Page 376 - The Tribology Handbook

c20 Design of storage tanks

Table 20.2 Tank components (continued)
VENTILATORS Purpose: to allow volume changes in oil; to remove volatile acidic
breakdown products and water vapour
Number: normally one per 5 mz (50 ft’) of tank top
Filtration: treated paper or felt filters, to be inspected regularly, desirable. -
Forced ventilation, by blower or exhauster, helps remove excess water
vapour provided air humidity is low -I---

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DRAINAGE Drainage: Located at lowest point of tank. Is helped by bottom slope of
POINTS AND 1 : 10 to 1 :30. Gravity or syphon or suction pump depending on space
ACCESS available below tank. Baffle over drain helps drainage of bottom layer
first
Access: Size and position to allow removal of fittings for repair and to let
all parts be easily cleaned. Manholes with ladders needed in large
tanks

LEVEL Dipstick: suitable only for small tanks
INDICATORS Saght-glass: simple and reliable unless heavy or dirty oil obscures glass.
Needs protection or ‘unbreakable’ glass. Ball-check stops draining if glass
breaks
Float and pressure gauges: various proprietary gauges can give local or
CHECK
remote reading or audible warning of high or low levels JBALL
~
DE-AERATION Purpose: removal of entrained air in relatively clean systems, to prevent
SCREEN recirculation
Position: typically as shown. Should be completely immersed as surface
foam can penetrate finest screen
Matmal: wire gauze of finest mesh that will not clog too quickly with
solid contaminants. Typically 100-mesh

HEATERS Purpose: aid cold-start circulation, promote settling by reducing viscosity,
assist water removal
Design features: Prevent debris covering elements. Provide cut-out
in case of oil loss. Take care that convection currents do not hinder
settling. Consider economics of tank lagging

COOLERS Purpose: reducing temperature under high ambient temperature con-
ditions. Usually better fitted as separate unit

STIFFENERS Purpose: prevention of excessive bulging of sides and reduction of stresses
at edges in large tanks
Location: external stiffening preferred for easy internal cleaning and
avoidance of dirt traps, but baffles may eliminate need for separate
stiffening

INSTRUMENTS, Thermometer M temperature gauge: desirable in tanks fitted with heaters
ETC. Magnetic drain-plug or strainers: often fitted both for removing ferrous
particles and to collect them for fault analysis
Sampling points : May be required at different levels for analysis

c20.2