Chemical Technology March 2015

New generation of encapsulated disc spring system from AESSEAL

AESSEAL recently launched LiveStar, a new-generation live-loading system, designed to be compact without requiring extra bolt length to accommodate the uncompressed disc spring stack – a system which will find a major market in control valves in environmentally sensitive applications.

The problem Valve live-loading systems are often complicated. Most re- quire the use of torque-measuring tools and incorporate a disc spring stack that is often too long for the available bolt length (see pics 1 and 2) . As a result, the bolts usually need to be replaced, which is both costly and time-consuming. The solution LiveStar, recently launched, has been designed as an en- capsulated disc spring configuration with defined compres- sion length to automatically adjust the gland and maintain constant pressure on the valve packing set. Relaxation of the spring set by volume loss of the packing stack will show a gap upon inspection (see pic 5). Simply tighten the nut until the gap closes. During operation, this closed gap serves as an indicator of valve packing wear or consolidation, either of which will cause the gap to reappear, whereupon the assembly is simply retightened to its optimal set point. The live loading system design is compact and provides plenty of extra length to accommodate the uncompressed disc spring stack (see pic 3). LiveStar needs no new longer bolts fitted to the valve to accommodate the system. The systemfits on existing gland bolts (see pic 4) and is tightened on installation until the visible assembly gap closes (see pic 6). No torque wrench required! A major advantage of the AESSEAL design over other live- loading systems is that the disc spring, which is encapsulated against environmental impact by an outer cylinder, slides on

1. 2. 3. 4.

Nut/Bolt extension

Spring cup

Spring

Spring cover

Figure 1: Cross-section of LiveStar valve live-loading components

an even, machined surface rather than on a bolt thread. The disc spring can therefore never become over-compressed, hang up on threads or shift asymmetrically on the bolt. Other features include compensation for thermal ex- pansion of the valve parts, optimum and pre-determined compression set by the dimension of the spring housing, protection of the spring set from dirt and outside contami- nants, and sustained maintenance of a constant gland load and sealing force. Available for all standard metric bolt diameters from 8 mm to 27 mm and Imperial UNC from 5/16” to 1”, the complete LiveStar range can be sourced from AESSEAL branches and distributors throughout Africa. For more information contact Rob Waites on tel: +27 11 466- 6500, or email rwaites@aesseal.co.za z

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Chemical Technology • March 2015