Fuel System Design and Reliability (Keith Klesner)

Overview

This 2014 article by Keith Klesner, published in the Uptime Institute Journal, argues that diesel fuel systems must be designed to the same Tier topology objective as the rest of the facility. It draws lessons from Superstorm Sandy, where a site had to hand-carry fuel up 18 floors. The example shows that the fuel chain is a link that gets less attention than the power and cooling chains but is just as critical.

The author explains how to evaluate fuel paths and components (tanks, pumps, valves, controls and power to pumps) for Concurrent Maintainability or Fault Tolerance: each element is removed in turn to test whether the system still meets the objective. Tier Standard: Topology requires a minimum of 12 hours of on-site fuel at N load for all Tiers. Usable capacity is counted after removing the redundant tank; two 24-hour tanks equal 24 hours of Concurrently Maintainable fuel, not 48.

The most common design errors are also listed. Chief among them is a single valve between two pumps or tanks in an N+1 arrangement, which cannot be serviced without losing more than the redundant component. Power feeds to fuel pumps and fuel control panels must follow the same principle; a single panel or single ATS feeding all pumps is a frequent flaw. Where fuel is pressurized or continuously returned from day tanks to bulk tanks, the return path is also critical.

The article also covers three topics under Operational Sustainability. Engine fuel pumps return heated diesel to the day tank; prolonged runs or hot ambient can overheat it and derate or trip the genset, and the mitigation is recirculating to underground bulk tanks or adding a fuel cooler. Fuel polishing is not a Tier requirement but is recommended for long-term availability. Outdoor tanks and gensets need bollards or structures against vehicle damage.

Key points

1. Tier Standard: Topology requires a minimum of 12 hours of on-site fuel at N load for all Tiers while still meeting the topology objective.
2. Usable fuel capacity is counted after removing the redundant tank: two 24-hour tanks equal 24 hours, not 48.
3. The most common error is a single valve between two pumps or tanks in an N+1 arrangement.
4. Power feeds to fuel pumps and control panels must be Concurrently Maintainable or Fault Tolerant; a single panel or ATS feeding all pumps is a frequent flaw.
5. Where fuel returns from day tanks to bulk tanks, the return path is critical and must meet the Tier objective.
6. Heated diesel returning to the day tank can derate or trip the genset; recirculation to underground bulk tanks or a fuel cooler is suggested.
7. Fuel polishing is not a Tier requirement but is recommended for long-term availability.
8. Outdoor tanks and gensets need bollards or structures against vehicle damage.

Using it in design

• Model fuel as a first-class subsystem: tanks, pumps, valves, day tanks and pump power feeds with redundancy checks.
• Compute autonomy hours with the largest tank removed and warn if under 12 hours at N load for a Tier claim.
• Flag single shared valves or an ATS feeding all fuel pumps.
• Add the fuel return path and day-tank overheating risk to the checklist.

Who should read it

Mechanical and electrical engineers and operations teams designing generators and fuel systems for Tier-targeted facilities.

Related standards

• Uptime Institute Tier Standard: Topology
• NFPA 110

Publication details

Authors

Keith Klesner

Publisher

Uptime Institute Journal

Year

2014

Document language

English

Source type

Industry body

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation