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Chemical Technology • March 2015
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New generation of
encapsulated disc spring system
from AESSEAL
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
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.zaz
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.
Figure 1: Cross-section of LiveStar valve live-loading components
1.
Nut/Bolt extension
2.
Spring cup
3.
Spring
4.
Spring cover