NR 463.04(3)(c)1.1. An owner or operator may demonstrate the size of a hard chromium electroplating facility by meeting the criteria of
s. NR 463.02 (20) or
(26). Alternatively, an owner or operator of a facility with a maximum cumulative potential rectifier capacity of 60 million A-hr/yr or more may be considered small if the actual cumulative rectifier capacity is less than 60 million A-hr/yr as demonstrated using one of the following procedures:
NR 463.04(3)(c)1.a.
a. If records show that the facility's previous annual actual rectifier capacity was less than 60 million A-hr/yr, by using nonresettable ampere-hour meters and keeping monthly records of actual ampere-hour usage for each 12-month rolling period following the compliance date in accordance with
s. NR 463.103 (2) (L). The actual cumulative rectifier capacity for the previous 12-month rolling period shall be tabulated monthly by adding the capacity for the current month to the capacities for the previous 11 months.
NR 463.04(3)(c)1.b.
b. By accepting a federally-enforceable limit on the maximum cumulative potential rectifier capacity of a hard chromium electroplating facility and by maintaining monthly records in accordance with
s. NR 463.103 (2) (L) to demonstrate that the limit has not been exceeded. The actual cumulative rectifier capacity for the previous 12-month rolling period shall be tabulated monthly by adding the capacity for the current month to the capacities for the previous 11 months.
NR 463.04(3)(c)2.
2. Once the monthly records required to be kept by
s. NR 463.103 (2) (L) and by this paragraph show that the actual cumulative rectifier capacity over the previous 12-month rolling period corresponds to the large designation, the owner or operator is subject to the emission limitation identified in
par. (a) 1. or
3. or
(b) 1.,
3. or
4., in accordance with the compliance schedule of
s. NR 463.06 (1) (e).
NR 463.04(4)
(4) Standards for decorative chromium electroplating tanks using a chromic acid bath and chromium anodizing tanks. During tank operation, each owner or operator of an existing, new or reconstructed decorative chromium electroplating tank using a chromic acid bath or chromium anodizing tank shall control chromium emissions discharged to the atmosphere from that affected source by one of the following:
NR 463.04(4)(a)
(a) By not allowing the concentration of total chromium in the exhaust gas stream discharged to the atmosphere to exceed 0.01 mg/dscm (4.4
×10
-6 gr/dscf).
NR 463.04(4)(b)
(b) If a chemical fume suppressant containing a wetting agent is used, by not allowing the surface tension of the electroplating or anodizing bath contained within the affected tank to exceed 45 dynes per centimeter (dynes/cm) (3.1 x 10
-3 pound-force per foot (lb
f /ft)) as measured by a stalagmometer or 35 dynes/cm (2.4 x 10
-3 lb
f /ft) as measured by a tensiometer at any time during operation of the tank.
NR 463.04(5)
(5) Standards for decorative chromium electroplating tanks using a trivalent chromium bath. NR 463.04(5)(a)(a) Each owner or operator of an existing, new or reconstructed decorative chromium electroplating tank that uses a trivalent chromium bath that incorporates a wetting agent as a bath ingredient is subject to the recordkeeping and reporting requirements of
ss. NR 463.103 (2) (n) and
463.106 (9), but is not subject to the work practice requirements of
s. NR 463.05, or the continuous compliance monitoring requirements in
s. NR 463.07. The wetting agent shall be an ingredient in the trivalent chromium bath components purchased from vendors.
NR 463.04(5)(b)
(b) Each owner or operator of an existing, new or reconstructed decorative chromium electroplating tank that uses a trivalent chromium bath that does not incorporate a wetting agent as a bath ingredient is subject to the standards of
sub. (4).
NR 463.04(5)(c)
(c) Each owner or operator of existing, new or reconstructed decorative chromium electroplating tank that had been using a trivalent chromium bath that incorporates a wetting agent and ceases using this type of bath shall fulfill the reporting requirements of
s. NR 463.106 (9) (c) and comply with the applicable emission limitation within the timeframe specified in
s. NR 463.06 (1) (f).
NR 463.04 History
History: Cr.
Register, September, 1997, No. 501, eff. 10-1-97;
CR 05-039: am. (3) (a), (4) (b), (5) (a) and (c), cr. (3) (a) 3. and (b), renum. (3) (b) to be (3) (c) and am. (3) (c) 1. a., b. and 2.
Register February 2006 No. 602, eff. 3-1-06;
CR 04-023: am. (1), (2) (a) and (b) 1. to 3.
Register December 2008 No. 636, eff. 1-1-09.
NR 463.05
NR 463.05 Operation and maintenance practices. NR 463.05(1)(1)
Work practice standards. All owners or operators subject to the standards in
s. NR 463.04 (3) and
(4) are subject to the following work practice standards:
NR 463.05(1)(a)
(a) At all times, including periods of startup, shutdown and malfunction, owners or operators shall operate and maintain any affected source, including associated air pollution control devices and monitoring equipment, in a manner consistent with good air pollution control practices, consistent with the operation and maintenance plan required by
sub. (2).
NR 463.05(1)(b)
(b) Malfunctions shall be corrected as soon as practicable after their occurrence in accordance with the operation and maintenance plan required by
sub. (2).
NR 463.05(1)(c)
(c) Determination of whether acceptable operation and maintenance procedures are being used will be based on information available to the department, which may include, but is not limited to, monitoring results; review of the operation and maintenance plan, procedures and records; and inspection of the source.
NR 463.05(1)(d)
(d) Based on the results of a determination made under
par. (c), the department may require that an owner or operator of an affected source make changes to the operation and maintenance plan required by
sub. (2) for that source. Revisions may be required if the department finds that the plan does any of the following:
NR 463.05(1)(d)2.
2. Fails to provide for the proper operation of the affected source, the air pollution control techniques, or the control system and process monitoring equipment during a malfunction in a manner consistent with good air pollution control practices.
NR 463.05(1)(d)3.
3. Does not provide adequate procedures for correcting malfunctioning process equipment, air pollution control techniques or monitoring equipment as quickly as practicable.
-
See PDF for table 
NR 463.05(2)(a)(a) The owner or operator of an affected source subject to the work practices of this section shall prepare an operation and maintenance plan to be implemented no later than the compliance date. The plan shall be incorporated by reference into the source's part 70 permit, if and when a part 70 permit is required under
ch. NR 407. The plan shall include all the following elements:
NR 463.05(2)(a)1.
1. The plan shall specify the operation and maintenance criteria for the affected source, the add-on air pollution control device, if such a device is used to comply with the emission limits, and the process and control system monitoring equipment, and shall include a standardized checklist to document the operation and maintenance of this equipment.
NR 463.05(2)(a)2.
2. For sources using an add-on air pollution control device or monitoring equipment to comply with this subchapter, the plan shall incorporate the work practice standards for that device or monitoring equipment, as identified in Table 1 of this subchapter, if the specific equipment used is identified in Table 1.
NR 463.05(2)(a)3.
3. If the specific equipment used is not identified in Table 1 of this subchapter, the plan shall incorporate proposed work practice standards. These proposed work practice standards shall be submitted to the department for approval as part of the submittal required under
s. NR 463.08.
NR 463.05(2)(a)4.
4. The plan shall specify procedures to be followed to ensure that equipment or process malfunctions due to poor maintenance or other preventable conditions do not occur.
NR 463.05(2)(a)5.
5. The plan shall include a systematic procedure for identifying malfunctions of process equipment, add-on air pollution control devices, and process and control system monitoring equipment and for implementing corrective actions to address the malfunctions.
NR 463.05(2)(b)
(b) If the operation and maintenance plan fails to address or inadequately addresses an event that meets the characteristics of a malfunction at the time the plan is initially developed, the owner or operator shall revise the operation and maintenance plan within 45 days after the event occurs. The revised plan shall include procedures for operating and maintaining the process equipment, add-on air pollution control device, or monitoring equipment during similar malfunction events, and a program for corrective action for the events.
NR 463.05(2)(d)
(d) If actions taken by the owner or operator during periods of malfunction are inconsistent with the procedures specified in the operation and maintenance plan required by
par. (a), the owner or operator shall record the actions taken for that event and shall report by phone the actions within 2 working days after commencing actions inconsistent with the plan. This report shall be followed by a letter within 7 working days after the end of the event, unless the owner or operator makes alternative reporting arrangements, in advance, with the department.
NR 463.05(2)(e)
(e) Each owner or operator shall keep the written operation and maintenance plan on record after it is developed to be made available for inspection, upon request, by the department for the life of the affected source or until the source is no longer subject to the provisions of this subchapter. In addition, if the operation and maintenance plan is revised, the owner or operator shall keep previous versions of the operation and maintenance plan on record to be made available for inspection, upon request, by the department for a period of 5 years after each revision to the plan.
NR 463.05(2)(f)
(f) To satisfy the requirements of this subsection, the owner or operator may use applicable standard operating procedure manuals, OSHA plans or other existing plans, provided the alternative plans meet the requirements of this subchapter.
NR 463.05(3)
(3) Chromic acid bath standards not met by using reducing agent. The standards in
s. NR 463.04 and this section that apply to chromic acid baths may not be met by using a reducing agent to change the form of chromium from hexavalent to trivalent.
NR 463.05 History
History: Cr.
Register, September, 1997, No. 501, eff. 10-1-97;
CR 05-039: am. (1) (d) 2., (2) (a) 2., 3. and (c)
Register February 2006 No. 602, eff. 3-1-06;
CR 04-023: am. (2) (e) and (f)
Register November 2008 No. 636, eff. 1-1-09.
NR 463.06(1)(a)(a) The owner or operator of an existing affected source shall comply with the emission limitations in
ss. NR 463.04 and
463.05 as follows:
NR 463.06(1)(a)1.
1. No later than October 1, 1998, if the affected source is a decorative chromium electroplating tank.
NR 463.06(1)(a)2.
2. No later October 1, 1999, if the affected source is a hard chromium electroplating tank or a chromium anodizing tank.
NR 463.06(1)(b)
(b) The owner or operator of a new or reconstructed affected source that has an initial startup after October 1, 1997, shall comply immediately upon startup of the source. The owner or operator of a new or reconstructed affected source that has an initial startup after December 16, 1993, but before October 1, 1997, shall follow the compliance schedule of
s. NR 460.05 (2) (a).
NR 463.06(1)(c)
(c) The owner or operator of an existing area source that increases actual or potential emissions of hazardous air pollutants such that the area source becomes a major source shall comply with the provisions for existing major sources, including the reporting provisions of
s. NR 463.106 (7), immediately upon becoming a major source.
NR 463.06(1)(d)
(d) The owner or operator of a new area source that increases actual or potential emissions of hazardous air pollutants such that the area source becomes a major source shall comply with the provisions for new major sources immediately upon becoming a major source.
NR 463.06(1)(e)
(e) An owner or operator of an existing hard chromium electroplating tank or tanks located at a small, hard chromium electroplating facility that increases its maximum cumulative potential rectifier capacity, or its actual cumulative rectifier capacity, such that the facility becomes a large, hard chromium electroplating facility shall comply with the requirements of
s. NR 463.04 (3) (a) 1. for all hard chromium electroplating tanks at the facility no later than one year after the month in which monthly records required by
ss. NR 463.04 (3) (c) and
463.103 (2) (L) show that the large designation is met, or by the compliance date specified in
par. (a) 2., whichever is later.
NR 463.06(1)(f)
(f) An owner or operator of a decorative chromium electroplating tank that uses a trivalent chromium bath that incorporates a wetting agent, and that ceases using the trivalent chromium process, shall comply with the emission limitation thereafter applicable to the tank within one year of switching from the bath operation.
NR 463.06(2)
(2) Request for a compliance date extension. An owner or operator of an affected source or sources that requests a compliance date extension shall do so in accordance with this subsection and the applicable paragraphs of
s. NR 460.05 (7). When the owner or operator is requesting the extension for more than one affected source located at the facility, then only one request may be submitted for all affected sources at the facility.
NR 463.06(2)(a)
(a) The owner or operator of an existing affected source who is unable to comply with a relevant standard under this subchapter may request that the department grant an extension allowing the owner or operator up to one additional year to comply with the standard for the affected source. The owner or operator of an affected source who has requested a compliance date extension under this subsection and is otherwise required to obtain a part 70 permit for the source shall apply for the permit or apply to have the part 70 permit revised to incorporate the conditions of the compliance date extension. The conditions of a compliance date extension granted under this subsection will be incorporated into the owner or operator's part 70 permit for the affected source according to
40 CFR part 70 or part
71, whichever is applicable.
NR 463.06(2)(b)
(b) Any request under this subsection for an extension of compliance with a relevant standard shall be submitted in writing to the department not later than 6 months before the affected source's compliance date as specified in this section.
NR 463.06(3)(a)(a) Except as provided in
pars. (b) and
(c), an owner or operator of an affected source subject to the requirements of this subchapter is required to conduct an initial performance test as required under
s. NR 460.06, using the procedures and test methods listed in
ss. NR 460.06 (2) and
(5) and
463.09.
NR 463.06(3)(b)
(b) If the owner or operator of an affected source meets all of the following criteria, an initial performance test is not required to be conducted under this subchapter:
NR 463.06(3)(b)1.
1. The affected source is a hard chromium electroplating tank, a decorative chromium electroplating tank or a chromium anodizing tank.
NR 463.06(3)(b)2.
2. A wetting agent is used in the plating or anodizing bath to inhibit chromium emissions from the affected source.
NR 463.06(3)(c)
(c) If the affected source is a decorative chromium electroplating tank using a trivalent chromium bath, and the owner or operator is subject to the provisions of
s. NR 463.04 (5), an initial performance test is not required to be conducted under this subchapter.
NR 463.06 History
History: Cr.
Register, September, 1997, No. 501, eff. 10-1-97;
CR 05-039: am. (1) (c), (e), (3) (b) 1. and 3.
Register February 2006 No. 602, eff. 3-1-06;
CR 04-023: am. (2) (a), (3) (a), (b) (intro.) and (c)
Register December 2008 No, 636, eff. 1-1-09.
NR 463.07
NR 463.07 Monitoring to demonstrate continuous compliance. The owner or operator of an affected source subject to the emission limitations of this subchapter shall conduct monitoring according to the type of air pollution control technique that is used to comply with the emission limitation. The monitoring required to demonstrate continuous compliance with the emission limitations is identified in this section for the air pollution control techniques expected to be used by the owners or operators of affected sources.
NR 463.07(1)(a)(a) During the initial performance test, the owner or operator of an affected source, or a group of affected sources under common control, complying with the emission limitations in
s. NR 463.04 through the use of a composite mesh-pad system shall determine the outlet chromium concentration using the test methods and procedures in
s. NR 463.09 (3), and shall establish as a site-specific operating parameter the pressure drop across the system, setting the value that corresponds to compliance with the applicable emission limitation, using the procedures in
s. NR 463.09 (4) (e). An owner or operator may conduct multiple performance tests to establish a range of compliant pressure drop values, or may set as the compliant value the average pressure drop measured over the 3 test runs of one performance test and accept
± 2 inches of water column from this value as the compliant range.
NR 463.07(1)(b)
(b) On and after the date on which the initial performance test is required to be completed under
s. NR 460.06, the owner or operator of an affected source, or group of affected sources under common control, shall monitor and record the pressure drop across the composite mesh-pad system once each day that any affected source is operating. To be in compliance with the standards in
s. NR 463.04, the composite mesh-pad system shall be operated within
± 2 inches of water column of the pressure drop value established during the initial performance test, or shall be operated within the range of compliant values for pressure drop established during multiple performance tests.
NR 463.07(1)(c)
(c) The owner or operator of an affected source complying with the emission limitation of
s. NR 463.04 through the use of a composite mesh-pad system may repeat the performance test and establish as a new site-specific operating parameter the pressure drop across the composite mesh-pad system according to the requirements in
par. (a) or
(b). To establish a new site-specific operating parameter for pressure drop, the owner or operator shall satisfy all of the following requirements:
NR 463.07(1)(d)
(d) The requirement to operate a composite mesh-pad system within the range of pressure drop values established under
pars. (a) to
(c) does not apply during the automatic-washdown cycles of the composite-mesh pad system.
NR 463.07(2)(a)(a) During the initial performance test, the owner or operator of an affected source, or group of affected sources under common control, complying with the emission limitations in
s. NR 463.04 through the use of a packed-bed scrubber system shall determine the outlet chromium concentration using the procedures in
s. NR 463.09 (3), and shall establish as site-specific operating parameters the pressure drop across the system and the velocity pressure at the common inlet of the control device, setting the value that corresponds to compliance with the applicable emission limitation using the procedures in
s. NR 463.09 (4) (d) and
(e). An owner or operator may conduct multiple performance tests to establish a range of compliant operating parameter values. Alternatively, the owner or operator may set as the compliant value the average pressure drop and inlet velocity pressure measured over the 3 test runs of one performance test, and accept
± 1 inch of water column from the pressure drop value and
± 10% from the velocity pressure value as the compliant range.
NR 463.07(2)(b)
(b) On and after the date on which the initial performance test is required to be completed under
s. NR 460.06, the owner or operator of an affected source, or group of affected sources under common control, shall monitor and record the velocity pressure at the inlet to the packed-bed scrubber and the pressure drop across the scrubber system once each day that any affected source is operating. To be in compliance with the standards in
s. NR 463.04, the scrubber system shall be operated within
±10% of the velocity pressure value established during the initial performance test, and within
±1 inch of water column of the pressure drop value established during the initial performance test, or within the range of compliant operating parameter values established during multiple performance tests.
NR 463.07(3)
(3) Packed-bed scrubber/composite mesh-pad system. The owner or operator of an affected source, or group of affected sources under common control, that uses a packed-bed scrubber in conjunction with a composite mesh-pad system to meet the emission limitations of
s. NR 463.04 shall comply with the monitoring requirements for composite mesh-pad systems as identified in
sub. (1).
NR 463.07(4)(a)(a) During the initial performance test, the owner or operator of an affected source, or group of affected sources under common control, complying with the emission limitations in
s. NR 463.04 through the use of a fiber-bed mist eliminator shall determine the outlet chromium concentration using the procedures in
s. NR 463.09 (3), and shall establish as a site-specific operating parameter the pressure drop across the fiber-bed mist eliminator and the pressure drop across the control device installed upstream of the fiber bed to prevent plugging, setting the value that corresponds to compliance with the applicable emission limitation using the procedures in
s. NR 463.09 (4) (e). An owner or operator may conduct multiple performance tests to establish a range of compliant pressure drop values, or may set as the compliant value the average pressure drop measured over the 3 test runs of one performance test and accept
±1 inch of water column from this value as the compliant range.
NR 463.07(4)(b)
(b) On and after the date on which the initial performance test is required to be completed under
s. NR 460.06, the owner or operator of an affected source, or group of affected sources under common control, shall monitor and record the pressure drop across the fiber-bed mist eliminator, and the control device installed upstream of the fiber bed to prevent plugging, once each day that any affected source is operating. To be in compliance with the standards in
s. NR 463.04, the fiber-bed mist eliminator and the upstream control device shall be operated within
±
1 inch of water column of the pressure drop value established during the initial performance test, or shall be operated within the range of compliant values for pressure drop established during multiple performance tests.
NR 463.07(5)
(5) Wetting agent-type or combination wetting agent-type/foam blanket fume suppressants. NR 463.07(5)(a)(a) During the initial performance test, the owner or operator of an affected source complying with the emission limitations in
s. NR 463.04 through the use of a wetting agent in the electroplating or anodizing bath shall determine the outlet chromium concentration using the procedures in
s. NR 463.09 (3). The owner or operator shall establish as the site-specific operating parameter the surface tension of the bath using Method 306B in Appendix A of
40 CFR part 63, incorporated by reference in
s. NR 484.04 (25), setting the maximum value that corresponds to compliance with the applicable emission limitation. In lieu of establishing the maximum surface tension during the performance test, the owner or operator may accept 45 dynes/cm (3.1 x 10
-3 pound-force per foot (lb
f /ft)) as measured by a stalagmometer or 35 dynes/cm (2.4 x 10
-3 lb
f /ft) as measured by a tensiometer as the maximum surface tension value that corresponds to compliance with the applicable emission limitation. However, the owner or operator is exempt from conducting a performance test only if the criteria of
s. NR 463.06 (3) (b) are met.
NR 463.07(5)(b)
(b) On and after the date on which the initial performance test is required to be completed under
s. NR 460.06, the owner or operator of an affected source shall monitor the surface tension of the electroplating or anodizing bath. Operation of the affected source at a surface tension greater than the value established during the performance test or greater than 45 dynes/cm (3.1 x 10
-3 lb
f /ft) as measured by a stalagmometer or 35 dynes/cm (2.4 x 10
-3 lb
f /ft) as measured by a tensiometer if the owner or operator is using this value in accordance with
par. (a), shall constitute noncompliance with the standards in
s. NR 463.04. The surface tension shall be monitored according to the following schedule:
NR 463.07(5)(b)1.
1. The surface tension shall be measured once every 4 hours during operation of the tank with a stalagmometer or a tensiometer as specified in Method 306B in Appendix A of
40 CFR part 63, incorporated by reference in
s. NR 484.04.
NR 463.07(5)(b)2.
2. The time between monitoring may be increased if there have been no exceedances. The surface tension shall be measured once every 4 hours of tank operation for the first 40 hours of tank operation after the compliance date. Once there are no exceedances during 40 hours of tank operation, surface tension measurement may be conducted once every 8 hours of tank operation. Once there are no exceedances during 40 more hours of tank operation, surface tension measurement may be conducted once every 40 hours of tank operation on an ongoing basis, until an exceedance occurs. The minimum frequency of monitoring allowed by this subchapter is once every 40 hours of tank operation.
NR 463.07(5)(b)3.
3. Once an exceedance occurs as indicated through surface tension monitoring, the original monitoring schedule of once every 4 hours shall be resumed. A subsequent decrease in frequency shall follow the schedule laid out in
subd. 2. For example, if an owner or operator had been monitoring an affected source once every 40 hours and an exceedance occurs, subsequent monitoring would take place once every 4 hours of tank operation. Once an exceedance does not occur for 40 hours of tank operation, monitoring may occur once every 8 hours of tank operation. Once an exceedance does not occur for 40 hours of tank operation on this schedule, monitoring may occur once every 40 hours of tank operation.
NR 463.07(5)(c)
(c) Once a bath solution is drained from the affected tank and a new solution added, the original monitoring schedule of once every 4 hours shall be resumed, with a decrease in monitoring frequency allowed following the procedures of
par. (b) 2. and
3.
NR 463.07(6)(a)(a) During the initial performance test, the owner or operator of an affected source complying with the emission limitations in
s. NR 463.04 through the use of a foam blanket in the electroplating or anodizing bath shall determine the outlet chromium concentration using the procedures in
s. NR 463.09 (3), and shall establish as the site-specific operating parameter the thickness of the foam blanket, setting the minimum thickness that corresponds to compliance with the applicable emission limitation. In lieu of establishing the minimum foam blanket thickness during the performance test, the owner or operator may accept 2.54 centimeters (1 inch) as the minimum foam blanket thickness that corresponds to compliance with the applicable emission limitation. All foam blanket measurements shall be taken in close proximity to the workpiece or cathode area in the plating tank.
NR 463.07(6)(b)
(b) On and after the date on which the initial performance test is required to be completed under
s. NR 460.06, the owner or operator of an affected source shall monitor the foam blanket thickness of the electroplating or anodizing bath. Operation of the affected source at a foam blanket thickness less than the value established during the performance test, or less than 2.54 cm (1 inch) if the owner or operator is using this value in accordance with
par. (a), constitutes noncompliance with the standards in
s. NR 463.04. The foam blanket thickness shall be measured according to the following schedule:
NR 463.07(6)(b)1.
1. The foam blanket thickness shall be measured once every hour of tank operation.
NR 463.07(6)(b)2.
2. The time between monitoring may be increased if there have been no exceedances. The foam blanket thickness shall be measured once every hour of tank operation for the first 40 hours of tank operation after the compliance date. Once there are no exceedances for 40 hours of tank operation, foam blanket thickness measurement may be conducted once every 4 hours of tank operation. Once there are no exceedances during 40 more hours of tank operation, foam blanket thickness measurement may be conducted once every 8 hours of tank operation on an ongoing basis, until an exceedance occurs. The minimum frequency of monitoring allowed by this subchapter is once per 8 hours of tank operation.
NR 463.07(6)(b)3.
3. Once an exceedance occurs as indicated through foam blanket thickness monitoring, the original monitoring schedule of once every hour shall be resumed. A subsequent decrease in frequency shall follow the schedule laid out in
subd. 2. For example, if an owner or operator had been monitoring an affected source once every 8 hours and an exceedance occurs, subsequent monitoring would take place once every hour of tank operation. Once an exceedance does not occur for 40 hours of tank operation, monitoring may occur once every 4 hours of tank operation. Once an exceedance does not occur for 40 hours of tank operation on this schedule, monitoring may occur once every 8 hours of tank operation.
