Integrated float and thermostatic steam trap

This invention pertains to a float and thermostatic steam trap with an improved mechanism less subject to failure than previous designs. In this design the venting and trapping functions are served by the same valve and a thermostatic actuator acts on the float or float linkage when temperature is below a predetermined value. In normal operation the float controls the discharge of condensate and the thermostatic actuator is out of contact with the float assembly and therefore is free to move. When the temperature within the trap housing drops below the predetermined value, the thermostatic actuator engages the float assembly, forces the valve opening and raises the float above the condensate level. This allows the removal of condensate and of the noncondensible gasses from the trap. This design eliminates the stressing of the thermostatic actuator by static or vibration loads at high temperatures and thereby reduces the fatigue failure of the actuator. At the same time, as the float is raised out of the water, the water level is lowered or completely drained, thereby reducing corrosion exposure during shutdown. In the embodiments wherein the housing is completely drained by the thermostatic actuator frost protection is provided and the accumulation of solids within the housing is prevented by flushing action.

BACKGROUND OF THE INVENTION 
1. FIELD OF THE INVENTION 
This invention pertains to a steam trap equipped with automatic drain and 
vent means configured to obviate the often needed external bypass, to 
eliminate shutdown corrosion, air vent fatigue, optionally, exit passage 
erosion, and to enhance the removal of sediments from the body. 
Some of the embodiments of this invention pertain to a steam trap with a 
valve arranged at the bottom of the trap body which, during normal 
operation, is controlled by a float, during shutdown and start-up is 
opened by a thermostatic device and is also controlled by said 
thermostatic device when non-condensible gases accumulate above the 
condensate level. 
2. BACKGROUND AND PRIOR ART 
Present float-type steam traps are typically provided with a thermostatic 
air vent. Therefore, most of the discussion will address such Float and 
Thermostatic (F&T) steam traps, although several of the innovations 
described herein are applicable to other types of steam traps as well. The 
problems addressed by this invention are related to corrosion, failure of 
the thermostatic vent, the handling of corrosion product accumulations, 
the need for trap bypass, and exit passage erosion, all inherent in 
present designs. Most present designs also tend to have failure modes 
which are not self-annunciating, thus go undetected for long periods. The 
hidden leakages into the common exit lines result in large losses of steam 
and in difficulties with the condensate handling equipment. 
Shut-down corrosion in float-type steam traps occurs because they are 
designed to retain condensate below a certain level in the body, and 
because sensitive parts of the device are not designed to prevent 
condensate retention during shut-down. Since most heating systems allow 
the entry of air during shut-down as the steam pressure drops below 
atmospheric pressure, the water and air together attack the sensitive 
parts. In addition, in F&T steam traps the thermostatic vent, connected to 
the exit passage and open during shut-down, allows the reentry of warm 
condensate vapors from the condensate return system. This, too, supports 
corrosive interaction with the system components. Corrosion, in addition 
to destroying surface and component integrity, also produces corrosion 
products which often interfere with the operation of system components and 
also can be the source of further corrosion. 
Thermostatic vents often fail due to vibrations transmitted to the bellows 
and to fatigue. 
It is well known that steam and condensate wash away corrosion products, 
scale and other solids, while flowing through a steam heating system. The 
larger pieces of these are screened out by strainers, usually arranged 
before steam traps. Fine rust and other minute particles, however, pass 
through the screens of the strainers and settle at the bottom of 
float-type steam traps. Accumulations of these fine particles often 
obstruct the free motion of the floats of steam traps, leading to their 
malfunction. 
Some F&T traps are installed with manual bypass valves in order to 
accelerate the removal of the air and the excessive amount of condensate 
present in the piping during start-up. These valves are supposed to be 
opened by the personnel for the duration of the start-up; however, they 
are often left open inadvertently or on purpose during the operating 
periods. They are also subject to shutdown corrosion. Both of the above 
conditions contribute to the hidden system failures. 
The air vents of most current F&T traps are connected to the exit passage. 
In some designs the exit passage is directly connected to the condensate 
return lines. Here vapors can re-enter the trap during shutdown and cause 
corrosion. In other designs an integral water seal is provided; here the 
corrosion of the flange between the internal passages can lead to hidden 
failures. 
A common damage mechanism in existing steam traps is exit passage erosion. 
This is due to the labyrinthine exit passages, designed to minimize the 
trap dimensions. The high velocity caused by the condensate flashing in 
the low pressure region results in the entrainment of water droplets. The 
fast moving droplets erode the components of the exit passage. Such 
erosion has been observed across from the float valve and around it, the 
latter due to turbulence. 
In the present art, an automatic drain valve is available to protect the 
steam traps from frost damage. Because of its limited purpose, this is 
available only with a small opening and is actuated either by thermostatic 
action or by differential pressure. Therefore it does not provide adequate 
bypass capacity for the air and condensate during start-up, and it is 
known to be prone to clogging by corrosion products and to cycling during 
low duty cycle operation when the condensate cools down. 
SUMMARY OF THE INVENTION 
The present invention overcomes the above mentioned disadvantages of the 
prior art and, in doing so, provides a steam trap of novel, improved 
design and unsurpassed simplicity. In several embodiments only one valve 
is used for normal operation, for venting and for draining. 
The shutdown corrosion is prevented as either all condensate or at least 
from corrosion sensitive parts (e.g., valve seats) of the device. The 
mechanisms inside the vessel of the trap are designed so that they do not 
retain condensate once the trap is drained. 
In one of the embodiments, air and condensate removal during start-up is 
accomplished by an automatic drain valve which is sized appropriately for 
the task, and concurrently by the float valve controlled by a thermostatic 
actuator during start-up. Practically all the non-condensible gases and 
excess condensate are removed from the body before the drain valve is 
closed. 
In the same embodiment, during normal operation, non-condensible gases are 
vented through the float valve controlled by a thermostatic actuator 
during the accumulation of such gases above the condensate level. The 
usual thermostatic valve is therefore obviated. 
In several other embodiments of this invention, only one actuator is used, 
alternately, controlled by a thermostatic valve and the float, for 
venting, for draining and for normal operation. Neither steady state nor 
vibration forces are transmitted from the float means to the thermostatic 
actuator while the float valve is controlled by the float. This isolation 
extends life of the thermostatic actuator. 
Exit passage erosion is mitigated because both the float valve and drain 
valve exit passages are straight lines ending in an optional water seal. 
The seal cushions the impact of the water droplets. 
Any accumulation of rust is removed through the drain valve at each 
shutdown and start-up when the embodiment with drain valve is used. 
Clogging of the drain valve is prevented by adequate sizing and clearance. 
No accumulation of sediments can occur in the embodiment applying only one 
valve because the semiments are constantly removed by the flow of the 
condensate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1, a body of a steam trap is denoted by 1, its cover by 2, a float 
by 3, a valve plug by 8, a valve ring by 9, a valve seat by 4, a fulcrum 
by 5, a float arm by 7, an extension arm by 17, a valve rod by 6, a pin by 
10, a thermostatic actuator by 20 and its extension by 21. 
The thermostatic actuator 20 is in the form of a bellows which expands when 
subjected to heat and contracts upon cooling. As shown in FIG. 1, the 
bellows is secured at one end to a fixed support 15 and is provided with 
an extension rod 21 projecting from its opposite end. The rod 21 passes 
through the extension arm 17 extending vertically from the arm 7. 
During operation, valve plug 8 is controlled by the float 3 pivoting around 
fulcrum 5 through float arm 7, pin connection 10 and valve rod 6 in a way 
well known in the art. As long as the space above the condensate level is 
filled with steam, thermostatic actuator 20 can freely expand without 
influencing the motion of float arm 7 so that the motion of valve plug 8 
is only controlled by the water level through the float 3. 
During shutdown and at other times during which the space above the 
condensate level is cool, the thermostatic actuator 20 contracts and lifts 
the float valve 8 regardless of how much condensate is contained in the 
trap, if any. This allows the non-condensible gases and condensate to be 
vented and drained, respectively, through the open valve passage 4 until 
such time that the space surrounding the thermostatic actuator is filled 
with steam which causes its expansion, turning over the control of the 
valve plug 8 to the float 3. 
In FIG. 2 a body of a free float steam trap is denoted by 31, its cover by 
32, its float by 33, a valve ring inserted into body 31 by 39 with orifice 
34. The float 33 rests on a boss 35 of the body when it closes the orifice 
34. A strainer 37 is arranged near an inlet shown by arrow a, and a 
thermostatic actuator 38 is mounted at the upper part of the body. 
During normal operation, the float 33 is lifted by the incoming condensate, 
the thermostatic element 38 is in its expanded position shown in solid 
line and condensate is discharged through the open orifice 34. 
At start-up and during shutdown the low temperature of the space 
surrounding the thermostat 38 causes its contraction, resulting in the 
displacement of the float in the direction of the arrow c. The float 33 
following the horizontal direction is lifted due to the reaction force 
generated at the edge 36 of the boss 35, thereby opening the orifice 34 
which vents and drains the body until steam heats up the thermostatic 
actuator. The following expansion of the thermostatic actuator allows the 
float to close the orifice 34 under the influence of its own weight after 
which the control of the valve is taken over by the float itself which is 
acting as a valve plug. Non-condensible gases possibly accumulating over 
the condensate level in the trap cool down the thermostatic actuator, its 
contraction also causing draining and venting until the upper space is 
heated up by the steam again due to which the expanding thermostatic 
actuator allows the float to close the orifice after which normal 
operation is restored. 
FIG. 2a shows an embodiment relating to a free float trap in which the 
thermostatic actuator is a bellows 40 which, during contraction, rotates 
through its extension 42, double armed lever 43, around fulcrum 41 in the 
clockwise direction and thereby displaces the float 33 in the direction of 
"C". The design and operation of this embodiment is in all other respects 
the same as that of FIG. 2. 
In FIG. 2b a valve ring 47 and orifice 46 are arranged at the bottom of the 
body 31 of a free float steam trap and a boss 44 is located at a somewhat 
higher level than in FIGS. 2 and 2a. When the thermostatic actuator 38 
contracts due to cold temperature, it moves the float in the direction of 
arrow c and rotates it in the counterclockwise direction around edge 45, 
thereby lifting it from the valve seat and opening the orifice 46. The 
design and operation of this embodiment is identical with that of FIGS. 2 
or 2a. 
FIGS. 2 and 2a show the axes of the inlet and exit openings as well as the 
direction of action of the thermostatic actuator in the same plane, namely 
the plane of the drawing. However, it is advantageously possible to 
arrange the exit opening with its axis in a plane perpendicular to the 
plane defined by the axis of the inlet opening and the direction of action 
of the thermostatic actuator. Conversely, the thermostatic actuator may be 
arranged with its direction of action in a plane perpendicular to the 
plane defined by the axes of the inlet and exit openings. 
FIG. 3 shows a partial cross-section of another embodiment of the 
invention. The salient feature of this embodiment is a thermostatic 
actuator which serves to vent the non-condensible gases during normal 
operation, and start-up as well as to drain the condensate during shutdown 
and start-up. 
During shutdown, the thermostatic actuator 20 cools down and thus lifts 
float arm 7 by link 21, attached to float valve assembly 9, opening float 
valve 8. 
During normal operation, the steam heats up the thermostatic actuator 20 
which then allows the float valve to function as known in the art. When 
air accumulating above the condensate level cools down the thermostatic 
actuator 20, the latter then opens float valve 8 via link 21 and float arm 
7. Consequently, the condensate level drops and the non-condensible gases 
escape through the float valve until the steam replacing the gases heats 
up the actuator 20 which then allows the float valve to resume its normal 
function. 
FIG. 3a is the cross-section of the same embodiment with water seals 24 and 
25 in place. 
During shutdown, the drain valve 11 is open and the vessel is empty. During 
start-up, the air and condensate are discharged through open float valve 8 
and drain valve 11. 
In order to prevent vapors re-entering into the body 1 from the connecting 
condensate line through the float valve opened by the thermostatic 
actuator 20, a condensate water seal 24 is arranged between the condensate 
discharge opening of the body 1 and the condensate line. 
When the drain valve exit opening is connected to a condensate line, a 
drain water seal 25 is arranged to prevent vapors from the connecting 
condensate line from re-entering into the body 1 through the open drain 
valve. When frost protection is needed, water seals 24 and 25 have to be 
omitted. If, for practical reasons, the recovery of the condensate 
discharged through the automatic drain valve is not desirable, the drain 
water seal 25 may be omitted. 
When the arrangement of an automatic drain valve as described before is not 
feasible within the body of the steam trap (e.g. to drain an existing 
steam trap), the automatic drain valve assembly can be installed in a 
drain line connected to the drain port of the steam trap. 
FIG. 4 represent a further embodiment of the invention wherein the primed 
(') numbers represent elements the same as previously described by the 
same unprimed numbers. The major difference herein as compared to the 
emoodiments of FIG. 1 is the use of a plug 8' extending through valve 
passage 4'. The double armed lever 7' pivots around the fulcrum 5'. The 
rising float 3' lowers the plug 8' through rod 6' opening valve passage 
4'. 
While I have illustrated and described this invention with respect to 
several embodiments, it should be understood that still other 
modifications may be made without departing from the spirit and scope of 
this invention as defined by the following claims.