CA1072050A - Electrocoating bath temperature control - Google Patents
Electrocoating bath temperature controlInfo
- Publication number
- CA1072050A CA1072050A CA277,911A CA277911A CA1072050A CA 1072050 A CA1072050 A CA 1072050A CA 277911 A CA277911 A CA 277911A CA 1072050 A CA1072050 A CA 1072050A
- Authority
- CA
- Canada
- Prior art keywords
- heat exchange
- temperature
- bath
- exchange fluid
- electrocoating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to an improved method and system for controlling the temperature of an electro-coating bath wherein the bath is passed through a heat exchanger wherein the heat exchange surfaces in contact with the bath do not exceed 180°F.
This invention relates to an improved method and system for controlling the temperature of an electro-coating bath wherein the bath is passed through a heat exchanger wherein the heat exchange surfaces in contact with the bath do not exceed 180°F.
Description
11)~Y2~50 l This invention generally relates to an improved method o~ electrodepositing a water-soluble or water-dispersible coating resin onto a conductive surface, and9 in particular, is directed to a method and system ~or :
controlling the temperature of the electrocoating bath within the temperature range of about 90-135Fo The electrodeposition of water-based coatings commonly termed electrocoating is a widely used process which has many advantages over other methods o-~ coating 7 `.''~
such as spraylng, dipping, rolling and the likea The advantages o~ electrocoating are well known~ The process deposits a ~ilm o~ uniform thickness on essentially any :
conductive sur~ace, eve~ those which have sharp points and edges. Electrocoated film when applied is relatively ~.:
water ~ree and thus will not run or drip when taken out o~
the bathO Because little or no organic solvents are used in the resin system, the process is essentially ~umeless and requires no extensive *ume collection and incineration equipmenta This latter point is important in view of the 20 increased concern over environmental pollutiona An addi- ~ ;
tional advantage is the :~act that a second or top coat can be applied over the electrocoated ~ilm without curing the ~ -electrocoated film and then both coats can be cured in one baking operationD By limiting the necessity o~ two baking 25 ~urnaces, the cost of a ~wo-coa~ process can be consider~
. ably reduced ~ lectrocoating process generally comprises im-mersing the article to be coated into the electrocoating bath, usually as the anode, and passing a current throug~ :
; 30
controlling the temperature of the electrocoating bath within the temperature range of about 90-135Fo The electrodeposition of water-based coatings commonly termed electrocoating is a widely used process which has many advantages over other methods o-~ coating 7 `.''~
such as spraylng, dipping, rolling and the likea The advantages o~ electrocoating are well known~ The process deposits a ~ilm o~ uniform thickness on essentially any :
conductive sur~ace, eve~ those which have sharp points and edges. Electrocoated film when applied is relatively ~.:
water ~ree and thus will not run or drip when taken out o~
the bathO Because little or no organic solvents are used in the resin system, the process is essentially ~umeless and requires no extensive *ume collection and incineration equipmenta This latter point is important in view of the 20 increased concern over environmental pollutiona An addi- ~ ;
tional advantage is the :~act that a second or top coat can be applied over the electrocoated ~ilm without curing the ~ -electrocoated film and then both coats can be cured in one baking operationD By limiting the necessity o~ two baking 25 ~urnaces, the cost of a ~wo-coa~ process can be consider~
. ably reduced ~ lectrocoating process generally comprises im-mersing the article to be coated into the electrocoating bath, usually as the anode, and passing a current throug~ :
; 30
-2-: , .
~or~oso 1 the bath between the article and electrodeO The process usually is self-arresting in that as the thickness oi the - coating increases, the resistance -thereo- also increases, thereby limiting the amount oi coating which is deposited~
During electrocoating, a considerable quantity o~ :-heat is generated in the bath which must be removed or dis-sipated in some manner so as to maintain the bath tempera~
ture at the desired levelO Most commercial electrocoating installations, which maintain the electrocoating bath tem- ~ ~:
10 perature at around ambient temperature, have extensive ~ ;
re~rigeration equipment to maintain the bath temperature .-at around ambient levels~ A higher temperature bath, eOgD, :
90 to about 135, would be more desirable because thc higher temperature bath would allow -for the use of tap water as a ;~
coolant and moreover provide a more ef~icient electrocoating process du0 to the acceleration o~ electroendosmosis at the higher temperatures~ Notwiths-tanding the advantages of a high -temperature bath, most commercial facili-ties employ a room temperature bath to eliminate the problems associated :`
with preheating the bath prior to the start o~ electrocoat~
ingO It was ~ound that heating elements tended to be quickly coated with a cured or semicured layer o~ resln which rendered the heating element more or less ine~ective and ~requently uselessO It would be conceivable to utilize the heat generated during electrocoating to bring the bath ~ temperature up to the desired level, bu~ all o~ the material ;~ electrocoated during this period would have to be scrapped due to its low qualityJ In electrocoating processes wherein - there is a large bath volume-to-workpiece area ratio~ pre- ~ .
heating the bath in -this manner to the higher le~el would
~or~oso 1 the bath between the article and electrodeO The process usually is self-arresting in that as the thickness oi the - coating increases, the resistance -thereo- also increases, thereby limiting the amount oi coating which is deposited~
During electrocoating, a considerable quantity o~ :-heat is generated in the bath which must be removed or dis-sipated in some manner so as to maintain the bath tempera~
ture at the desired levelO Most commercial electrocoating installations, which maintain the electrocoating bath tem- ~ ~:
10 perature at around ambient temperature, have extensive ~ ;
re~rigeration equipment to maintain the bath temperature .-at around ambient levels~ A higher temperature bath, eOgD, :
90 to about 135, would be more desirable because thc higher temperature bath would allow -for the use of tap water as a ;~
coolant and moreover provide a more ef~icient electrocoating process du0 to the acceleration o~ electroendosmosis at the higher temperatures~ Notwiths-tanding the advantages of a high -temperature bath, most commercial facili-ties employ a room temperature bath to eliminate the problems associated :`
with preheating the bath prior to the start o~ electrocoat~
ingO It was ~ound that heating elements tended to be quickly coated with a cured or semicured layer o~ resln which rendered the heating element more or less ine~ective and ~requently uselessO It would be conceivable to utilize the heat generated during electrocoating to bring the bath ~ temperature up to the desired level, bu~ all o~ the material ;~ electrocoated during this period would have to be scrapped due to its low qualityJ In electrocoating processes wherein - there is a large bath volume-to-workpiece area ratio~ pre- ~ .
heating the bath in -this manner to the higher le~el would
-3~
,' `' ~ 5 1 be prohibitive due to the excessive amounts of scrap which :~
would be generated~ Against this background, the present invention was developedO
Figure 1 is a schematic drawing of the overall bath treatment facilities, and Figure 2 is a schematic draw-ing of the temperature control system of the present inventionO
The present invention is direct~d to an improved method of controlling the temperature of a. high temperature electrocoating bath~ and, in particular, to heating an electrocoating bath to an operating temperature between about 90 and 135F prior to start-up~
In accordance with the present invention, the electrocoating bath is passed through an i~direct heat exchanger wherein the temperature of the heat exchange surfaces does not exceed 180F, pre~erably less than 150Fo In one embodiment of the present in~ention~ the heating and cooling systems are integrated to pro~ide one operative . :~
systemO It is preferred to use tap water as the heat ex-change ~luid because it is readily available and because it facilitates the integration of the heating and cooling systemsO The temperature o~ the cooling medium should be below about 90Fo Reference is made to Figure 1 which is a schematic diagram o~ the electrocoating tank and the bath treating facilities~ Electrocoating bath is continuously withdrawn ~ :
from the electrocoating tank and transferred to a storage or make-up tankO Bath from the storage or ma~e-up tank is withdrawn and pumped through a heat exchanger to control ;~
the temperature at the desired operative le~els and then to , :
1OtY'~SO
1 an ultrafilter wherein low molecular weight materials are removed fr~m the bath. The permeate or ultra~iltrate ~rom the ultrafilter, which contains low molecular weight ma-terials, such as organic amines and the like, can be dis-carded to the drain as shown or further treated to recoverthe low molecular weight species therein~ Th~ treated bath can be transferred back to the holding and ma~e-up tank, returned directly to the electrocoating tank or proportioned -therebetweenO ;;
In Figure 2, the features of the present invention ;~
are shown in greater detailO As shown in this figure, tap water (or other cool hea~ exchange ~uid) is introduced into line 10 which is split into conduits 11 and 12 containing valves 13 and 14, respectivelyO These conduits rejoin into a conduit containing a check valve 16 which is in fluid com-munication with conduits 17 and 180 Conduit 17 directs the tap water directly to ~he heat exchanger 200 Conduit 18 ;~
directs the tap water to pump 21 which is in fluid communi-cation with heater 220 The heated heat exchange fluid , passes through conduit 23 which contains temperature sens~
ing eleme~t 24 which is utilized to sense the temperature of the heat exchange fluid and thereby control the tempera-ture at the desired level. Conduit 23 is in fluid communi-cation with conduit 16 so as to direct heat exchange fluid to the heat exchanger 20~ ~Ieat exchange fluid exits the heat exchanger 20 through conduit 25 which can direct the expended heat exchange medium to the drain or return to the ;~
pump 21 through conduit 26 depending upon whether val~e 27 is open or closed~ The electrocoating bath enters the heat ~-30 exchanger 20 at inlet 30, passes in an indirect heat '~.
_5_ 1~7'~0 1 exchan~e relationship with the heat exchange medium and then out o~ the heat exchanger through outlet 31 where the temperature of the electrocoating bath is sensed by tempera ture sensor 32~ The indirect heat exchange device can be of any convenient design, such as a conventional shell and tube-type heat exchangerO
For improved bath temperature control, it is pre- `-ferred in the present invention to automatically control ~.
the heating and cooling system. ~his can be conveniently 10 accomplished by utilizing the temperature sensed by sensor ~.
32 for control purposesD Thus, ~or heating when the tem-perature of the bath is below a desired level, valves 13 ~::
and 27 will be automatically closed, valve 14 automatically opened and pump 21 and heater 22 automatically activated, all in response to the temperature sensed by sensor 32.
For cooling when the bath temperature is above a desired level, valves 13 and 27 would automatically be opened, valve 14 automatically closed and pump 21 and heater 22 automatically deactivated in response to the temperature 20 signal~ The system shown in Figure 2 was designed to : ::
employ an automatically adjustable valve 13 to provide closer control o~ the bath temperature by providing a con-tinuous operation rather than an on-o-Pf type cooling system~
The valves 14 and 27 can be conventional open-closed, solonoid-operated valvesO With the use o~ an automatically adjustable valve 13, the temperature sensor 32 ge.nerally will provide two signals, one an on-o~ or open-closed signal to operate valves 14 and 27, pump 21 and heater 22 and a second signal which adjusts valve 13 so as to provide . :
the coolant flow necessary to control the bath temperature . -6- .
':', ,:
,, lV~ZQ50 1 at the desired levelO This latter 5ignal, in ac~ordance ~:
with conventional practice, will be compared by suitable means with a signal representing the desired bath signal -~-and ~y control means responsive to the error signal gener~
ated by the comparator control position of valve 13. Pre-ferably, sensor 32 comprises two sensing elements, one which generates the on-off signal or open-closed signal and -the other the signal for controlling valve 13. A suitable on-off, open-closed sensing element is Honeywell Tempera- -~
ture Controller Model T654A1602. Adjustable valve 13 can ~ . , , be a Fulton Silphon valve manufactured by the Fulton Valve ,:
CorporationO The solonoid valves are of a conventional natureO
During the start-up of elec$rocoating operations, 15 the bath temperature will be below the desired level for :
high temperature operation. In that instance, the tempera-ture sensor 32 will direct a suitable signal to close valve 1~, open valve 14, and actuate the pump 21 and the heater 220 The tap water or other heat exchange fluid will then pass through valve 1~, pump 21, and heater 22, where it is heated and then passed to the heat exchanger 20. The tem-perature of the heated fluid is controlled so that the heat exchange surfaces in the heat exchanger 20 do not exceed . 180Fg preferably less than 150F o The check valve located in line 15 precludes back flow of water into the supply system. Little or no fluid is introduced into the system except that needed for make-up~ Upon discharging from the heat exchanger, the expended heated fluid then returns to the pump 21 through conduit 26 As soon as the temperature of the electrocoating ~ -7- :
; :' ,.~ , ~ 50 1 bath reaches the desired operating level, the electrocoat ing process is startedO The bath immediately begins to .
heat up due to the normal heat i~put of the electrocoating process. When the temperature reaches a predetermined level, the temperature sensor 32 generates a second signal which activates the coolîng system. Val~e 14 closes and valve 13 opens. Pump 21 and heater 22 are shut o~ Valve 27 to the drain is openedO The cool tap water or other cool heat exchange medium then passes directly to the heat `;
exchanger through conduit 16 and the expended heat exchange fluid is discarded through conduit 25 and valve 27 a The volume of tap water or other heat exchange medium through valve 13 is automatically controlled by suitable means in ~.
accordance with the temperature sensed by temperature :
15 sensor 32. ~.
If for some reason the elec$rocoating process is shut down, e~gO, for repairs and the like, the system will :
~- automatically switch off the cooling system when the tem-; perature of the bath is reduced below a predetermined mini-mum le~el and the heating system will be acti.vated~ The heating system thereby maintains the temperature of the bath at the desired levels during the dowmtime so that no ; delays occur during start-up and most importantly no sig-ni~icant amount o~ scrap is generated because efficient electrocoating begins immediately~
The following is given as an example of the present in~ention utilizing the system shown in Figure 2u ~ Prior to start-up of the electrocoating operations~ the : bath is at ambient temperature and tap water at about 60F
is directed to a heater wherein the temperature is raised :~`: ~.
.: . .
~ -8- :
,; :
."' . ~ .
2C\S~
1 to about 110F. The heated water is passed through a shell and tube-typc heat exchanger and in an indirect heat ex-change relationship with the electrocoating bath to heat the bathO When the temperature sensor determines that the ~ 5 bath temperature is at an operating level at about 108F, ; the heating system is deactivated and the electrocoating process is started~ Shortly therea~ter, due to the heat ;~
generated by the electrocoating process 9 the bath tempera~
, ture rises~ When the temperature rises 1F above the oper-ating level, the cooling system is activated and tap water is directed to the heat exchanger ~or cooling purposes.
Close control o~ the electrocoating bath tempera- -ture is essential because the rates of the various electro coating phenomena, such as electrophoretic deposition, 15 electrocoagulation, electroendosmosis and the like, are all temperature dependent. Small changes in temperature can generate signi~icant changes in the electrocoating process.
It is pre~erred to maintain ba-th temperature variation dur~
ing operations to less than 2F ~rom a desired temperature.
It is obvious that various modifications and ~' improvements can be made to the presant in~ention without departing ~rom the spir~t o~ the present invention and the scope o~ the appended claims.
, "
~; ~
:' .
; 30 _g_ :
:` ~
: , ., ~
,' `' ~ 5 1 be prohibitive due to the excessive amounts of scrap which :~
would be generated~ Against this background, the present invention was developedO
Figure 1 is a schematic drawing of the overall bath treatment facilities, and Figure 2 is a schematic draw-ing of the temperature control system of the present inventionO
The present invention is direct~d to an improved method of controlling the temperature of a. high temperature electrocoating bath~ and, in particular, to heating an electrocoating bath to an operating temperature between about 90 and 135F prior to start-up~
In accordance with the present invention, the electrocoating bath is passed through an i~direct heat exchanger wherein the temperature of the heat exchange surfaces does not exceed 180F, pre~erably less than 150Fo In one embodiment of the present in~ention~ the heating and cooling systems are integrated to pro~ide one operative . :~
systemO It is preferred to use tap water as the heat ex-change ~luid because it is readily available and because it facilitates the integration of the heating and cooling systemsO The temperature o~ the cooling medium should be below about 90Fo Reference is made to Figure 1 which is a schematic diagram o~ the electrocoating tank and the bath treating facilities~ Electrocoating bath is continuously withdrawn ~ :
from the electrocoating tank and transferred to a storage or make-up tankO Bath from the storage or ma~e-up tank is withdrawn and pumped through a heat exchanger to control ;~
the temperature at the desired operative le~els and then to , :
1OtY'~SO
1 an ultrafilter wherein low molecular weight materials are removed fr~m the bath. The permeate or ultra~iltrate ~rom the ultrafilter, which contains low molecular weight ma-terials, such as organic amines and the like, can be dis-carded to the drain as shown or further treated to recoverthe low molecular weight species therein~ Th~ treated bath can be transferred back to the holding and ma~e-up tank, returned directly to the electrocoating tank or proportioned -therebetweenO ;;
In Figure 2, the features of the present invention ;~
are shown in greater detailO As shown in this figure, tap water (or other cool hea~ exchange ~uid) is introduced into line 10 which is split into conduits 11 and 12 containing valves 13 and 14, respectivelyO These conduits rejoin into a conduit containing a check valve 16 which is in fluid com-munication with conduits 17 and 180 Conduit 17 directs the tap water directly to ~he heat exchanger 200 Conduit 18 ;~
directs the tap water to pump 21 which is in fluid communi-cation with heater 220 The heated heat exchange fluid , passes through conduit 23 which contains temperature sens~
ing eleme~t 24 which is utilized to sense the temperature of the heat exchange fluid and thereby control the tempera-ture at the desired level. Conduit 23 is in fluid communi-cation with conduit 16 so as to direct heat exchange fluid to the heat exchanger 20~ ~Ieat exchange fluid exits the heat exchanger 20 through conduit 25 which can direct the expended heat exchange medium to the drain or return to the ;~
pump 21 through conduit 26 depending upon whether val~e 27 is open or closed~ The electrocoating bath enters the heat ~-30 exchanger 20 at inlet 30, passes in an indirect heat '~.
_5_ 1~7'~0 1 exchan~e relationship with the heat exchange medium and then out o~ the heat exchanger through outlet 31 where the temperature of the electrocoating bath is sensed by tempera ture sensor 32~ The indirect heat exchange device can be of any convenient design, such as a conventional shell and tube-type heat exchangerO
For improved bath temperature control, it is pre- `-ferred in the present invention to automatically control ~.
the heating and cooling system. ~his can be conveniently 10 accomplished by utilizing the temperature sensed by sensor ~.
32 for control purposesD Thus, ~or heating when the tem-perature of the bath is below a desired level, valves 13 ~::
and 27 will be automatically closed, valve 14 automatically opened and pump 21 and heater 22 automatically activated, all in response to the temperature sensed by sensor 32.
For cooling when the bath temperature is above a desired level, valves 13 and 27 would automatically be opened, valve 14 automatically closed and pump 21 and heater 22 automatically deactivated in response to the temperature 20 signal~ The system shown in Figure 2 was designed to : ::
employ an automatically adjustable valve 13 to provide closer control o~ the bath temperature by providing a con-tinuous operation rather than an on-o-Pf type cooling system~
The valves 14 and 27 can be conventional open-closed, solonoid-operated valvesO With the use o~ an automatically adjustable valve 13, the temperature sensor 32 ge.nerally will provide two signals, one an on-o~ or open-closed signal to operate valves 14 and 27, pump 21 and heater 22 and a second signal which adjusts valve 13 so as to provide . :
the coolant flow necessary to control the bath temperature . -6- .
':', ,:
,, lV~ZQ50 1 at the desired levelO This latter 5ignal, in ac~ordance ~:
with conventional practice, will be compared by suitable means with a signal representing the desired bath signal -~-and ~y control means responsive to the error signal gener~
ated by the comparator control position of valve 13. Pre-ferably, sensor 32 comprises two sensing elements, one which generates the on-off signal or open-closed signal and -the other the signal for controlling valve 13. A suitable on-off, open-closed sensing element is Honeywell Tempera- -~
ture Controller Model T654A1602. Adjustable valve 13 can ~ . , , be a Fulton Silphon valve manufactured by the Fulton Valve ,:
CorporationO The solonoid valves are of a conventional natureO
During the start-up of elec$rocoating operations, 15 the bath temperature will be below the desired level for :
high temperature operation. In that instance, the tempera-ture sensor 32 will direct a suitable signal to close valve 1~, open valve 14, and actuate the pump 21 and the heater 220 The tap water or other heat exchange fluid will then pass through valve 1~, pump 21, and heater 22, where it is heated and then passed to the heat exchanger 20. The tem-perature of the heated fluid is controlled so that the heat exchange surfaces in the heat exchanger 20 do not exceed . 180Fg preferably less than 150F o The check valve located in line 15 precludes back flow of water into the supply system. Little or no fluid is introduced into the system except that needed for make-up~ Upon discharging from the heat exchanger, the expended heated fluid then returns to the pump 21 through conduit 26 As soon as the temperature of the electrocoating ~ -7- :
; :' ,.~ , ~ 50 1 bath reaches the desired operating level, the electrocoat ing process is startedO The bath immediately begins to .
heat up due to the normal heat i~put of the electrocoating process. When the temperature reaches a predetermined level, the temperature sensor 32 generates a second signal which activates the coolîng system. Val~e 14 closes and valve 13 opens. Pump 21 and heater 22 are shut o~ Valve 27 to the drain is openedO The cool tap water or other cool heat exchange medium then passes directly to the heat `;
exchanger through conduit 16 and the expended heat exchange fluid is discarded through conduit 25 and valve 27 a The volume of tap water or other heat exchange medium through valve 13 is automatically controlled by suitable means in ~.
accordance with the temperature sensed by temperature :
15 sensor 32. ~.
If for some reason the elec$rocoating process is shut down, e~gO, for repairs and the like, the system will :
~- automatically switch off the cooling system when the tem-; perature of the bath is reduced below a predetermined mini-mum le~el and the heating system will be acti.vated~ The heating system thereby maintains the temperature of the bath at the desired levels during the dowmtime so that no ; delays occur during start-up and most importantly no sig-ni~icant amount o~ scrap is generated because efficient electrocoating begins immediately~
The following is given as an example of the present in~ention utilizing the system shown in Figure 2u ~ Prior to start-up of the electrocoating operations~ the : bath is at ambient temperature and tap water at about 60F
is directed to a heater wherein the temperature is raised :~`: ~.
.: . .
~ -8- :
,; :
."' . ~ .
2C\S~
1 to about 110F. The heated water is passed through a shell and tube-typc heat exchanger and in an indirect heat ex-change relationship with the electrocoating bath to heat the bathO When the temperature sensor determines that the ~ 5 bath temperature is at an operating level at about 108F, ; the heating system is deactivated and the electrocoating process is started~ Shortly therea~ter, due to the heat ;~
generated by the electrocoating process 9 the bath tempera~
, ture rises~ When the temperature rises 1F above the oper-ating level, the cooling system is activated and tap water is directed to the heat exchanger ~or cooling purposes.
Close control o~ the electrocoating bath tempera- -ture is essential because the rates of the various electro coating phenomena, such as electrophoretic deposition, 15 electrocoagulation, electroendosmosis and the like, are all temperature dependent. Small changes in temperature can generate signi~icant changes in the electrocoating process.
It is pre~erred to maintain ba-th temperature variation dur~
ing operations to less than 2F ~rom a desired temperature.
It is obvious that various modifications and ~' improvements can be made to the presant in~ention without departing ~rom the spir~t o~ the present invention and the scope o~ the appended claims.
, "
~; ~
:' .
; 30 _g_ :
:` ~
: , ., ~
Claims (7)
1. In the process of electrocoating resinous ma-terial onto a metal substrate wherein the temperature of the electrocoating bath containing said resinous material is maintained within the range from 90°F to about 135°F, the improvement in the process of controlling the temperature of the bath comprising (a) withdrawing electrocoating bath from a tank containing same;
(b) sensing the temperature of the electrocoating bath;
(c) passing withdrawn bath through a heat exchange device in an indirect heat exchange relationship with heat exchange fluid flowing therethrough, with the temperature of the heat exchange fluid being controlled so that the temperature of the surfaces of the heat exchange device in contact with the electrocoating bath does not exceed 150°F;
(d) supplying all of the heat exchange fluid from a single source thereof, wherein the temperature of the heat exchange fluid from said source is less than 90°F;
(e) controlling the temperature of the bath at a level within the range from 90°F to about 135°F in the following manner:
(i) if the sensed bath temperature exceeds a predetermined maximum temperature between 90°
and about 135°F, directing cool heat exchange fluid to the heat exchange device to reduce the temperature of the bath to at least the pre-determined maximum temperature, with at least part of the said cool heat exchange fluid com-ing directly from said source;
(ii) if the sensed bath temperature is less than a predetermined minimum temperature between 90° and about 135°F, passing heat ex-change fluid through a heating device to raise the temperature thereof and then directing the heated heat exchange fluid to the heat exchange device to raise the temperature of the bath to at least the predetermined minimum temperature.
(b) sensing the temperature of the electrocoating bath;
(c) passing withdrawn bath through a heat exchange device in an indirect heat exchange relationship with heat exchange fluid flowing therethrough, with the temperature of the heat exchange fluid being controlled so that the temperature of the surfaces of the heat exchange device in contact with the electrocoating bath does not exceed 150°F;
(d) supplying all of the heat exchange fluid from a single source thereof, wherein the temperature of the heat exchange fluid from said source is less than 90°F;
(e) controlling the temperature of the bath at a level within the range from 90°F to about 135°F in the following manner:
(i) if the sensed bath temperature exceeds a predetermined maximum temperature between 90°
and about 135°F, directing cool heat exchange fluid to the heat exchange device to reduce the temperature of the bath to at least the pre-determined maximum temperature, with at least part of the said cool heat exchange fluid com-ing directly from said source;
(ii) if the sensed bath temperature is less than a predetermined minimum temperature between 90° and about 135°F, passing heat ex-change fluid through a heating device to raise the temperature thereof and then directing the heated heat exchange fluid to the heat exchange device to raise the temperature of the bath to at least the predetermined minimum temperature.
2. The method of claim 1 wherein at least part of the heat exchange fluid which is passed through the heating device comprises heat exchange fluid discharged from the heat exchange device.
3. In a system for electrocoating resinous ma-terial onto a metal surface, wherein the temperature of electrocoating bath containing resinous material is main-tained at a level within the range from 90°F to about 135°F, the improvement comprising (a) a heat exchange fluid source;
(b) a heat exchange device having heat exchange surfaces adapted to contact the electro-coating bath and to maintain an indirect heat exchange relationship between heat exchange fluid and electrocoating bath;
(c) means in fluid communication with said source and said heat exchange device to heat the heat exchange fluid and adapted to control the temperature of the heat exchange fluid so that the heat exchange surfaces of the heat exchange device in contact with the electrocoating bath do not exceed 180°F;
(d) means to sense the temperature of the electrocoating bath and generate a signal when the temperature sensed is below a predetermined level;
and:
(e) means responsive to said signal to direct heat exchange fluid from said source through the heating means wherein the heat exchange fluid is heated and then to the heat exchange device wherein the bath is heated.
(b) a heat exchange device having heat exchange surfaces adapted to contact the electro-coating bath and to maintain an indirect heat exchange relationship between heat exchange fluid and electrocoating bath;
(c) means in fluid communication with said source and said heat exchange device to heat the heat exchange fluid and adapted to control the temperature of the heat exchange fluid so that the heat exchange surfaces of the heat exchange device in contact with the electrocoating bath do not exceed 180°F;
(d) means to sense the temperature of the electrocoating bath and generate a signal when the temperature sensed is below a predetermined level;
and:
(e) means responsive to said signal to direct heat exchange fluid from said source through the heating means wherein the heat exchange fluid is heated and then to the heat exchange device wherein the bath is heated.
4. The system of claim 3 including (a) means to sense the temperature of the electrocoating bath and generate a signal when the temperature sensed exceeds a predetermined level;
and (b) means responsive to said signal to dir-ect the heat exchange fluid from the source directly to the heat exchange device wherein the bath is cooled.
and (b) means responsive to said signal to dir-ect the heat exchange fluid from the source directly to the heat exchange device wherein the bath is cooled.
5. The system of claim 3 wherein the heat exchange fluid source provides water at a temperature less than 90°F.
6. The system of claim 4 including a second means responsive to said signal to control the volume of heat exchange fluid directed from the source directly to the heat exchange device so as to control the temperature of the bath to within 2°F of a predetermined level.
7. The system of claim 3 including means to recirculate expended heat exchange fluid discharged from the heat exchange device back to said heating means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA277,911A CA1072050A (en) | 1977-05-06 | 1977-05-06 | Electrocoating bath temperature control |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA277,911A CA1072050A (en) | 1977-05-06 | 1977-05-06 | Electrocoating bath temperature control |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1072050A true CA1072050A (en) | 1980-02-19 |
Family
ID=4108607
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA277,911A Expired CA1072050A (en) | 1977-05-06 | 1977-05-06 | Electrocoating bath temperature control |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1072050A (en) |
-
1977
- 1977-05-06 CA CA277,911A patent/CA1072050A/en not_active Expired
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