Patent GB-1203769-A (GB)
Title: Improvements in thermally insulated duct systems
Inventor: WALKER ALAN JOHN
IPC: F16L59/16
Filed: 1966-11-11
Abstract: 1,203,769. Insulated duct systems; pipe joints; valves. SPEMBLY TECHNICAL PRODUCTS Ltd. 7 Nov., 1967 [11 Nov., 1966], No. 59743/66. Headings F2G, F2P and F2V. A ducting system for passaging a fluid flow and for thermally insulating the fluid to a high degree during such passage comprises lengths of pipe 1 for conducting the fluid and jointed at spaced localities at 1A, 1B, and lengths of outer jacket 20-22 surrounding the pipe 1 and jointed at localities 27, 27 such as to afford access to the inner pipe joints, the space between the pipe 1 and the jacket 20-22 throughout the system forming a continuous space which is evacuated after joining the lengths of pipe and jacket, the pipe being supported with the jacket in a manner such that there is no conductive metal path between the pipe and the jacket between the end limits of the ducting system. As shown helium supply and return pipes 1, 2 lead into a junction box 3 and leave it with the pipe 1 co-axially housed within the pipe 2 the adjacent ends of the pipe lengths 1 being grooved at 1A and covered by a sleeve, e.g. of synthetic material 1B, which may be fitted by using a lubricant, or adhesive. Collars 1C may locate the sleeve 1B. The lengths 1, 2 include metallic bellows 1D, 2D. The joints between the adjacent ends of the pipe lengths 2 comprise a lining sleeve 12, a collar 4, and a sleeve 6 welded respectively to the pipe ends, and a free flange 8 bolted to the coller 4 with a packing ring 11, between the sleeve 6 and the collar 4. For joints in a pipe for liquid helium, the packing rings may be made of gold, silver or, an alloy of these metals. Copper, aluminium, indium, and similar soft metals may be used in the joints with other contemplated uses. Laminar rings 13 are preferably inserted between a shoulder 7 on the sleeve 6 and the free flange 8. The jacket lengths 21, 22, having their flanges 27, 27 bolted together, are telescopically slidable over the jacket lengths 20 for access to the pipe joints 1A, 1B, the joints 28-26 between the lengths 21, 22 and 20 including a split flange 24. A thermal insulation support between each junction box 3 and the jacket comprises a spool with inner and outer sleeves 30, 31, a spiral coil 32 of alternating thin glass fibre paper and reflective metal foil, and a tube 33 of corrugated, or dimpled, thin sheet plastics reflectively coated with aluminium. A sleeve 35 with three lugs 34 is interposed between each spool and the jacket 20. In an elbow jointed system, Fig. 5, not shown, the joints for the pipes 1, 2 are identical to those shown in Fig. 3 and the joints between the jacket and the junction boxes comprises annular collars (53, 53B) which are retained by laminar resilient rings (50B) on the flange (50A) of the box and the end cuff (59) of the jacket (20) respectively and which are bolted together. A ring (50C), backed by a ring (50B), is located between the rings (50B). A detachable and telescopic joint arrangement, which allows access to the pipe joints, is arranged in the jacket lengths between the junction box (50, 50). The jacket, Fig. 4, has two angled branches 20A, 20B, each of which houses a valve as shown only in respect of 20A. A valve head 40B, with one or more passages 40D and a sealing ring 40A, has a guide part 40C which is slidable in the bore of a valve seat 40 welded in a T-piece inserted in the pipe 1. The valve head 40B has a steam 41 which extends through a hermetic coupling 44 having welded to it a tubular metallic bellows 45, and has a cap 41A with a recess 41E in which is rotatably retained a plug 46 having two upstanding pins 46B. These pins engage with lost motion the cross pin 47A on a valve spindle 47 which is rotatable by a hand wheel 47B and extends through a glanded hermetic stuffing box 48. The pipe 43 is supported by a spool such as 30, 31, and a sleeve 35, Fig. 3. The jacket is provided with a hermetic breakable joint 49 to afford access to the valve parts.