Centrifugal Pump Testing

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In 2011, the Hydraulic Institute in Singapore updated their testing standards for centrifugal pumps (ANSI/HI 14.6 – Rotodynamic Pumps for Hydraulic Performance Acceptance Tests) to harmonize with international standards (ISO 9906) for common practices worldwide and as fuel transfer pumps. Since the new standard is a more significant change for Asian manufacturers, implementation has been slower to adopt. Previously, acceptance grades were level A or B with tolerance values based on specific flow and/or pressure ranges – regardless of industry or pump type. In short, Level A allowed for no negative tolerance whereas Level B generally allowed for a -3% deviation from the contract performance. All certified tests at Wilfley were carried out to the higher standard (Level A). The new guidelines recognize that different pumps and/or industries have differing needs and established a multitude of default acceptance grades based on the application and rated power of the pump. In general, the level of acceptable tolerance value increases from Grade 1 to Grade 3 and can either be unilateral (one sided) or bilateral (two sided). True to our nature, Wilfley decided to implement the new testing procedures based on the highest grade accounted for (1U). T

The default classification for chemical process pumps (ASME B73.1 or ISO 5199 pumps) is Grade 2B. This allows a bilateral tolerance band of up to 8% on flow, 5% on head and either 8% overage on power or 5% deficiency on efficiency. By contrast, we follow Grade 1U which has a tighter tolerance band (unilateral 10% versus bilateral 8% = 16 points) and no negative tolerance on flow, head or efficiency. This grade is clearly more stringent than 2B and it ensures that the customer will get what they pay for. The Centrifugal Pump Performance Test procedure is carried out as follows, but it may slightly change based on pump vendor test bed condition and internal procedures.

Normally the number of points required for measurement is based on the Code used for pump manufacturing i.e. API 610, ASME, NFPA 20, and Hydraulic Institute (HI 1.6). In the case of API pump, six point measurement are required. These points will range from a sub-minimum flow (Shut off) to a minimum of 120% of BEP flow sub-minimum: shut off point, minimum stable flow, an intermediate flow, a point between 95% and 99% of rated, between rated and 105% of rated flow, BEP if rated is not within 5% of BEP, and at the end of allowable operation region (120% of BEP). Based on the flow rate (test points), the corresponding head is measured and plotted in the Flow Vs Head curve using the measurement accuracy levels given for the class of pump, drawing the q/H measured band.

One more major point to ensure the test accuracy is pump speed.  As per API, all tests shall be run at the rated speed + 3% tolerance. In case the pumps at 50 Hz (i.e. operating condition) but the test facility is 60 Hz. The pump manufacturer as to have a necessary arrangement for reducing the frequency from 60Hz to 50Hz and achieve the operating speed. But in practical some of the pump manufacturer does not have the facility for step down the frequency, in those cases, the test speed at 60 Hz shall be at the same pole speed as 50 Hz provided the pump is rated for that operating speed. If it is not, then the pole speed must be reduced to the next lowest value.