1. Drip Leg. Process Heat Exchanger. The capacity should be C. Critical Process. Fail Cold. Fail Hot. Steam heats a solid or slurry indirectly through a metallic wall. SHEMA ratings have a all moisture in the product be evaporated. Steam heats a solid through direct Formulas contact. Steam heats a liquid indirectly through W x Sh x T2-T1 a metallic wall. EDR yields.
EDR to Ibs. Steam heats air or a gas indirectly. Size condensate pumps at 2 to 3 times condensate return rate. The table also provides Btu heat to change 1 Ib. This same amount Steam pressures and shows the specific volume of of heat must be given off to condense 1 Ib. The heat value is different for every pressure temperature Saturated Steam: combination shown. Pure steam at the temperature corresponding to the boiling point of water.
Total Heat: The sum of the sensible heat in the conden- Pressure psig: sate and the latent heat. It is the total heat Gauge pressure expressed as Ibs.
It is pres- sure indicated on an ordinary pressure gauge. Specific Volume Cu. Per Lb. Heat which only increases the temperature of objects as opposed to latent heat.
In the sat- See Properties of Saturated Steam table on uration tables it is the Btu remaining in the the following page. Heat of Inches of Temp Cu.
Liquid Vapor Btu per Ib. Heat of 1. Saturated Saturated Vaporization 1. Velocity taken at ft. Based on standard formulas. Flash steam is important because it contains H. Latent Heat in Steam at heat which can often be utilized for economy. It is necessary to know how it is formed and how much will be formed under given condi- I. To obtain annual loss multiply Ibs. Ioss x hr. Flash Steam Heat Loss Calculation The form provided to the right will allow you to Calculation of Energy Loss: easily calculate the flash steam loss and This calculation must take into consideration associated energy cost.
It may be necessary removed in the form of flash steam must be to estimate the average conditions when replaced with cooler make-up water. Steam table. The calculation for flash loss may now be made with the annual loss determined. The amount of make-up water and water cost can also be determined using this form. Per Hr.. When actual 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 that will be encountered. A high pressure seat may be used at lower differential pressures, however, the capacity rating will be less than the same size trap with a low pressure rated seat. A shut-off Calculating condensate outlet of equipment or steam valve should be provided ahead of the trap to mains being drained.
A 15 inch static head at permit service. During start-up, before a positive steam pressure is achieved, trap. Dirt entering the trap can deposit on the the static head is the only differential pres- seat and prevent tight closing.
A blow-off valve sure across the trap. When the steam equip- on the strainer will permit strainer screen ment is controlled by a temperature regulator, cleaning. Unions or flanges should be provid- the steam pressure will be reduced as the ed to allow removal of the trap for testing, valve modulates toward the closed position.
When the pressure drops to O psi, the static A test and relief valve installed after the trap head is the only differential pressure across permits visual indication of the trap operation, the trap.
The differential pressure across the and assures that internal pressures are trap can be increased by lowering the trap be- relieved prior to servicing. A greater differential pres- A shut-off valve in the trap outlet to the return sure will reduce the size of the trap required. Bypass valves, if The differential pressure across the trap will opened, may cause pressurization of conden- be the sum of the minimum operating pres- sate receivers and cause a safety hazard. Trap capacities should be calculated at the Where the trap drains into a pressurized minimum differential pressure to assure com- return line or to an overhead return, a check plete condensate drainage.
High temperature conden- steam is off. The check valve also helps pro- sate discharging from the trap may flash at tect the trap from cavitation water hammer the lower return line pressure. The flashing that may occur when traps discharge high into a wet return line will cause steam pock- temperature condensate into wet return lines. As these steam pockets lose their latent Water hammer occurs when high temperature heat they implode, causing water hammer. The high temperature condensate flashes, causing steam pockets to form.
When these Lifts in the discharge piping after a trap will steam pockets give up their heat they implode cause back-pressure. Iift is equal to and cause water hammer. This is especially important on low pressure operation or where a modu- lating control valve is used to control the flow of steam. Reduced flow will cause pressure drops. The drip traps must handle the The steam piping must be kept free of air and full condensing load during start-up of the condensate.
This requirement is met with the system. The In systems using supervised start-up the oper- traps used for draining the steam mains are ator opens manual valves in the steam piping commonly referred to as drip traps. If the before steam is admitted to the system. The drip traps for supervised start-up sate traveling at high speed in the steam are sized only for the running load.
The sizing of drip traps will depend on the Drip traps are installed in the steam mains at type of start-up used. During the initial start- all risers, ahead of all reducing valves, ahead up of automatic startup systems, a large of all regulators, at the end of mains, through- amount of condensing occurs, bringing the out the piping at intervals at least every steam piping from ambient temperature up to feet, at expansion joints and at all steam the final steam temperature.
When supervised start-up is used the drip trap The size and type of drip traps used will is sized only to handle the heat loss through depend on the method used in heating the the steam piping. The two methods commonly used are automatic start-up and supervised start-up. Per Linear Ft. Assuming a gravity return line, this would be 30 psi.
Step 1 Running load Ib. Assuming a warm-up of 15 minutes, the steam main for pipe size up to 4 inches. Above 4 inch size the drip connection should Thus, the trap must be sized for Ibs. The factor.
Normal psig. When the valve opens with con- densate backed up on the inlet side, the con- densate will cause water hammer. When the branch line is over 10 ft. As the temperature tial to prevent tube damage due to water for Heat regulator controls the flow of steam, condesa- hammer. The steam flow in the heat exchang- tion causes a change in pressure. Thus, the er shell must pass around the tube support Exchangers steam trap must be capable of handling a sheets.
If condensate builds up in the heat wide range of capacities at varying pressures. The water hammer is often evident by or steam equipment operating at constant indentations in the tubes and collapsed pressure. A heat exchanger is sized to heat a maximum Thus, it becomes evident that the design con- expected flow rate through the tubes, over the densing rate at design pressure is not the maximum expected temperature rise with a only load the trap must handle.
The condens- predetermined maximum steam operating ing load of a heat exchanger designed for 15 pressure. When the heat exchanger is selected, a foul- When the tube side flow rate is reduced, or ing factor is added to assure adequate tube the incoming fluid being heated requires less area as scale builds up on the tube walls.
The condensing of the steam under reduced load conditions results A steam trap must then be selected to handle in a lower steam pressure in the shell of the the full condensing load with the heat heat exchanger. The heat exchanger may operate at a slight vacuum During very low load conditions the condens- due to the condensing of steam.
A vacuum ing of the steam can create an induced vacu- breaker is required on a heat exchanger to um in the shell of the heat exchanger. This prevent induced vacuum. The differential condition requires that a vacuum breaker be required to open the vacuum breaker is usual- installed to allow air to enter and relieve the ly less than 0. Without a vacuum breaker, the induced vacuum would cause a negative Recommended practice is to install the trap pressure differential across the trap and the as far below the heat exchanger as possible.
A 15 inch static head will develop approxi- mately 0. Assuming 0. A static head of 2. Traps that operate in response to tem- perature should be avoided for heat exchang- er operation. The two types of traps that can meet these requirements are Float and Thermostatic Traps and Bucket Traps. The Float and Thermostatic Trap also ture regulators are as follows: has a separate thermostatic vent to provide quick passage of air during start-up or during —Select capacity based on maximum con- a change of condition.
The bucket trap will densing load at minimum differential pressure completely drain the condensate but operates that can occur. The heat exchanger manufac- in cycles between full open and close. The turer can provide this information. The trap must drain into an atmo- ment. Return line sizing can be minimized spheric gravity return line. During start-up when the heat exchanger shell is cold, the —Install the trap as far below the heat steam piping is cold and the fluid to be heat- exchanger as possible to develop a static ed may be at less than design temperature.
The minimum All these conditions will cause a higher steam should be 15 inches. Float and Thermostatic Trap —Select a trap that provides complete safety factors are normally 1.
Avoid use of temper- rated load. Bucket Trap safety factors are nor- ature controlled traps. They also modulate to handle varying condensate loads associated with temperature regulators. A separate Thermostatic With a condensate cooler, the discharge from Trap should be provided to allow the air to be the trap on the primary heat exchanger is vented when the pressure increases above O piped through a water-to-water heat exchanger.
This trap bypasses the condensate cool- This lowers the condensate temperature and er to allow free passage of the air into the recovers wasted heat. A second trap is then gravity return line. When the The water-to-water heat exchanger design dif- initial temperature of the fluid is too high to fers from steam heat exchangers. Heating domestic hot water to direct the water flow across the tubes to or pre-heating boiler make-up water are two improve heat transfer.
The water-to-water heat possibilities. The steam-to-water heat exchangers have a large opening in the top for the steam inlet and a smaller bottom outlet for the condensate drainage. Underground Steam Main. In the discussion of trap operation, we point- One application of a lock-out trap is to drain Traps for ed out that if the differential pressure across condensate from underground steam lines Start-Up the trap seat exceeds the trap pressure rat- during start-up.
The low pressure trap con- Loads ing, the trap will fail closed. This occurs when nected to an open drain or sump drains con- the differential force across the seat and pin densate during start-up. When the steam line exceeds the drop-away force created by the pressure exceeds the trap rating it will close weight of the float or bucket and linkage. The differential pressure Under certain conditions we can use a trap will then allow the condensate to flow through with a low differential pressure in a high pres- the high pressure drip trap and be recovered sure application to drain condensate during through the return line.
When the regulator reduces the flow of steam, the pressure in the steam space drops due to the condensing rate in relation to steam flow.
The low pres- sure trap connected to a sump or drain will then operate when the pressure drops approx- imately to the rated pressure of the trap. When a positive pressure is not Returns assured, such as the case when using a steam control valve, provision must be made to drain condensate at reduced pressure loads and during initial start-up. The use of a second trap installed at a higher elevation and connected to a drain may be used as shown below. The normal trap is connected 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 condensate into a floor drain or sump. When a trap drains into an overhead return line or pressurized return line, water hammer may occur due to high temperature conden- sate flashing as it drains through the trap into a lower pressure. The check valve after the trap protects it from the forces created by water hammer. It also prevents backflow through the trap when the steam is off.
Use a the coil. The lift fitting tube is usually sized Coils safety factor of 2 for trap sizing. When it is not practical to install the trap below the tank level, a lift fitting or water seal The coils in Figures 2,3 and 4 are of the con- must be provided to bring the condensate to tinuous type. Coils are often multi-circuited.
A the trap level over the heated tank. Figure 3 safety factor of 4 is needed where this is the shows a water seal arrangement. Note that case because of the higher warm-up load. Condensate collects fashion as ordinary pipe coils.
Where the coil in the water seal and is elevated to the is of the continuous type and gravity drained, siphon loop by the differential pressure. A the safety factor is 2 to 1. Siphon drained safety factor of 3 should be used. Multiple Large diameter coils may require yet another header plate coils should have a safety factor type of installation. Where the coil diameter is of 3 to 1 if they are gravity drained and 4 to 1 larger than the trap inlet size, the installation if siphon drained.
Figure 5 illustrates these shown in Figure 4 should be used. A smaller coil types. These The excellent air handling capability of Kettles require the use of a siphon drain. Siphon Thermostatic Traps makes them suitable for drains may either be internal or external. The trapping applications where quick air removal Fig. For example, batch processes resulting in on-off operation of steam heating As shown in the illustration, external siphons equipment are prone to air problems.
The are surrounded by ambient air, while the inter- steam space becomes filled with air in nal siphon is surrounded by steam. Unless this air is Flash steam tends to form in siphons and the quickly removed with the condensate, slow trap must be able to operate properly with a heating of the batch results.
Thermostatic certain amount of it present in the conden- Traps must be fitted with a cooling leg, when sate. Figure 7 illustrates how this takes used for this purpose, to minimize back up of place, and how a steam main is drained. First, condensate drains into the water seal. Figure 8 shows a steam kettle serviced by a Steam in the siphon above the water seal Thermostatic Trap. A cooling leg with a mini- condenses, dropping the pressure.
The siphon may form and break several trap. Notice the check valve provided at the trap outlet. This prevents back drainage of the A check valve must be used to hold the condensate in the vertical line.
A check valve siphon while it is forming. This should be should always be provided at the trap outlet installed after the strainer as shown. Once where vertical lifts exists. An external type siphon loses some heat Traps. As a result, the amount of flash steam is less than in an internal siphon, which absorbs heat from the steam surrounding it.
Since they are usually rotating in area, traps for this type of application should Dryers, Unit nature, siphon drainage of the condensate is be sized with a substantial safety factor. This Heaters involved. Figure 9 shows a typical arrange- is required to eliminate the air and handle the ment. Condensate is drained from the bottom large warm-up load.
It is not uncommon to of the rotating cylinder by a typical siphon use safety factors of between 5 and 8 for arrangement. Operation may have maintained steam pressure in coils with Unit heater a thermostat to control the fan or steam con- trol may be on-off as heat load is required.
Induced vacuum causes a reverse differential pressure across the trap and holds up condensate in the coils. The recommended safety factor for sizing traps for unit heaters is 3 times rated capacity. The Thermostatic Trap is a ply valves are used, water hammer may occur pressure balanced device that will open usual- when the valve closes.
This implode as they lose their heat. A solid fill Hoffman Specialty 17K is designed to withstand this service. Low pressure Thermostatic Traps are normally rated in sq. Thermostatic Traps are inexpensive in relation to other types of traps. This makes them attractive for heating systems where many large numbers of traps are required. They are not dimensional and cannot be scaled for for Steam pipe size or product size. When more than one tracer line is manifolded Steam Tracer into a common trap, condensate can back up Lines in the line with the greatest pressure drop.
Individual tracer line trap selection guide: 1. Bucket Traps may be used for tracer lines in areas not subject to freezing. The tracer lines should be installed for gravity drainage when Bucket Traps are used.
Condensate will drain at saturation temper- ature for maximum heat transfer. Bucket Traps are normally too expensive for larger tracer applications. Thermodisc Traps were designed for tracer line applications. Thermodisc Traps drain conden- sate at saturation temperature for maxi- mum heat transfer. They are inexpensive and the Hoffman Series allow com- plete replacement of the seat and disc without removing the trap body from the line.
Thermostatic Traps open in response to temperature, not condensate level. Use where maximum heat transfer is not impor- tant. Applications using Thermostatic Traps should be pitched to allow gravity conden- sate drainage.
Thermostatic Traps select- ed for tracer lines should fail open. When the steam is off, the thermostatic element will open draining condensate to prevent freezing. They are subject to freezing when located in low ambient con- ditions when the steam is off. They are 1. Each tracer line must have its own trap. A common trap with manifold tracer lines may cause short cir- cuiting through lines with lower pressure drop.
Longer lines will back-up condensate and will not provide ade- quate heat transfer. Enter left column Charts Fig. General Heating Application—2, Ibs. Read corrected velocity of 6, fpm in right Required at 30 psi supply pressure. Use velocity chart to correct 6, fpm, required velocity, to 10, fpm before using Step 1 basic chart.
Correct 30 psi flow rate to O psi on basic chart. This is done by entering bottom at 2, Ibs. Follow this point vertically to the 30 Ib. Iine, then follow slope to the 0 psi 2. Heat exchanger steam entrance nozzles line. Check with heat exchange manufacturer Draw vertical line from 0 point into upper for nozzle size. Stop at some point above 6, fpm.
Velocity shown is O psi steam and requires correction. Given: a. Find: a. Size of Schedule 40 pipe required. Velocity of steam in pipe. Solution: The following steps are illustrated by the broken line on Fig.
Enter Fig. Step 2. Follow along inclined multiplier line upward and to the left to horizontal 0 psig line. The equivalent weight flow at 0 psig is about Ib. Step 3. Follow the Ib. Iine vertically until it intersects the hori- zontal line at 11 psi per ft. The equivalent steam velocity at 0 psig is about 32, fpm. Step 4. To find the steam velocity at psig, locate the value of 32, fpm on the ordinate of the velocity multiplier chart at 0 psig.
Step 5. Move along the inclined multiplier line downward and to the right until it intersects the vertical psig pressure line. The velocity as read from the right or left scale is about 13, fpm. Selections for Method for temperature and corresponds to the operating pressure.
Lines temperature at atmospheric pressure. The return steam supply at psig and the return line is lines must be sized to handle the volume of at 0 psig and not vented. The return line is steam and condensate at reasonable horizontal and must have a capacity of velocities to minimize any backpressure. What size pipe is required?
The volume of steam is normally several Solution: Since the system will be throttling times the volume of condensate and is non-subcooled condensate from psig to 0 generally maintained at less than 7, feet psig there will be flash steam and the system per minute.
Reprinted by permission of the American Society of Heating, Refrigeration and Air-Conditioning Select another combination of sizes and pressure loss.
If the trap is blowing live Testing Steam charge piping, visual inspection is the most steam the ball will move inside the housing. Due to the high cost in operation. The discharge should be steady.
When this high temperature condensate dis- charges to atmosphere flash steam may be present. Flash steam is normal and is not an indication of trap failure. Flash steam is a low velocity white colored discharge with a large stream of condensate. If the trap is blowing START live steam it will be at high velocity—a clear area will be present ahead of where the steam begins to condense.
Then, a bluish steam will begin and there will be less condensate along with the steam. When the piping ahead of the steam trap is YES cold, this is an indication that the trap has failed in a closed position.
The temperature immediately ahead of the trap should be lower than the steam coil, radiator, etc. The linkage or disc closing can then YES be heard. No other sound should follow. A fast response tempera- ture scanner may be used to test operation.
Check list—step by step You will be looking for two-phase flow in the discharge line. Flash steam normally con- denses in a short length of piping and will Testing Steam Traps drop in temperature along the pipe. Types of Tests: Where several traps are used in similar appli- Temperature, pressure, flow. You will soon be How to Check: able to pick out a defective trap. Both a listen- Listening device, temperature device, visual. Screwdriver, stethoscope, ultrasonic tester. Sight checkers provide a positive way to check steam traps.
A sight checker would be Temperature Devices: installed in the outlet piping from the trap. Gloves, water gun, crayons, pyrometer, infrared. When the trap opens the ball check lifts off Real Reason: the seat.
The differential pressure Under certain conditions we can use a trap will then allow the condensate to flow through with a low differential pressure in a high pres- the high pressure drip trap and be recovered sure application to drain condensate during through the return line.
When the regulator reduces the flow of steam, the pressure in the steam space drops due to the condensing rate in relation to steam flow. The low pres- sure trap connected to a sump or drain will then operate when the pressure drops approx- imately to the rated pressure of the trap.
When a positive pressure is not Returns assured, such as the case when using a steam control valve, provision must be made to drain condensate at reduced pressure loads and during initial start-up. The use of a second trap installed at a higher elevation and connected to a drain may be used as shown below.
The normal trap is connected 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 condensate into a floor drain or sump. When a trap drains into an overhead return line or pressurized return line, water hammer may occur due to high temperature conden- sate flashing as it drains through the trap into a lower pressure.
The check valve after the trap protects it from the forces created by water hammer. It also prevents backflow through the trap when the steam is off. Use a the coil. The lift fitting tube is usually sized Coils safety factor of 2 for trap sizing. When it is not practical to install the trap below the tank level, a lift fitting or water seal The coils in Figures 2,3 and 4 are of the con- must be provided to bring the condensate to tinuous type.
Coils are often multi-circuited. A the trap level over the heated tank. Figure 3 safety factor of 4 is needed where this is the shows a water seal arrangement. Note that case because of the higher warm-up load. Condensate collects fashion as ordinary pipe coils. Where the coil in the water seal and is elevated to the is of the continuous type and gravity drained, siphon loop by the differential pressure.
A the safety factor is 2 to 1. Siphon drained safety factor of 3 should be used. Multiple Large diameter coils may require yet another header plate coils should have a safety factor type of installation. Where the coil diameter is of 3 to 1 if they are gravity drained and 4 to 1 larger than the trap inlet size, the installation if siphon drained. Figure 5 illustrates these shown in Figure 4 should be used.
A smaller coil types. These The excellent air handling capability of Kettles require the use of a siphon drain. Siphon Thermostatic Traps makes them suitable for drains may either be internal or external.
The trapping applications where quick air removal Fig. For example, batch processes resulting in on-off operation of steam heating As shown in the illustration, external siphons equipment are prone to air problems. The are surrounded by ambient air, while the inter- steam space becomes filled with air in nal siphon is surrounded by steam.
Unless this air is Flash steam tends to form in siphons and the quickly removed with the condensate, slow trap must be able to operate properly with a heating of the batch results. Thermostatic certain amount of it present in the conden- Traps must be fitted with a cooling leg, when sate. Figure 7 illustrates how this takes used for this purpose, to minimize back up of place, and how a steam main is drained.
First, condensate drains into the water seal. Figure 8 shows a steam kettle serviced by a Steam in the siphon above the water seal Thermostatic Trap. A cooling leg with a mini- condenses, dropping the pressure. The siphon may form and break several trap. Notice the check valve provided at the trap outlet. This prevents back drainage of the A check valve must be used to hold the condensate in the vertical line. A check valve siphon while it is forming. This should be should always be provided at the trap outlet installed after the strainer as shown.
Once where vertical lifts exists. An external type siphon loses some heat Traps. As a result, the amount of flash steam is less than in an internal siphon, which absorbs heat from the steam surrounding it. Since they are usually rotating in area, traps for this type of application should Dryers, Unit nature, siphon drainage of the condensate is be sized with a substantial safety factor.
This Heaters involved. Figure 9 shows a typical arrange- is required to eliminate the air and handle the ment. Condensate is drained from the bottom large warm-up load. It is not uncommon to of the rotating cylinder by a typical siphon use safety factors of between 5 and 8 for arrangement.
Operation may have maintained steam pressure in coils with Unit heater a thermostat to control the fan or steam con- trol may be on-off as heat load is required. Induced vacuum causes a reverse differential pressure across the trap and holds up condensate in the coils.
The recommended safety factor for sizing traps for unit heaters is 3 times rated capacity. The Thermostatic Trap is a ply valves are used, water hammer may occur pressure balanced device that will open usual- when the valve closes. This implode as they lose their heat. A solid fill Hoffman Specialty 17K is designed to withstand this service. Low pressure Thermostatic Traps are normally rated in sq. Thermostatic Traps are inexpensive in relation to other types of traps. This makes them attractive for heating systems where many large numbers of traps are required.
They are not dimensional and cannot be scaled for for Steam pipe size or product size. When more than one tracer line is manifolded Steam Tracer into a common trap, condensate can back up Lines in the line with the greatest pressure drop. Individual tracer line trap selection guide: 1. Bucket Traps may be used for tracer lines in areas not subject to freezing.
The tracer lines should be installed for gravity drainage when Bucket Traps are used. Condensate will drain at saturation temper- ature for maximum heat transfer. Bucket Traps are normally too expensive for larger tracer applications. Thermodisc Traps were designed for tracer line applications.
Thermodisc Traps drain conden- sate at saturation temperature for maxi- mum heat transfer. They are inexpensive and the Hoffman Series allow com- plete replacement of the seat and disc without removing the trap body from the line. Thermostatic Traps open in response to temperature, not condensate level.
Use where maximum heat transfer is not impor- tant. Applications using Thermostatic Traps should be pitched to allow gravity conden- sate drainage.
Thermostatic Traps select- ed for tracer lines should fail open. When the steam is off, the thermostatic element will open draining condensate to prevent freezing.
They are subject to freezing when located in low ambient con- ditions when the steam is off. They are 1. Each tracer line must have its own trap. A common trap with manifold tracer lines may cause short cir- cuiting through lines with lower pressure drop.
Longer lines will back-up condensate and will not provide ade- quate heat transfer. Enter left column Charts Fig. General Heating Application—2, Ibs. Read corrected velocity of 6, fpm in right Required at 30 psi supply pressure. Use velocity chart to correct 6, fpm, required velocity, to 10, fpm before using Step 1 basic chart. Correct 30 psi flow rate to O psi on basic chart. This is done by entering bottom at 2, Ibs. Follow this point vertically to the 30 Ib.
Iine, then follow slope to the 0 psi 2. Heat exchanger steam entrance nozzles line. Check with heat exchange manufacturer Draw vertical line from 0 point into upper for nozzle size. Stop at some point above 6, fpm. Velocity shown is O psi steam and requires correction.
Given: a. Find: a. Size of Schedule 40 pipe required. Velocity of steam in pipe. Solution: The following steps are illustrated by the broken line on Fig. Enter Fig. Step 2. Follow along inclined multiplier line upward and to the left to horizontal 0 psig line. The equivalent weight flow at 0 psig is about Ib. Step 3. Follow the Ib. Iine vertically until it intersects the hori- zontal line at 11 psi per ft.
The equivalent steam velocity at 0 psig is about 32, fpm. Step 4. To find the steam velocity at psig, locate the value of 32, fpm on the ordinate of the velocity multiplier chart at 0 psig. Step 5. Move along the inclined multiplier line downward and to the right until it intersects the vertical psig pressure line. The velocity as read from the right or left scale is about 13, fpm. Selections for Method for temperature and corresponds to the operating pressure. Lines temperature at atmospheric pressure.
The return steam supply at psig and the return line is lines must be sized to handle the volume of at 0 psig and not vented.
The return line is steam and condensate at reasonable horizontal and must have a capacity of velocities to minimize any backpressure. What size pipe is required? The volume of steam is normally several Solution: Since the system will be throttling times the volume of condensate and is non-subcooled condensate from psig to 0 generally maintained at less than 7, feet psig there will be flash steam and the system per minute. Reprinted by permission of the American Society of Heating, Refrigeration and Air-Conditioning Select another combination of sizes and pressure loss.
If the trap is blowing live Testing Steam charge piping, visual inspection is the most steam the ball will move inside the housing. Due to the high cost in operation. The discharge should be steady. When this high temperature condensate dis- charges to atmosphere flash steam may be present. Flash steam is normal and is not an indication of trap failure.
Flash steam is a low velocity white colored discharge with a large stream of condensate. If the trap is blowing START live steam it will be at high velocity—a clear area will be present ahead of where the steam begins to condense. Then, a bluish steam will begin and there will be less condensate along with the steam. When the piping ahead of the steam trap is YES cold, this is an indication that the trap has failed in a closed position. The temperature immediately ahead of the trap should be lower than the steam coil, radiator, etc.
The linkage or disc closing can then YES be heard. No other sound should follow. A fast response tempera- ture scanner may be used to test operation. Check list—step by step You will be looking for two-phase flow in the discharge line. Flash steam normally con- denses in a short length of piping and will Testing Steam Traps drop in temperature along the pipe. Types of Tests: Where several traps are used in similar appli- Temperature, pressure, flow.
You will soon be How to Check: able to pick out a defective trap. Both a listen- Listening device, temperature device, visual. Screwdriver, stethoscope, ultrasonic tester. Sight checkers provide a positive way to check steam traps. A sight checker would be Temperature Devices: installed in the outlet piping from the trap. Gloves, water gun, crayons, pyrometer, infrared. When the trap opens the ball check lifts off Real Reason: the seat.
Some do not define the terms extending from the earth to the upper level of for all usages. This air exerts a pressure of It is the atmospheric pressure added to the Boiler: A closed vessel in which steam is gener- gauge pressure. It is expressed as a unit pres- ated or in which water is heated by fire. Boiler Heating Surface: The area of the heat Absolute Temperature: The temperature of a transmitting surfaces in contact with the water substance measured above absolute zero.
To or steam in the boiler on one side and the fire express a temperature as absolute temperature or hot gases on the other. Boiler Horsepower: The equivalent evaporation of This is equal to a heat output approx. Air: An elastic gas. It is a mechanical mixture of British Thermal Unit Btu : The quantity of heat oxygen and nitrogen and slight traces of other required to raise the temperature of 1 Ib.
This is somewhat approximate but humidity. Dry air weighs 0. The float or bucket is open at the its volume for each degree of rise or fall in tem- bottom. Water surrounding the bucket keeps it floating and the pin is pressed against its Air Cleaner: A device designed for the purpose seat. Condensate from the system drains into of removing air-borne impurities such as dust, the bucket. When enough has drained into it so fumes, and smokes.
Air cleaners include air that the bucket loses its buoyancy it sinks and washers and air filters. Chimney Effect: The tendency in a duct or other vertical air passage for air to rise when heated due to its decrease in density. A thermo- inside and outside of the wall, floor, roof, or static trap may require a cooling leg to permit ceiling. Column Radiator: A type of direct radiator. This radiator has not been sold by manufacturers Degree-Day: Standard A unit which is the differ- since Comfort Zone Average : The range of effective Dew-Point Temperature: The air temperature temperatures over which the majority of adults corresponding to saturation percent rela- feel comfortable.
It is Concealed Radiator: See Convector. Condensate: Water formed by cooling steam. The capacity of traps, pumps, etc. One pound of condensate per is fully or partially closed. The enclosed portion hour is equal to approximately 4 sq. Btu transmitted from surface to surface, in one Domestic Hot Water: Hot water used for purpos- hour through one square foot of a material or es other than house heating such as laundering, construction for the thickness or type under con- dishwashing, bathing, etc.
Down-Feed One-Pipe Riser Steam : A pipe which carries steam downward to the heating Conduction Thermal : The transmission of heat units and into which heating units drain through and by means of matter.
Conductivity Thermal -k-: The amount of heat Down-Feed System Steam : A steam heating Btu transmitted in one hour through one system in which the supply mains are above the square foot of a homogenous material one inch level of the heating units which they serve.
Conductor Thermal : A material capable of read- Dry Return Steam : A return pipe in a steam ily transmitting heat by means of conduction. Convection: The transmission of heat by the cir- culation either natural or forced of a liquid or a Dry Saturated Steam: Saturated steam contain- gas such as air. If natural, it is caused by the ing no water in suspension. Equivalent Direct Radiation E.
An enclosed Square Foot of Heating Surface. A shielded heating prime surface. If the heating unit is located exterior to the room or space to Extended Surface Heating Unit: A heating unit be heated, the heat is transferred through one having a relatively large amount of extended sur- or more ducts or pipes.
It may or by being soldered to the core or by both pres- be used for supplying hot water for domestic sure and soldering. An extended surface heating purposes or for a hot water heating system. One horsepower equals Btu per hour or watts. Flash Steam : The rapid passing into steam of water at a high temperature when the pressure Hot Water Heating System: A heating system in it is under is reduced so that its temperature is which water is used as the medium by which above that of its boiling point for the reduced heat is carried through pipes from the boiler to pressure.
For example: If hot condensate is dis- the heating units. It is also called re-evaporation. Humidity: The water vapor mixed with air. Latent Heat of Evaporation: The heat Btu per Float Trap: A steam trap which is operated by a pound necessary to change 1 pound of liquid float.
When enough condensate has drained by into vapor without raising its temperature. In gravity into the trap body the float is lifted. In round numbers this is equal to Btu per turn, the pin lifts off its seat. This permits the pound of water. The latent float trap. Mechanical Equivalent of Heat: The mechanical Complete heating unit of a warm air heating energy equivalent to 1 Btu which is equal to system.
Gauge Pressure: The pressure above that of the Mil-lnch: One one-thousandth of an inch 0. It is the pressure indicated on an ordinary pressure gauge. Head: Unit pressure usually expressed in ft. Heat always flows from a One-Pipe System Hot Water : A hot water heat- body of higher temperature to a body of lower tem- ing system in which one pipe serves both as a perature. See also: Latent Heat, Sensible Heat, supply main and as a return main.
There is one connection to each heating unit Heat Unit: In the foot-pound-second system, the which serves as both the supply and the return. British Thermal Unit Btu in the centimeter-gram- Overhead System: Any steam or hot water sys- second system, the calorie cal.
With a steam system the return must steam, or air used to convey heat from the boil- be below the heating units; with a water system, er, furnace, or other source of heat to the heat- the return may be above the heating units. Panel Heating: A method of heating involving Heating Surface: The exterior surface of a heat- the installation of the heating units pipe coils ing unit. See also Extended Heating Surface. Heating Unit: Radiators, convectors, base Panel Radiator: A heating unit placed on, or boards, finned tubing, coils embedded in floor, flush with, a flat wall surface and intended to wall, or ceiling, or any device which transmits function as a radiator.
Do not confuse with panel the heat from the heating system to the room heating system. Square Foot of Heating Surface: Equivalent inch. Unless otherwise qualified, it refers to unit direct radiation EDR. By definition, that amount static gauge pressure. The Pressure Reducing Valve: A device used to equivalent square foot of heating surface may decrease the pressure of a gas or liquid. It is used to overcome the frictional Radiant Heating: A heating system in which the resistance to flow through the pipe.
It is heating is by radiation only. Sometimes used in expressed as a unit pressure and may be in a Panel Heating System. It is frequently expressed in feet of water column or in the case Radiation: The transmission of heat in a straight of pipe friction in mil-inches of water column line through space. Radiator: A heating unit located in the room to Steam: Water in the vapor phase.
The vapor be heated and exposed to view. See also Dry Saturated Steam, Wet turn is circulated by natural convection. Saturated Steam, Superheated Steam. Re-Evaporation: See Flash. See Thermostatic, Float, Bucket given quantity of air compared with the maxi- Trap.
It is temperature corresponding to its pressure. Supply Mains: The pipes through which the heat- Return Mains: The pipes which return the heat- ing medium flows from the boiler or source of ing medium from the heating units to the source supply to the run-outs and risers leading to the of heat supply. Sensible Heat: Heat which increases the tem- perature of objects as opposed to latent heat. Thermostat: An instrument which responds to changes in temperature and which directly or Specific Heat: In the foot-pound-second system, indirectly controls the room temperature.
In Thermostatic Trap: A steam trap which closes the centimeter-gram-second system, the amount when the steam reaches it and opens when the of heat cal. This occurs substance one degree C. The specific heat of when cold condensate or air reaches it. The tem- water is 1. Ton of Refrigeration: The heat which must be extracted from one ton 2, Ibs. If the motive head pro- ty pressures.
It is also used as the total static ducing flow depends on the difference in weight pressure over an entire area, that is, the unit between the heated air leaving the casing and pressure multiplied by the area on which it acts. A booster fan may, Trap, and Bucket Trap. If a fan is used to produce circu- Two-Pipe System Steam or Water : A heating lation and the system is designed especially for system in which one pipe is used for the supply fan circulation, it is termed a fan furnace system main and another for the return main.
In a two- or a central fan furnace system. A fan furnace pipe hot water system each heating unit system may include air washer, filters, etc. Wet Bulb Temperature: The lowest temperature Unit Heater: A heating unit consisting of a heat which a water-wetted body will attain when transfer element, housing, fan with motor, and exposed to an air current. It is usually sus- pended from the ceiling and its heat output is Wet Return Steam : That part of the return controlled by starting and stopping the fan by a main of a steam heating system which is com- room thermostat.
The circulation of the heating pletely filled with water of condensation. It is used primarily for industrial heating. Unit Pressure: Pressure per unit area as Ibs.
Up-Feed System Hot Water or Steam : A heat- ing system in which the supply mains are below the level of the heating units which they serve.
Vacuum Heating System Steam : A one- or two-pipe heating system equipped with the nec- essary accessory apparatus to permit the pres- sure in the system to go below atmospheric. Vapor: Any substance in the gaseous state. Vapor Heating System Steam : A two-pipe heating system which operates at or near 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 pressure. Ventilation: Air circulated through a room for ventilating purposes. It may be mechanically circulated with a blower system or through circulation with an open window, etc. Vent Valve Steam : A device that permits air to be forced out of a heating unit or pipe and closes against water and steam. Vent Valve Water : A device that permits air to be forced out of a heating unit or pipe and closes against water.
George A. Israel Jr. Verne Simmonds Co. Thermoflo Equipment Co. Dawson Co. Bitzer Co. The Bernard M. Packtor Co. Langley Co. Pittsburgh, PA F. Pleasants Co. Deppmann Co. Mulcahy Co. TLA, Inc. Hydro-Flo Products, Inc. Miami Bernard J. Sandberg Co. McNevin Co. Spaulding Avenue Chicago, Illinois tel: fax: www.
Printed in U. Technical stuff for power plant engineers By Dilawar Handa.
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