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Pressure Testing Safety | Concrete | Corrosion

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DGEP/SE & DGEP/TDO/PJC SAFETY FEEDBACK NOTICE 16-2002 THE HAZARDS OF PRESSURE TESTING Why this subject ? During hydrotesting and pressure testing operations incidents sometimes happen. This Safety Feedback Notice provides some typical examples which can be used as an aid in highlighting the hazards and dangers involved are what are often seen as routine operations. Details of the 5 incidents 1. Hydro-test of a new vertical vessel The root cause of the incident is not fully known but there was
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  DGEP/SE &DGEP/TDO/PJC SAFETY FEEDBACKNOTICE 16-2002 For further information please contact Jean-Marc PECQUOIS  ( + 33 (0)5 59 83 45 50  * jean-marc.pecquois@totalfinaelf.com  DGEP/SE 16/2002 October 2002 Page 1/4 THE HAZARDS OF PRESSURE TESTING Why this subject ? During hydrotesting and pressure testing operations incidents sometimes happen. ThisSafety Feedback Notice provides some typical examples which can be used as an aidin highlighting the hazards and dangers involved are what are often seen as routineoperations. Details of the 5 incidents 1. Hydro-test of a new vertical vessel The root cause of the incident is not fullyknown but there was some thought that hydro-testing with very cold water was acontributing factor.Fortunately no injuries occurred. 2. Filling of a vertical tank The filling of the tank was made with water from a fire hydrant.The top of tank blew off because therelief valve could not displace the airfast enough for the volume of waterthat was being pumped in.Fortunately no injury happened, but anoperator was ontop of the tank afew secondsbefore.   Wall Thickness  DGEP/SE &DGEP/TDO/PJC SAFETY FEEDBACKNOTICE 16-2002 For further information please contact Jean-Marc PECQUOIS  ( + 33 (0)5 59 83 45 50  * jean-marc.pecquois@totalfinaelf.com  DGEP/SE 16/2002 October 2002 Page 2/4 3. Emptying of a vertical tank The collapse of this tank happened while it was being emptied. A plastic sheet protecting theroof was trapped in the vent;hence a vacuum was caused.There was no injury. It should benoted that this type of incidentis not that unusual. 4. Sphere collapse The accident happened during the filling of a2000 m 3 LPG sphere. Its legs collapsed. One person was killed and one seriouslyinjured. At the time of the accident, the sphere wasapproximately 80% full of fresh water.The vessels last hydro-test was 10 years agoand the last inspection of its legs was 5 yearsago.Severe corrosion of the legs under theconcrete fire protection was the main cause.The corrosion occurred due to water ingressbetween the concrete and the steel legs.The water protective cap located over the concrete was not sufficient to keep the water out.After the accident, it was verified that the steel legs had thickness reductions of up to 8mm,with pitting holes of up to 10cm 2 .After analysis and tests, it has been found that the following factors caused the collapse: ♦ Water caps over the fire-proofing concrete were of poor design thereby lettingwater penetrate between the steel beams and the concrete.   The plastic sheeton top of the tank  DGEP/SE &DGEP/TDO/PJC SAFETY FEEDBACKNOTICE 16-2002 For further information please contact Jean-Marc PECQUOIS  ( + 33 (0)5 59 83 45 50  * jean-marc.pecquois@totalfinaelf.com  DGEP/SE 16/2002 October 2002 Page 3/4 ♦ Vertical cracks in the concrete let water in. ♦ Repairs had been done to the concrete, but with poor workmanship. ♦ The new concrete had not adhered to the old concrete, again letting water in. ♦ The deluge system had been tested with salt water, increasing the possibility ofcorrosion. 5. Emptying of a gear box To speed up the removal of 250l of oil from a gear-box, the gauge hole was plugged and thebreather was connected to the 6 bar air network.The gear box exploded, and threw missiles around seriously damaging surrounding pipingand structure. Fortunately there was no injury. SPECIFIC RECOMMENDATIONS For each case the specific recommendation are generally obvious : 1 st incident : Water temperature is critical when hydro testing. TFE specification (GSPVV 211) states that both metal and water temperature during pressure testing shall bemaintained at least at 16°C or at least 10°C above the impact test temperature of themetal. 2 nd and 3 rd incidents : venting systems shall be inspected and checked before fillingand emptying operations. 4 th incident : Is a maintenance problem ? Before testing an old vessel, a completeinspection must be performed visually and with NDT. This inspection shall include thevessel, nozzles, appurtenances, and supporting structures. 5 th incident : obviously a gear-box is not a pressure vessel, but productivity may leadto a risky attitude. Breather connectedto air compressor  DGEP/SE &DGEP/TDO/PJC SAFETY FEEDBACKNOTICE 16-2002 For further information please contact Jean-Marc PECQUOIS  ( + 33 (0)5 59 83 45 50  * jean-marc.pecquois@totalfinaelf.com  DGEP/SE 16/2002 October 2002 Page 4/4 RECOMMENDED ACTIONS FOR PRESSURE TESTING Tests may be a routine operation pressure for you, however, do not forget that in fact pressurisation is energy storage. Its instantaneous release works as a bomb and may cause severe damage to persons and equipment. M As for most of the operations, good preparation is essential to avoid incidents. It is recommended to use the following check list :  ð   A detailed check list procedure must be prepared as per the standards and specifications. It must cover the testing operation from filling up to emptying the vessel. ð   G  ood co-ordination is essential to avoid performing the hydro-test at the same time as other operations. A work permit procedure / Job Hazard Analysis should be used, ð   T  he equipment should be in good condition and adequately maintained and certified, ð   T  esting equipment must be as far as practicable from the recording and pumping station, ð   T  esting equipment (even if brand new) must be checked. ð   T  he test area must be roped off, ð   D  uring the test, from filling up until the end of depressurisation, all non-essential people must be out of the test area, ð   T  he test crew must attend a toolbox talk, ð   A ll people must wear their appropriate PPE, ð   I  nspection for leaks shall be performed at least 15mn after the test pressure has been reached and only by designated personnel, ð   N  ever tamper with, or tighten any fittings (i.e. connections, bolts, hoses and the like) while under pressure or during pressure-up stages. M Also  do not forget that as pipeline pigging is similar to pressure testing. As a minimum the same checklist should be used.
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