Stainless Steel Screw Fuel Oil Pump

I. Product Overview

Stainless steel screw fuel oil pumps feature high-precision screw meshing structures, using austenitic stainless steel (316/316L) or duplex stainless steel (2205) as the main material. Designed based on positive displacement transportation principles, they provide low-pulsation and high-pressure transportation solutions for fuel media such as diesel, heavy oil, and biodiesel. The screw profile adopts a 5:6 asymmetric tooth design (tri-screw pump) or single-screw eccentric design with a meshing clearance ≤0.03mm, enabling stable transportation of fuel with viscosity 10-5000cSt under 0.5-4.0MPa pressure, with a volumetric efficiency of 92%-96%. They are suitable for high-viscosity fuel scenarios such as marine fuel supply, industrial fuel boilers, and mobile power generation equipment.

II. Core Materials and Performance Adaptation

1.316 Stainless Steel (Medium-Sulfur Fuel Scenarios)

Characteristics: Contains 2-3% molybdenum, corrosion rate <0.008mm/year in diesel/heavy oil with sulfur content ≤1%, tensile strength ≥520MPa, resistant to fuel temperatures of -40℃~150℃. The screw surface is sprayed with tungsten carbide (thickness 50-80μm), hardness reaches HRC65-70, and wear resistance to solid particles in fuel is 6 times higher than cast iron.

Applications: Marine main engine light diesel systems (0# diesel, viscosity 3-8cSt), industrial gas turbine fuel pumps, suitable for medium-sulfur fuel media (such as crude oil with API gravity >20).

2.316L Stainless Steel (Low-Sulfur Fuel/Clean Scenarios)

Improved Design: Carbon content ≤0.03%, excellent intergranular corrosion resistance after welding, screw surface electrolytic polishing (Ra≤0.4μm), wear rate 35% lower than 316 stainless steel in ultra-low sulfur diesel with sulfur content ≤0.5%, suitable for biodiesel (blend ratio ≤30%) transportation.

Typical Scenarios: Marine fuel systems after IMO 2020 sulfur restrictions, LNG-powered ship auxiliary pumps, or food-grade vegetable oil transportation (requiring NSF H1 certification) to avoid fuel contamination and corrosion.

3.Duplex Stainless Steel (2205/2507)

High-Strength Corrosion Resistance: Ferritic-austenitic duplex structure, pitting corrosion resistance index (PREN) ≥40, stress corrosion resistance 2.5 times higher than 316L in high-sulfur heavy oil with sulfur content 1-3%, tensile strength ≥620MPa, can withstand 4.0MPa high-pressure fuel impact, and resist acidic substances (pH≤3) from fuel high-temperature cracking.

Special Applications: 380cSt heavy oil supply for ocean-going ships (viscosity 380cSt, preheated to 120℃), sulfur-containing residue oil transport pumps in refineries, resisting composite corrosion from asphaltenes and sulfides.

III. Technical Advantages and Application Limitations

Core Technical Advantages

1. Low-Pulsation Transportation and High-Viscosity Adaptability

The spiral meshing of tri-screw pumps forms continuous sealing chambers, with outlet pressure pulsation ≤±0.5%, suitable for precision fuel injection systems (such as common rail diesel engines). In 5000cSt heavy oil (preheated to 130℃), it still maintains 90% volumetric efficiency, with a self-priming height ≥6m (20% better than gear pumps).

2. Long Life and Low-Noise Design

Duplex stainless steel screws undergo ion nitriding treatment (depth 0.3mm), surface hardness HRC58-62, service life reaches 100,000 hours in fuel containing 0.2% solid impurities; operation noise ≤70dB (at 1500rpm), 15-20dB lower than gear pumps, suitable for marine engine room noise reduction requirements.

3. High Safety and Compliance Design

The pump body adopts an explosion-proof design (Ex d IIB T4 Gb), and the motor junction box explosion-proof rating meets ATEX certification, with static grounding resistance ≤1Ω. Equipped with bellows mechanical seal + PTFE lip seal double protection, fuel leakage ≤2 drops/hour, complying with MARPOL Annex I anti-pollution requirements.

Performance Limitations

1. High-Temperature and Impurity Sensitivity Boundaries

When the fuel temperature of 316 stainless steel pumps >180℃, fuel carbonization causes screw wear to increase by 60%, requiring a cooling jacket (heat exchange area ≥4m²). When transporting fuel with particles >15μm, a double-barrel filter (accuracy ≤5μm) is required; otherwise, meshing clearance wear increases by 0.015mm monthly.

2. Viscosity and Speed Matching Limitations

When transporting low-viscosity fuel with viscosity <15cSt (such as gasoline), the speed should be controlled ≥2500rpm to avoid increased internal leakage; when viscosity >3000cSt (unpreheated), pump efficiency decreases by 35%, requiring a pre-installed electric heating (power configured as 2.5kW/100L/h flow).

3. Cost and Installation Requirements

Duplex stainless steel pumps cost 10-12 times more than cast iron pumps, with a 70% increase in weight (e.g., DN100 pump weighs about 48kg), requiring a rigid foundation (levelness ≤0.05mm/m). Large-flow models (≥500m³/h) need an inlet flow stabilizer to prevent cavitation (NPSHa≥4m).

IV. Typical Application Scenarios

1. Marine Fuel Systems

Main Engine Heavy Oil Supply: Duplex stainless steel tri-screw pump transports 380cSt heavy oil for low-speed two-stroke main engines, configured with steam tracing jackets (temperature maintained at 120℃), achieving large-flow supply of 1000m³/h under 2.0MPa pressure to meet the fuel pressure requirements of MAN B&W main engines.

Emergency Fuel Pumps: 316L stainless steel single-screw pumps serve as fuel supply equipment for marine emergency generators, started by hand pumps, providing at least 4 hours of fuel supply when the main power fails, complying with SOLAS convention emergency system requirements.

2. Industrial Fuel Transportation

Boiler Fuel Supply: 316 stainless steel twin-screw pump transports 0# diesel for industrial boilers converted from coal to fuel, with a flow rate of 10-100m³/h and pressure of 1.0-1.6MPa, combined with a PLC constant pressure control system, meeting TSG G0001 Boiler Safety Technical Supervision Regulations.

Mobile Power Generation Equipment: Integrated into container-type diesel generator sets, 316L stainless steel pumps transport -35# diesel, started through a fuel preheater (power 8kW) in -30℃ environments to ensure continuous power supply for field operations.

3. Special Fuels and Working Conditions

Biodiesel Mixed Transportation: 316L stainless steel pumps transport B30 biodiesel (30% vegetable oil + 70% diesel), using perfluororubber seals (FFKM), heat-resistant up to 220℃, resisting the swelling effect of fatty acid methyl esters on metals to avoid seal failure.

Offshore Platform Fuel Loading: Duplex stainless steel pumps transport high-sulfur crude oil (sulfur content 2.8%) for offshore drilling platforms, configured with online sulfur content monitors to adjust anti-corrosion measures in real-time, meeting API RP 521 relief and system requirements.

V. Usage and Maintenance Specifications

1. Fuel Pretreatment Requirements

High-viscosity heavy oil must be preheated to viscosity ≤800cSt (corresponding temperature ~120-140℃), using steam coils or electric heating (power density ≤3W/cm²). When fuel sulfur content >1.5%, add anti-corrosion additives (dosage 0.2-0.5%) to inhibit stainless steel pitting.

2. Operation Monitoring Key Points

Real-Time Parameters: Monitor inlet and outlet pressure (fluctuation ≤±3%), bearing temperature (temperature rise ≤40℃), fuel temperature (not exceeding material tolerance), equipped with pressure transmitters (accuracy 0.2 class) and vibration sensors (accuracy 0.01mm/s), and automatically shut down in case of abnormalities (such as vibration value >0.08mm/s).

Regular Maintenance: Inspect screw meshing clearance every 3000 hours (allowable wear ≤0.02mm), replace mechanical seals every 8000 hours (replace in advance when leakage >5 drops/hour), and clean the pump cavity with diesel (50% of rated flow, run for 30 minutes) when changing fuel seasons.

3. Safety and Compliance Requirements

Marine pumps must pass CCS/ABS classification society certification, providing sulfur corrosion test reports for stainless steel materials (ASTM G35 standard, no pitting after 96-hour immersion). Industrial pumps must comply with API 676 standards, with an explosion-proof rating not lower than Ex d IIB T4, and static grounding systems tested annually (resistance ≤4Ω).

Fuel systems should have dual protection: low-pressure alarm value ≤0.3MPa (prevent oil shortage), high-pressure cut-off value ≥4.2MPa (prevent overpressure). Install magnetic filters at the pump inlet (adsorbing iron filings) and safety valves at the outlet (opening pressure 1.1 times working pressure).