Chemical Technology October 2015

PUMPS & VALVES

• 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

• 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, 10 th Edition, exist. The pressure oil system for hydrody- namic bearings should be in accordance with Chapter-3 of API 614, 4 th Edition - General purpose oil system. Some users favour special purpose oil systems as specified in Chapter-2 of API 614, 4 th Edition, for unspared pumps requiring hydrodynamic lubrication.

19

Chemical Technology • October 2015