SPP’s Field service engineers can provide a full commissioning service for a wide range of pumps. Contact your local SPP office for details
• Check all guards are fitted correctly before starting the pump
• Make sure pump will turn freely
• Check driver and pump rotations agree, with driver uncoupled
• Make sure bearings are adequately charged with clean lubricant
• Check stuffing boxes are packed and correctly adjusted
• Make sure any external lubricating, cooling, sealing, etc., services and connections are turned on and operative
• Make sure pump is effectively primed before starting up
• Check that pump runs without undue overheating, noise or vibration:
otherwise refer to detailed operating instructions for possible defects and rectify accordingly
• On no account must a pump be allowed to continue running unprimed, or with a closed discharge valve
• On no account should a pump be regulated by closing a valve on the suction side
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Potential Fault or Defect:
• Pump not primed.
• • • Speed too low.
• • Speed too high.
• • • • • Air leak in suction pipework.
• • Air leak in mechanical seal.
• • • • Air or gas in liquid.
• • • Discharge head too high (above rating).
• Suction lift too high.
• Not enough head for hot liquid.
• • • • • Inlet pipe not submerged enough.
• • • Viscosity of liquid greater than rating.
• Liquid density higher than rating.
• • • • • Insufficient nett inlet head.
• • • Impeller blocked.
• • • Wrong direction of rotation.
• • Excessive impeller clearance.
• • • Damaged impeller.
• Rotor binding.
• Defects in motor.
• Voltage and/or frequency lower than rating.
• Lubricating grease or dirty oil or contaminated.
• Foundation not rigid.
• • • Misalignment of pump and driver.
• Bearing worn.
• • Rotor out of balance.
• • • Shaft bent.
• Impeller too small.
sECtIon 5
Excessive noise from pump cavitation.
Pump bearings run hotter than normal.
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FaUlts anD REMEDIal aCtIon
SPP’s service division can carry out fault identification and rectification on a wide range of pumps. Contact your local SPP office for details
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CAUSE REMEDIAL ACTION
Pump not primed. Fill pump and suction pipe completely with fluid.
Speed too low. Check that the motor is correctly connected and receiving the full supply voltage also confirm that the supply frequency is correct.
Speed too high. Check the motor voltage.
Air leak in suction pipework. Check each flange for suction draught, rectify as necessary.
Air leak in mechanical seal.
Check all joints, plugs and flushing lines, if fitted. Note that prolonged running with air in the mechanical seal will result in damage and failure of the seal.
Air or gas in liquid. It may be possible to increase the pump performance to provide adequate pumping.
Discharge head too high (above rating).
Check that valves are fully open and for pipe friction losses. An increase in pipe diameter may reduce the discharge pressure.
Suction lift too high.
Check for obstruction of pump inlet and for inlet pipe friction losses.
Measure the static lift, if above rating, raise the liquid level or lower the pump.
Not enough head for hot liquid. Reduce the positive suction head by raising the liquid level.
Inlet pipe not submerged enough.
If the pump inlet cannot be lowered, provide a baffle to smother the inlet vortex and prevent air entering with the liquid.
Viscosity of liquid greater than rating.
Refer to SPP Pumps Ltd for guidance to increase the size or power of the motor or engine.
Liquid density higher than rating.
Refer to SPP Pumps Ltd for guidance to increase the size or power of the motor or engine.
Insufficient nett inlet head. Increase the positive suction head by lowering the pump or raising the liquid level.
Impeller blocked. Dismantle the pump and clean the impeller.
Wrong direction of rotation. Check driver rotation with the direction arrow on the pump casing.
Excessive impeller clearance. Replace the impeller when clearance exceeds the maximum adjustment.
Rotor binding. Check for shaft deflection, check and replace bearings if necessary.
Defects in motor. Ensure that motor is adequately ventilated. Refer to manufacturers’
instructions.
Voltage and/or frequency lower than rating.
If voltage and frequency are lower than the motor rating, arrange for provision of correct supply.
Lubricating grease or oil dirty or contaminated.
Dismantle the pump, clean the bearings, reassemble the pump and fill with new grease or oil.
Foundation not rigid. Ensure that the foundation bolts are tight, check that foundations match SPP Pumps Ltd recommendations.
Misalignment of pump and
driver. Realign the pump and driver as specified.
Bearings worn. Remove the bearings, clean and inspect for damage and wear, replace as necessary.
Rotor out of balance. Check impeller for damage, replace as necessary.
Shaft bent. Check shaft run-out and replace if necessary.
Impeller too small. Refer to SPP Pumps Ltd for options to fit a larger impeller.
SPP’s service division can carry out fault identification and rectification on a wide range of pumps.
Contact your local SPP office for details
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sECtIon 6
VIbRatIon tolERanCE
In every pump there are dynamic forces of hydraulic or mechanical origin that will inevitably lead to a certain level of vibration. To maintain the integrity of the pump unit and associated equipment the level of vibration must be kept within certain limits.
acceptance Criteria
The following table defines the maximum allowable level of vibration measured in mm/s RMS overall velocity during a factory acceptance test.
It should be noted that the factory acceptance test is not necessarily an accurate representation of the vibration on site, when the unit is grouted in with permanent pipe supports etc.
Pump Classes
Class 1 pumps will only include those that have been designed in full accordance with A.P.I. 610, for use in critical applications. None of the standard ranges of SPP fall into this class and pumps that meet it are only available on an engineered to order basis.
Class 2 pumps will include all SPP general purpose industrial designs apart from those specifically identified as class 3 below.
Class 3 pumps shall include any pumps with less than three impeller vanes, split case pumps of the “through bore” type and any unit driven by a diesel engine of four or more cylinders. (Refer to SPP Engineering for units driven by engines of three or less cylinders).
application / Class Class 1 Class 2 Class 3
Continuous operation over the preferred operating range
3.0 4.7 7.1
Continuous operation over the allowable operating range
3.9 5.6 9.0
Intermittent operation over the allowable operaing range
Not applicable 9.0 13.0
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Method
Vibration measurements will be made on the pump bearing housings, as close as is practical to the bearing positions.
For each bearing position two measurements will be taken perpendicular to the pump rotation axis. In addition an axial measurement will be taken at the thrust bearing position.
The measurements will be of velocity, overall RMS values, in mm/s.
In order to reliably achieve the stated acceptance limits the pump must be rigidly restrained, aligned to the driver within the coupling makers recommendations, operating without cavitation or air entrainment. Pipe work must be arranged to provide straight uniform flow into the pump and be connected and anchored so as avoid strains and resonance.
SPP’s field service engineers can undertake vibration analysis. Contact your local SPP office for details
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sECtIon 7
ConDItIon MonItoRIng
In order to minimise the ownership costs of capital equipment, it is critical for the user to monitor and maintain the equipment once installed. Failure to do so will impact both on the mechanical integrity and economic performance of the installed equipment.
Early diagnosis of potential equipment failure can result in considerable repair cost savings and crucially a reduction in unplanned downtime.
Monitoring of pump energy consumption and system efficiency will bring visibility to pump wear, operating efficiency and highlight any system irregularities. All of these factors will help minimise energy consumption and reduce operating costs.
The SPP condition monitoring systems can provide this level of security by detecting, analysing and evaluating key equipment performance. These include the following:
• Performance/Efficiency degradation
• Bearing vibration levels
• Bearing element damage
• Bearing operating temperatures
• Driver alignment condition
• Residual unbalance
• Cavitation
The system provides considerable flexibility in the display and use of the diagnostic output. The options include web based user configurable dashboard for live and trend data, automatic notification of alerts by text or email and local download of data to PC for detailed evaluation.
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sECtIon 8
FloW EstIMatIon MEthoDs
Many pumping systems are fitted with permanently installed flowmeters which enable a reasonably accurate measurement of system flow to be obtained. Where permanent flowmeters are not installed, it is often possible to use external clamp-on meters, insertion meters or thermodynamic testing equipment to determine system flow. However, it is not always practical to use these devices – either for financial reasons or system layout constraints – and where this is the case, alternative indirect methods need to be used for estimating system flow.
There are a number of methods available to enable an estimation of flow to be made in the field. Each of these methods requires some form of knowledge of the system or the pump, and all have inherent inaccuracies of varying degrees.
However, in the absence of any more accurate flow measuring apparatus, these can be the only alternatives available.
There are four main indirect methods of determining pump flow in the field:
• Pressure method
• Power method
• Drop test
• Suction pressure measurement
The Pressure and Power methods require the use of the pump curve, whilst the drop test requires sump geometry and level details.
PREssURE MEasUREMEnt
This is the more accurate and simplest of the four methods, requiring suction and delivery pressure gauge readings, a copy of the pump performance curve at the correct operational speed and knowledge of the impeller diameter.
Determine the differential head across the pump by subtracting the suction head from the discharge head. Then use the pump performance curve to obtain the pump flow at the measured head and impeller diameter.
For example, if the suction head is measured as 3m and the discharge head as 63m, the pump differential head is 60m. Using the pump manufacturers original test curve for the pump, the flow can be estimated as 150 l/s.
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Over time, a pump’s Flow/Head curve will change as wear occurs within the pump. Therefore, the accuracy of this method will tend to reduce as the pump gets older. However, this will remain a more accurate method than the others detailed below.
Where existing installed site gauges are used, it should be remembered that their accuracy may be far from ideal.
Remember that the pump Q/H curve is based on differential head, normally pumping water with an SG of 1. If the site liquid being pumped has an SG other than 1, SG correction should be applied to the site pressure readings to match the performance curve being used.
PoWER MEasUREMEnt
Power meters are rarely available on site, but amps (I) and volts (V) are commonly displayed at the control panel. These readings can be used to calculate power, although this also requires motor efficiency and power factor data - which will need to be estimated if motor manufacturers information is not available.
Power (kW) = (1.732 x I x V x eff x pf)/1000
Using this equation, the pump power can be calculated and from this, the flow can be read off the pump curve.
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Reading across the power scale on the pump manufacturers curve, the flow at this absorbed power can be obtained – 150 l/s in this example.
As mentioned above, a pump’s Flow/Head curve and efficiency curve will change as wear occurs within the pump. This will affect the pump’s power curve and therefore, as with the pressure measurement method, accuracy will tend to reduce as the pump gets older.
It should also be remembered that the installed instruments from which readings are taken may themselves be inaccurate, as it is unlikely that they will not have been calibrated to any significant accuracy since their original installation.
As an alternative to the above calculation, taking a simple current ratio (actual current/full load current) and applying it to the motor rated power can give a reasonable estimation of the motor output power. In the above example, assuming a 132kW motor with a full load current of 230A, this method would result in a duty power of (165/230)*132 = 95kW, and a resultant flow of around 135 l/s.
For example, if the current is read as 165A, the voltage as 400V and motor efficiency and pf from manufacturers’
data are 95% and 0.92 respectively, the calculated power becomes:
Power = (1.732 x 400 x 165 x 0.95 x 0.92)/1000
= 100kW
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Although the power method can be used very effectively in situations where a quick approximate on site estimate is required, it should not be applied to high specific speed pumps such as vertical turbine or mixed flow pumps, whose power curves can follow significantly different rules.
DRoP tEst
This is the least accurate method, and requires knowledge of sump dimensions and levels. It is often used on sewage pump installations, where sump emptying occurs over a relatively short period of time.
In this method, the time taken for a pump to lower the sump level over a known depth is recorded. The volume of liquid pumped is then calculated based on the sump level change and the sump area, and is divided by the time taken to arrive at a volume flow rate.
For example, if a sump has dimensions of 4m x 3m, and the level is reduced by 1m over a time period of 10 minutes, the average pump flow is (4 x 3 x 1)/10 = 1.2 m3/min, or 72 m3/h
This method has a number of inherent inaccuracies:
• During the drop test, it is likely that flow will continue to enter the sump.
This will affect the result – the extent of the effect will depend upon the rate of inflow in proportion to the outflow.
• The sump may not have a uniform section, making volume calculation less accurate.
• As the level is lowered, the total head on the pump changes which will affect the pump output. Any resultant calculation will only give an average flow over the range of heads.
• Measurement of pumped depth may be difficult if there is no installed measuring equipment.
sUCtIon PREssURE MEasUREMEnt
In most pumping stations, it is possible to obtain a pressure reading on the suction side of the pumps. The velocity and friction head components of this reading can be used to estimate the flow. To use this method, it is necessary to know the pressure drop on the pump suction (static suction pressure - operational suction pressure), the type and number of pipe fittings up to the pressure measurement point and fittings diameter. An estimation of the fittings friction (K) factor is also required.
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Convert the suction pressure drop (P in kPA) into a head drop (Zd in meters) using the equation:
Zd = P x 0.102 sg
(note that this Zd calculation will change depending on your site measured units) Obtain a total K factor for the suction fittings up to the measurement point.
Assuming there are no significant straight pipe losses in the suction, the following equation can then be used to determine the flow velocity:
Zd = V2 x (1+K) 2g
Once the velocity is known, the flow rate can be calculated using the suction diameter. This method can be adapted to suit a wide variety of suction and pump configuration and the available locations for pressure measurement.
Although there are potential inaccuracies in determining K factors and internal diameters, careful use of this method can allow the velocity to be estimated to within a few percent.
ConClUsIon
There is no single simple and accurate method of determining flow in systems where installed meters are not present, or where the use of alternative temporary flow metering equipment cannot be fitted. Instead there are a number of methods that can be utilised to obtain an approximate pumping rate, which in many cases may be sufficient for the purposes required.
All these methods have limitations and inherent inaccuracies. Where these methods need to be employed, it is worthwhile applying at least two methods to get comparative results.
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sECtIon 9
aPPlICatIon Do’s anD Don’ts suction & Delivery Piping
Ensure that bolt grouting or chemical anchors are allowed to dry thoroughly before connecting any pipework.
Note that fire pumpsets have regulatory requirements for piping and these must be strictly observed. Refer to the appropriate standard for details.
Both suction and discharge piping should be supported independently and close to the pump so that no strain is transmitted to the pump when the flange bolts are tightened. Use pipe hangers or other supports at intervals necessary to provide support. When expansion joints are used in the piping system, they must be installed beyond the piping supports closest to the pump.
Install piping as straight as possible, avoiding unnecessary bends. Where necessary, use 45º or long sweep 90º bends to decrease friction losses.
Eccentric Reducer on a Split Case Pump
Typical End Suction Pump Piping Installation
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Make sure that all piping joints are airtight. Where reducers are used, eccentric or ‘flat top’ reducers are to be fitted in suction lines and concentric or straight taper reducers in discharge lines. The length of eccentric reducers should be about four times the pump suction diameter. Undulations in the pipe runs are also to be avoided. Failure to comply with this may cause the formation of air pockets in the pipework and thus prevent the correct operation of the pump and measuring equipment.
The suction pipe should be as short and direct as possible, and should be flushed clean before connecting to the pump. For suction lift applications, it is advisable to use a foot valve. Horizontal suction lines must have a gradual rise to the pump. If the pumped fluid is likely to contain foreign matter then a filter or coarse strainer should be fitted to prevent ingress to the pump.
The discharge pipe is usually preceded by a non-return valve or check valve and a discharge gate valve. The check valve is to maintain system pressure in case of stoppage or failure of the driver. The discharge valve is used to prevent back flow when shutting down the pump for maintenance.
CoUPlIng alIgnMEnt
Periodical checks of shaft alignments should be undertaken and if necessary adjusted accordingly. In order to maintain the warranty status of your SPP pump it is recommended to take out an SPP preventative maintenance contract. SPP’s field service engineers have extensive experience in pump and coupling alignment. Refer to the pump and coupling
instruction manuals for details of shaft alignment procedures and tolerances or proceed generally thus:
instruction manuals for details of shaft alignment procedures and tolerances or proceed generally thus: