Centrifugal Pump Performance Test Procedure

This content provides you with a sample Centrifugal Pump Performance Test Procedure in the manufacturing shop.

This article is a supplementary article for the Third Party Inspection for Centrifugal Pump article. Please review this article first; we will wait here for you. This is also a sample procedure for the Centrifugal Pump Factory acceptance test.

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Centrifugal Pump Performance Test Procedure

1.Scope

This description of procedure defines the conditions for the hydraulic testing of centrifugal pumps according to API Standard 610.

Scope of test, type of test, test class and guarantee values are defined by standardized test plans agreed between pump manufacturer and pump purchaser.


2. Objective

Objective of the tests is the continuous control of performance data as process control, keeping the guarantees given according to the supply agreement, testing of relevant pump functions.

Preparation of test reports and test curves according to the supply agreement as integral part of the test documentation.

3. Standards and Other Regulations Applicable

  • API 610
  • Manufacture Standard

4. Centrifugal Pump Performance Test procedure

4.1 Testing Personnel

For the handling of the test beds, only trained personnel is employed. The setting of test data is done semi-automatically and requires appropriate test experience and accuracy.

4.2 Place and Time Of Testing

The testing is done on the test bay of the manufacturer. Only pure cold water with a density of ρ= 1 kg/dm3 is used as the test medium.

Pump block units are normally tested with installed motor. In case of acceptance by the customer, the readiness for the acceptance inspection is notified in time to the sales departments.

4.3 Pump Test Beds

Both of following test beds are available and will be utilized as per purchase order specification

  • Closed System
  • Open System, Alternatively With Booster Pump

4.4 Measurement And Testing Methods

The measurement and evaluation of hydraulic characteristic values is made by means of an electronic data logger.

All relevant data are recorded at the site by means of electronic measuring devices and presented with online electronic data processing at the test sites. After termination of the measurements, the data is transferred to the central computer of the test bay supervision. Unless otherwise specified, the acceptance performance tests are carried out in acc. with API 610, para. 7.3.3.

4.4.1 Measurements Of Flow Rate Q

The flow rate is measured using magnetic inductive flow measuring devices having the specified stabilization distances in front and after the measuring unit. The setting of the capacity is effected by control valves in the discharge pipe.

4.4.2 Measurement of head H (Hd - Hs)

Pressure measurements are made using calibrated measuring transmitters for the measuring point Hs (measuring range -10 up to +40 m wc), for measuring point Hd (measuring range -10 up to +180 m, 150 up to 630 m wc). For visual comparison, calibrated spring manometers are connected in parallel for analogous display.

4.4.3 Measurement of Velocity Head

The velocity head is calculated using the flow rate and the flow cross-section at the pressure measuring point.

LaTeX4Web 1.3 OUTPUT Δ v2 /2g=(v2 d-v2 s)/2g

Vd = velocity discharge side

Vs = velocity suction side

Δ = velocity difference between suction and discharge side

4.4.4 Measurement of power input (P)

The power input of the pump is determined either electrically by means of a calibrated test motor or by directly measuring the speed of rotation using a torque measuring hub.

The electrical measurement is made according to the two-watt meter method for determining the motor power input. The motor power output is calculated using the motor efficiency curve stored in the test system.

For comparison of guaranteed data, the test system converts the pump power input required for the customer conditions, i.e to the standardized speed and the density of the acually pumped medium.

4.4.5 Measurement Of Speed (n)

The speed measurment occurs by means of a light barrier or photo sensor. For canned motor pumps, not accessible from the outside, the speed is determined by means of a bend coil or by frequency analysis.

4.4.6 Measurement of Pump Effeciency (η)

The pump efficiency is determined for each measuring point immediately following the measurement by the testing system.

According to the following formula:

LaTeX4Web 1.3 OUTPUT η=(Q×H×ρ×100)/(367×P)

Flow rate Q [m³/h]

Head H [m]

Density ρ [kg/dm3] of pumped medium

Power P [kW]

4.4.7 Measurement of the NPSH value of the pump (NPSH required)

Normally in the closed circuit, the measurement of the NPSH value is made by reducing the system pressure by means of a vacuum pump. Measurement also is done by throttling using a throttle valve in the suction line, as the case may be.

Reaching the guaranteed value at the required NPSH value can be proven using the following 2 measuring methods.

a) Standard

Proof of reaching the required NPSH value by setting the peripheral conditions which are equal inthe system such as flow rate, head when reducing the suction pressure depending on the water temperature and the barometric level.

Comparison of head, taken from the characteristic curve measurement above, with the head measured at actual suction negative pressure where the guaranteed NPSH value is achieved or is not achieved.

The head decrease may not exceed 3 % of H, but does not have to achieve 3 % (for single-stage pumps).

According to the specifications in the order, 1 or 3 to 5 measuring points are used. For 2 stage pumps, the max head decrease may not be ΔH≤1.5 %

So NPSH test for multi stage pump is not possible.

b) Optional as Head Breakdown Curve

Proof of the min. achievable NPSH value at a specific constant flow. By reducing the suctionhead, starting at NPSH = 40 m, a number of measuring points (8-12) are recorded until the pumping breaks down. The cut-off point at 3 % head decrease since the beginning of the measurement results in the cavitation condition of the pump at this point and is defined in the applicable standards as NPSH required (for 2 stage pumps 1.5% ΔH)

Reference level for calculation of the NPSH

a) Horizontal Pumps

Horizontal level through the shaft axis

b) Vertical Pumps

Plane surface vertical to shaft axis at impeller inlet

Calculation of The NPSH Based on The Measured or Known Parameters:

The calculation of the NPSH value occurs simultaneously with the measurement.

The following parameters are required for this:

Suction head

LaTeX4Web 1.3 OUTPUT H_S [m]

Water temperature

LaTeX4Web 1.3 OUTPUT t_w [°C]

Steam pressure of water(absolute vaporization pressure)

LaTeX4Web 1.3 OUTPUT H_t [m]=P_D/(ρ×g)

Atmospheric pressure (absolute)

Atmospheric height (absolute)

LaTeX4Web 1.3 OUTPUT b_0 [m]=P_O/(ρ×g)

Distance reference level/measurement level

LaTeX4Web 1.3 OUTPUT Y[m]

Speed at suction side

LaTeX4Web 1.3 OUTPUT (V_S2 )/2g[m]

Density of test field water

LaTeX4Web 1.3 OUTPUT ρ[kg/(dm3 )]

Acceleration due to gravity

LaTeX4Web 1.3 OUTPUT g [m/s²]

The NPSH is calculated according to the following formula:

LaTeX4Web 1.3 OUTPUTNPSH=P_O/(ρ×g)-H_S-P_D/(ρ×g)+(V_S2)/2g∓Y
LaTeX4Web 1.3 OUTPUT NPSH=b_0-H_S-H_t+(V_S2 )/2g

The conversion of the NPSH value from the measured speed to the nominal speed is made according to the following formula (only valid for the speed range ± 3 %):

LaTeX4Web 1.3 OUTPUT n* /n>0.97<1.03
LaTeX4Web 1.3 OUTPUT 〖NPSH〗* =NPSH×〖[n* /n]〗2 [m]
LaTeX4Web 1.3 OUTPUT Q* =Q×n* /n [m3 /h]

4.4.8 Additional measurements

Upon request, the electrical current I [A] and the voltage U [V] can also be measured.

4.5 Number of measuring points

The number of measuring points for the pump characteristic curve or NPSH measurements must

be agreed in the supply agreement.

Characteristic curve at 0, Qmin, Qmean, Qnom, Q120%, standard measurement of 5 points (9 max.)

NPSH measurement 0, Qmin, Qmean, Qnom, Q120% 4 points (7 max.)

5 Centrifugal Pump Performance Test - Guarantees

The rated values of the pump are guaranteed in compliance with API 610 provided that no other customer requirements exist. The measuring of tolerances is done automatically by the measuring system.

For viscous media, only the specified data for cold water is guaranteed. The results with viscosity will be shown for information as conversion curves according to Hydraulic Institute.

6 Centrifugal Pump Performance Test - Vibration measurement

To assess the mechanical and hydraulic operating behavior of the pump tested, vibrations are recorded at the same time as the hydraulic date (min. 5 points).

Measurement is carried out in three planes - horizontal, vertical and axial - by means of vibration pick-ups fitted on the bearing bracket. The measureng criterion is the root mean square velocity of all vibrations determined (vibration velocity RMS in mm/s).

The limit stipulated by API 610 is for horizontal pumps 3 mm/s in the preferred operating range of the pump. In the allowable operating range, a vibration velocity of up to 3.9 mm/s (max.) is permissible. For vertical pumps the limit 5 mm/s in the preferred range and 6,5 mm/s in the allowable range is applicable.

Alternatively, it is also possible to measure the max. vibration amplitude (peak-to-peak).

Horizontal

Limit in preferred range: 2,0 mils (50 μm)

Limit in allowable range: 2,6 mils (65 μm)

Vertical

4,0 mils (100 μm)

5,2 mils (130 μm)

The frequency spectrum (FFT analysis) can be measured, if requested.

7 Centrifugal Pump Performance Test - Measurement of Bearing Temperature

If required, the measurement of the bearing temperature will be performed for a specified operating time. The measurement is taken on the bearing bracket on the outside at the level and position of the pump side or motor side bearing in horizontal direction.

8 Centrifugal Pump Performance Test report

The test results are stored in the central computer of the test bay supervision and on other electronic data carriers. Upon request, test reports and test curves are prepared for the customer.

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