Contents
Preheat a ROTAN internal gear pump when the liquid at the planned start temperature is too viscous to feed the pump and turn safely, or when it may solidify in the pump. A heating jacket can keep the pump body and, in some configurations, the seal area warm. It does not by itself heat a cold tank, a blocked suction line or the whole discharge system. Determine the required jacket and heating sequence from the actual liquid, lowest ambient temperature, viscosity-versus-temperature data and the exact ROTAN configuration.
This guide is for engineers planning viscous-liquid transfer and buyers comparing pump options. The photograph shows a representative ROTAN HD product family, not evidence that the pictured unit has a jacket or matches a customer’s installed build. Confirm every option against the nameplate, drawing and current manufacturer documentation.
Why a cold start changes the pump duty
Many oils, resins, waxes and bitumen-like liquids become much more viscous as they cool. A pump selected around normal process temperature can see a very different duty after a long shutdown. Thick liquid raises suction-line losses, may starve the inlet, and can increase the torque needed to turn the pump. If a product forms crystals or a solid plug, trying to force rotation may damage the pump or drive. The label “high viscosity” alone is insufficient: request a measured viscosity curve and the coldest credible starting condition.
Internal gear pumps are positive-displacement machines. They need an open and correctly protected flow path. Heating is not a substitute for a suitable suction design, motor selection, speed, clearance, relief arrangement or process procedure. If the process has changed since the original selection, review all of these together.
What a heating jacket can and cannot do
DESMI describes front-cover and rear-cover heating or cooling jackets as configuration options on ROTAN pumps. The heating medium circulates in a separate chamber to keep liquid in the relevant pump area fluid. A rear-cover jacket may also serve a seal-related temperature duty on an applicable configuration. A front-cover jacket, rear-cover jacket, electrical heater and pipe heat tracing are different options; none should be assumed from the ROTAN family name alone.
Swipe the table horizontally to view all columns.
| Cold-start observation | Likely review | What a pump jacket does not solve |
|---|---|---|
| Liquid remains mobile at the pump, but the suction line is cold or plugged | Tank outlet, strainer, valve, suction diameter and line tracing | It cannot clear or heat an isolated upstream blockage |
| Liquid thickens or sets inside the stopped pump | Pump jacket location, heating medium and warm-up procedure | It cannot confirm adequate motor torque or pressure protection |
| Seal area needs a controlled temperature | Exact seal design and rear-cover temperature arrangement | It does not replace seal compatibility or the required seal plan |
| Whole process starts cold and reaches high pressure | System-wide heat balance, line losses, speed and drive | It cannot heat the entire circuit or make a closed valve safe |
Do not select a jacket by copying another installation’s heating-medium temperature or pressure. The permitted medium, chamber limits and safety provisions belong to the exact manufacturer drawing and manual. Ask for the applicable instructions before connecting utilities.
Decide whether to specify preheat
1. Establish the coldest real operating state
Record the lowest ambient and liquid temperature after a normal overnight stop, extended shutdown and seasonal outage. Note whether the liquid settles, crystallizes, gels or separates while idle. Obtain viscosity at those temperatures and at normal running temperature; one viscosity value at room temperature cannot define startup. Include the time available to warm the system before the pump must run.
2. Check the whole fluid path
Trace the vessel outlet, suction line, strainer, inlet nozzle, pump, discharge line and destination. Identify any cold spot that could prevent feed or create a high differential pressure. A warm pump with a solid plug upstream may run dry or fail to prime. A warm pump with a closed downstream valve may rapidly overpressure. Review the ROTAN suction diagnosis guide if inlet starvation is suspected.
3. Match jacket location and utilities to the pump build
Ask whether the proposed pump is actually available with the needed front or rear jacket, or another approved heating option. Specify the proposed heat-transfer medium, available supply and return connections, temperature control, warm-up time and shutdown behavior. Confirm material compatibility and the allowed chamber conditions with the manufacturer’s current documents. Do not improvise a utility connection on a port whose function has not been identified.
4. Recheck mechanical and electrical duty
Even after preheat, the liquid may be thicker than at its normal operating temperature. Check the expected startup viscosity against the selected speed, torque, motor current, differential pressure, relief setting, seal arrangement and clearances. If the drive has tripped before, collect current and pressure readings rather than simply fitting a larger motor. Changes to heating, speed or clearance need a configuration-specific engineering review.
A safe warm-up and first-start checklist
- Identify the installed ROTAN code, serial number, jacket ports, seal arrangement and operating manual. Apply site isolation and hot-surface procedures before inspection.
- Confirm that the vessel outlet and suction line contain fluid and that any required tank or line heating is functioning. Inspect the strainer and valve positions.
- Circulate the approved heating medium through the designated jacket circuit using the approved temperature and pressure controls. Allow sufficient time for the pump and liquid within it to reach the reviewed starting condition.
- Check that the intended discharge path is open and the system pressure protection is correctly arranged. The pump bypass is not a substitute for whole-system relief; see the ROTAN relief guide.
- Start using the manufacturer and plant procedure. Monitor inlet condition, discharge pressure, flow, motor current, vibration, seal area and temperature trend. Stop if the readings depart from the approved start envelope.
- After stable operation, record the successful warm-up time, liquid temperatures and readings as a baseline for the next restart. Investigate changes instead of assuming the same time always suffices.
Never loosen a jacket connection, seal or pump cover while pressurized or hot. Follow the exact ROTAN instructions and the plant’s lockout and hazardous-liquid rules. For a new installation, have the installer verify rotation, alignment, piping support and instrumentation before the first heated run. Our broader ROTAN startup checklist covers those general steps.
How to write an RFQ for a heated ROTAN pump
Send a complete duty description rather than asking for a “jacketed ROTAN” alone. DFIN can then review the family, exact configuration and scope with the manufacturer. The purchase price depends on the confirmed pump build, jacket or heater arrangement, materials, seal, drive, controls and delivery scope; request a quotation for the specified duty.
- Liquid name and composition, concentration, solids and any tendency to crystallize or harden.
- Viscosity at the coldest start and normal operation, with the temperature for each value and a curve if available.
- Required flow, suction conditions, differential pressure, operating schedule and shutdown duration.
- Tank, suction and discharge line heating arrangements, ambient range and required warm-up time.
- Available heating medium, supply and return conditions, control method and utility connection standard.
- Required wetted materials, seal and leakage constraints, electrical area requirements and documentation.
- For replacement: full nameplate and configuration code, serial number, photos, drawing, existing utility connections and observed cold-start problem.
Submit this package through the DFIN RFQ contact page. The family guide helps compare DESMI ROTAN options, while the exact heated execution still needs confirmation.
Frequently asked questions
Does every viscous-liquid ROTAN pump need a jacket?
No. The decision depends on liquid behavior at the actual starting temperature, the suction and discharge system, the available warm-up procedure and the selected pump build. Some systems keep the entire process hot; others require jacket or line heating. Ask for a configuration review rather than treating viscosity at one temperature as a universal rule.
Can I start as soon as the jacket feels warm?
No. Surface feel does not show that the liquid in the pump and piping has reached the reviewed starting condition. Use approved temperature measurements, the documented warm-up procedure and an open, protected flow path.
Will a rear-cover jacket heat the suction line?
No. It acts on its designated pump area. A cold or plugged suction line needs its own process and heating review. Verify the port and jacket function on the exact drawing.
Can heating cure a pump that trips on startup?
Only if cold liquid is actually the cause and the proposed heating plan addresses it. A blocked line, closed valve, wrong rotation, mechanical damage or unsuitable drive can also cause a trip. Preserve the trip and operating readings for diagnosis before changing hardware.