1. Helicoflex Seals Stephen Haywood Rutherford Appleton Lab & Martin Gibson With input from Jason, Ian and Garlock

2. 4 Apr 2006 Helicoflex Seals 2 Stephen Haywood The Order Ordered on Fri 10 Feb. Arrive Mon 27 Mar – 6 weeks later. Cost £23k Understood to be a simple change of coating from Al to Cu – therefore similar mechanical properties. Qualify surface effects – crushing of Cu into Cu-Ni Housing. Garlock quoted and supplied a “  ” Seal – in order to make easier to compress.

3. 4 Apr 2006 Helicoflex Seals 3 Stephen Haywood First Assessment Martin Gibson was ready to test Seals when they arrived. Immediately realised they were difficult to tighten:  Not able to completely compress.  Broke Ti bolt. Should bottom out Seal:

4. 4 Apr 2006 Helicoflex Seals 4 Stephen Haywood Bottoming Out Seal Bottoming out is important:  Gives correct compression of Seal (good sealing, retain elasticity provided by internal spring).  Requires “groove” in Housing to be correctly designed.  When clamped in position, ensures that joint cannot flex.  Flexing may allow Seal to be compressed and then since elasticity is small (10%?), may not spring back and result in leak. Seal nominally 1.64 mm (measure 1.68 mm). Housing groove 1.2 mm Compressed by ~0.32 mm. Implies 0.12-0.16 mm to go until bottom out.

5. 4 Apr 2006 Helicoflex Seals 5 Stephen Haywood Seals in Housings

6. 4 Apr 2006 Helicoflex Seals 6 Stephen Haywood PPF0

7. 4 Apr 2006 Helicoflex Seals 7 Stephen Haywood Housing

8. 4 Apr 2006 Helicoflex Seals 8 Stephen Haywood Investigation Dissect old Al and new Cu Seals. Jacket is solid metal. Cu has larger Young’s Modulus than Al (factor of 2). Cu supposed to be 0.25 mm thick; Al 0.30 mm – but Cu looks thicker (optical effect ?). Cu Seal is much harder to twist. “  ” Seal is not quite as we expected: Martin and Stephen trying to progress while Jason and Ian saturated with HEX work.

9. 4 Apr 2006 Helicoflex Seals 9 Stephen Haywood Cu Seal

10. 4 Apr 2006 Helicoflex Seals 10 Stephen Haywood Dissected Seals

11. 4 Apr 2006 Helicoflex Seals 11 Stephen Haywood Were We Sold Wrong Seal? We supplied design of Housings and asked for Cu Seal. Seals are made to order, but not to measure. The Seal we bought should be compressed by 0.34  0.1 mm. Our Housing would require this seal to compress 0.44 mm. No discussions about compression forces. Should design Housing to suit a Seal. Flukey (in retrospect) that this Seal does “suit” design. Appears that compression forces for Al and Cu Seals are same – albeit Al not compressed enough and Cu required to be compressed to upper limit. Cannot complain that we were sold wrong Seal.

12. 4 Apr 2006 Helicoflex Seals 12 Stephen Haywood Qualification Pursued 1 st half of Qualification to see if the Seals could work. Tightened Seals to nominal torque (100 or 170 cN.m). Qualification:  He Vac leak check  25 bar N 2 proof test  7 bar He leak check at 0 o C  1 bar He leak check at -35 o C  (Thermal Cycle)  (Pressure Cycle) Takes much longer than originally suggested. 8/9 OK so far; one fails on 25 bar test – not yet investigated.

13. 4 Apr 2006 Helicoflex Seals 13 Stephen Haywood Possibilities Keep Al Seals – worried about corrosion. Cu-plate Al Seals – already squashed; need new ones. Some new type of material for seal ? Cu Seal:  Increase torque with washers & lubricant – damage Al clamp plates (bend; strip thread)  Leave them not bottomed-out – Jason is not happy  Change Housing – no way !  Thin washer to force earlier bottoming out – very fiddly  Thin ring to force earlier bottoming out – very fiddly; not room  Pre-squash by 0.2-0.3 mm  Could Garlock supply a better suited Seal or modify existing Seals – I would be very nervous about this

14. 4 Apr 2006 Helicoflex Seals 14 Stephen Haywood Questions Does it work if only compress by ~0.2-0.3 mm – do surfaces (Seal/Housing) conform ? How does Seal behave if pre-squash by ~0.2-0.3 mm – will compression forces required still be large ? Will ask Garlock for advice.

15. 4 Apr 2006 Helicoflex Seals 15 Stephen Haywood Pre-squash Use washers and lubricate – allows torque to give greater compression (reduces friction). Pre-squash by ~0.20 mm; ~0.24 mm to b-o; stops with ~0.10 mm to go – but ripped threads. Use nuts. Pre-squash by ~0.30 mm; ~0.14 mm to b-o; bottoms out – but badly bend Al compression plates. Will repeat with new Al plates. Check Al plates are Dural – as in production.

16. 4 Apr 2006 Helicoflex Seals 16 Stephen Haywood … And If pre-squashing fails, consider washers. Thin and hard to locate. When we have found solution which is OK:  Mechanically – bottoms out, doesn’t wreck clamps/bolts  Leak tight will qualify from scratch. Note: assuming we replace Al Seals, must be very careful not to scratch Housings – use plastic tweezers. 0.6 mm 0.8 mm