the armstrong inverted bucket steam trap

the armstrong inverted bucket steam trap
AIR SPACE
The design, operation and flex i b i l i t y o f t h e
inverted bucket steam trap has made it the
dominant trap in the marketpla C e .
Since it
was introduced by Armstrong in 1911, the
inverted bucket trap has saved millions of
dol lars in industrial fuel bills because
of its ability to respond to the characteristics of such a wide variety of heatexchange applications.
AIR
VENT
j
\
BODY
INLET TUBE
The free floating linkage, hemispherical
v a l v e , and square-edged orifice provide
line contact in any position. The valve
is free to close in many positions because the lever is secured by a linkage
which employs no fixed pivot points or
valve guides to wear out.
Long life is
further ensured by using a seat material
slightly softer than that of the valve.
This difference in hardness allows the
combination to be self-lapping, guaranteeing a tight seal over a long period
of time without any adjustment.
Armstrong IB Valve Seating/Ball Valve
Line Contact
Single Seat
IB
As an Armstrong inverted bucket trap wears,
The Armits tight seal actually improves!
strong inverted bucket trap must seal only
The ball valve and seat of the
one orifice.
Armstrong trap provide essentially line
contact - - r e s u l t i n g in a tighter seal because the entire closing force is concentrated on one narrow sealing ring.
Infinite Number of Center Lines
and Seating Circumferences
Valve Wear Characteristics
Armstrong IB Ball
Valve continues to
seat itself deeper
continuing to
provide a tight seal,
1
OPERATION AT PRESSURES CLOSE TO MAXIMUM
KEY
a
Steam
a Air
Condensate
m flashing Condensate
Steam trap is installed in drain line bet w e e n steam heated unit and condensate reAt this point, bucket is
turn header.
down and valve is wide open. As initial
flood of condensate enters the trap and
flows under bottom edge of bucket, it
fills trap body and completely submerges
Condensate then discharges
bucket.
through wide open valve to return header.
On start-up, condensate fills the trap body
and the weight of the bucket holds the valve
fully open, providing full-capacity drainage
of large start-up loads.
Steam also enters trap under bottom of
bucket, where it rises and collects at
Bucket then
top, impart i ng buoyancy.
rises and lifts valve toward its seat
until valve is snapped tightly shut by
the pressure differential.
Air and
carbon dioxide cont inual ly pass through
bucket vent and collect at top of trap.
Any steam passing through vent is condensed by radiation from trap. Noncondensibles are vented promptly at
steam temperature.
Steam flow through the bucket vent is
limited by the vent size and low differential pressure created between the
height of the steam beneath the bucket,
and the level of the water seal above
it.
All steam passing through the vent
is condensed, and discharged as a liquid.
This prevents live steam loss and the
single-phase flow lengthens the service
life of the discharge orifice.
VALVE
When entering condensate brings the
condensate level slightly above the
neutral line the bucket exerts a slight
pull on the lever. The valve does not
open, however, until the condensate
level rises to the opening line for
the existing pressure differential
between the steam and the condensate
return header.
Condensate, at steam temperature, enters
the trap continuously, even when the valve is
This continuous drainage keeps the
closed.
lines and system ahead of the trap free of
eliminating the hazards of water
condensate,
hammer, freezing and corrosion, and the loss
of heat exchange efficiency which can result
from flooded lines and heat exchange surfaces.
When the condensate level reaches opening
line, the weight of the bucket, times leverage,
exceeds the pressure holding valve to its
Bucket then sinks and opens trap valve.
seat.
Any accumulated air is discharged first followed by condensate. Discharge continues
until more steam floats bucket at which time
cycle begins to repeat.
With the orifice located at the top, dirt,
scale and other matter settling to the bottom of the trap will not plug the discharge
The intermittent discharge of an IB
port.
trap creates a self-scrubbing effect at the
bottom of the trap. Dirt particles, smaller
than the orifice diameter are flushed from
the system.
All of these advantages combine
to allow usage of the IB without a strainer
in relatively clean systems.
Because pressure inside the bucket equals
Pressure outside the bucket, sudden pressure
changes and water hammer...which tend to
crush ball floats & thermo-bellows devices...
will not damage Armstrong’s open float,
inverted bucket design.
Low
..
“‘I
Force
required
to open Valve.
iO0 PStG
- 3 0 . 4 02
320 PSI0 - 24.32 02
240 PSI0
- 18.24 02
180 PSI0 - 1 2 . 1 6 02
SO PSI0 - 6.08 02
Pressure
Continuously
Modulating
Mode
of
Operation
Today’s energy consciousness suggests the use of inverted bucket traps in all applications to take advantage of their unique combination of energy efIn order to minimize the
ficiency and long life.
number of different trap and orifice size combinations
used in plants with multiple pressure levels in steam
main drain and steam tracing applications, the orifice
size for the highest pressure is applied to all presWhen orifices suited for high pressures
sure ranges.
are used at low pressures, the “normal” mode of operation will not be an intermittent discharge. The discharge will appear to be continuous.
A S/64" orifice in an 1811 suitable for operation at
a maximum pressure differential of 400 psi will reA high
quire a force of 30.4 oz. to open the valve.
1 eve1 of water under the bucket is required to provide sufficient force. The same or if ice used at 80
psig requires only 6.08 oz. to open the valve. Only
l/5 as much force is required so only l/5 as much
bucket length must be filled with water. A much
lower water level is adequate to provide the necessary force.
The weight of the bucket times the lever arm ratio
supplies the valve opening force.
At 80 psi different ial, an 0.32 oz. pull by the bucket is required to open the valve. This amount of water
must be removed from under the bucket with each
discharge for intermittent operation.
I f 200#/hr.
or 0.9 oz/sec of condensate load is present, the
cycle rate of the trap must be 3cps. Obviously,
a 3.29 oz. bucket submerged in water cannot move
this rapidly so the bucket merely positions the
valve to provide the continuously modulating flow.
Low
Loads
Continuously
Modulating
Mode
of
Operation
The same operating mode is exhibited in inverted
bucket traps which are used in extremely low
condensate load applications even if the orifice
is closely matched to the pressure differential.
When the valve in an inverted bucket trap is closed
the bucket weight, FB is low and the forces attempting to hold the valve closed exceed those
trying to open it.
As the condensate level under
the bucket rises, the net buoyancy of the bucket
decreases until the opening forces balance and
begin to exceed the closing forces. At this
point the valve begins to crack open, a small
flow of condensate starts through the cracked
valve and water flows from under the bucket.
+ FB
P,*oL2>P2*oL2
+fB
P, A, L2 = P2 A0 L, + FB
L,-CLOSED
L, - BALANCED
P2
pl
P2A0
*L
I.
I
t-L,- t PlAo
P, AoL2 > PpAo
L2 + Fg L, - Df’EN
If the condensate flow into the trap is large
enough relative to the instantaneous flow rate
out through the cracked open valve, the water
level under the bucket rises fast enough to
reduce bucket boayancy sufficiently so that
the opening force grows to overcome the closing
force permitting the valve to be pulled fully
open.
If the condensate flow into the trap is small
enough relative to the instantaneous flow rate
out through the cracked open valve, water level
under the bucket does not increase rapidly enough
to reduce bucket buoyancy sufficiently and the
closing force snaps the valve closed. T h i s
partially opening-instantly closing mode of
operation then continues at a relatively rapid
cycle rate which gives the appearance of continuous flow.
Regardless of the mode, it is the ever-present
w a t e r s e a l , rather than the valve, which prevents
live steam loss.
Once the condensate level in the trap seals
t h e b o t t o m o f t h e b u c k e t w h e n i t i s in the
E position, the inverted-bucket is “primed”
and cannot pass live steam to the valve.
The water level outside the bucket rises
until it forms a water seal above the bucket.
The inverted bucket trap will retain its
prime throughout the operating cycle unless
subjected to a pressure drop so sudden and
severe as to let the prime re-evaporate.
Since this boiling-away takes several minutes,
determined by the amount of pressure change,
the reduced pressure must go unaltered for an
extended period of time.
Loss of prime can
be identified by a violent rattling of the
bucket inside the trap.
Regaining prime can
be accomplished, even on light loads, simply
by closing a valve ahead of the trap, permitting the accumulation of condensate, then
slowly opening the valve, allowing the condensate to enter the trap.
It must be stressed that all traps, regardl e s s o f t y p e , use a small amount of steam
through heat radiation from the body surface.
F o r e v e r y 1 0 0 0 B.T.U.‘s r a d i a t e d ,
approximately one pound of steam is condensed.
This is not to be confused with
live steam loss.
I
H e a t L o s s = (f) A, x bt
= (f) A, x (Tl - T2)
A,= S u r f a c e A r e a o f t r a p
Tl= Temperature of condensate
Tz= Ambient Temperature
ARMSTRONG CAST IRON INVERTED BUCKET
TRAPS FOR GENERAL SERVICE
for pressures to 250 psig . . . capacities to 20,000 Ibs/hr
No 800
No.880
No 814
Side inlet, side outlet traps. Cap
and mechanism can be removed without
disturbing pipe connections.
No.211
No 883
Side inlet, side outlet traps with
integral strainers. This type costs less
than standard trap plus standard strainer.
Saves fittings.
Armstrong offers the inverted
bucket steam trap in a wide selection of materials, pressure ranges,
connection sizes and piping configurations to ensure the right
trap is available for each application.
No.216
Bottom inlet, top outlet traps. Cap
and mechanism can be removed without
taking body from the line.
FORGED STEEL TRAPS FOR HIGH PRESSURE SERVICE
No. 312-416 forged steel traps.
7
This allows combinations to be
chosen to give lowest steam use,
lowest maintenance, and longest
life, while minimizing purchase
and installation costs.
SERIES TEN-TEN STAINLESS STEEL TRAPS
for pressures to 450 psig . . . and capacities to 4400 Ibs/hr
SERIES EIGHTEEN TEN STAINLESS STEEL TRAPS
for pressures to 400 psig . . . and capacities to 1000 Ibs/hr
For pressures to 400 psig
capacities to 900 IbsJhr.
and
The stainless steel inverted buckets
are low cost, all-welded traps which
require no maintenance during their
long service life. The thin-wall
construction can expand to withstand
freezing and they are so lightweight
that, generally, the piping can support the weight of the trap.
Horizontal and vertical piping can be
accomodated with
side-inlet/opposite
side-outlet connections, bottom in/
top out, and top in/bottom out.
The
2011, Armstrong’s newest I.B. trap
can be piped in any configuration,
and can be renewed in-line.
Inverted bucket traps are available to suit
a l m o s t a n y p r o c e s s o r speace h e a t i n g a p p l i c a t i o n , and the fact that they can operate on
any differential pressure below maximum is
of special interest for drip and tracer and
A single
modulated pressure applications.
orifice size can be used over a wide presThis lowers inventory costs
sure range.
and lessens the likelihood that the wrong
trap will be installed.
1811 TRAP
CAPACITY
Continuous
discharge
capacities
in pounds
of hot
condensate
perhourat
pressure
differential
indicated
Armstrong has long believed that energy conservation is best served through education.
PRESSURE DIFFERENTIAL, PSI
A portion of Armstrong’s one-and-one-half
day Energy Management Serminar is devoted
to the theoretical construction of the ideal
steam trap.
Engineers,
pipefitters, maintenance supervisors, energy coordinators
and others from around the country have
volunteered their criteria for a perfect
steam trap.
While the list often grows
q u i t e l o n g , and includes such requests as
“a trap that will last forever”, the
following are some of the more common denands:
No live steam loss
Fast
drainage
Long
life
Stainless Steel Traps
Withstands freeze-up
Not affected by dirt
Continuous air venting
Low maintenance
Won’t
promote
corrosion
Won’t promote water hammer
Operates
Adaptable
over
to
wide
piping
pressure
ranges
configuration
No single trap is ideally suited to all applications.
However, f o r o v e r s e v e n t y y e a r s ,
the inverted bucket steam trap has successful1
met severe challenges in countless installations throughout the world.
Its versatility,
e f f i c i e n c y , and long life have placed the
inverted bucket at the forefront of Armstrong’
energy
conservation
campaign.
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