Chemical Technology Oct 2015

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Chemical Technology • October 2015 19
• Oil lubricated anti-friction bearings with non-metallic
cages can continuously operate at elevated temperature
up to 120 ºC. Polyamide, pressed steel and machined
brass bearing cages are suitable for different operating
temperatures (steel cages can operate up to 300 ºC,
machined brass cages are suitable up to 250 ºC while
glass fibre reinforced polyamide cages have an operating
temperature range of -40 to 120 ºC). Bearing manufactur-
ers should be consulted to make the most appropriate
choice of bearing type, clearance and materials. Thrust
bearing cages should be specified in non-sparking metal-
lic construction.
• Consideration should be given to using a pure oil mist
method when bearing operating temperature is in excess
of 120 ºC. It is known from experience that pure oil mist
helps bearings to run cooler.
• Hydrodynamic bearings are required when the conditions
as specified in “Table 9 – Bearing Selection” of API 610,
10th Edition, exist. The pressure oil system for hydrody-
namic bearings should be in accordance with Chapter-3
of API 614, 4th Edition - General purpose oil system. Some
users favour special purpose oil systems as specified in
Chapter-2 of API 614, 4th Edition, for unspared pumps
requiring hydrodynamic lubrication.
• Specify finned bearing housings and fan cooling if the
operating temperature of the pumped fluid is below
200 ºC. Beyond 200 ºC, finned tube oil cooler mounted
inside the bearing housing should be stipulated.
Pump baseplate grouting
considerations
• For baseplate mounted pumps and drivers rated up to
150 KW, cementatious grout can be used. The cost of
cementatious grout is typically one third that of epoxy
grout but it lacks the bond strength and nonporous sur-
face finish of epoxy grout. Epoxy grout should be used
beyond 150 KW driver rating.
• For centrifugal pumps handling acids, oils and aggres-
sive/reactive chemicals, epoxy grout should be specified
regardless of the driver rating.
• Epoxy grout should be a standard for reciprocating pump
baseplates.
• Baseplate surfaces which will come in contact with grout
must be cleaned as outlined in SSPC-SP6 (Society for
Protective Coatings).
• Most epoxy primers (except inorganic zinc silicate primer)
applied in preparation of epoxy grout is typically effective
only for 90 days. If grout work on site is expected to take
PUMPS & VALVES