How to Run a Multi-Pump Test Rig Experiment: Step-by-Step Procedure for Fluid Mechanics Labs

This guide walks you through the multi pump test rig experiment procedure the way I’d actually run it on a Monday morning in a diploma or B.Tech fluid mechanics lab. It’s written for the lab-in-charge who has to demonstrate series and parallel pump operation to a batch of 20 students, the faculty coordinator writing the SOP, and the procurement head who wants to know what the rig has to do before they sign a purchase order. I’ve commissioned enough multi-pump rigs to know where students blow the priming and where the readings drift, so I’ll flag those inline instead of hiding them at the end.

A multi-pump test rig lets you characterise a single centrifugal pump, then combine two identical pumps in series (more head, same discharge) or in parallel (more discharge, same head). If your syllabus is NBA or AICTE aligned, this experiment usually sits in the second-year hydraulic machines lab, right after the impact-of-jet setup and the Reynolds apparatus. Get it right and students actually understand why municipal water supply schemes buy two small pumps instead of one big one.

What you need before you start

Before anyone touches the mains switch, line these up:

• The rig itself. A multi-pump test rig with two identical centrifugal pumps, isolation valves for series and parallel switching, suction and delivery pressure gauges on each pump, a common sump, and either a collecting tank with a piezometer or a rotameter for discharge measurement.
• Floor space. Expect roughly a 1.5 m by 1 m footprint, plus 600 mm clearance on the operator side. Rigs with a tall rotameter column need about 2.1 m of ceiling height.
• Power. Two single-phase 0.5 HP motors will draw around 8 to 10 A combined at start-up. I’d insist on a dedicated 16 A MCB, not a shared lab circuit.
• Water. The sump typically holds 80 to 120 L. Use clean tap water. Nobody I know actually does this, but if your city water is hard, one flush per semester saves the impeller.
• Reference standards. Keep ISO 9001:2015 QA documentation and the CE marking declaration in the lab file. Auditors from NBA and AICTE ask.
• Budget sanity. Teaching-grade rigs for undergraduate use sit in a very different price band than research-grade units with variable-frequency drives and data acquisition. Decide which one your syllabus actually needs before you shortlist. Our multi-pump test rig buyer’s guide breaks the tiers down.

Step-by-step: multi-pump test rig procedure

Run the experiment in this sequence. Don’t skip the priming check, and don’t let a student open the delivery valve fully before start-up. That’s how you throw a coupling.

1. Inspect and prime. Fill the sump to the marked level. Open the priming plug on each pump casing and top up until water spills, then close. A dry-primed centrifugal pump will run for maybe 30 seconds before the mechanical seal cooks.
2. Set the valve configuration. For single-pump characterisation, close the interconnecting valve so Pump 2 is isolated. For series, connect Pump 1 delivery to Pump 2 suction. For parallel, both suctions from sump, both deliveries into a common header. Label the valves with numbered tags if your rig doesn’t already.
3. Zero the instruments. Bleed air from the pressure gauge lines. Check that both suction and delivery gauges read atmospheric when the pump is off. A stuck needle here is the single most common source of a garbage lab report.
4. Close the delivery valve, then start the pump. Centrifugal pumps start against a closed delivery to keep starting current low. Once the motor is at rated speed (usually 2 to 3 seconds), crack the delivery valve open.
5. Take the shut-off head reading first. With the delivery valve fully closed and the pump running, record the delivery pressure. This is your maximum head point on the H-Q curve.
6. Open the valve in 6 to 8 steps. At each step, wait 20 to 30 seconds for the flow to stabilise, then record: delivery pressure, suction pressure, discharge (from rotameter or timed collecting-tank rise), and motor input if the rig has an energy meter.
7. Compute total head at each step. H = (P_delivery minus P_suction) converted to metres of water column, plus the velocity-head difference if the suction and delivery pipe diameters differ. Most teaching rigs use equal diameters so students can skip the velocity term, but a good report notes the assumption.
8. Repeat for series and parallel. Reconfigure the valves, re-prime if you drained anything, and run the same 6 to 8 point sweep. You now have three H-Q curves on the same axes.
9. Compute efficiency at each operating point. Hydraulic power out = rho x g x Q x H. Electrical power in = read from energy meter or wattmeter. Overall efficiency = P_out divided by P_in. Expect 35 to 55 percent on small teaching pumps. Anything above 65 percent, check the calculation.
10. Shut down cleanly. Close the delivery valve, switch off the motor, then open the delivery valve again to drain pressure. Don’t leave a pressurised delivery line overnight, the gauge diaphragm creeps.

Common mistakes and pitfalls

• Priming shortcuts. Students top up the priming cup, see water, and assume it’s primed. If the suction line has an air pocket the pump will still run dry. Watch for delivery pressure that never rises past 0.2 bar, that’s your tell.
• Reading the gauge under vibration. Small delivery gauges swing ±0.1 bar at low flow. Use a snubber, or take three readings and average. Better rigs ship with glycerine-filled gauges for exactly this reason.
• Parallel operation with unequal pumps. If the two pumps aren’t matched, the stronger one back-flows through the weaker one. Insist on identical pump-motor sets at purchase time, not just identical impellers.
• Collecting-tank measurement error. A 1-second stopwatch error on a 20-second collection is 5 percent flow error, which is bigger than your differences between series and parallel operating points. Time at least 60 seconds, or use the rotameter.
• Ignoring cavitation. If suction pressure drops close to vacuum and you hear gravel-in-the-casing noise, throttle the suction side up and re-prime. Cavitation eats impellers in a semester if unchecked.

Standards and compliance

For the equipment itself, insist on ISO 9001:2015 manufacturing quality and a CE conformity declaration for electrical safety. If your institution runs a NABL-accredited testing lab alongside teaching, calibration of the pressure gauges and flow meters has to be traceable under ISO 17025. AICTE and NBA audits ask for the manufacturer’s test certificate and the last calibration report, keep both in the lab file. For pump curve terminology and test conditions, stick with the ISO 9906 method even in teaching write-ups, it makes final-year projects portable to industry work.

The Scientico angle

Scientico has been manufacturing fluid mechanics equipment out of Ambala since 1993 and ships to 60+ countries, so the rigs are built to survive shipping to a college in East Africa or Southeast Asia, not just a local delivery van. The multi-pump test rig apparatus (FluidoSurge X) is the standard teaching unit, matched pumps, clearly labelled valves, and a rotameter that a first-year student can read without a magnifier. If you’re planning the wider hydraulic machines lab, pair it with the Kaplan turbine apparatus (FluidoSurge X 208) so students see both energy conversion directions in the same room. Both are covered by the ISO 9001:2015 QA process and CE-marked for electrical safety.

Related reading

• Multi-pump test rig buyer’s guide (India), tier-by-tier price bands and specification checklist.
• Hydraulic bench buyer’s guide, the companion instrument you’ll want alongside the multi-pump rig.
• Complete fluid mechanics lab setup guide, what a full 20-student lab actually needs.
• Lab equipment for engineering colleges, hub page for B.Tech and M.Tech procurement.
• Lab equipment for polytechnics and TVET, diploma-grade specification guidance.

Ready to specify or quote a rig? Send your syllabus and target student batch size to our engineering team via the Scientico contact page and we’ll come back with a configuration and a delivery timeline, no fluff.

Frequently Asked Questions

How long does one multi-pump test rig experiment take in a teaching lab?

Plan for a 2-hour lab slot. Priming, single-pump sweep, series sweep, and parallel sweep with 6 to 8 readings each typically fills 90 minutes for a group of four students, plus 30 minutes for calculations and the H-Q plot.

Do I need three-phase power for a teaching-grade multi-pump test rig?

No. Most teaching units use two 0.5 HP single-phase motors and run off a dedicated 16 A single-phase circuit. Three-phase is only needed for research-grade rigs with variable-frequency drives on larger pumps.

What's the difference between series and parallel pump operation for students to understand?

Series doubles the head at the same flow rate, useful when you need to push water higher. Parallel doubles the flow at the same head, useful for higher demand at the same elevation. The rig lets students plot both curves and see the trade-off.

What discharge measurement method is more accurate, rotameter or collecting tank?

A well-calibrated rotameter is faster and repeatable to about 2 percent. The collecting tank method is more accurate at low flows if you time at least 60 seconds, but stopwatch error dominates at short collection times.

Which standards should the multi-pump test rig comply with for NBA or AICTE audit?

Manufacturing quality under ISO 9001:2015, electrical safety under CE marking, and calibration traceability under ISO 17025 for the gauges and flow meter. Keep the manufacturer’s test certificate and last calibration report in the lab file.