GRIP TEST REPORT NOVA SIRIA, ROLETTO, 07.10.2013 1. Premise The present report covers the witnessing of the test conducted in the Nova Siria Factory in Roletto (Torino, Italy) to verify the behavior of high pressure fittings type MGR F10 1500 10 1515 with the new double grip system. The test has been executed on a spool of pipe OD 1500, 1600 mm long, supplied by KWH Pipe Poland. The primary scope of the test has been to verify both the hydraulic tightness and the action of the double grip system of flanged compression couplings installed on a spool of HDPE pipe, and has been conducted in three stages: A. according to the specifications issued by the Client, with a cycle of pressurization and control of tightness and grip resistance B. according to Nova Siria internal programs, extending the test to verify the tightness and grip resistance under long term operating pressure C. executing a crash test increasing the pressure until the start of leakage, to verify the the grip axial resistance.. The test has been fully successful in the first 2 stages/ In the third stage, during the crash test no movement of the pipe in the coupling has been recorded. Drop leaks have started around 21 bar; the test has stopped at 23 bar. At the end of the test, the HDPE pipe showed only incisions due to the grip elements, but no sign of slippage. 2. Pipe The section of pipe supplied by the client KWH Pipe Poland Sp. z o.o was: WehoPipe DN/OD 1500 x 88,9 SDR17 PN10 PE100 (acc.to AT/15 8441/2010) OD 1508 1510; Thickness 89,2 96,6: Ovality 22,0 34,0 Elongation at break >350 % (PN EN ISO 6259 1/ISO 6259 3:1997) GRIP TEST REPORT-en.docx - page 1 of 9 date 17/12/13
Length 1800 mm It shall be noted that the diameter 1500 is foreseen by the Polish Standards, while not considered in the EN Standards.. The modulus of elasticity of the pipe is within the standard range for PE 100. The pipe has shown a visible increase in diameter, but, due to the limited length, only a minor elongation. However, the variation in diameter and the relaxation of the material has contributed to oscillations of the pressure, as visible in the diagrams. It has been found that the pipe spool presented a slightly higher outer diameter and a visible ovalization. NS has been obliged to reduce the ovalization with internal spanners in order to insert the couplings without scratching the pipe. 3. Flanged compression couplings NS has produced for the test 2 flanged compression couplings with double grip system, rated for 10 bar operating pressure and 15 bar test pressure. In relation to the test scope, it has considered unnecessary to coat the couplings with the standard Rilsan corrosion coating. Dimensional characteristics of the 2 couplings, whose classification is MGR F10 1500 10 1515, have been: Nominal diameter: 1500 mm Tolerance on diameter: 30 mm (between 1485 AND 1515 mm) Length after compression on pipe OD: 2408 mm Pressure rating (nominal and operation): 10 bar / 1 MPa Test pressure: 15 bar / 1,5 MPa The coupling components are shown as split and as assembled in the figure above. The photo shows a phase of the coupling assembly. It is well visible the sealing gasket and the back follower with the grip assembly. GRIP TEST REPORT-en.docx - page 2 of 9 date 17/12/13
Torque on closure bolts: 200 Nm Torque on grip bolts: 160 Nm The assembly has presented some minor problems due to the pipe OD and ovalization, since the couplings are custom built on a given OD with a tolerance, in case of the use of a grip system, OD=±15 mm. As mentioned, the 2 flanged grip couplings have been designed for 15 bar test pressure. The drawing shows the applied torque values: On the followers (for the correct gasket compression) 200 Nm On the twin grip elements, 170 200 Nm producer in order to define the outer layer characteristics. In the test, a 160 Nm torque has been used. In case of presence of grip system, the coupling shall be properly centered. For HDPE, the torque is limited to avoid a relevant penetration of the grip elements in the pipe wall. The torque could be greater for steel, but the eventual penetration on the external coating shall be taken into consideration. For GRP/FRP the eventual use of a single or double grip system shall be studied with a pipe The assembled test piece has been installed on 2 sleds. Each sled has been welded to the closure flanges and retained loosely with threaded rods, calculated to resist to the movement of the couplings in case of a sudden loss of grip. It was not expected that the test piece would have presented a visible axial movement; nevertheless one of the two sleds was free to move on steel GRIP TEST REPORT-en.docx - page 3 of 9 date 17/12/13
rods, working as rollers. The movement was controlled by measuring the distance of the internal flange of the grip and the pipe diametric deformation on the circumference. In the photo, the ruler on the pipe shows the center deformation. The lateral white marks have been drawn as reference for the movement of the coupling on the pipe. During all the test deformations and elongations have been measured. It shall be mentioned that the couplings have been only sandblasted to NACE No. 4/SSPC SP7 (Sa.1) and left uncoated, instead sandblasting to NACE No. 2/SSPC SP10 (Sa.2.5) as required for the application of the standard Rilsan corrosion coating. This has likely caused some problems in the settlement of the gaskets (particularly at the right end) and the minor point leaks which have been observed mostly during the crash test. 4. Preconditioning Before the test, the system has been subject to a preconditioning cycle, during which the variations of the system dimensions (diameter and length of the spool) have been observed. The pressurization has had also the scope to release the internal tensions in the heavy wall of the spool. The preconditioning has been executed as follows: Raising the pressure to 15 bar with steps of 3 bar/5 min total time 25 min Decreasing the pressure to 0 Leaving depressurized for 30 min. Repeating the same cycle one more time. During the preconditioning it been has observed a variation of the diameter both in correspondence of the grip system and of the spool center. At the two ends the diameter has changed between 1505,6 mm and 1511,9 mm, while at the center it has passed from 1505,6 mm to 1518,4 mm. The change of 3,15 mm on diameter near the grip flanges has obviously be attributed to the pipe, and has been permitted by a first settling of the grip elements. No initial penetration of the teeth of the grip system has been visible at this stage. The length of the spool between the flanges has shown a change less than 5 mm in average, also likely due to the settling of the grip. GRIP TEST REPORT-en.docx - page 4 of 9 date 17/12/13
5. Phase A The test of tightness under test pressure and of axial resistance of the grip has been requested by the Client who supplied the pipe. The test has been made in two following steps: 1 Hydraulic tightness 1 hour after the end of the pre conditioning, pressure has been raised to 15 bar in 10 minutes The 15 bar pressure has been maintained approximately stable by reestablishing the pressure with pumping. The period of stabilization wad indicated as 10 min. The pumping has been stopped for 60 min. observing the decrease of the pressure due to the pipe expansion. The limit of pressure drop had been indicated in 30% of the test pressure The pressure is further reduced suddenly by 10/15% of the test pressure The pressure curve is observed for the following 30 min. It shall be observed an initial increase in the pressure and a following stabilization at a constant value. The graph hereafter shows the trend of the curve. It is interesting to see how the pressure was decreasing more rapidly at the start of the maintaining period than at the end, due to the different speed of the change in dimensions of the pipe spool. Further on, the decrease has been only 1,2 bar against an expected maximum (indicated by the client) of 4,5 bar, therefore acceptable After the final decrease of 1 1,2 bar, the pressure has jumped up by some tenth of bar and at the end of the 30 minutes has still remained above the initial level. GRIP TEST REPORT-en.docx - page 5 of 9 date 17/12/13
According to the requests, the tightness test has had positive results. The pressure has kept a positive performance. The dimensional values of the pipe have remained identical to the ones mentioned above, meaning that the changes take place at short term and do not increase so fast with the creep to be visualized. 2 Mechanical resistance of the grip system (anti slippage test) The test has been conducted as follows: After a short rest time, the pressure has been raised to 15 bar in 10 min The decrease of the pressure in the time is observed for a period of 1+ hour The pressure is decreased to 0 After a first period of about 30 min, the pressure is raised again to 15 bar, let decrease for about 30 min. and brought again to 0 The cycle is repeated once for shorter time (as shown in the diagram) This cycle has had a duration of 3,5 hrs. (first part of the diagram below). During the repeated increase/decrease in the pressure no leak, nor movement of the couplings has been noted. The values of diameter and distance between the grip flanges have remained practically unchanged. The second part of the test has been therefore successful. 6. Phase B The phase be has been executed by common decision as an accessory to the requested Phase A. At the end of the preceeding A2, the pressure has been increased again to 15 bar, decreased to the 10 bar operating pressure and after that left to stand for 16 hours without any intervention. GRIP TEST REPORT-en.docx - page 6 of 9 date 17/12/13
It can be noted from the diagram that after the closure of the valves, the pressure has immediately slightly increased and the it has continuously decreased until reaching approximately 9,8 bar, with a minimal change. Again, at the control after the 16 hours, it has been verified that there have been no detectable changes in the dimensional parameters. It shall be noted that the test equipment has remained in the open during the night (from 1800 to 0800 of the following day), with a drop in the temperature from 22 of the day to 14 15 in the night. 7. Phase D After the observation of the situation at the end of Phase C, it has been decided to test the system till the maximum resistance. It has been called crash test and has been intended to give the limits of the hydraulic tightness and of the mechanical resistance of the grip system. The scale has been changed, expecting to be able to reach 24 25 bar. The pressure has been increased slowly, stopping for some time at 17, 21, 22,2 and 22,8 bar observing in the meanwhile the behavior of the system. The pressure has been increased further to 22,1 bar, detecting at this stage the start of a leak at the right flange. Despite it, the pressure has been further raised to 23 bar, but it was starting to decrease immediately due to the increase of the leaks from the flange. For safety, it was decided to stop the test and release the pressure. 8. Dismantling of the system After the test, the pipe spool has been extracted and the gaskets of the couplings and of the flanges have been verified. GRIP TEST REPORT-en.docx - page 7 of 9 date 17/12/13
The results of the observation have been the following: Pipe surface: The indentations of the grip elements are different in the external grip (left in the photo) and in the internal one. Since the torque on the bolts of the grip elements have been equal for the 2 sets, it may mean that each single contact has been slightly different in the orientation, also because the fixing bolts have some tolerance in the inclination, which permits movements in the vertical plan. Inclination and rotations can be seen in the photo. The indentation is deeper in the internal set but not the same in all positions. Maximum measured depth of the indentations has been 2,7 mm with an estimated average of less than 1,8 2 mm, well within the tolerance for surface scratches and indentations indicated commonly as 10% of pipe thickness. There is absolutely no visible sign of excavation with removal of material due to axial movement of the grip elements. With reference to the signs made in front of some elements, no movement of the pipe in the coupling has taken place To the right of the photo, the sign of the gasket is well visible. Measuring the track, it results that the gasket has compressed regularly in most of the areas, with no significant sign in the gasket of the left coupling which could theoretically justify the dropping. Coupling s gasket No particular problem has been observed in the gaskets of the couplings, except some small incisions likely due to the uncoated surface of the coupling and of the follower. It shall be mentioned that in operation the gaskets require 2 3 days before completely sitting in position. Flange gasket. The installed flange gasket has been a traditional flat flange PN10. The extension of the test to 23 bar has caused a crack in the gasket which has caused the leak and suggested to interrupt the test. GRIP TEST REPORT-en.docx - page 8 of 9 date 17/12/13
9. Conclusions The test has been successful under all aspects. Conclusions are: No leak has developed in the coupling itself at pressures well above the design test pressure. The significant leak which has started around 2 2,1 time the operating pressure has been without doubts due to the flange s gasket. No movement of the pipe in the coupling has taken place. The double grip system is therefore fully efficient against axial movements. There is no sign of surface erosion to indicate movement. It is assumed that the depth of the indentation is more due to the inclination of the grip surface (incisions are largely different in direction and depth) than on the effect of the axial pull. In the last phase of the test, the force on the flanges has been roughly 415 tons. Considering that the extension of the grip line has been in this case 2x470 cm (twice the pipe circumference) the resistance can be estimated in 900 kg/cm circumference. This value can be assumed as an indicative value to assess the capability of the coupling to resist to axial pull. The corresponding axial tension in the pipe has therefore been around 104 kg/cm 2. In practical terms: straight couplings with double grip can be used for joining pipes under axial pull in axial force conditions which will be evaluated case by case, but will be in most cases greater that the axial resistance of the pipe flanged couplings with double grip present the same resistance to axial forces and can be used without problems as test ends, and more generally as flanged connections between two different types of pipe the test has resulted positive for HDPE pipes, without damaging the pipe surface, which was the major consideration. For steel and cast iron, it is expected that the results will be even better, eventually modifying the grip surface or the grip material. For GRP, the possible use can be obtained again by changing the type and size of the surface of the grip elements, in order to reduce the specific pressure on the pipe skin to avoid superficial cracks or deformations. The study on other pipe materials will be conducted in the next future. Dr.Ing. Carlo Avanzini GRIP TEST REPORT-en.docx - page 9 of 9 date 17/12/13