Soot blowing apparatus

A soot blowing system for cleaning banks or clusters of heat exchange tubes or the like contained in a furnace or flue housing comprising a movable platform carrying an apertured lance which is inserted sequentially into spaced openings in the wall of the furnace or flue housing so as to pass in proximity to the banks of the heat exchange tubes; the lance is directly connected to a flexible steam supply hose and is incrementally rotatable over a pre-determined area within the furnace or flue housing to steam clean the tubes in that area; upon withdrawal from the housing the platform and lance move to the next aperture in the housing where it is inserted and again incrementally rotated to clean that area of the tube bank.

BACKGROUND OF THE INVENTION 
This invention relates to the art involving cleaning devices which are used 
to remove deposits of soot, dirt and debris from heat exchange tube 
surfaces and particularly on the surfaces of tubes used in connection with 
furnaces and boilers. To remove such deposits, it has long been customary 
to use air or steam under high pressure to literally blow the deposits off 
the tubes and thus prevent the deposits from becoming a layer of 
insulation which would reduce the exchange or transfer of heat by the 
tubes and adversely affect their function. Such means are usually referred 
to in the trade as soot blowers. 
The heat exchange tubes are customarily provided in banks or clusters. The 
hot combustion gases from the boiler or furnace pass over these banks of 
tubes which absorb the heat therefrom and thus heat the contents of each 
tube in the usual heat exchange function. In so doing, the exterior of the 
tubes collect dust or soot emitting from the furnace or boiler which makes 
the tubes less effective as heat exchange units unless thoroughly cleansed 
from time to time. 
The problems involved in the deposit of dust or soot on or in heat exchange 
tubes have long been realized, and many attempts have been made to 
overcome these problems. Among these attempts are the structures set forth 
in the following U.S. Pat. Nos.: 1,677,383; 1,688,482; 1,760,589; 
1,811,346; 1,896,565; 2,001,881; 2,112,896; 2,406,687; 2,696,016; 
2,710,225; 3,049,738; 3,068,507; 3,138,819; 3,115,016; 3,184,774; 
3,191,211; 3,436,786; 3,448,477; 3,794,051. 
While, as aforesaid, many attempts have been suggested to overcome the 
problems, two structures are for the most part in commercial use. 
One of the commercially used soot blowers utilizes a tube, called a lance, 
which extends across the width of the tube bank. The lance is provided 
with apertures or nozzles extending thereover at pre-determined spaced 
distances. High pressure steam is introduced into the lance and this steam 
emits through the various nozzles in order to enable jets of steam to pass 
therethrough and blow away the soot, dust and other debris. This device is 
usually provided with motor driven means disposed exteriorly of the 
furnace whereby the lance is continuously rotated through 360.degree. 
continuing cycles thus attempting to blow the soot and debris away in a 
complete circle around the lance. This type cannot accommodate a flexible 
hose feed for the steam supply as it would become overly twisted and block 
the passage. Thus it was necessary to use seals between a rigid steam 
supply pipe and the rotating lance, and it also has been found that the 
soot blowing range of any one lance is very limited because the steam 
velocity decreases rapidly as it leaves each nozzle. Thus soot blowers of 
this type must be mounted in proximity to each other along the length of 
the bank of tubes which is a relatively costly arrangement. 
In addition, such soot blowers have other disadvantages. Among them is the 
arrangement whereby the lances remain interiorly of the housing carrying 
the banks of tubes when not in use. Thus the lances are exposed to the 
condition or atmosphere of the hot corrosive flue gases at all times which 
causes the lance to deteriorate and necessitates eventual replacement of 
the lances or use of an expensive corrosion resistant alloy. Furthermore, 
the lances, as aforesaid, are multi-nozzled or apertured. In fact, 
customarily, nozzles are provided every 8 to 12 inches along the length of 
the lance in order to assure its effectiveness. As this system is used in 
furnaces of varying widths including extremely wide furnaces, many nozzles 
are required. It has been found that in order to be effective, each jet 
nozzle requires a flow rate of thousands of pounds an hour to provide the 
high momentum needed to effectively clean the banks of tubes. Obviously, 
with the number of steam nozzles required per lance, it is necessary to 
install an expensive steam generator because of the high simultaneous 
capacity required. Since sootblowing is carried out for a small fraction 
of the time that the boiler or furnace operates, the expensive steam 
generating capacity is idle most of the time. 
Another soot blower in current commercial use is one which also constantly 
rotates through 360.degree. continuous cycles but is insertable and 
retractable. Such a soot blower is described in U.S. Pat. No. 2,696,016. 
In this device, a "lance" is also utilized but of a slightly different 
construction. This lance has two opposed nozzles at its terminus and 
rotates as it is advanced into the tube. The lance continuously rotates a 
full 360.degree. in continuing cycles throughout the entire width of the 
tube bank. Furthermore, a reversing mechanism is provided to retract the 
lance after it reaches the end of its forward travel and it is brought 
back to a position outside of the housing containing the tube bank. 
Because there are only two jet nozzles, the steam generation capacity 
required is much smaller and there is a consequent saving in capital 
investment. In addition, the stored position of the lance outside of the 
furnace prevents it from becoming subject to the destructive effects of 
the hot corrosive flue gases. 
However, the aforesaid construction has specific disadvantages. For 
example, a separate lance is required at predetermined spaced intervals 
along the length of the tube bank because the effective area which may be 
cleaned by the soot blower is quite limited extending only to about a 3 or 
4 foot radius. In addition, there is a solid steam supply tube which is 
stationary and the lance rotates therearound. As a result, costly seals 
must also be provided in the construction between the rotating lance and 
its interior supply tube. As a result of the high pressure required in the 
steam supply, it has been found that no matter how effective the original 
seal, deterioration and steam leaks regularly develop and constant 
maintenance and expensive replacement is required. 
The soot blower of the present invention overcomes the problems described 
above with regard to these commercial soot blowers presently provided and 
presents a unit which is extremely efficient while requiring only a 
minimum amount of parts and little maintenance while nonetheless 
effectively cleaning the surfaces of the tube banks in an extremely 
efficient manner. 
SUMMARY OF THE INVENTION 
The present invention provides a soot blowing system. Conceptually, it can 
utilize only one soot blowing lance which is carried by a carriage to 
transport it from station to station which immediately eliminates the need 
for multiple soot blowing lances. 
Furthermore, the present invention contemplates the utilization of a step 
by step sequential cleansing operation in which there is no 360.degree. 
continuous rotation of the lance around the supply tube and consequently 
there is no need for seals. In addition, the lance of the soot blower of 
the present invention uses only two nozzles and thus requires only a low 
steam generating capacity for cleansing purposes with the consequent large 
saving in steam generation capacity. 
The present invention specifically provides a lance which is directly 
attached to a relatively elongate flexible hose. In one version the lance 
does not rotate or turn in any way while traveling into and through and 
steam cleaning an area of the aforesaid tube bank. In this version at the 
terminus of its original path of travel, the lance is turned about between 
50.degree. to 20.degree. and is then gradually withdrawn from the tube 
bank housing while continuing to emit steam for cleansing purposes during 
the withdrawal operation. The flexible tube to which the lance is attached 
is also twisted between 5.degree. to 20.degree. in the step. At the end of 
the withdrawal sequence, which stops short of complete withdrawal from the 
housing, an area covered by an arc of between 5.degree. to 20.degree. on 
the tube banks above and below the lance have been cleansed. At this 
point, the lance is rotated or twisted an additional 50.degree. to 
20.degree. in which position it re-enters the tube bank housing and steam 
continues to be emitted through the nozzles for cleansing in this 
additional area. At the terminus of this cycle of entry, the lance makes 
an additional 5.degree. to 20.degree. rotation or twist and withdrawn with 
steam emitting therefrom for cleansing thoroughly this additional arcuate 
area. As a result, these sequential operations at differing angles of 
steam emission ultimately provides a twisting up to about 180.degree. by 
the lance which because of the presence of the two divergent emitting 
nozzles cleanses the entire area in the tube bank above and below the 
lance. 
After the final pass of the lance to clean the tubes has been accomplished 
in a particular area, the lance is completely removed from the tube bank 
housing and the steam is shut off. The carriage arrangement utilized in 
the present invention moves the soot blower lance to the next station. 
While the lance and attached hose may be returned to its original 
straightened position before entering the next station, it is preferable 
that the lance and the hose remain in the "twisted" position upon entering 
the next port and then be rotated in a reversed direction or untwisted in 
sequential increments of about 5.degree. to 20.degree. as aforesaid in a 
direction reverse to the previous direction so that the flexible tube to 
which it is attached retraces its previous path of twisting cycle and 
finishes the second cycle in a straightened condition as it was at the 
starting position of the previous cycle. 
While two nozzles are described in connection with this and the later 
version of the invention, it is obvious that a greater number may be 
utilized within the purview of the inventive concept or only one nozzle 
rotating sequentially an increment of about 360.degree. may be used. 
In another version of this invention, the lance enters the housing 
containing the tube banks but does not travel immediately to the other end 
of the tube bank. Instead, the lance enters the tube bank a relatively 
short pre-determined distance equivalent to the distance of the arc of 
5.degree. to 20.degree. set forth above with its nozzles on a 
substantially horizontal plane. The travel of the lance is stopped and the 
lance is turned or twisted over an arc up to 180.degree.. The apertures or 
nozzles have thus emitted steam over a sector of the banks above and below 
the lance. The lance is then moved forward another pre-determined 
increment also equivalent to the distance of the aforesaid arc of from 
5.degree. to 20.degree. and turned or twisted in a direction reverse to 
the direction of the previous turn or twist above described. As the steam 
is emitted through the apertures or nozzles, the next segment of tube 
banks above and below the lance is also cleaned. This step by step 
sequential procedure continues over the entire width of the bank tube area 
whereupon the lance is withdrawn and moved with the carriage to the next 
cleaning station. The lance is then reinserted into the housing and the 
above described sequential operation continues. 
Thus the cleaning system of the present invention utilizes sequential 
stepped operations of slightly different form to accomplish the highly 
desirable result. The relatively rigid lance utilizes a flexible hose 
attached thereto by a clamp, or held by any other attaching means for the 
supply of steam because the approximate 180.degree. twist required for the 
cycle in either version of the invention can be accommodated by the 
flexible hose without the requirement of any seal. This twist in no way 
blocks the passage in the hose. These aforedescribed cyclical steps are 
continued in each version throughout the entire tube bank area and thus 
cleansing of the entire tube bank is accomplished. 
The invention therefore takes advantage of the flexibility of the elongate 
feed hose to which the lance is attached and which can without rupturing 
and blocking, turn or twist through the 180.degree. position of rotation 
without deleterious effects and thereafter be returned sequentially in 
either version of the invention to its original position to effectively 
provide a total cleansing operation. The invention eliminates the 
necessity for multiple lances, continuous rotation, excessive steam 
generation, seals or any of the other disadvantages of previously utilized 
soot blowers. 
The soot blower of the present invention accomplishes many other objects 
and provides distinct advantages which are described in detail in the 
accompanying specification.

DETAILED DESCRIPTION OF THE INVENTION 
As illustrated in the drawings, there is shown a furnace or boiler area 10 
though which hot flue or exhaust gases flow. This area is within the 
furnace or it can be located in an area adjacent thereto for heat exchange 
purposes as is well-known in the art. Tubes 11 are disposed within the 
housing 10 which comprises the furnace or flue area and are distributed in 
banks or clusters 12. Tubes 11 become covered with soot and other debris 
as a result of combustion in the furnace when in use. This soot and debris 
provide an undesirable insulating cover over the area and detracts from 
the conventional heat exchange function of the tubes. The system and 
apparatus of the invention provides a novel, relatively inexpensive and 
unique means for cleansing the tubes to remove the deposited soot and 
other debris and permit the tubes to perform their function. 
In accordance with the invention, a movable cleansing system 13 is disposed 
adjacent to the housing 10 and is shielded therefrom by wall 14 extending 
between the compartment 15 carrying the system and the housing 10. The 
system 13 comprises a track 16 which carries a movable platform 17 on 
wheels 18 riding on track 16. Secured to the upper part of the platform is 
a lance 19 which travels with the platform along the track 16 to 
predetermined desired positions. These stop positions are located in each 
instance adjacent to one of the entry ports 20, 20a, etc., in the side 
wall 14 of the furnace or flue housing 10. The ports make accessible the 
clusters of tubes 11 disposed within the housing. When the movable 
cleansing system is located adjacent to the port 20, and the platform 17 
comes to a stop, the lance 19 is automatically thrust through the port 20 
into the interior of the furnace or flue housing 10. 
In the method of operation of the cleaning system of the present invention 
shown in FIGS. 3-6, the lance 19 is inserted into the housing through the 
port in the direction of the arrow shown in FIG. 3. The lance is 
substantially hollow and, as hereinafter set forth, is at predetermined 
times filled with steam under pressure from the flexible steam hose 21. 
In accordance with the present invention, the lance 19 is directly 
connected to the flexible steam hose 21 by means of a clamp 22. While a 
clamp has been illustrated, it is to be understood that any suitable means 
for affixing the steam hose to the lance is within the purview of this 
disclosure. There is no extraneous or separate seal required between the 
lance 19 and the flexible hose 21 and the hose twists as the lance 
rotates. The lance 19 is preferably provided near its terminal end with 
two diagonally opposed apertures 23 and 24. The steam hose 21 is provided 
with a condensation hose ending in steam trap 25 to prevent condensation 
from entering the furnace which could cause damage to the walls 10. 
As the lance is inserted into the housing 10, steam under pressure is 
admitted to the lance and is emitted from the lance through the diagonal 
apertures 23 and 24. This steam cleanses the arcuate area of tubes in the 
path of its emission. The arcuate area of the tube banks 12 which are 
cleansed may amount to that area which is covered by an arc of from almost 
5.degree. to 20.degree. from each emitting point 23 and 24. 
In accordance with the invention, when the lance approximately reaches the 
side of the housing 10 opposite the port 20, it is automatically twisted 
approximately 5.degree. to 20.degree. in the direction of the arrow shown 
in FIG. 4 while steam is still constantly being emitted from the apertures 
23 and 24. The lance is then in position for withdrawal movement and 
automatically begins the return while cleansing the area of the tube bank 
12 adjacent the heretofore serviced area described with relation to the 
first pass. This cleansing operation affects an additional area covered by 
an arc between 5.degree. to 20.degree. during this second pass of the 
operation. The withdrawal movement of the lance 19 is automatically 
terminated prior to the time when the emitting apertures 23 and 24 reach 
port 20. At this position, the lance is again automatically stopped and 
rotated an additional 5.degree. to 10.degree. in the same direction as 
that of the first two passes. Forward movement of the lance in the 
direction of the arrow shown in FIG. 3 is again resumed thereby cleaning 
an additional area in the tube bank covered by an arc of from 5.degree. to 
20.degree. from each aperture 23 and 24 by steam which is continuously 
emitted through these apertures. 
The sequential action of forward movement, arcuate rotation, withdrawal 
movement, arcuate rotation and forward movement, etc. continues throughout 
the pattern diagramatically set forth in FIG. 5 until each of the emitting 
apertures 23 and 24 shall have rotated approximately 180.degree. while the 
lance remains within the housing adjacent port 20. Thus, a complete 
360.degree. area is cleansed by the emitting steam in this thrust of the 
lance 19 from the cleansing system 13. As a consequence, the steam hose 
supplying the steam to the lance will also be twisted only 180.degree. 
during this operation which, in view of the length of the hose, has no 
deleterious or adverse effect. 
At the terminus of the aforedescribed sequence of operations, the lance is 
totally withdrawn from the port hole 20 at which time the supply of steam 
to the lance is automatically discontinued. The platform or carriage 17 is 
then automatically moved along the track to the next adjacent port hole 
20a where an automatic stop terminates movement of the carriage 17. In 
this second position the lance is automatically reinserted into this next 
adjacent port hole 20a and the cleansing cycle is continued. However, in 
accordance with the invention, the operative sequence does not follow the 
diagramatic arrangement set forth in FIG. 5 but instead provides an 
oppositely turning sequence. The 5.degree. to 20.degree. increments of 
turn in rotation of the lance are in a direction opposite to the direction 
of rotation set forth with regard to the first thrust and thus opposite to 
the direction of the arrows in FIG. 5. As the insertion, turning, 
withdrawal, turning, insertion sequence continues, the steam hose 21 
attached to the lance for its steam supply is untwisted and returns to its 
normal straight position. As a consequence, in accordance with the present 
invention, the hose need never be twisted over an arc comprising more than 
approximately 180.degree. while nevertheless accomplishing all of the 
desired cleansing operations over the entire area of the tube bank in 
sequential passes entering each port hole in turn. 
When the lance is totally retracted, it is withdrawn into the soot blower 
carrier and the hinged door 26 closes to cover the port 20 and prevent the 
flow of gases in and out of the furnace in flue area 10. 
The aforesaid arrangement completely prevents any blockage of the passage 
of steam which might result from any overtwisting of the supply hose and 
as a result of the incremental arcuate rotation. There is little, if any, 
need for replacement of parts and the system can operate efficiently over 
indefinite periods of time. The steam generation capacity is small since 
only two apertures are used. Obviously only one lance would be required to 
service the entire length of even a huge tube cluster housing area. In 
addition, there are no extraneous seals necessary because there is no 
360.degree. continuous rotation of the lance around the supply tube. In 
fact, the 180.degree. twist can be easily accomplished with little stress 
or strain on the steam hose supply. Thus, a novel and efficient method and 
system has been provided to overcome the long standing problem of 
efficiently and economically cleansing heat exchange tubes in the path of 
hot flue gases. It is understood that as a result of the above concept, 
the steam emitting sequence of the lance can be so timed that steam is 
emitted only when heat exchange tubes are in the path of the aperture from 
the lance. Thus, in the illustration shown in FIG. 3, no steam need be 
emitted from the lance when the apertures 23 and 24 are on a substantially 
horizontal plane as opposed to those vertical planes in which the tube 
banks 12 would be in the path of the emitted steam. 
Furthermore, in accordance with the invention, the lance need not be 
removed from port 20 and inserted in port 20a before it is rotated to 
untwist the steam hose 21. In other words, either prior to or during its 
withdrawal from port 21, the lance may be automatically rotated in a 
direction opposite to the incremental rotation shown in FIG. 5 so that the 
hose is untwisted and straightened before it enters port 20a. Upon entry 
into port 20a, it will thereupon be understood that the lance can again 
rotate in the sequential steps shown in FIG. 5 or alternatively rotate 
sequentially in the opposite direction. 
While a double apertured lance has been shown, it is understood that the 
lance may have a single aperture and be rotated over 360.degree. in the 
5.degree. to 20.degree. increments as such rotation will not twist the 
elongate steam hose 21 in such fashion as to prevent it from appropriately 
functioning. The sequential steps described above would be repeated. 
However, the rotation of the lance would pass through 360.degree. with the 
steam being emitted when necessary to clean the tube banks in the path of 
the lance aperture or whenever desired. 
A modified form of the inventive concept is illustrated in FIGS. 6-7. FIG. 
6 shows the lance structure inserted into the port hole 20 in the wall 14 
of the housing 10. The lance is carried by the same type platform 17 
riding on tracks and has the same steam hose arrangement as the structure 
illustrated in FIGS. 1 and 2. In the modified form, however, the lance 19 
is inserted into the housing 10 to a lesser extent in the first portion of 
the thrust than the extent of the insertion in FIGS. 3-5. As illustrated 
in FIG. 7 the thrust extends from the "start" position to position 30. The 
lance at this point is then rotated approximately a full 180.degree. to 
position 31 shown in FIG. 7 which cleanses the tube banks in a 360.degree. 
area in the vicinity of the lance itself because the two emitting 
apertures 23 and 24 each rotates 180.degree.. The lance is then 
automatically inserted further into the housing to position 32 in FIG. 7 
where it is rotated 180.degree. in the direction of the sequential arrow 
which is reverse to that of the rotation between position 30 and 31. When 
the lance has made this rotation to position 33, it is again moved forward 
into the housing to position 34 and rotated in the same direction as the 
rotation accomplished between positions 30 and 31, as is indicated by the 
arrow. 
The aforesaid sequential operation continues through the entire path of the 
lance insertion into the housing as diagramatically illustrated in FIG. 7 
until it reaches approximately the wall of the housing opposite the port 
20. At this position, the lance makes its final 180.degree. arcuate sweep 
and then is automatically withdrawn from the housing whereupon the steam 
feed is automatically stopped. Thus, a complete cleansing operation takes 
place within the housing in the area covered by this thrust of the lance 
through the complete 360.degree. in proximity to the lance as it 
progresses inwardly. 
The lance is then carried forward on the carriage 17 to port 20a were it is 
again inserted into the housing and the sequence described hereinbefore 
and shown in the diagrammatic illustration in FIG. 7 is repeated. The 
sequential operation continues until the entire bank of tubes is cleansed 
from the debris and soot and maintained in functioning and operational 
condition. As a consequence, in this operation the steam hose is not 
twisted by any increment exceeding approximately 180.degree.. Further, 
there is little stress or strain and all of the benefits described with 
reference to the form of the invention shown in FIGS. 3-5 are accomplished 
and obtained by this modified form. 
It is to be noted that increments of travel of the lance into the furnace 
area 10 between points 31-32, 33-34, etc., are substantially equivalent of 
the distance covered by the 5.degree. to 20.degree. incremental rotation 
of the lance as shown in FIGS. 4 and 5. This accomplishes a total 
cleansing of the tube area in a highly efficient manner. It is also to be 
understood that steam may be emitted from the lance only at such times 
when tube banks 11 are in the path of the apertures 23 and 24 in order 
that energy be conserved. 
FIG. 8 is a simplified diagramatic disclosure of the electrical 
arrangemennt including the motors and switching structure utilized in 
connection with the invention herein described in FIGS. 1-5. Three motors 
may be involved as follows: 
Motor I--for the travel of the lance in and out of the tube bank; and 
Motor II--for the sequential rotation of the lance; and 
Motor III--for transporting the carriage along the tracks outside of the 
furnace housing. 
All three motors are essentially standard Direct Current motors so that 
when the polarity of the current to the motor is reversed, the motor turns 
in the opposite direction. Also, since the motors have a gear drive, only 
a fraction of a horsepower each is required for the necessary functions. 
Each motor is supplied current through a number of switches. These switches 
are multiple pole, double throw. They are capable of performing one or 
both of the following two functions, depending on the way they are wired: 
1. Reverse the polarity of the current to a motor. 
2. Interrupt the flow of current to a motor until another switch in the 
circuit is actuated. This is similar to the multi-switch home light 
circuit where any one switch when actuated changes whether current is 
flowing to the light bulb or not. 
The cycle set forth with relation to the illustrated form of the invention 
in FIGS. 1-5 is started by actuating switch A (interrupt) which is mounted 
anywhere convenient to the operating personnel. This supplies current to 
the carriage travel Motor III. The carriage travels until it reaches the 
first sootblowing station, a position where switch B (interrupt) engages a 
strikerplate. Switch B interrupts the current to Motor III and starts the 
current to Motor I propelling the lance into the furnace. After the head 
of the lance is in the furnace, switch C (interrupt) is actuated which 
opens the solenoid valve admitting the blowing medium to the lance. Just 
immediately before the end of the inward stroke, switch D (interrupt) is 
actuated which will start the rotation Motor II. Just after that, switch E 
(reverse) is actuated which reverses the lance travel. Then switch F 
(interrupt) is actuated which stops the rotational travel of Motor II. The 
lance then is withdrawn from the furnace and properly positioned stops 
rapidly actuate switches D, E and F so that the lance is traveling inward 
again after a slight rotation. After completing an in and out cycle 
covering almost 180.degree. the lance travels outward from the furnace. 
There are no stops located in the path of the outgoing lance to activate 
any of the switches which had previously been used to reverse and rotate 
the lance. As the lance is withdrawn, switch C is activated, stopping 
steam flow. Once the lance is withdrawn from the furnace, a striker plate 
on the lance actuates switch G thereby causing motor I, which was 
operating to move the lance 19 outward from the furnace area 10, to stop 
and starting motor III. The carriage 17 is thereupon moved until it 
reaches the next sootblowing position where a striker plate has been 
positioned to reactuate switch B which stops motor III and starts motor I. 
The lance continues its outward movement and immediately thereafter 
engages a striker plate to actuate switch E and reverse the lance travel 
so that it begins to move through the port 20a and inwardly of the furnace 
10. That striker plate also actuates switch H which reverses the polarity 
of the current to motor II. In this manner, when the lance reaches the end 
of its inward movement it will rotate sequentially in a direction opposite 
the direction of the prior rotational sequences. The aforedescribed series 
of sequential operations continues until all the soot-blower stations 
behind each port hole has been serviced. When this is accomplished, the 
carriage travel motor III will begin to carry the carriage past the last 
sootblower station whereupon it contacts a striker plate which engages 
switch I which serves to simultaneously interrupt the current and reverse 
the polarity thereof in preparation for the next cycle wherein the 
carriage will traverse the furnace in the direction opposite to the 
afore-described direction of travel. 
It is to be understood that the wiring schematics are merely illustrative 
of one means for carrying out the basic concepts of the present invention 
which provide a novel and unique system and method for overcoming problems 
of great concern in connection with the use of energy saving devices such 
as heat exchangers without requiring the expenditure of enormous energy 
for this purpose. Also, the result is accomplished without necessitating 
the use of expensive and complicated machinery. In effect, a continuous 
maintenance of the energy saving devices is accomplished efficiently by 
the incremental and toatal cleansing described in this specification. 
It is to be understood, however, that this description is merely to effect 
a complete understanding of the invention and the inventive concept and is 
in no way intended to limit the scope of the invention as defined in the 
appended claim.