GB824452A - A mechanical shaft seal structure - Google Patents

Abstract

824,452. Stuffing-box substitutes. COMBUSTION ENGINEERING Inc. Aug. 13, 1957 [Oct. 10, 1956], No. 25513/57. Class 122 (5). A mechanical seal structure between a vertical shaft 12, Fig. 1, and housing 10 comprises a ring 17 mounted on the shaft, a seal ring 24 urged into contact with the mating ring, a seal 26 mounted between the seal ring and housing permitting relative movement therebetween, and a chamber 42 containing a fluid which separates the seal 26 from the working fluid. As shown applied to the shaft of a centrifugal pump, the chamber 42 is formed in the seal ring 24 by an annular wall 40 extending up to or slightly past the level of the seal 26 which is located in a lip 30 on a member 32 forming part of the housing 10. The separating fluid, such as mercury, is heavier than and immiscible with the working fluid so that, when the chamber is filled, the working fluid is prevented from flowing round the seal 26 and depositing any sludge which would impede the free movement between the seal ring 24 and mating ring 17. The latter rings may be urged into contact by a spring 46 assisted by the weight of the separating fluid or, alternatively, if the chamber 42 is suitably designed, by the weight of the separating fluid alone. Separating fluid may also be retained above the seal 26 in a chamber 58 formed between the skirt 28 of the seal ring 24 and an annular flange 60 on the member 32 in order to prevent lubricating oil supplied through an inlet 56 for the shaft packing 48 from contacting the seal 26. If desired, a small amount of lubricating oil may be trapped between the lower side of the seal 26 and the separating fluid. In the case of a low-pressure pump (Fig. 3, not shown), in which the mechanical seal is required to prevent the flow of fluid downwardly along the shaft, the separating fluid is retained in a chamber above the seal 26 only, any foreign matter then floating on the surface of the separating fluid. In the modification shown in Fig. 4, the seal 26 is arranged in an extending lip 72 formed on the seal ring 24b and projects into a chamber 70 formed by an annular wall 68 integral with the housing 10. The separating fluid extends upwardly in a chamber 58a which is enlarged at the top by an annular wall 76 formed on the sealing ring 24b in order to avoid the bridging of foreign matter across the gap between the seal ring and housing. If the gap between the seal ring and housing be made sufficiently large to prevent " bridging," the separating fluid need only be contained in the chamber 70.