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PUMPS, VALVES & ACTUATORS PUMP REFURBISHMENT OFFERS ROBUST SAVINGS


By refurbishing five pumps, optimisation experts Riventa have identified annual savings of almost £20,000 for a food processor’s chilled water cooling system


found to be showing significant signs of wear, especially pumps 4 & 5, which were failing to achieve manufacturer performance levels. With an average load of 45% (equivalent to 2.2


S


pumps running at any one time), the five pumps had even more demands placed on them during warmer weather, sending their Best Efficiency Point (BEP) even lower. To evaluate the horizontal end-suction


pumps, which are driven by a motor with an inverter drive (to allow control of the flow rate), Riventa utilised its specialist FREEFLOW technology to employ thermodynamic measurement technique (ISO 5198). This


included suction and discharge pressures either side of the pump, differential temperature, and motor input power. These measurements enabled Riventa to calculate differential head across the pump, hydraulic efficiency and volumetric flow. Pumps were altered gradually. After each


change, a test point was taken, while allowing enough time to obtain the best statistical


MATERIALS UPGRADE ROI IS LESS THAN A YEAR


A materials upgrade performed by the aftermarket team at Celeros Flow Technology (Celeros FT), has prevented repeated pump failures at an oil refinery in the US, delivering a return on investment (ROI) of less than one year. The Celeros FT aftermarket team was called in to


investigate the cause of repeated failures of the casings and casing covers on the refinery’s OH2 pumps in boiler feed water service. The client asked Celeros FT to evaluate the failed components and make recommendations to prevent future damage. Initial inspection showed that the damage was to random


areas of the casing and cover, and limited to cast steel (ASTM A216-WCB) components only. In order to determine the root cause of the failure, the operating parameters of the pump were investigated. Particular emphasis was placed on the temperature and conductivity of the water, with key properties of interest as follows: Temperature – 132˚C; Conductivity – 11 μmho/cm; pH - 9. Inspection of the failed components revealed damage consistent with the use of carbon


steel in hot, low conductivity water service. The type and random nature of the damage along with service conditions were key factors in making this determination, which was later supported by an independent metallurgical examination. For this boiler feed water application, the pump experts at Celeros FT recommended the


replacement of the carbon steel components with 12% chrome (CA-6NM), 316 stainless, and 400 series stainless steels (CA-6NM and CA-15), which are not affected by this failure mechanism. The customer approved the recommended course of action and replacement pump casing and casing covers were provided in upgraded materials. Celeros FT estimates that the one-off cost of the materials upgrade is approximately one


third of the annual maintenance cost of replacing or repairing the carbon steel pump casings. Taking all savings into account, the materials upgrade has paid for itself within 12 months of implementation.


www.celerosft.com


ending chilled water from heat- exchangers, the food processor’s pumps (annual energy costs of £181,400) were all


FREEFLOW technology helps identify significant energy savings


average. Tests also involved a routine of testing performance at an incumbent set point, followed by throttling the pump to reduce its flow rate. The latter action allowed other pumps running in parallel to increase in speed to compensate, with a final test point taken at this moment. By throttling, Riventa could carefully observe the maximum possible flow through each pump under test, without altering the overall flow to the plant. Relative to the manufacturer’s typical performance, data showed that the shape of the pump curves indicated severe internal recirculation due to high wear ring


clearances. Steve Barrett, managing


director of Riventa, commented: “While pumps 1-3 achieved a


good relationship between power


and flow, pumps 4 & 5 were not performing when at lower flows. This indicated a high likelihood of internal recirculation – from high to low pressure parts of the impeller – being caused by high wear.” He added: “Our measurements provided


the food processor with a very strong case for robust savings: basic refurbishment with internal coating plus replacement of wear- rings, bearings and seals - or a comprehensive refurbishment, which would also include a new, tailored impeller. As energy costs become more of a concern than ever before, food processors can make big savings on equipment such as pumps by having them tested properly. As well as reducing energy bills, companies can maximise reliability and minimise whole life costs.”


Riventa www.riventa.com


APRIL 2022 | PROCESS & CONTROL 33


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