Page 22 - Uninterruptible Power Supplies

Standby Power Generating Sets
20 Chapter One

injection pump. For service tanks up to about 1000 liters the tank can
be mounted on a stand fixed to the engine underbase, but larger tanks
will for practical reasons be mounted on a floor-mounted stand. Fuel
tanks and pipework should not be of galvanized iron as zinc and fuel oil
are incompatible.
If extended running is required the daily service tank is normally
topped up automatically, by gravity or by an electric pump, from a
remote bulk fuel tank. Where there is no bulk fuel supply topping up of
small or moderate-sized sets can be achieved manually using a semiro-
tary hand pump attached to the engine base frame and provided with
a flexible hose for extracting fuel from manually handled barrels at
floor level. As an alternative a portable electric pump may be used but
this would not be available for “black start” conditions. For larger sets
arrangements can be made for fuel to be delivered by a small tanker
vehicle; where this is intended a vehicle earthing facility should be pro-
vided to prevent any build up of a static electrical charge.
The daily service tank should be fitted with pipe connections for the
fuel supply to the engine (the outlet pipe), the injector spill and excess fuel
return from the engine, the fuel supply from the bulk tank, and a drain
valve which may be plugged. There should be an easily visible contents
gauge and, depending on the arrangement of the fuel system, a filler cap,
an overflow connection, and a high-level alarm switch arranged to alert
personnel and to shut down any transfer pumps. Within the tank the out-
let pipe should finish above the base of the tank to prevent water and sed-
iment from entering the fuel line.
In order to allow fuel to be extracted and supplied to the engine the
daily service tank must be vented. If the supply to the daily service
tank is automatically controlled as described in Figs. 1.9 or 1.10, the
daily service tank is normally vented to the bulk tank which in turn is
vented to atmosphere; there must be no shut-off valves in vent pipes. If
the daily service tank is topped up manually, the tank must be provided
with its own filler cap and vent.
Before the fuel enters the fuel pump it should pass through a fine fil-
ter which is invariably fitted to the engine. If long periods of running are
envisaged, a dual filter arrangement can be provided; this enables a
change of filter element to be undertaken while the engine is running.

Bulk Fuel Tanks
A detailed description of the bulk fuel tank installation is beyond the
scope of this book but the following comments may be helpful.
If the bulk tank is mounted below the daily service tank, Fig. 1.9 indi-
cates the basic interconnecting requirements. An electrically driven

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.