What You Should Know About Flash Tanks
by J. E. TROCOLLI • Sarco Co., Inc. • Allentown, PA (Actual Specifying Engineer/71)
High-pressure steam systems
require flash tanks -
here is a guide to determining sizes
Condensate temperatures in high-pressure steam systems
generally are only slightly less than the saturated
temperature of the steam. When hot condensates are discharged
into lower-pressure areas, condensate temperature
immediately drops to the saturated temperature of
the low-pressure area. As the result of the drop in temperature,
heat released evaporates a portion of the condensate,
generating flash steam.
To return condensate to the boiler or to discharge it to
the sewer, it is necessary to separate flash steam from
the condensate. This is accomplished by discharging condensate
through steam traps into a vented tank, referred
to as a flash tank.
Flash steam produced in the flash tank may be vented
to the atmosphere or piped to a low-pressure main. Condensate
remaining may then be returned to the boiler or
discharged to drain.
Tanks must be large enough to ensure dryness of the
released steam and to avoid carryover by the steam of
water in droplet form. When using horizontal flash tanks,
the required area is found by multiplying the diameter of
the tank by its length. This measures the tank's capacity
to handle condensate. Table 1 illustrates the required area
for each 1,000 lb. of condensate/hour with varying steam
and flash pressures.
How big a tank?
Problem:
An absorption machine condenses 12,000
lb. of steam/hr. Assuming the flash tank is vented to the
atmosphere, determine the size of the flash tank required
with a steam pressure of 12 PSIG.
Solution:
Enter table 1 at 12 PSIG steam pressure,
moving horizontally to 0 PSIG. Find .75, which is the number
of square feet required for each 1,000 lb. of condensate.
Since 12,000 lb. of steam are generated, it may be
determined that by multiplying 12 x .75, 9 sq. ft. of surface
will be required, or that the diameter of the tank in
feet times its length in feet must equal 9. Thus, a tank 2
ft. by 4.5 ft. may be used.
Problem:
A dryer operating at 100 PSIG condenses
18,000 lb. of steam/hr. The flash tank is to discharge its
flash into a 5-PSIG heating main. Determine the size of
the flash tank required.
Solution:
Again, using table 1, enter at 100 PSIG
initial pressure. Move horizontally to the 5-PSIG column
and find 1.92.
Then:
18 x 1.92 = 34.6 sq. ft.
A flash tank 4 ft. by 9 ft. will be satisfactory for the
application.
Sizing vent lines
If flash steam is to be discharged to the atmosphere,
a properly sized vent line must be provided. To determine
the proper size, first find the area of the flash tank,
using the method described above.
Problem:
Determine the size of the vent line using
table 2. If, as in the first problem, tank size is 2 ft. by 4.5
ft. (9 sq. ft.), refer again to table 2, where 9 sq. ft. falls on
7.4-to-12 line. For this range, a 2-in. vent line would be
satisfactory.
Problem:
Determine the size of the vent line if the
flash tank size is 4 ft. by 9 ft. or 36 sq. ft. In table 2, 36 is
in the 27-to-36 line, and, in this case, a 3
1/2 in. vent would
be needed.
Figure 1 shows a typical flash-tank piping diagram
in which the flash is discharged to the atmosphere.
If it is desired to utilize the flash steam by discharging
it into a low-pressure main, refer to figure 2. In this
instance, it will be necessary to properly size the line
connecting the flash tank to the low-pressure main.
Using table 3, determine the percent of flash. Multiply
this percentage by the condensate load in lb./hr. to
determine the number of pounds of steam that are flashed.
Determine what steam velocity will be acceptable in the
line. If a low noise level is desired, a relatively low velocity
must be selected - 4,000 to 6,000 FPM.
Where noise is not a factor, a velocity of 12,000 FPM
or higher may be used. After velocity has been determined,
the required pipe size can be found in table 4.
Problem:
10,000 lb./hr. of condensate is discharged
into a flash tank from a 125-PSI steam system. Flash
steam is to be piped into a 10-PSIG low-pressure heating
main. Determine the size pipe required for connecting
the flash tank to the steam main.
Enter table 3 at 125-PSI initial pressure. Move horizontally
to the 10-PSIG column and find 12.2 percent
flash. Then the amount of flash steam/hr. is found this
way:
10,000 x 12.2 percent = 1,220 lb./hr.
SECTION ENG - PAGE 0100
FLASH TANKS
TABLE 1 FLASH TANK IN SQ. FT. = DIAMETER x LENGTH OF HORIZONTAL
TANK FOR 1,000 LB. CONDENSATE PER HOUR BEING DISCHARGED
TABLE 2 VENT LINE SIZE TABLE 3 PERCENT FLASH
FOR HORIZONTAL
FLASH TANKS
½"
FLASH TANKS
TABLE 4 STEAM VELOCITY CHART
FORM FLASH TANKS
Revised 4/04 SHIPCO® IS A REGISTERED TRADEMARK OF SHIPPENSBURG PUMP CO., INC.
SHIPPENSBURG PUMP COMPANY, INC.,
P.O. BOX 279, SHIPPENSBURG, PA 17257 • PHONE 717-532-7321 • FAX 717-532-7704 • WWW.SHIPCOPUMPS.COM
PRINTED IN THE U.S.A. • BEIDEL PRINTING HOUSE, INC., 717-532-5063 PERMISSION TO REPRINT BY SPIRAX SARCO INC.
Since low noise level is important, a velocity in the
4,000 to 6,000 FPM range must be selected. Enter table
4 at 1,220 lb./hr., moving horizontally to a flash-steam
pressure of 10 PSIG. Then move up to 4,000 to 6,000
FPM velocity. Here, the chart shows that a 3-in. pipe will
handle about 6,000 FPM, or a 4-in. line would handle
about 3,500 FPM.
When vent lines cannot be extended to discharge
outside the buildings, it is important that the condensate
be cooled below the dewpoint to prevent the exhaust
from condensing and wetting walls, machinery, floors and
so on.
Estimating temperature
Since the dewpoint depends on several factors, including
relative humidity and temperature (which are variable),
the temperature to which the condensate must be
cooled should be estimated for individual cases.
The following is the recommended procedure:
Calculate the size of the flash tank in the method
described above:
Estimate the dewpoint, assuming unfavorable conditions,
and, when making the estimate, take ventilation into
account - it is a factor in determining relative humidity:
Once the dewpoint is known, estimate the quantity
of cooling water that will be required and finally:
Determine the pipe size and size of temperature
regulator valve required. A self-contained regulator with
a normally closed valve to open when the temperature
rises is recommended. All such controls have an ample
range over and under the calibration point so that setting
may be adjusted after installation.
Problem:
Calculate the quantity of cooling water required
to cool condensate in a flash tank vented to an
enclosed space, assuming the following data:
Steam pressure is 100 PSIG;
Condensate is entering the flash tank at 1,550 lb./hr.
at 335°F;
Ambient temperature of the space into which vent
discharges is 75°F; and
Cold water temperature is 50°F.
Assuming that ventilation at the above temperature
will be sufficient to have not more than 70 percent relative
humidity, the dewpoint will be 64.5°F (determined
from psychrometric chart).
To allow 1°F for safety, condensate should be cooled
from 338°F to 63.5°F. When the installation is completed,
further adjustment can be made by resetting the regulator.
The heat to be extracted from the condensate is equal
to:
1,500 lb./hr. x (338-63.5)°F = 410,000 BTUH
The quantity of cooling water required:
410,000 BTUH
(63.5 -50)°F
= 30,500 lb./hr.
or 3,670 GPH = 61 GPM
A 1.5-in. pipe to supply the water and a 1.25-in. temperature
regulator are recommended for this application.
Flash tanks separate flash steam from the condensate
by venting the flash steam to the atmosphere or
piping it to a low-pressure main, while returning the remaining
condensate to the boiler or discharging it to the
drain. If flash steam is discharged to the atmosphere, a
flash tank and a properly sized vent line must be determined;
if discharged to low-pressure mains it is necessary
to calculate the correctly sized line connecting the
flash tank to the low-pressure main. Also, the proper temperature
for cooling the condensate must be determined
for projects in which vent lines cannot be extended to
discharge outside the buildings.
Different situations require individual solutions to determine
the correctly sized flash tank, connecting pipe
and cooling temperature needed, but the calculation examples
offered here provide the means to determine the
necessary installations and accessories required.
Figure 1
A typical flash tank piping
diagram discharging to atmosphere.
NOTE: Omit trap if condensate is
discharged into vented pump receiver.
Figure 2
A typical flash tank piping
diagram with flash discharging to lowpressure
steam system.
Figure 3
This diagram depicts a
combination flash tank installation with
subcooling condensate.
VENT
PRESSURE
RELIEF VALVE
VENT IF
DESIRED
TO LOW
PRESSURE MAIN
HIGH PRESSURE
FROM
CONDENSATE
HIGH PRESSURE
SYSTEM
FLASH TANK
STRAINER
FLOAT AND
THERMOSTATIC
TRAP
FIN TUBE
COOLING LEG
REQUIRED
TO LOW PRESSURE
RETURN LINE OR
DRAIN
VENT TO
ATMOSPHERE
HIGH PRESSURE
FROM
CONDENSATE
HIGH PRESSURE
SYSTEM
FLASH TANK
STRAINER
FLOAT AND
THERMOSTATIC
TRAP
FIN TUBE
COOLING LEG
REQUIRED
TO DRAIN
CONDENSATE
FROM HIGH
PRESSURE
STEAM SYSTEM
TEMPERATURE
REGULATOR
STRAINER
COLD WATER
SUPPLY
VENT TO
T ATMOSPHERE
WATER LEVEL
COIL
DRAIN
TO SEWER
FLASH TANKS
No
by drain the sludge of secondary tank from time to time....and one may also maintain mlss by the addition of jaggery ...
A calorifier is a sealed tank, which heats water indirectly. Usually in the form of a heated coil which is immersed in the water. Commonly known as a hot water tank. A chlorifier is a water tank in which the water is heated via an external source.
It can be at any pressure less than the main steam pressure. I've operated steam systems with condensate tanks at widely varying pressures. The pressure a condensate tank, (which condenses some steam, but typically takes returns from steam traps) is wholly dependent on the system is installed in. Some heating system condensate tanks are designed to handle no more than 30 psig (minimum design requirement) yet take condensate at 1 or 2 psi from the steam traps. Other high pressure production lines operating at 50 - 100 psig could discharge to a tank at 50 - 100 psi, though the actual pressure would be reduced by the length of pipe transferring it to the tank. And the highest pressure I've operated a condensate system at was 600 psig, the steam system drew the steam for process from an extraction stage on the turbine at nominally 600 psi, though at low loads it was typically a much lower pressure.
It's self-evident if you understand the basic terminology. A "pilot plant" is sort of like a smaller-scale mockup of a factory. It's used to prove that a particular design will work and produce the desired substance, without going to the expense of building a full-scale production facility. A "fermenter" is, basically, a big tank in which bacteria or fungi "ferment" some feedstock and produce the desired substance. What this substance is varies. A pilot plant fermenter, then, would be a small ("small" is relative here, it could be several hundred gallons) tank in which fermentation of some kind takes place.
Define flash tank
The Basic tank course is 3 months.
The basic principle is the bigger the better. This is because the more water there is, the more stable it will be. I would not consider using anything under 100 gallons as a Marine tank. There are experts who can set up successfull 15 gallon marine environments that I have been very impressed by.
You plug it in and the tank starts operating so you can shoot bad men
it makes your tank use less gas
Yes, water can cause a misfire, which will cause the check engine light to flash.
The speed of water flowing through the tank in a given distance.
In thew tank right by the filler hole , just look in tank with a flash light.
Unban tank 2006
Electrical equipments (circuit breakers, current transformers etc.) can be categorized, based on their construction, in to two broad types 1. Live tank type 2. Dead tank type As the name suggests, a Live tank equipment's operating system (interruptor chamber in case of CB and tank in case of CT/PT) are live parts during operating and are placed at a height governed by the statutory norms of the country of use. Whereas in case of Dead tank equipments, the operating system is placed in a chamber which is ground during service and hence no statutory norms regarding height of chamber are applicable.
5 - 60 psi
The basic tank for a '95 Camry holds 18.5 Gal/70 L of fuel.