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Quick answer: Before starting a ROTAN internal gear pump, identify its exact configuration, make sure the pump turns freely, check alignment and lubrication, open the suction and discharge paths, verify the correctly installed pressure protection, and fill the casing with a compatible liquid. At first start, confirm that it actually draws liquid and that rotation, pressure, flow, sound, seal condition and temperature are normal. Stop promptly if liquid flow does not begin. The checklist below turns those checks into a commissioning record for engineers, maintenance teams and procurement managers; the manual for the installed pump and the plant procedure always set the final limits.
Why a gear pump start-up checklist matters
A ROTAN pump is a positive-displacement internal gear pump. Every revolution moves a volume of liquid, so a closed discharge or a blocked line can raise pressure quickly. An internal bypass, where fitted, provides pump protection only when installed and set for the actual configuration; it does not automatically protect every downstream item or serve as a continuous flow-control method. A pump that starts without sufficient liquid can heat and wear its bearings and shaft seal. These are installation and operating questions, not reasons to order a replacement pump immediately.
Use one record for a new installation, a pump returned from service, or a changed liquid. Note what has changed since the last satisfactory run. A different viscosity, temperature, suction level, hose route or valve position can invalidate an old commissioning result. The photograph on this page shows a DESMI ROTAN HD catalog example; it does not identify the reader’s installed size, seal, relief valve or drive.
Confirm the pump and the duty before anyone energizes it
Read the pump and driver nameplates and record the full type and serial details. Confirm the wetted construction, seal arrangement, speed, rotation, liquid, temperature, viscosity, required flow and normal differential pressure against the purchase and process documents. Do not borrow limits from another ROTAN size or family. For a hazardous-area installation, verify the supplied equipment, protection devices and site approval against the exact documentation; a catalog photograph is never evidence of certification.
Check whether the pump has a fitted bypass valve and whether the complete piping system also needs separate overpressure protection. Verify the bypass orientation and approved opening setting from the correct manual or documented engineering design. Never adjust a bypass while the pump is operating. If the required overpressure protection is missing or connected incorrectly, do not start the motor. DFIN’s ROTAN bypass protection guide explains the difference between protecting the pump and protecting the complete piping system.
Pre-start inspection: five required checks
1. Cleanliness and compatibility
Confirm that the intended liquid is compatible with every wetted component, the shaft seal and any residual test or preservation liquid. DESMI notes that factory test oil can remain in a pump even after draining; clean it to the required standard when it is incompatible with the process liquid. Inspect the source vessel, suction strainer and pipework for debris or coagulated material from a previous shutdown. A clogged strainer can prevent an otherwise functioning pump from drawing liquid.
2. Mechanical readiness
With the drive isolated, confirm that the shaft can turn freely by the method permitted for this installation. Check the base, coupling, guard, pipe supports and alignment after piping is connected. Piping should not force the pump flanges into position. Confirm bearing lubrication where the supplied bearing arrangement requires it. If a mechanical seal, packing, jacket or monitoring device has just been serviced, verify its assembly and auxiliary connections against its own instructions before start-up.
3. Liquid path and prime
Trace the complete path from the tank to the discharge destination. Open the correct suction and discharge isolating valves. Confirm that a strainer, non-return valve, filter, hose or nozzle is not blocking the intended path. Fill the pump casing with a compatible liquid as required by the ROTAN manual to support self-priming. Make sure there is enough liquid in the source vessel to maintain supply. Never rely on the words “self-priming” as permission for sustained dry running.
4. Drive, direction and protection
Verify the motor’s electrical protection and the specified rotation without running the connected pump dry. Confirm the direction of flow for this exact installed arrangement; if the drive or piping has changed, do not assume old rotation labels still apply. Check pressure indication, available flow measurement, temperature or dry-run protection and emergency stop where specified. Test interlocks by the approved site method. Record the bypass or relief configuration and its authorized setting rather than turning an adjustment screw during commissioning.
5. Final checks before start
Remove tools. Refit the protective covers around moving parts. Clear the work area and inform the operator of the downstream process. Check that the destination can accept liquid and the relevant drains and vents are in their operating positions. If the liquid is hot, corrosive, toxic or flammable, use the plant’s isolation and personal-protection procedure. Never loosen a vent or seal connection on a running or pressurized pump to investigate missing flow.
Record the first start and decide whether to continue
Start only after all five required checks are complete. Watch for liquid flow immediately and compare the observed direction with the intended line. Log inlet and discharge pressure, flow, motor current, pump speed, seal condition, vibration or unusual sound, and temperatures at the intervals required by the site. Where process design allows a controlled speed increase, increase it under the operating procedure while watching suction and differential pressure. Avoid extended bypass recirculation: it can add heat without useful liquid flow.
Swipe the table horizontally to view all columns.
| Observation at first start | First checks | Decision |
|---|---|---|
| No liquid flow | Source level, open suction valve, casing fill, trapped air, rotation and strainer | Stop and restore the liquid path before another attempt. |
| Pressure rises rapidly with weak flow | Discharge valve, blocked line, filter, hose and bypass route | Stop; do not use the bypass as a prolonged operating path. |
| Rattling or unstable inlet pressure | Suction restriction, air ingress, viscosity at temperature and source level | Stop or reduce duty per procedure; correct suction conditions. |
| Seal leakage or rising bearing temperature | Seal type, lubrication, alignment, liquid supply and compatible materials | Stop at the model’s specified limit; inspect before ordering parts. |
| Flow and pressure stable | Current, speed, temperature and leak checks against design duty | Document a baseline for later troubleshooting. |
A brief self-priming period is not a license to continue with no liquid flow. DESMI’s ROTAN manual requires checking that the pump draws liquid after start and says operation without liquid flow is limited to the short period needed for self-priming because of slide bearings and seals. If liquid flow does not begin, stop, isolate and find the cause. The ROTAN suction troubleshooting guide helps distinguish restriction and air ingress from a pump fault.
After maintenance or a long shutdown, add these checks
Confirm the service scope before reusing an old baseline. A replaced seal can change flush or lubrication requirements. A rebuilt wet end may need model-specific axial-clearance and free-rotation checks by qualified personnel. A changed motor, coupling or control setting requires rotation and speed verification. Long storage raises separate questions about preservation liquid, corrosion, elastomer condition and bearing grease; use the applicable DESMI instructions for the actual storage period and pump version. Do not infer a universal replacement interval from a different model.
Once the pump runs normally, retain the first-start readings and note the liquid batch, temperature, source level, valve positions and control settings. These observations make later low-flow, heat or seal-leak reports far more useful than a statement that the pump “sounds wrong.” If temperature rises or discharge falls during subsequent operation, compare against this baseline and investigate the changed system condition before specifying spares.
What to send with a pump or spare-parts RFQ
A procurement request should let the supplier match the installed pump and the duty, not just a visible casting. Include:
- Clear photographs of pump and motor nameplates, full ROTAN type, serial number and existing part numbers.
- Liquid identity, composition, temperature range, viscosity at operating temperature and any solids or cleaning fluids.
- Required and observed flow, suction arrangement, inlet and discharge pressures, speed and motor details.
- Seal, bearing, bypass and monitoring arrangement, plus the service history and the failed inspection result.
- Whether the request is for a complete pump, seal or bearing parts, a bypass component, or a commissioning review; include quantity and destination.
Review the ROTAN HD product family only as a configuration reference, then send the actual duty and identification through DFIN’s request-for-quotation form. Price depends on the verified configuration, materials, repair scope, quantity and delivery terms. An unspecified “ROTAN gear pump” does not support a reliable universal price.
Frequently asked questions
Can a ROTAN internal gear pump start with an empty casing?
Do not plan a dry start. The applicable DESMI manual calls for liquid in the casing to support self-priming and protection against dry running. Verify the specific liquid and filling method for the installed pump and process.
Should the discharge valve be closed for start-up?
No. A positive-displacement gear pump needs a safe open discharge path and verified overpressure protection before start. The ROTAN manual calls for suction and pressure-line isolating valves to be fully open in its pre-start checks. Follow the actual system procedure and relief design.
Can I test the bypass by adjusting it during operation?
No. Use the manufacturer’s prescribed isolated adjustment and verification procedure with qualified personnel. Do not turn the bypass adjustment while the pump is operating, and do not use continuous bypass flow as normal capacity control.
What if the pump runs but does not deliver after service?
Stop rather than waiting for it to recover. Check casing fill, source level, open valves, air entry, strainer, rotation and line routing. If those are sound, investigate internal wear or an incorrectly assembled component using the exact service manual. Record the checks before ordering a replacement.
Commissioning decision
Begin routine operation only when the liquid path, overpressure protection and liquid in the casing are confirmed and a stable operating baseline has been recorded. A repeatable start-up record separates an installation issue from a damaged part and gives maintenance and procurement the evidence needed to specify the right action.