Incident details
Operator, cause, commodity and consequences with raw source fields.
GTG incident on 2010-06-23 — NE
Operator
Northern Natural Gas Co
Cause
Incorrect Operation
Commodity
Natural Gas
Program
GTG
Damage and Injuries
0 fatalities
0 injuries
Property damage (nominal)
$25,335
Incident datetime
2010-06-23 09:28
Report number
Location
NE
Narrative
On june 23, 2010, a landowner, eugene mulligan, called northern natural gas company's operations communication center to report blowing gas to atmosphere at a valve site near where he lived. Northern employees immediately responded. It was determined that it was natural gas blowing from northern's mnm80104-m500d mainline at a valve site at approximate milepost 95.89. Pipeline pressure on the line was 739 psig. The line has an maop of 1,000 psig. A pir of 563 feet was calculated. Local police assisted with barricading off 320th street which passes by the valve site. There was no fire, no explosion and no injuries. As a precaution 5 people were evacuated from residences in the near area. Approximately 13 miles of c line and 6 miles of d line were shut in to enable isolation of the line segment. An attempt was made to draw gas pressure down with compression horsepower @ the farmington compressor station. At 490 psig compression was shut down due to high rod load on units. An emergency 1-call was made and contractor personnel were called to assist with repairs. It was determine that line would be blown down to 50 psig for overnight, one person would man site thru the night. On june 24 the line was blown down to zero pressure. Four farmtap customers were impacted. Excavation was commenced and it was found that there was a significant frost ball. A hot water hydro vac was utilized to remove frost. Investigation indicated that there was a portion of the flange gasket blown out, which allowed gas leakage. The flange was disassembled and a new lamons 30" 600 asme b16 47a, asme b1620, 304ir gasket was installed. The flange bolts were re-installed and retorqued. Additional concrete support blocks were installed and allowed to cure. On june 28th the line was purged and slowly reloaded to operational pressure, leak checked, coated and backfilled. A supplemental final report will be filed when all cost of repairs is calculated. Final cost were calculated and initial costs were changed/updated. On april18,2011 a supplemental final report was filed as PHMSA requested to provide additional information on pipe spec's, part c, item 3 of the report and cost of gas released unintentionally in part d, item 7b. This information has been added to this supplemental final report as requested. Supplemental/final report - this report is being filed as a supplemental/final report to report # 20100039-15215 dated 08/31/2010 as a follow up to discussion with PHMSA representatives. Part a item 7 was changed to match time on the nrc form, the cause of the event was changed from equipment failure to incorrect operations. An analysis of the event indicates that there was adequate, proper support for the piping, no indication of subsidence and although the gasket material was not analyzed due to it's damaged condition, there are two other similar 30-inch valves with the same type of gaskets installed on this piping and neither of those have had any problems or leaks, this is a very good, high quality gasket. The leakage appears to have been between the 6 o'clock and 9 o'clock position only. Northern believes that the root cause of this event is most likely that all of the bolts on the flange were not consistently torqued which led to leakage, which ultimately led to the gasket failure. Northern is issuing a technical bulletin to all employees, inspectors and construction personnel re-emphasizing the importance of proper torqueing and the requirements of engineering standard 7570 when joining of pipe & piping components other than by welding. Should there be an event of this nature in the future every effort will be made to ensure that even though the gasket material may be damaged it will be sent to a laboratory for analysis to determine if the quality of the gasket was or is a factor in the event.
Detailed record list
Report Received Date
2010-07-14 00:00:00
Iyear
2010
Report Number
20100039
Supplemental Number
16807
Report Type
Supplemental Final
Operator Id
13750
Name
Northern Natural Gas Co
Operator Street Address
1111 South 103rd Street
Operator City Name
Omaha
Operator State Abbreviation
NE
Operator Postal Code
68124
Local Datetime
2010-06-23 09:22:00
Location Latitude
44.48661
Location Longitude
-93.22225
Nrc Rpt Num
945138
Nrc Rpt Datetime
2010-06-23 10:45:00
Commodity Released Type
Natural Gas
Unintentional Release
1000
Intentional Release
17933
Accompanying Liquid
0
Fatality Ind
No
Fatal
0
Injury Ind
No
Injure
0
Shutdown Due Accident Ind
Yes
Shutdown Datetime
2010-06-24 08:00:00
Restart Datetime
2010-06-25 19:00:00
Ignite Ind
No
Explode Ind
No
Num Pub Evacuated
5
Incident Identified Datetime
2010-06-23 09:28:00
On Site Datetime
2010-06-23 10:05:00
On Off Shore
Onshore
Onshore State Abbreviation
Mn
Onshore Postal Code
55057
Onshore City Name
Northfield
Onshore County Name
Dakota
Designated Location
Milepost
Designated Name
95.89
Pipe Fac Name
30-Inch D Line
Segment Name
Mnm80104
Federal
No
Location Type
Pipeline Right-Of-Way
Incident Area Type
Underground
Incident Area Subtype
Under Soil
Depth Of Cover
84
Crossing
No
Pipe Facility Type
Interstate
System Part Involved
Onshore Pipeline, Including Valve Sites
Item Involved
Pipe
Pipe Type
Pipe Body
Pipe Diameter
30
Pipe Wall Thickness
0.375
Pipe Smys
75000
Pipe Specification
Api 5l
Pipe Seam Type
Single Saw
Pipe Manufacturer
Berg Steel Pipe Co.
Pipe Coating Type
Epoxy
Installation Year
2009
Manufactured Year
2008
Material Involved
Material Other Than Carbon Steel Or Plastic
Material Details
9000 Series Garlock Flange Gasket
Release Type
Leak
Leak Type
Other
Leak Type Other
Flange Gasket
Class Location Type
Class 1 Location
Could Be Hca
No
Pir Radius
563
Heat Damage Ind
No
Non Heat Damage Ind
No
Hca Fatalities Ind
No
Est Cost Oper Paid
0
Est Cost Unintentional Release
5295
Est Cost Intentional Release
89665
Est Cost Prop Damage
25335
Est Cost Emergency
10000
Est Cost Other
0
Prpty
130295
Accident Psig
739
Mop Psig
1000
Mop Cfr Section
192.619(A)(2)
Accident Pressure
Pressure Did Not Exceed Maop
Pressure Restriction Ind
No
Upstream Valve Type Ind
Manual
Downstream Valve Type Ind
Manual
Length Segment Isolated
100320
Internal Inspection Ind
Yes
Operation Complications Ind
No
Pipeline Function
Transmission System
Scada In Place Ind
Yes
Scada Operating Ind
Yes
Scada Functional Ind
Yes
Scada Detection Ind
No
Scada Conf Ind
No
Accident Identifier
Notification From Public
Investigation Status
No, the operator did not find that an investigation of the controller(s) actions or control room issues was necessary due to: (provide an explanation for why the operator did not investigate)
Investigation Status Details
The leak was from an underground manually operated valve's flange gasket. Controllers do not have any remote control of this part of pipelines operation. Leak was not significant enough, when found that it would typically be detected by any change in scada pressures.
Employee Drug Test Ind
No
Contractor Drug Test Ind
No
Cause
Incorrect Operation
Cause Details
Equipment Not Installed Properly
Operation Type
Equipment Not Installed Properly
Related Other Ind
Yes
Operation Related Details
It Appears That Engineering Standard 7570 Joining Of Pipe & Piping Components Other Than By Welding Was Not Adequately And Successfully Followed As All Indications Are That The Flange, In Which The Gasket Failed, Was Not Consistently Torqued On All Bolts Around The Flange.
Category Type
Construction
Operator Qualification Ind
Yes
Qualified Individuals
Yes, They Were Qualified For The Task(S)
Preparer Name
B**** W***
Preparer Title
Sr. Pipeline Safety Specialist
Preparer Email
B*********@n****.com
Preparer Telephone
402-398-7396
Preparer Fax
402-398-7706
Authorizer Name
T***** C******
Authorizer Title
Director Of Pipeline Safety And Integrity
Authorizer Telephone
402-398-7715
Authorizer Email
T*************@n****.com
Narrative
O**************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************@ the farmington compressor station. At 490 psig compression was shut down due to high rod load on units. An emergency 1-call was made and contractor personnel were called to assist with repairs. It was determine that line would be blown down to 50 psig for overnight, one person would man site thru the night. On june 24 the line was blown down to zero pressure. Four farmtap customers were impacted. Excavation was commenced and it was found that there was a significant frost ball. A hot water hydro vac was utilized to remove frost. Investigation indicated that there was a portion of the flange gasket blown out, which allowed gas leakage. The flange was disassembled and a new lamons 30" 600 asme b16 47a, asme b1620, 304ir gasket was installed. The flange bolts were re-installed and retorqued. Additional concrete support blocks were installed and allowed to cure. On june 28th the line was purged and slowly reloaded to operational pressure, leak checked, coated and backfilled. A supplemental final report will be filed when all cost of repairs is calculated. Final cost were calculated and initial costs were changed/updated. On april18,2011 a supplemental final report was filed as PHMSA requested to provide additional information on pipe spec's, part c, item 3 of the report and cost of gas released unintentionally in part d, item 7b. This information has been added to this supplemental final report as requested. Supplemental/final report - this report is being filed as a supplemental/final report to report # 20100039-15215 dated 08/31/2010 as a follow up to discussion with PHMSA representatives. Part a item 7 was changed to match time on the nrc form, the cause of the event was changed from equipment failure to incorrect operations. An analysis of the event indicates that there was adequate, proper support for the piping, no indication of subsidence and although the gasket material was not analyzed due to it's damaged condition, there are two other similar 30-inch valves with the same type of gaskets installed on this piping and neither of those have had any problems or leaks, this is a very good, high quality gasket. The leakage appears to have been between the 6 o'clock and 9 o'clock position only. Northern believes that the root cause of this event is most likely that all of the bolts on the flange were not consistently torqued which led to leakage, which ultimately led to the gasket failure. Northern is issuing a technical bulletin to all employees, inspectors and construction personnel re-emphasizing the importance of proper torqueing and the requirements of engineering standard 7570 when joining of pipe & piping components other than by welding. ********************************************************************************************************************************************************************************************************************************************************************.
| Report Received Date | 2010-07-14 00:00:00 |
|---|---|
| Iyear | 2010 |
| Report Number | 20100039 |
| Supplemental Number | 16807 |
| Report Type | Supplemental Final |
| Operator Id | 13750 PHMSA Enforcement |
| Name | Northern Natural Gas Co |
| Operator Street Address | 1111 South 103rd Street |
| Operator City Name | Omaha |
| Operator State Abbreviation | NE |
| Operator Postal Code | 68124 |
| Local Datetime | 2010-06-23 09:22:00 |
| Location Latitude | 44.48661 Google Maps OpenStreetMap |
| Location Longitude | -93.22225 Google Maps OpenStreetMap |
| Nrc Rpt Num | 945138 NRC Report How to search |
| Nrc Rpt Datetime | 2010-06-23 10:45:00 |
| Commodity Released Type | Natural Gas |
| Unintentional Release | 1000 |
| Intentional Release | 17933 |
| Accompanying Liquid | 0 |
| Fatality Ind | No |
| Fatal | 0 |
| Injury Ind | No |
| Injure | 0 |
| Shutdown Due Accident Ind | Yes |
| Shutdown Datetime | 2010-06-24 08:00:00 |
| Restart Datetime | 2010-06-25 19:00:00 |
| Ignite Ind | No |
| Explode Ind | No |
| Num Pub Evacuated | 5 |
| Incident Identified Datetime | 2010-06-23 09:28:00 |
| On Site Datetime | 2010-06-23 10:05:00 |
| On Off Shore | Onshore |
| Onshore State Abbreviation | Mn |
| Onshore Postal Code | 55057 |
| Onshore City Name | Northfield |
| Onshore County Name | Dakota |
| Designated Location | Milepost |
| Designated Name | 95.89 |
| Pipe Fac Name | 30-Inch D Line |
| Segment Name | Mnm80104 |
| Federal | No |
| Location Type | Pipeline Right-Of-Way |
| Incident Area Type | Underground |
| Incident Area Subtype | Under Soil |
| Depth Of Cover | 84 |
| Crossing | No |
| Pipe Facility Type | Interstate |
| System Part Involved | Onshore Pipeline, Including Valve Sites |
| Item Involved | Pipe |
| Pipe Type | Pipe Body |
| Pipe Diameter | 30 |
| Pipe Wall Thickness | 0.375 |
| Pipe Smys | 75000 |
| Pipe Specification | Api 5l |
| Pipe Seam Type | Single Saw |
| Pipe Manufacturer | Berg Steel Pipe Co. |
| Pipe Coating Type | Epoxy |
| Installation Year | 2009 |
| Manufactured Year | 2008 |
| Material Involved | Material Other Than Carbon Steel Or Plastic |
| Material Details | 9000 Series Garlock Flange Gasket |
| Release Type | Leak |
| Leak Type | Other |
| Leak Type Other | Flange Gasket |
| Class Location Type | Class 1 Location |
| Could Be Hca | No |
| Pir Radius | 563 |
| Heat Damage Ind | No |
| Non Heat Damage Ind | No |
| Hca Fatalities Ind | No |
| Est Cost Oper Paid | 0 |
| Est Cost Unintentional Release | 5295 |
| Est Cost Intentional Release | 89665 |
| Est Cost Prop Damage | 25335 |
| Est Cost Emergency | 10000 |
| Est Cost Other | 0 |
| Prpty | 130295 |
| Accident Psig | 739 |
| Mop Psig | 1000 |
| Mop Cfr Section | 192.619(A)(2) View CFR 49 §192 |
| Accident Pressure | Pressure Did Not Exceed Maop |
| Pressure Restriction Ind | No |
| Upstream Valve Type Ind | Manual |
| Downstream Valve Type Ind | Manual |
| Length Segment Isolated | 100320 |
| Internal Inspection Ind | Yes |
| Operation Complications Ind | No |
| Pipeline Function | Transmission System |
| Scada In Place Ind | Yes |
| Scada Operating Ind | Yes |
| Scada Functional Ind | Yes |
| Scada Detection Ind | No |
| Scada Conf Ind | No |
| Accident Identifier | Notification From Public |
| Investigation Status | No, the operator did not find that an investigation of the controller(s) actions or control room issues was necessary due to: (provide an explanation for why the operator did not investigate) |
| Investigation Status Details | The leak was from an underground manually operated valve's flange gasket. Controllers do not have any remote control of this part of pipelines operation. Leak was not significant enough, when found that it would typically be detected by any change in scada pressures. |
| Employee Drug Test Ind | No |
| Contractor Drug Test Ind | No |
| Cause | Incorrect Operation |
| Cause Details | Equipment Not Installed Properly |
| Operation Type | Equipment Not Installed Properly |
| Related Other Ind | Yes |
| Operation Related Details | It Appears That Engineering Standard 7570 Joining Of Pipe & Piping Components Other Than By Welding Was Not Adequately And Successfully Followed As All Indications Are That The Flange, In Which The Gasket Failed, Was Not Consistently Torqued On All Bolts Around The Flange. |
| Category Type | Construction |
| Operator Qualification Ind | Yes |
| Qualified Individuals | Yes, They Were Qualified For The Task(S) |
| Preparer Name | B**** W*** |
| Preparer Title | Sr. Pipeline Safety Specialist |
| Preparer Email | B*********@n****.com |
| Preparer Telephone | 402-398-7396 |
| Preparer Fax | 402-398-7706 |
| Authorizer Name | T***** C****** |
| Authorizer Title | Director Of Pipeline Safety And Integrity |
| Authorizer Telephone | 402-398-7715 |
| Authorizer Email | T*************@n****.com |
| Narrative | O**************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************@ the farmington compressor station. At 490 psig compression was shut down due to high rod load on units. An emergency 1-call was made and contractor personnel were called to assist with repairs. It was determine that line would be blown down to 50 psig for overnight, one person would man site thru the night. On june 24 the line was blown down to zero pressure. Four farmtap customers were impacted. Excavation was commenced and it was found that there was a significant frost ball. A hot water hydro vac was utilized to remove frost. Investigation indicated that there was a portion of the flange gasket blown out, which allowed gas leakage. The flange was disassembled and a new lamons 30" 600 asme b16 47a, asme b1620, 304ir gasket was installed. The flange bolts were re-installed and retorqued. Additional concrete support blocks were installed and allowed to cure. On june 28th the line was purged and slowly reloaded to operational pressure, leak checked, coated and backfilled. A supplemental final report will be filed when all cost of repairs is calculated. Final cost were calculated and initial costs were changed/updated. On april18,2011 a supplemental final report was filed as PHMSA requested to provide additional information on pipe spec's, part c, item 3 of the report and cost of gas released unintentionally in part d, item 7b. This information has been added to this supplemental final report as requested. Supplemental/final report - this report is being filed as a supplemental/final report to report # 20100039-15215 dated 08/31/2010 as a follow up to discussion with PHMSA representatives. Part a item 7 was changed to match time on the nrc form, the cause of the event was changed from equipment failure to incorrect operations. An analysis of the event indicates that there was adequate, proper support for the piping, no indication of subsidence and although the gasket material was not analyzed due to it's damaged condition, there are two other similar 30-inch valves with the same type of gaskets installed on this piping and neither of those have had any problems or leaks, this is a very good, high quality gasket. The leakage appears to have been between the 6 o'clock and 9 o'clock position only. Northern believes that the root cause of this event is most likely that all of the bolts on the flange were not consistently torqued which led to leakage, which ultimately led to the gasket failure. Northern is issuing a technical bulletin to all employees, inspectors and construction personnel re-emphasizing the importance of proper torqueing and the requirements of engineering standard 7570 when joining of pipe & piping components other than by welding. ********************************************************************************************************************************************************************************************************************************************************************. |
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