Once buying decision is made; what to order and whom to order, after due care on the various techno-commercial points highlighted in the 1st article, vendor would manufacturer, test and
supply the Centrifugal pumps according to order specifications. This article is all about post-supply journey of Centrifugal pump.
To pump up the bottom line of any process plant, one of the requisite conditions is to keep pumps’ up and running. Various steps outlined in this article would help to enhance reliability, ensure
availability and optimize the performance over its entire lifecycle.
Sit back, read, think and learn!! Off course share your views and insights too.
- Installation and commissioning
Skid Inspection: On arrival of the pump package at site, verify all the material as per the PO scope of supply, correctness of information available on tag plate, check for obvious shipping or
installation damage, all plugs / caps / blinds are in place.
Preservation: Equipment requires to be stored or preserved as per the manufacturer’s recommendation. Oil lube bearing housings, seal housings, stuffing boxes to be kept 1/4 filled with
approved oil. Apply coating or protective grease on shaft, coupling hub and machined surface of base plate. Horizontal Pump shaft turned 2-3 revolutions once per week to avoid preloaded
bearing damage and prevent permanent rotor sag.
If pump is not to be installed immediately, Long-term storage to prevent the humidity / temperature and airborne chemicals from contacting the internal components of the equipment. Climatecontrolled storage, Oil flooding of bearing housing, Gearbox (for integrally geared pump), Nitrogen purging, Desiccant bags are some of the options.
Foundation: The purpose of foundation to provide solid support and dampen external as well as equipment generated shocks and vibrations. Preferred foundation material is cement concrete.
Elevated pump may be directly supported by structural steel provided adequate stiffness and strength.
The recommended ratio of foundation mass to total equipment mass (including base plate) for centrifugal pumps is 3:1 and 5:1. The foundation shall be free of resonant frequencies within a
minimum of 20 % of the operating speed range of the equipment. The typical foundation arrangement and anchor bolt size / location information are provided in the figure 1.
Grouting and Levelling: Grout is used to stiffen the baseplate and to provide even load to the foundation. If the grout is not added or if it does not make full contact with the base and foundation,
the forces from pipe strain and machine vibrations cannot be successfully transmitted to the foundation.
General-purpose pump mounting surface → levelled within 0.4 mm per meter.
API pump baseplate mounting surfaces → levelled within 0.25 mm per meter.
Suction Piping: Some of the key check points are listed below.
Use suction pipe with one size larger diameter than the pump inlet, velocity below 2m/s.
Pipework is aligned with the pump’s flange and straight for at least 5 pipe diameters
Y Strainer is to be used for permanent or temporary
Long-radius elbows are preferred for suction lines.
Use an eccentric reducer orientated to eliminate air pockets.
Piping should have proper support and alignment with pump nozzle
Driver test: No load test of driver to be conducted to check reliability (winding and bearing temperature, vibration), performance (Input currant, speed) and direct of rotation.
Coupling alignment and installation: Driver and driven shaft should be aligned to each other according to coupling OEM recommendation. Normal range is 0.1 mm TIR (Parallel and angular) and
0.05 mm TIR pre-piping and post-piping respectively. DBSE to be maintained within + / – 0.25 mm unless specified.
Instrumentations and control: Calibrate all the process, lube oil system and seal system instruments. Set up process logic and equipment logic into PLC / DCS / MCMS / ESD system.
Bearing housing / Lube oil system: For oil ring lubrication, fill the recommended oil and drain it once. Fill up the lube oil at 3 to 6 mm from the lower edge of the flinger. If pump or / and driver
has forced lubrication system, flush the system and make it ready with filter and breather. Clean lube oil at right pressure should be available.
Mechanical Seal system: Prepare seal system according to the requirement. General check list is provided in table 1
Start up : It is to be done in following sequence.
Mark up the process loop in P&ID where the pump is planned to be operated
Energize the driver
Applicable for API Plan Description Important parameter Inspection check points
Primary Seal Plan 01 Internal circulation in pump Recirculation flow Internal path erosion or chocking
Plan 02 Dead ended, for clean medium, no flush Temperature of cooling jacket Vent hole on throat bush
Plan 03 Tapered seal chamber bore No Check points or inspection parameter
Plan 11 Circulation from discharge to Seal, RO P of flush fluid RO for oversize or choke
Plan 12 Plan 11 + Strainer P of flush, ΔP across strainer RO and strainer
Plan 13 Circulation from Seal to Suction piping, RO
Plan 13M Circulation from Seal to suction vessel, back pressure of vessel RO, NRV and piping
Plan 14 Plan 11 + Plan 13 As per the plan 11 and 13
Plan 21 Plan 11 + Cooler P of flush, Cooler ΔT RO, Cooler
Plan 22 Plan 21 + Strainer P and T of flush, Cooler ΔT, strainer ΔP RO, Cooler, strainer
Plan 23 Internal recirculation within Seal box P and T of flush, cooler ΔT Throat bush, Pumping ring
Plan 31 Circulation through Cyclone separator P and T of flush Separator and its piping, Throat bush
Plan 32 External clean / cool flush P, T and Q of external flush Pressure regulator, FCV, Throat bush
Plan 41 Plan 11 + Cooler + Cyclone separator As per plan 11, 21 and 31
Between Seals Plan 52 Buffer to containment seal L and P of buffer, ΔT buffer in / out Vent RO, Instrumentations, cooler, hand pump, NRV
Plan 53A Barrier to double Seal, Simple reservoir L and P of barrier, ΔT barrier in / out Instrumentations, cooler, pumping ring, hand pump, NRV
Plan 53B Barrier to double seal, bladder accumulator L and P of barrier, ΔT barrier in / out Instrumentations, cooler, bladder, pumping ring, hand pump, NRV
Plan 53C Barrier to double seal, Piston accumulator L and P of barrier, ΔT barrier in / out Instrumentations, cooler, Piston regulator, PRV, hand pump, NRV
Plan 54 External barrier to double seal P and Q of barrier, ΔT barrier in / out Instrumentations, FO or FCV, PRV
Plan 55 External buffer to double seal P and Q of barrier, ΔT barrier in / out Instrumentations, FO or FCV, PRV
Gas Seal Plan 71 Future provision for plan 72 Not applicable
Plan 72 Buffer gas system P and Q of buffer gas Instrumentations, PRV, FO or FCV, check valve
Plan 74 Barrier gas system P and Q of buffer gas Instrumentations, PRV, FO or FCV, check valve
Plan 75 Liquid leakage collection, drain L and P of reservoir, Instrumentations, RO,
Plan 76 Vapor leakage collection, flare P of Vent / flare line Instrumentations and RO
Leak detection / Quench Plan 51 Dead end quench, Vertical pump L of reservoir RO
Plan 61 Future provision for plan 62 Not applicable
Plan 62 Quenching P and Q of quench Seal quenching port, throttle bush, check valve
Plan 65A Leak detection system and alarm Level of leakage LT, RO
Plan 65B Leak detection system and alarm Level of leakage LT, RO
Plan 66A Leak detection system and alarm, reservoir and bushing Pressure of seal leakage PT. Throttle bush
Plan 66B Leak detection system and alarm reservoir and orifice Pressure of seal leakage PT, Throttle bush, Orifice plug
Special note: Buffer: External fluid having lower pressure than the seal box pressure
Barrier: External fluid having higher pressure than the seal box pressure
P – Pressure, Q – Flow, T – Temperature, L – Level, Δ – Differential
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Inspect suction strainer condition and suction spool for any object
Open suction valve. Do start up drain and vent.
Open discharge valve partially. Suction pressure to be in line with the requirement. Do not operate any OH6 pump against closed discharge valve
Kick start the pump, verify DOR, observe no abnormal rubbing or cavitation sound
Start the pump, observe discharge pressure, flow and input currant. Bring the pump operation at close to rated condition.
Record all equipment and process parameter till the bearing temperature gets stabilize. It may take 30 minutes to 2 hours depending on pump type, size, design and process load.
sample log sheet is given below
Operating parameters Unit Start up 5 10 15 30 60 120
Process parameters Flow, Pressure, Valve Opening %, Amps, Power
Lube Oil systems Level, Pressure, Temperature
Mechanical Seal Systems Level, Pressure, Temperature
MCMS / VTMS Brg /winding temperature, Offline/online vibration
Table 2: Sample log sheet
- Operation and Maintenance
If pump is the part of any new project or expansion project, once mechanical integrity and performance is proved, project team hand over it to plant operation and maintenance.
Operation: While defining SOP for start-up, change over and shut down following points required to be considered.
Observe suction pressure and suction temperature in line with the data sheet.
Mechanical seal plan start-up and operational requisite condition should be maintained. Please refer the table 1.
Pump to be operated close to rated or BEP or within preferred operating range. If plant throughput requirement is lower than MCSF, some amount of flow must be recirculated to
ensure pump never ever operate close to or lower than MCSF.
If throughput required is higher than the rated condition, verify NPSH available and required margin for that duty point based on the performance curve and actual suction condition
For parallel operation of the pumps, discharge pressure variation should be minimum within 2% margin. Special precautions for parallel operation of pumps having non-rising curve.
Changeover duration between 2 units should not be too short or too much long.
Maintenance: Preventive maintenance of pump can be categorized into 2 different categories.
Short interval: It could be Daily or weekly, depending upon equipment criticality and its reliability.
Lube oil quality and quantity, for pressurize lubrication system, lube pressure and temperature are the additional check points. Adequate lubrication of driver and coupling to be ensured.
Mechanical Seal leak detection and API plan operating parameters to be monitored and maintained as per the table 1.
Periodical vibration monitoring. API 610 states that vibration levels must be less than 3mm/s for horizontal pumps and less than 5mm/s for vertical pumps within the Preferred operating
region. this can increase by 30% when moving outside the Preferred operating region. If excessive vibration or increasing trend is observed, it is crucial to capture the data and carry out
trend analysis to detect the possible source of high vibration, it could be process induced or due to equipment fault like bent shaft, unbalance, bearing failure, misalignment, looseness
etc.
Suction pressure, discharge pressure, total flow, power or input current and specific gravity to be recorded periodically to get indication on duty point and assess the performance.
Long-interval: It covers following activities.
Replacement of lube oil and filter after 6 months or 4000 operational hours, whichever is earlier.
Inspection and replacement of wear parts and consumables according to its life cycle or condition based.
Overhaul and inspection of entire equipment once in a 4 years or condition based.
Inspection, test and overhaul of auxiliary devices like filter, cooler, piping, valves as well as driver
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Breakdown maintenance: Sometimes equipment encounter breakdown due to some lapse, known or unknown reason. In the event of failure, maintenance or reliability engineers have 2 major
challenges - To fix the problem and put the pump into operation in shortest possible time
- To find out root cause and avoid repeating the similar occurrence in future
Troubleshooting and Root cause analysis is complex process, but interesting as well as exciting process. Accurate information like sequence of events, first information report, , failed parts
observation and pictures, process parameters trends, vibration and temperature trends, presence of any operational, instrument or electrical related anomalies etc. need to be collected, closely
reviewed from different perspective and through brainstorming across various discipline experts to arrive at the right conclusion. Table 3 would give more insights on the process of root cause
analysis.
Conclusion: All the steps covered in this article as well as in the previous article are the best to the knowledge and experience of the author. Some of the points may be
debatable or may not be necessarily 100% true as centrifugal pump is quite vast subject and general practice may vary pump to pump and vendor to vendor. Discussion related
to some of the special pumps are also excluded to keep the article short, simple and easy to understand. Finally, I am very much grateful to all the people, books and publications
whom I learned from. Wherever the source of information is known, due credit is given by quoting it into the below reference list.
