Chapter 8. Low-Emission Gland Packing System
8-1. Overview
Azbil’s low-emission gland packing system employs a live-loaded packing system to maintain
valve seal performance for a long period of time. In order to meet the emission regulations
for volatile organic compounds (VOC) required by U.S. Clean Air Act Amendments (CAAA),
we confirmed that the amount of leakage from the gland was the equivalent of not more than
500 ppm in terms of atmospheric concentration of methane based on Azbil Corporation’s own
evaluation criteria.*
For the structure of the gland,
Figure 8-1. Structure of Azbil’s low-emission gland packing
system.
* As of October 2005, there were no industrial standards that specify the method of evaluation
for gland leakage, either in Japan or overseas.
No. Name
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(1) Gland stud bolt
(2) Gland nut
(3) Packing flange
(4) Spring case
(5) Belleville spring
(6) Packing follower
(7)
O-ring for inner side of packing
follower
(8)
O-ring for outer side of the packing
follower
(9) Gland packing
(10) Spacer
(11) Stem
(12) Stuffing box
Figure 8-1. Structure of Azbil’s low-emission gland packing system
8-2. Structure
The gland packing (P4519) is PTFE yarn with a carbon fiber core. It features asbestos-free
properties in addition to low sliding friction and adaptability to heat cycles, and can be used
for various types of fluids.
The gland packing is fastened by the live-loaded packing system composed of Belleville
springs. At the initial fastening, the Belleville springs should be fully compressed. With other
systems, in the course of valve operation, seal performance deteriorates due to loosening of
the gland packing. The restoring force of the Belleville springs automatically retightens the
packing to maintain the seal. The Belleville springs are installed in the spring case for the
purposes of positioning and protection from the surrounding environment. The load on the
Belleville springs can be observed by checking their position through the front window of the
spring case using the scale on the case.
The low-emission gland packing system can be added to an existing control valve, if it is an
applicable model, without replacing the valve body or actuator.
8-1
To Next Page
Loading...
