e-mosty June 2017: Osman Gazi B. US Suspension. Hålogaland B. e-mosty June 2017: Suspension Bridges | Page 59

3.5 Dry Air Supply Piping and Injection/Exhaust Sleeves
The dry air developed in the plant rooms was required
to be delivered to the cable by High-Density
Polyethylene (HDPE) piping. The pipework was routed
to the injection sleeves on the cable by messenger
strands connected to the hand rope stanchions on the
cable. The HDPE pipework was spirally lashed to the
messenger strands for near-continuous support
(Figure 22).
The injection and exhaust sleeves are horizontally split
stainless steel assemblies that accommodate either
the injection pipe or exhaust port and integrate a
network sensor box for data collection and monitoring
purposes (Figure 24).
Figure 24. Cable injection sleeve (note sensor box on top)
Figure 22. HDPE dry air supply pipework
The rigid HDPE pipework was transitioned to flexible
stainless steel braided pipes where relative movement
needed to be accommodated, such as at the injection
sleeves on the cables (Figure 23).
Prior to installing the sleeves, the wrapping material
and any existing wire wrapping was removed. The
cable wires were wedged slightly open with zinc
wedges to promote air ingress or egress. The two
halves of the sleeves were then installed with specific
circumferential and longitudinal gaskets and sealants.
Similar to the cable bands, the objective is a robust,
airtight and weather resistant seal.
3.6 Supervisory Control and Data Acquisition System
A supervisory control and data acquisition (SCADA)
system was developed based on contract
requirements to remotely monitor the plant rooms
and cable sensors, as well as continuously collect the
data from each. In addition, the SCADA network
provides the feedback loop between the cable sensors
and the plant room, as well as the plant room
equipment and plant room program logic controller,
such that the control system can adjust the system to
maintain set-points for cable injection pressures and
plant room relative humidity, respectively.
Figure 23. Flexible stainless steel pipe
transition to injection sleeve
To monitor the dehumidification process, sensors are
installed at the injection and exhaust sleeves on the
cables in NEMA 4X boxes to protect them from the
harsh atmospheric environment (Figure 25).
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