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Marine Cargo Pumps and Piping Systems

Marine cargo pumps and piping systems handle the loading, internal transfer and discharge of liquid cargo on tankers (oil tanker, chemical tanker, LNG carrier) and product carriers. The dominant cargo pump technology is centrifugal pumps for high-volume operations (oil tankers, product tankers) with capacities from 500 to 10,000 cubic metres per hour, supplemented by deep-well submerged pumps on chemical tankers and stripping pumps for low-residue tank emptying. The piping system delivers cargo from cargo tanks through pumps, deck manifolds, and shore connections, with shipyard-grade welded carbon steel typical for oil cargo and stainless steel or special alloys for chemicals. Operational considerations include pump selection (centrifugal vs deep-well based on cargo properties), suction conditions (avoiding cavitation), discharge head limits, sequencing during loading and discharge, tank stripping (final emptying), inert gas system integration on flammable cargoes (SOLAS Chapter II-2), cargo segregation between grades, and the comprehensive maintenance regime required for reliable operation through the ship’s typical 25 to 30 year operational life. ShipCalculators.com hosts the relevant computational tools through the calculator catalogue including the main cargo pump centrifugal deep-well article.

Contents

Background

Cargo pump applications

Cargo pump applications by ship type:

  • Crude oil tankers (VLCC, Suezmax, Aframax): very high volume, 6,000 to 10,000 m³/h cargo discharge.
  • Product tankers (LR2, LR1, MR, Handysize): medium volume, 1,500 to 5,000 m³/h.
  • Chemical tankers: lower volume per pump but more pumps for cargo segregation; deep-well pumps typical.
  • Gas carriers (LPG, ethylene, ammonia): refrigerated cargo with cryogenic pumps.
  • LNG carriers: cryogenic submerged pumps in cargo tanks.
  • Bunker barges and small tankers: smaller capacity centrifugal pumps.

Major manufacturers

Cargo pump manufacturers:

  • Framo (Norway): leading supplier of submerged hydraulic deep-well pumps for chemical tankers.
  • Wartsila Hamworthy: cargo pumps and pump rooms.
  • Sulzer: centrifugal cargo pumps for oil tankers.
  • Shinko (Japan): cargo pumps for Japanese-built tankers.
  • DESMI: smaller cargo pumps and pump rooms.
  • Onyx (Korea): cargo pumps for Korean-built tankers.

The market is dominated by Framo for chemical tankers and a more diverse mix for oil tankers.

Cargo pump types

Centrifugal cargo pumps

Centrifugal cargo pumps:

  • Configuration: typically vertical centrifugal with motor on top, pump impeller in cargo line.
  • Capacity: 500 to 10,000 m³/h depending on size.
  • Discharge head: 50 to 200 metres typical.
  • Drive: electric motor (typically 200-2,000 kW).
  • Casing: cast iron for oil, stainless steel or alloy for chemicals.
  • Suction location: in pump room (oil tankers) or in cargo tank (deep-well).

Centrifugal pumps are the workhorse for high-volume cargo operations. The main cargo pump centrifugal deep-well article provides further detail.

Deep-well submerged pumps

Deep-well submerged pumps:

  • Configuration: pump unit submerged in the cargo tank, with motor or hydraulic motor at the top.
  • Capacity: 100 to 1,000 m³/h per unit.
  • Discharge head: 100 to 200 metres typical.
  • Drive: hydraulic (Framo system) or electric (less common for chemicals due to explosion-protection complexity).
  • Materials: stainless steel for chemical tankers, special alloys for specific cargoes.
  • Suction: at the bottom of the cargo tank for low-residue stripping.

Deep-well pumps eliminate the pump room (a hazardous space on conventional tankers) and allow strict cargo segregation. Each cargo tank typically has its own deep-well pump.

Stripping pumps

Stripping pumps:

  • Function: removing the last few percent of cargo (residue) from cargo tanks.
  • Capacity: lower than main pumps (typically 50-200 m³/h).
  • Type: typically positive displacement (reciprocating or rotary lobe).
  • Operation: at end of main cargo discharge, pumping out the remaining cargo.

The bulk loading rate-arm calculator addresses related operational considerations for bulk cargo (which is different but uses similar concepts).

Cryogenic pumps

Cryogenic cargo pumps for LNG and ethylene carriers:

  • Materials: stainless steel and special alloys for low temperature service.
  • Sealing: dry-running mechanical seals (no shaft seal lubrication possible at cryogenic temperature).
  • Insulation: of pump and piping to limit heat ingress.
  • Boil-off gas (BOG) management: integrated with cargo system.

LNG cargo pumps operate at minus 162 degrees Celsius and require specific design for thermal cycling and material compatibility.

Piping systems

Pump room piping

Pump room piping (oil tankers, chemical tankers without deep-well configuration):

  • Material: carbon steel for oil, stainless or special alloys for chemicals.
  • Flange connections: typically welded throughout, with flanged connections at pumps and valves.
  • Coating: external coating for corrosion protection.
  • Insulation: thermal insulation for heated cargoes.
  • Ventilation: pump room is hazardous area requiring continuous ventilation.

Deck piping

Deck piping (cargo manifold, transfer lines):

  • Material: same as pump room piping (matched to cargo).
  • Manifold connections: standardised flanges (ANSI 150, 300 lb depending on pressure).
  • Valves: ball, gate, or butterfly depending on application.
  • Drip trays: under flanged connections.
  • Insulation: as required for heated or refrigerated cargo.

Inert gas integration

Inert gas system (IGS) integration:

  • Tank inerting during cargo discharge: IGS replaces the discharged volume.
  • Pressure-vacuum valves on each tank for atmospheric breathing.
  • IGS pipework parallel to cargo system in some configurations.
  • Oxygen monitoring maintaining tank ullage below 8 percent oxygen.

SOLAS Chapter II-2 requires IGS on tankers above 20,000 deadweight tonnes for crude oil.

Cargo handling operations

Loading

Loading sequence:

  1. Pre-loading checklist: with shore terminal, ship-shore safety checklist completed.
  2. Cargo distribution plan: agreed for required tank-by-tank loading.
  3. Manifold connection: hoses or arms connected, leak-tested.
  4. Loading commences: at moderate rate initially, increasing to full rate.
  5. Tank-by-tank monitoring: ullage, temperature, pressure observed.
  6. Topping off: final loading at reduced rate to fill to design ullage.
  7. Sample collection: representative samples for cargo quality verification.
  8. Departure preparation: closing valves, disconnecting hoses.

Discharge

Discharge sequence:

  1. Pre-discharge checklist with shore terminal.
  2. Manifold connection to shore-side reception.
  3. Cargo pumps started: typically multiple pumps in parallel.
  4. Bulk discharge: at maximum rate compatible with shore reception capacity.
  5. Stripping: as tanks empty, switching to stripping pumps for residue.
  6. Final stripping: minimising tank residue.
  7. Slop tank operations: collecting residual oil for environmental compliance.
  8. Tank cleaning preparation: before next cargo if changeover.

Tank cleaning

Tank cleaning operations:

  • Purpose: removing previous cargo residue before new cargo.
  • Methods: water washing, COW (Crude Oil Washing) for crude tankers, chemical cleaning for chemicals.
  • Tank entry: requires pre-entry atmospheric testing under permit-to-enter procedures.
  • Slops: collected for shore disposal under MARPOL Annex I.
  • Documentation: in Cargo Record Book (chemical tankers) or Oil Record Book Part II (oil tankers).

Operational considerations

NPSH and cavitation

Net Positive Suction Head (NPSH):

  • NPSH-A (Available): from cargo tank head minus losses.
  • NPSH-R (Required): pump-specific from manufacturer.
  • Cavitation: occurs when NPSH-A drops below NPSH-R, causing vapour bubbles that damage impeller.
  • Mitigation: maintain adequate suction head, control discharge rate, avoid running pump dry.

Vibration and noise

Cargo pump vibration and noise:

  • Vibration monitoring: typical operating vibration is moderate; excessive vibration indicates imbalance or bearing wear.
  • Noise levels: typically 85-95 dB at 1 metre during operation.
  • Hearing protection: required for crew working near operating pumps.

Cargo segregation

Cargo segregation on chemical tankers:

  • Each cargo grade has its own pump and piping.
  • No cross-contamination between grades.
  • Material compatibility: pump materials matched to cargo for each grade.
  • Cleaning between cargoes: comprehensive when grades change.

The segregation requirements drive the deep-well pump configuration on chemical tankers.

Cargo heating

Heated cargo operations:

  • Cargo heating coils in cargo tanks (steam from auxiliary boiler).
  • Pump room heating: maintaining cargo at correct temperature in piping.
  • Insulation: of cargo lines.
  • Temperature monitoring: continuous through tank temperature sensors.

The cargo heating coil steam rate calculator and cargo steam heating time calculator address heated cargo operations.

Maintenance and surveys

Routine maintenance

Routine cargo pump maintenance:

  • Daily: visual inspection during operation.
  • Weekly: bearing temperature checks, oil sample.
  • Monthly: more detailed inspection of accessible parts.
  • Quarterly: vibration analysis.
  • Annual: comprehensive inspection.
  • Major overhaul: every 10,000 to 30,000 hours depending on application.

Class society surveys

Class society surveys:

  • Annual surveys: visual examination of accessible components.
  • Internal examination: at periodic surveys with pump opened.
  • Pressure test: of cargo piping at intervals.
  • Documentation review: of operating hours and maintenance records.

Common operational issues

Common cargo pump issues:

  • Cavitation damage: from inadequate suction conditions.
  • Bearing wear: from extended operation or contamination.
  • Mechanical seal failure: from extreme service conditions or improper installation.
  • Impeller wear: from cargo containing solids or abrasives.
  • Vibration: from imbalance, alignment issues, or worn components.
  • Drive coupling failure: from misalignment or overload.

Each issue has specific diagnosis and repair procedures in the maintenance manual.

Decarbonisation impact

Energy efficiency

Cargo pump energy efficiency:

  • Variable-speed drives: matching pump speed to actual demand.
  • High-efficiency motors: meeting IE3/IE4 efficiency standards.
  • Optimal sizing: avoiding over-sized pumps that operate inefficiently.
  • Heat recovery: from pump motor cooling where applicable.

Alternative fuels for cargo pumps

Cargo pump prime mover transition:

  • Electric motors: standard, with electricity from auxiliary engines (subject to fuel transition).
  • Hydraulic drives: with the hydraulic power source subject to fuel transition.
  • Steam turbine drives: very rare on modern tankers but historically used.

CII implications

CII rating implications:

  • Cargo pump fuel consumption during loading and discharge contributes to overall fuel use.
  • Reduced loading time (within terminal capacity) reduces port-side fuel.
  • Optimised discharge sequencing minimises pump operating time.

See also

Additional calculators:

Additional formula references:

Additional related wiki articles:

References

  • IMO SOLAS Chapter II-2 (cargo space fire protection).
  • IMO MARPOL Annex I (oil pollution prevention).
  • IMO MARPOL Annex II (noxious liquid substances).
  • IBC Code (International Bulk Chemical Code).
  • IGC Code (International Gas Carrier Code).
  • IACS Common Structural Rules.
  • Class society marine cargo pump rules.
  • Framo, Wartsila, Sulzer, Shinko technical documentation.