2011 AIChE Ammonia Safety Symposium Questions & Answers PART 2




Paper 3c:    Severe Safety Problems during Ammonia Converter Optimization

 

Authors :    Leonhard Werner, Ignaz Mayr and Richard Brandmair - 

Borealis Agrolinz Melamine GmbH

 

Presenter:  Leonhard Werner - Borealis Agrolinz Melamine GmbH

 

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By :    Ravindra P. Jawale – Rashtriya Chemical and Fertilisers (Thal Unit), India
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Q 3c.1:           Whether the hydro-test / pressure-test to confirm the integrity of shell is carried out specially when refractory is at bottom dish end? How the safety regulation law in the state taken care of?
A 3c.1:           In case the catalyst is removed a hydro / pressure test is done. The installations in Linz do not have a refractory in the synthesis section. In case the catalyst is in the converter an acoustic emission test is also accepted by the Austrian regulator.

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By :    Mark E. Jackson – FM Global, USA
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Q 3c.2:           Incident 2 – In the incident review and corrective measures taken - Was the installation of sprinkler protection to reduce the fire exposure considered?  (Ref. 2007 Symposium paper – Fire protection turbine syngas compresors)?
A 3c.2:           The installation of a sprinkler system was considered, but then rejected, because the consequences of a malfunction (i.e. watering a hot plant). In the opinion of our investigation team a damage of electrical or mechanical equipment is most likely. Therefore it was decided to increase the punch of our fire brigade with a remote controlled mobile quencher.

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Paper 3e:    Failure Analysis of High Pressure Synthesis Gas Compressor Cooler

 

Authors :    Imran M. Saeed and Patrick Van Opdorp - Qatar Fertilizer Company

 

Presenter:  Patrick Van Opdorp - Qatar Fertilizer Company

 

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By :    Dorothy F. Shaffer – Baker Risk
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Q 3e.1:           You mentioned that the damage occurred only on the inlet of the exchanger. Have you considered whether that was related to material differences such as hardness, or process temperatures??
A 3e.1:           Process temperature related. Cracking only observed at cold tube-sheet. Seawater inlet side.

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By :    Kang Xu – Praxair Inc., USA
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Q 3e.2:           Any hardness was done on the cladding ?
A 3e.2:           Yes.

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Paper 3f:    Understanding the Risk of Legionella Bacteria in Industrial Cooling Water Circuits

 

Authors :    Loraine Huchler - MarTech Systems, Inc.

 

Presenter:  Loraine Huchler - MarTech Systems, Inc.

 

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By :    Mike Antony – Pro Plant Inc.
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Q 3f.1:            Is Free chlorine level of 0.2 - 0.5 ppm good enough to control legionella? What is the preferred non-oxidizing biocide?
A 3f.1:            The optimal free chlorine concentration to control legionella depends on the conditions of the specific cooling tower. For cooling towers that have no process contamination (e.g. leaks from heat exchangers) and continuous feed of chlorine, it is likely that concentrations of free chlorine between 0.2 to 0.5 ppm will control the bacteria growth below the generally accepted threshold of 10,000 CFU/ml. This includes control of legionella bacteria; however, there is no way to guarantee that there will be no legionella bacteria at these dosages.
                        The preferred non-oxidizing biocide will depend on the nature of the water circuit and any process contaminants. In the U. S., the most commonly used non-oxidizing biocides are gluteraldehyde and isothiazoline. Water treatment professionals can conduct a lab study to determine the optimal non-oxidizing biocide for a specific system.


Q 3f.2:            Is there a legally allowable limit on colony count?
A 3f.2:            Most experts agree that the only rational limit is zero (0) detectable legionella bacteria.

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Paper 4a:     Avoiding the Conventional Revamp Philosophy for an Ammonia Plant

 

Authors :     Sahban Zafar Ali - Fauji Fertilizer Company Ltd., Pakistan

 

Presenter:     Sahban Zafar Ali - Fauji Fertilizer Company Ltd., Pakistan

 

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By :    Sachchida Nand – Fertiliser Association of India
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Q 4a.1:           Was there any foaming or corrosion problem after increasing amine concentration from 40% to 50% in CO2 removal section?
A 4a.1:           No. As per BASF, aMDEA HICAP is non corrosive like aMDEA.

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By :    Harrie Duisters – OCI Nitrogen
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Q 4a.2:           What is the negative side of using BASF HICAP aMDEA Solution?  If there is no negative side, why should conventional, aMDEA still be used?
A 4a.2:           I can only share the experience at our plant and no negative side was observed at our plant against the HICAP quantities added. However, evaluating effectiveness and suitability of HICAP for other plants is something between the licensor and the respective plant / client. 

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By :    C. M. T. Britto – Rashtriya Chemicals and Fertilisers, India
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Q 4a.3:           Did you face any foaming problems in your aMDEA system? 
A 4a.3:           No


Q 4a.4:           Do you monitor pressure drop across aMDEA absorber and flash vessel (online)?  If yes, is the measurement reliable?
A 4a.4:           On line reading is available across the Upper - lean absorber and across both the flash vessels. Accuracy can vary but it is the trend that is given more consideration.

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By :    Upendra Singh – Chambal Fertilisers and Chemicals Ltd., India
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Q 4a.5:           Plant operates at 2.5 S/C. What is the design S/C for plant?  Wish 2.5 S/C, is there high CH4 recycle to furnace because it reduces H2 generation?
A 4a.5:           Design S/C ratio of this plant is 2.5. It has ammonia and hydrogen recovery units and operates on the design ratio of 2.5.


Q 4a.6:           What guarantee BASF gave with “HICAP” solvent – w.r.t. CO2 slip?
A 4a.6:           500ppm


Q 4a.7:           Any solution draining was done to accommodate “HICAP”? If yes, where drained?
A 4a.7:           40 tons of standard aMDEA solution was swapped with HICAP. Drained solution was stored in the aMDEA solution tank and a certain quantity of HICAP was also added in the tank to match the stored solution composition with the in service solution. The purpose of this was to use this drained quantity as make up during operation.


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Paper 4b:   Energy Efficiency and CO2 Generation in Indian Ammonia Plants

 

Authors :    Dr. S. Nand and Manish Goswami - The Fertiliser Association of India

 

Presenter:  Dr. S. Nand - The Fertiliser Association of India

 

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By :    Venkat Pattabathula – Incitec Pivot Ltd., Australia
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Q 4b.1:           The energy efficiency figures reported were in GJ/t. Please confirm whether those were HHV or LHV?
A 4b.1:           The energy efficiency figures are reported in LHV.


Q 4b.2:           What do you mean by Forced Downtime?
A 4b.2:           Forced downtime in a plant is when plant is shutdown due to any reasons like equipment failure, disruption in supply of gas or utilities, labour problems, etc. Shutdown taken for scheduled maintenance planned before hand is not counted as forced shutdown.

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Paper 4c:    Urea Reactor Height Extension to Increase Capacity

 

Authors :    Hermann Kernberger - Schoeller-Bleckmann Nitec GmbH (SBN), Austria

Bob Edmondson - Yara Belle Plaine, Canada

 

Presenter:  Hermann Kernberger - Schoeller-Bleckmann Nitec GmbH (SBN), Austria

 

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By :    G. K. Gautam – IFFCO Aonla Unit, India
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Q 4c.1:           What methods were employed to avoid PWHT & reduced residual stress in closing weld seam.?
A 4c.1:           At first the review of the type of Reactor and the materials used are the determining factors whether a modification as executed can be applied. The welding was done with carefully selected materials and special attention has been paid to pre heating and soaking afterwards.


Q 4c.2:           Hardness measurement were done or not ?
A 4c.2:           Hardness measurements have been executed during the welding/ welders qualifications as well as after welding.


Q 4c.3:           Leak detection system hose were extended?
A 4c.3:           Leak detection system was adequately modified to the latest standard.


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By :    B. G. Singh – NFL Nangal Unit, India
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Q 4c.4:           The old urea reactor, a multi-layered vessel, was welded with another add-on vessel, also a multi-layered vessel. The weld joint is uniform & not multilayered.  How does it will affect the life of the reactor?
A 4c.4:           the weld joint to connect two multilayered barrels is using the temper bead method, which is the standard weld procedure for such weld joints.


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By :    Kang Xu – Praxair, U.S.A.
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Q 4c.5:           How was the hydro test done in the new vessel?
A 4c.5:           No hydro test was executed after completing the work since there was no need due to statutory requirements and for the liners to yield. The new shell section had already been subjected to Hydrostatic test during fabrication in the shop. The field weld was subjected in line with the code requirements i.e.  Phased Array UT-test after one third, two thirds and full thickness of the weld.


Q 4c.6:           To confirm no PWHT for the seam weld?
A 4c.6:           Confirmed. The connection weld between multilayered shell section do not require PWHT

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By :    Alfredo Medina Vilar – Jacobs Consultancy, Venezuela
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Q 4c.7:           In the event of corrosion at the end of the 316L-UG Liner to the weld overlay and from there to inside the reactor, how it will be determined / prevented?
A 4c.7:           the reactor will be subject to regular inspections as is normal in a urea plant, at intervals of 4 to 6 years. The techniques for inspection are the usual ones, UT, EC and visual. a weld overlay is not any longer present; the connection welding is made by a Safurex connection weld (liner to liner)


Q 4c.8:           As this was a reactor for 2000 MTPD and now is over 3000 MTPD will the 316 Liner affected by erosion / corrosion?
A 4c.8:           Since the operating conditions are not changing also the corrosion rate will not change. An advantage is that after the shell extension no longer 316L will be exposed to condensing conditions at                 the top of the reactor and with this the chance for active corrosion will be eliminated

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By :    Dorothy F. Shaffer – Baker Risk
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Q 4c.9:           Was a hydro test performed after the addition was completed?
A 4c.9:           No hydro test was executed after completing the work since there was no need due to statutory requirements and for the liners to yield. The new shell section had already been subjected to Hydrostatic test during fabrication in the shop. The field weld was subjected in line with the code requirements i.e.  Phased Array UT-test after one third, two thirds and full thickness of the weld.

Q 4c.10:         Was the foundation found to be adequate or were modifications required to accommodate the higher height & weight?
A 4c.10:         The structure had been built so rigidly that no extra precautions were needed as was the case with the foundation. The existing foundation could carry the extra load.

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By :    Muhammad Abdullah – Fauji Fertiliser Company, Pakistan
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Q 4c.11:         During welding high temperature and heat is generated. Did you remove the stainless steel lining from the barrel of old reactor before welding?
A 4c.11:         No since there was no need to do so. We calculated with help of the theoretical heat input the zone exposed to temperatures above 400 deg C; in that area the liner had been spared initially and then covered by weld deposit

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Paper 4e:     Urea GV Absorber Shell Leak in Ammonia Plant-II at IFFCO, Aonla Unit, India

 

Authors :     A K Maheshwari, Rajiv Srivastava, and G K Gautam - IFFCO Aonla Unit, India

 

Presenter:     Rajiv Srivastava, and G K Gautam - IFFCO Aonla Unit, India

 

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By :    David Firth – Quest Integrity Group, New Zealand
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Q 4e.1:           Has the actual corrosion allowance been calculated for the damaged area to API-579 and if so what limit was found. 
A 4e.1:           The corrosion allowance has not been calculated as per API 579 FFS Program. The local metal loss due to corrosion was carefully built up by using special welding process to obtain minimum required design thickness plus corrosion allowance of 3mm. Minimum required thickness of 43mm was obtained throughout the affected area. At some places the thickness is higher than 43 mm due mainly to welding built up process.
As weld built up is considered having provided minimum design sound wall thickness without having any flaws, FFS according to API was not considered. However, the area will be thoroughly inspected in the next turnaround in addition to the online thickness measurement of the pressure shell from outside on accessible areas.


Q 4e.2:           Has the use of a coating been considered after the weld repair?
A 4e.2:           No


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By :    Ken Wohlgeschaffen – Chevron
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Q 4e.3:           Is the CO2 removal system in the other ammonia plant also GV, and if so, what is different about that plant and why wasn’t similar corrosion experienced there?
A 4e.3:           Yes, There is no 5th Bed in Aonla-I Ammonia plant. Hence no similar corrosion problems experienced in that plant.


Q 4e.4:           Was GV consulted on this problem and what did they say was the root cause (s) of the corrosion?
A 4e.4:           Yes, They were contacted.  In their opinion, failure of No. 5 bed limiter locking mechanisms is likely the root cause. This mechanical failure could eventually damage the passivated layer by scratching the column wall, thus non-passivated metal to corrosion attack.

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By :    Venkat Pattabthula – Incitec Pivot Ltd.
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Q 4e.5:           What was the purpose of Bed No. 5?
A 4e.5:           To dampen the effect of level fluctuations and also act as Vortex Breaker.

Q 4e.6:           What are vanadium levels?
A 4e.6:           Normally Vanadium level is kept above 0.5 % as V2O5

Q 4e.7:           Do you carryout passivation on each start up ?
A 4e.7:           Yes, We carryout static Vanadation and Dynamic Vanadation during each start up of the Ammonia Plant after long shutdown.

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By :    Fahad Alsawat – SAFCO
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Q 4e.8:           Do you consider the repair, which has been adopted, is a temporary repair or permanent repair?
A 4e.8:           The repair is considered as permanent repair subject to inspections in turnarounds.


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By :    Tarek Okasha – Egyptian Ferti;zers Co., Egypt
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Q 4e.9:           Was there any changes in differential pressure or foam content prior to leakage?
A 4e.9:           No, There was no evidence of Delta P increase or foaming tendency prior to leakage.

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By :    Bode Agagu – Notore Chemical Industries Limited
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Q 4e.10:         Have you considered the provision of an SS liner for the section of the vessel due to its in accessibility now that you have experienced corrosion?
A 4e.10:         No, SS liner is not considered.

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Paper 4f:      Stress Corrosion Cracking in an Atmospheric Ammonia Storage Tank

 

Authors :     Wim Versteele and Arie de Bruyne - Yara Belgium S.A.

Giuseppe Franceschini - Yara International ASA

 

Presenter:     Wim Versteele - Yara Belgium S.A.

 

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By :    Fahad Alsawat – SAFCO
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Q 4f.1:            What is the internal inspection frequency for atmospheric Ammonia Storage Tank in Yara Plants. 
A 4f.1:            The inspection frequency of the tanks is based upon the EFMA risk evaluation as described in EFMA document : ‘Guidance for inspection of refrigerated ammonia storage tanks, 2008’.  Inspection does not automatically imply internal inspection, as Yara also applies non intrusive inspection using UT techniques if the tank design allows for it and if the preconditions for non intrusive inspection ( par 5.5.1 of above EFMA guidance) are obtained.

Q 4f.2:            Did you explore to apply any coating internally?
A 4f.2:            No, we did not


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By :    Abdulrahman Mohammed Al-Hafs – Maaden Phosphate Company, Saudi Arabia
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Q 4f.3:            How you start measuring O2 content in the importing ammonia from truck?
A 4f.3:            Several measuring devices are available on the market which allows determination of oxygen in gaseous ammonia at the required low levels of concentration. Appendix 4 of EFMA document: ‘Guidance for inspection of refrigerated ammonia storage tanks, 2008’ provides additional info on this issue. 

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By :    Venkat Pattabthula – Incitec Pivot Ltd.
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Q 4f.4:            Has Acoustic Emission Testing (AET) been done ?
A 4f.4:            On the tank in question, AET has not been applied            


Q 4f.5:            To what levels of O2, the tank purged with N2 during commission?
A 4f.5:            The maximum levels of oxygen to switch from one commissioning phase to another are specified in par 7 of EFMA document: ‘Guidance for inspection of refrigerated ammonia storage tanks, 2008’


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By :    SK Safi Ahmed – Karnaphuli Fertilizer Company Limited, Bangladesh
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Q 4f.6:            Whether the bottom plate welds checked  for cracks.
A 4f.6:            Yes, it was   

Q 4f.7:            Course No. 9 to 11: 8.4/ 8/ 8mm – what was max depth of crack (you mentioned 1.3 mm – 5 mm) critical crack size?
A 4f.7:            In courses 10 and 11, no cracks were observed. In course 9, a limited number of cracks with dimensions below the critical crack size were found.         

Q 4f.8:            How to monitor and control O2 content in vapors from truck and train?
A 4f.8:            Several  measuring devices are available on the market which allow determination of oxygen in gaseous ammonia at the required low levels of concentration. Appendix 4 of EFMA document : ‘Guidance for inspection of refrigerated ammonia storage tanks, 2008’ provides additional info on this issue. Train wagons returning in service after maintenance or inspection represents the most important risk of introducing oxygen into the system, as most of the workshops performing such maintenance or inspection do not have the appropriate purging facilities.            

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By :    Reinaldo Caldera V. – Petroquimica de Venezuela
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Q 4f.9:            How can we avoid SCC during a commissioning?
A 4f.9:            Recommendations for commissioning are given in par 7 of EFMA document : ‘Guidance for inspection of refrigerated ammonia storage tanks, 2008’           

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By :    B. G. Singh – National Fertiliser Limited, India
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Q 4f.10:          What are the recommended guidelines for internal inspection of Atmospheric Ammonia Storage Tanks?
A 4f.10:          Recommended guidelines for inspection of atmospheric ammonia storage tanks are given in EFMA document : ‘Guidance for inspection of refrigerated ammonia storage tanks, 2008’, both in terms of inspection frequency as well as in terms of inspection scope and methods. This EFMA document also allows non intrusive inspection , if some preconditions are met.     

Q 4f.11:          What code for internal inspection & repair, if required?
A 4f.11:          The maximum grinding depth has been determined based upon a ‘ Fitness for service ‘ evaluation.            

Q 4f.12:          How to remove residual ammonia from the tank?
A 4f.12:          The tank should be emptied as far as possible using pumps. The remaining tank inventory should evaporate gradually by the normal heat input in the tank.   

Q 4f.13:          Detailed Procedure for decommissioning, inspection, repairs and re-commissioning of these tanks?
A 4f.13:          For each tank , a procedure should be developed based upon the guidelines given in par 7 of EFMA document : ‘Guidance for inspection of refrigerated ammonia storage tanks, 2008’

Q 4f.14:          What are the regular checks/ monitoring systems for an operational tank strength?
A 4f.14:          During operation, external UT inspection can be done to confirm the absence of Stress Corrosion Cracking , if the tank design allows for it.         


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By :    Dorothy F. Shaffer – Baker Risk
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Q 4f.15:          SCC has been a concern for some time. Did the tank fabricator have a yield strength range maximum at the time of fabrication?
A 4f.15:          At the time of construction of the tank, the tank fabricator was not given a yield strength maximum. If a new tank was to be constructed, a maximum yield strength should be given as well.  

Q 4f.16:          Would you recommend a check of yield strength?
A 4f.16:          If a new tank was to be constructed, a check of the yield strength should be part of the Quality assurance plan to verify minimum as well as maximum yield strength.          

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By :    Upendra Singh – Chambal Fertilisers and Chemicals Ltd., India
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Q 4f.17:          Is there any statutory requirement for internal inspection of Ammonia Tanks in France.
A 4f.17:          No statutory requirements as for pressure vessels are present. Inspection requirements are defined in the operating permit for the site.      

Q 4f.18:          During intrusive inspection of tank, how care is taken to avoid condensation on tank surface from outside?
A 4f.18:          Condensation can be prevented by installing a local sheltered zone at the spot where the insulation is removed and introducing dry air into this shelter.        


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By :    Kang Xu – Praxair
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Q 4f.19:          Was any PWHT done to the weld.
A 4f.19:          No PWHT was applied.    

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Paper 5a:     Ammonia Vapor Cloud from Vent Stack of Safety Relief Valve Collector System

 

Authors :     Hans H. Wagner - INEOS, Cologne

 

Presenter:     Hans H. Wagner - INEOS, Cologne

 

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By :    Dorothy Shaffer – Baker Risk
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Q 5a.1:           There was a similar serious incident in a urea plant years ago. Have you looked at the hazard potential for vent systems in other types of process units as well? 
A 5a.1:           The incident had been communicated within our company and in various meetings of ammonia producers and consumers.

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By :    Patric de Konink – OCI Nitrogen, The Nethrelands
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Q 5a.2:           Did you also consider the design temperature of the line behind the safety valve.  Temperature of liquid NH3 could get as low as – 30 deg C? If N2 Gas is used to purge the Line?
A 5a.2:           The pipe system is designed and fit for low temperatures. Temperature measurements with low alarm for indication of gas release through safety valves were present in the original design and continue to be part of the safety concept.

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By :    Dallas Robinson – LSB Chemical Corporation
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Q 5a.3:           For the 107 pump – For the requirement to have the discharge valve partially open – Was this requirement an operator administrative control procedure or an instrument safety interlock?
A 5a.3:           Until the incident it was not required but practiced by some operators. As an immediate action of the incident it was required by procedure. With the later redesign of the pump discharge piping and removal of the safety valve it became obsolete.

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Paper 5c:     Management of Dissimilar Metal Welds

 

Authors :     Colin Alexis - PCS Nitrogen Trinidad Limited

 

Presenter:     Colin Alexis - PCS Nitrogen Trinidad Limited

 

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By :    Venkat Pattabathula – Incitec Pivot Limited
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Q 5c.1:           Did PCS N2 experience any failure of DMWs?
A 5c.1:           Yes PCS has experienced about three failures in Critical DMW’s. These were located in different areas/systems, and across different Ammonia plants. These were the genesis for the DMW Management Program.

Q 5c.2:           Do you have any DMWs in reformer? 
A 5c.2:           There is a DMW on the top of the catalyst tubes, a 304 SS flange connected to the centrifugally-cast nickel alloy tube. Due to the relatively ‘lower’ operating temperature of this weld, located outside of the firing zone, and both the parent metals being an austenitic structure it is generally not considered a critical DMW.

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By :    Kang Xu – Praxair
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Q 5c.3:           What kind of thermal cycles did the subject joints experience before exhibiting cracks?
A 5c.3:           The exact number has not determined. The DMWs that PCS has had failures on had been in service for a number of years. During this period these would have experienced a number of thermal cycles, from plant outages, both planned and unplanned.


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By :    Dorothy F. Shaffer – Baker Risk
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Q 5c.4:           For clarification, does your criterion for critical welds need to meet all three items?
A 5c.4:           In general yes. If a DMW has one of its operating parameters below the stated criteria, but is on a critical system or has experienced failures in the past, then it will be treated as critical.    

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Paper 5d:      Cracking of a Closing Weld in a Secondary Autothermal Reformer in a Mega Methanol Plant

 

Authors :     D M Firth, Q Rowson, A Saunders-Tack, C Thomas, K Lichti and J Soltis - Quest Integrity NZL Limited

P Tait - Methanex Global

M Wei, R Dookran, S Ramjattan and W Boodram - Methanex Trinidad

 

Presenter:     D M Firth - Quest Integrity NZL Limited

 

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By :    John McGrath – Incitec Pivot Limited
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Q 5d.1:           Has this problem been seen in other methanol plant secondary reformers?
A 5d.1:           Not as far as we are aware. However the risks of CO2 SCC has been listed in Risk Based Assessments of similar secondary reformers especially at welds that may not have had an adequate PWHT and operate well below the dew point.


Q 5d.2:           Would plant burning non-standard amounts of air in secondary reformer be more susceptible? 
A 5d.2:           The susceptibility to cracking may be associated with the partial pressure of CO2 and the CO/CO2 ratio. However, once condensate is formed this may make little difference. 

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