FREEZE SEAL EVALUATION
LABORATORY PRACTICAL EVALUATION
FOR
PLANT HVAC TECHNICIANS
TASK NUMBER(S) TASK STATEMENTS
8059330208 Perform pre-job freeze seal walk down
8059340208 Perform a freeze seal
8059350208 Implement safety requirements working with LN2
8059320208 Fill dewars with liquid nitrogen
8059300208 Install freeze seal chaamber
EMPLOYEE'S NAME: SSN:
LAST FIRST MI
UNIT # DATE APS SUPERVISOR NAME CONTRACTOR AFFIL
EXAM # NMH06-P-001-97 SECTION #
COURSE TITLE: Freeze Seals APPROVED BY:
DATE:
PASS FAIL EVALUATOR (print)
LAST FIRST MI
EVALUATOR SIGNATURE
DIRECTIONS TO EMPLOYEE: When I tell you to begin, you are to perform the practical exercise attached to this LPE for Freeze Seals . I will describe general conditions and provide equipment to perform this task. Before starting, I will state the task standard(s) and initiating cues and answer any questions you might have. If you perform more than three critical step improperly, you will not achieve mastery of this Lab Practical Evaluation.
A. GENERAL CONDITIONS: (Under which task will be performed)
1. Practical exercise in training labratory
B. GENERAL TOOLS AND EQUIPMENT: (Required for task performance)
1. All tools and equipment shown on the tools hand out sheet.
6
33MT-9ZZ02
Basic sequence of work
to perform a freeze seal
in conjunction with 33MT-9ZZ02
(Not to be used without reference to 33MT-9ZZ02’s applicable sections.)
1.Review the W.O. and 33MT-9ZZ02, sections 1.0 through 6.0, and Appendix “B & “C”. Participate in the Team Leader or designee “tailboard information meeting”.
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2.Determine by reviewing with OPS the purpose of the freeze seal and the scope of the work to be performed.
· Discuss other disciplines concerns that may be affected by the freeze seal
and the work it is supporting.
(Industrial Safety, RP, Effluent group, Operations, Insulators, ISI, heavy
equipment operators, supported work group, HVAC manpower, etc.)
Notify the Shift Supervisor prior to starting work. Record this in Appendix “D” (FSDR)
Pg. 1 of 5.
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3.Determine the optimum lowest level of the U1; U2 and U3 liquid nitrogen supply tanks and obtain approval from Operations to fill the LN2 dewars.
Have S.S./A.S.S. record the LN2 approval in Appendix “F”, Pg. 1 of 2.
(Plan where to obtain sufficient LN2 throughout the freeze seal.)
· How do you determine a sufficient amount of LN2 dewars to begin supporting the freeze seal.
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4.Walk down the freeze seal location.
· Take into consideration the complete scope of the work.
· Complete the “Freeze Seal Equipment Checklist” to determine the equipment needed and the length of LN2 hoses, cables, etc.
· If the W.O. and the job scope are not compatible - STOP - and notify the
Planner/Scheduler and/or the Team Leader to make the appropriate changes.
· If insulation is present, remove at least 6” from each side of the freeze chamber.
Record this in Appendix “D”, (FSDR), Pg. 3 of 5.
· Examine the freeze seal area for cracks, etc., and mark the freeze seal pipe area.
Record the ‘Surface Exam” results in Appendix “D”, (FSDR), Pg. 3 of 5.
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5. From the “Freeze Seal Equipment Checklist”... Gather the necessary items and
check that everything is in good working order.
· Prepare the appropriate size freeze chamber and temperature probe with sealant. (Do not install chamber or temperature probe on the pipe at this time.)
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6. Install equipment as needed from the checklist.
State why you selected what you have?
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7. Discuss the main topics of a Freeze Seal Briefing with Operations and the associated disciplines involved with the freeze seal and work evolution.
· Discuss and understand the contingencies for a freeze seal failure with OPS.
· This is the time to address any concerns or better ideas concerning the freeze seal and the associated work evolution.
· Have the appropriate personnel sign the “Freeze Seal Briefing” and the Appendix “D”
Contingencies, Pg. 2 of 5.
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8. Install the freeze chamber on the pipe snug enough to seal, creating a half tight fit.
· Secure the freeze chamber to prevent slippage if necessary.
· Connect LN2 lines.
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9. How can you verify the line is full of liquid and that the flow is stopped/reduced.
Record the condition in Appendix “D”, (FSDR), Pg. 3 of 5.
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10. Record the completion of Section 1.0 in Appendix “D”, (FSDR), Pg. 3 of 5.
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11. Snug freeze seal chamber bolts to a tight fit.
· Why do you trim and/or form fit sealant around each end of the freeze chamber.
· Install thermoprobe and tighten good and snug.
· Connect the thermoprobe cable and verify the pre-freeze pipe temperature.
· Install the freeze chamber vent and secure the overflow bucket properly.
· Adjust the vent and snug it to maintain a flooded freeze chamber level.
·
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12. Verify that all LN2 line fittings are connected and tightened.
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13. Install and secure any herculite that is necessary to protect / shield personnel
and / or equipment from LN2 safety hazards.
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14. Place oxygen monitors at the appropriate work locations to ensure a safe work area.
· Ensure the appropriate caution signs, barrier tape, etc. are in place to ensure a
safe work area.
· Sometimes a mop and bucket will be necessary to keep the floors dry.
This prevents a slipping hazard and maintains a clean work area.
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15. Record that the “Freeze Seal Equipment” is installed in Appendix “D”, (FSDR),
Section 2.0, Pg. 3 of 5.
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16. Obtain Operations S.S. / A.S.S. approval to start the freeze seal.
Record in Appendix “D”, (FSDR), Pg. 3 of 5, Section 2.0.
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17. Gradually open the liquid LN2 valve and flood the freeze chamber.
· Maintain a flooded freeze chamber.
· Monitor and record the pipe temperature at required time intervals in Appendix “D”,
(FSDR), Pg. 4 of 5, “Temp. Log”.
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18. Create a solid freeze plug considering the time, temperature, and frost line.
(cryogenic technical judgment)
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19. Verify a solid freeze plug has been established by venting the line or component
determined by Operations.
· This evolution is usually accomplished with Operations support and the
manipulation of the clearance. Evaluator can act as verifier.
· Attention should be made to accomplish this evolution cautiously and
patiently to verify the freeze plug is going to remain in place.
· At the same time having a contingency which all personnel involved
understand, that allows the system to be secured safely and promptly if
the plug fails.
· REMEMBER WHEN A FREEZE PLUG FAILS IT IS NOT A GRADUAL
PROCESS. PAY CLOSE ATTENTION TO THE FROST LINE AT BOTH ENDS OF THE CHAMBER, WHICH IS ONLY A STEP USED TO PROVE THAT A SEAL IS ESTABLISHED.
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20. Notify Operations and the supported work group that the freeze plug is established
and the seal integrity has been verified... the work supported may begin.
Record the “time” at which the freeze seal is established in Appendix “D”,
(FSDR), Pg. 3 of 5, Section 2.0.
· Monitor the pipe temperature and maintain the pressure and volume of LN2 at a
level which maintains the integrity of the freeze plug.
Continue maintaining the “Temp. Log” in Appendix “D”, (FSDR), Pg. 4 of 5.
· It is not necessary to log pipe temperatures if the thermoprobe assembly in
the freeze chamber becomes flooded.
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21. When the work is completed that the freeze seal supports, the associated
work group notifies the Operations S.S. or the A.S.S.
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22. After the above authorization from the Operations S.S. or the A.S.S. is obtained to
terminate the freeze seal...
· The method used to thaw the seal should be discussed with Operations to
assure no damage results to the system during the thaw process.
· Any desired or undesired change in the condition of the system, that the
thawing of the freeze plug could bring about... Should be understood.
(This understanding should be the same as what was understood at the
Pre-Freeze Seal Briefing and it may be associated with manipulations of
the clearance.)
· Record the thawing method preferred, in Appendix “D”, (FSDR Post-Seal Data),
Section 3.0, Pg. 5 of 5.
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23. Document that Section 2.0 is complete in Appendix “D”, (FSDR), Pg. 3 of 5,
Section 2.0.
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24. Document the authorization from the Operations S.S. or the A.S.S. to remove the
freeze seal in Appendix “D”, (FSDR), Pg. 5 of 5.
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25. Terminate the freeze seal by closing the liquid LN2 dewar valve.
· Let all the remaining LN2 in the line and freeze chamber boil off.
· Disconnect the LN2 line from the dewar and the freeze chamber.
· Remove the freeze chamber and the sealant from the pipe when it’s thawed.
· Verify the recorded thawing method to be used, in Appendix “D”,
(FSDR Post-Seal Data), Section 3.0, Pg. 5 of 5.
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26. Dismantle freeze seal equipment from the work area. Clean equipment and area for the next group.
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27. At this time, Engineering Evaluations ISI Group to test the freeze seal pipe area for
any relevant defects. ISI shall record the results in Appendix “D”,
(FSDR Post-Seal Data), Section 3.0, Pg. 5 of 5.
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28.Insulation removed. Record the insulation condition or W.R.# in
Appendix “D”, (FSDR Post-Seal Data), Section 3.0, Pg. 5 of 5.
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29. Ensure all the data has been recorded on the FSDR and the signoffs are complete.
· Record the completion of the FSDR in Appendix “D”, (FSDR Post-Seal Data)
Pg. 5 of 5.
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30. Record the completion of Section 3.0 in Appendix “D”, (FSDR Post-Seal Data)
Pg. 5 of 5.
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31. Review the completion of the W.O. and close the W.O.
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