Page 293 - Design of Simple and Robust Process Plants

7.7 Site Vulnerability 279
Table 7.7. Measures practiced to achieve reliable utility supplies.

General
. Utilities systems should operate as independently as practicable in order to avoid the loss of
one utility causing the loss of another.
. The power supply for utility systems should have the highest priority for supply through the
load-shedding system
. Emergency systems should be totally independent
. A quantitative common cause failure analysis is a requirement for utility systems
Power supply
. Redundant power generators executed as independent systems*
. External back-up with redundant transformers and supply lines
. Inventory, limited to power for instruments on batteries
. Load-shedding system
. Emergency generator driven by combustion engine
Steam supply
. Redundant steam generators executed as independent systems*
. Boiler feed water inventory
. Redundant feed pumps with different drivers (electrical, steam)
. Redundant de-superheaters
. Load-shedding system
. Emergency provision locally electric heating
Air supply
. Redundancy on compressors executed as independent system*
. Separate drying units per compressor set
. Different types of drivers for compressors
. Separate power supplies for drivers
. Back-up from air compressors of gas turbines with dedicated drying units
Hydrogen supply
. Alternative sources
. Purification and compressor systems single due to high reliability
. External back-up preferable at specification to obtain redundancy for purification and compres-
sor system
. Load shedding
Process water
. Inventory tank/pond
. Redundant pumps with different drivers (electrical, steam)
. Redundant power supplies
Demineralized water
. Inventory of demineralized water
. Redundant pumps with different drivers (electrical, steam)
. Redundant power supplies
Cooling water system (centralized)
. Cooling water circulation pumps redundant with different drivers (electrical, steam)
. Cooling towers with more cells
. Redundant power supplies
. Emergency cooling with independent fire water system driven by combustion engine
* For power, steam and air supply, gas turbines with waste heat boiler
and air compressor can be designed totally as independent systems.