Screw Pump Datasheet Key Parameters - Specification Guide
Complete guide to screw pump datasheet parameters including viscosity, pressure, speed, slip, and NPSH specifications for Equipment Engineers.
API 676ISO 4412
Process Conditions
Flow Parameters
| Parameter | Unit | Description | Notes |
|---|
| Rated flow | m³/h or L/min | Design operating flow | Including margin |
| Normal flow | m³/h or L/min | Typical operation | Most frequent condition |
| Minimum flow | m³/h or L/min | Lowest stable flow | Thermal limit |
| Maximum flow | m³/h or L/min | End of speed range | Verify with vendor |
Pressure Parameters
| Parameter | Unit | Description | Notes |
|---|
| Suction pressure | barg | At pump inlet | Include worst case |
| Discharge pressure | barg | At pump outlet | Normal operation |
| Differential pressure | bar | Discharge - Suction | Key sizing parameter |
| Maximum discharge | barg | Maximum allowable | For relief valve |
| Design pressure | barg | For casing rating | ≥ Max discharge |
Temperature Parameters
| Parameter | Unit | Description | Notes |
|---|
| Operating temperature | °C | Normal operation | For viscosity |
| Maximum temperature | °C | Highest expected | Material limit |
| Minimum temperature | °C | Lowest expected | Cold start |
| Ambient temperature | °C | Site conditions | Motor cooling |
Viscosity Specification
Critical Importance
Viscosity is the single most important parameter for screw pump specification.
Viscosity Data Requirements
| Condition | Temperature | Viscosity | Purpose |
|---|
| Operating | Normal °C | cSt | Pump sizing |
| Maximum | Minimum °C | cSt | Cold start, motor |
| Minimum | Maximum °C | cSt | Slip calculation |
Unit Conversion
Kinematic Viscosity (cSt) = Dynamic Viscosity (cP) / Specific Gravity
1 cSt = 1 mm²/s
1 cP = 1 mPa·s
Viscosity Ranges by Pump Type
| Pump Type | Optimal Range | Maximum |
|---|
| Twin screw | 100-1000 cSt | 1,000,000 cSt* |
| Triple screw | 30-300 cSt | 1,000 cSt |
| Single screw | 100-100,000 cSt | 1,000,000 cSt |
*Special low-speed design required
Temperature-Viscosity Relationship
Specification Format:
VISCOSITY DATA:
Temperature (°C): 10 25 40 60 80 100
Viscosity (cSt): 2500 800 300 120 60 35
Note: Include viscosity-temperature curve or ASTM slope
Slip Specification
What is Slip?
Slip = Theoretical Flow - Actual Flow
Slip (%) = (Slip / Theoretical Flow) × 100
Factors Affecting Slip
| Factor | Effect on Slip |
|---|
| Higher viscosity | ↓ Decreases slip |
| Higher pressure | ↑ Increases slip |
| Larger clearances | ↑ Increases slip |
| Higher speed | Minimal direct effect |
Typical Slip Values
| Viscosity Range | Typical Slip | Notes |
|---|
| < 50 cSt | 8-15% | High slip expected |
| 50-200 cSt | 5-10% | Moderate |
| 200-500 cSt | 3-6% | Good efficiency |
| > 500 cSt | 1-3% | Excellent efficiency |
SLIP DATA (from vendor):
At rated conditions:
- Theoretical displacement: ___ cc/rev
- Slip at operating viscosity: ___ %
- Actual flow at rated speed: ___ L/min
- Flow tolerance: ±___% of rated
NPSH Requirements
NPSHr for Screw Pumps
Screw pumps have lower NPSH requirements than centrifugal pumps:
| Pump Type | Typical NPSHr | Notes |
|---|
| Twin screw | 1.0-3.0 m | Speed dependent |
| Triple screw | 2.0-4.0 m | Higher than twin |
| Single screw | 0.5-2.0 m | Lowest requirement |
NPSH Margin
NPSHa ≥ NPSHr × Safety Factor
Safety Factors:
- Standard service: 1.3
- Viscous fluids: 1.5
- Critical service: 2.0
NPSH DATA:
NPSHa (calculated): ___ m
NPSHr (vendor): ___ m
Margin: ___ m
Safety factor: ___
Speed Specification
Speed vs Viscosity
| Viscosity (cSt) | Recommended Max Speed |
|---|
| < 100 | 2800-3600 RPM |
| 100-500 | 1400-2800 RPM |
| 500-2000 | 500-1400 RPM |
| 2000-10,000 | 200-500 RPM |
| > 10,000 | 50-200 RPM |
SPEED DATA:
Rated speed: ___ RPM
Speed range (VFD): ___-___ RPM
Minimum continuous: ___ RPM
Maximum allowable: ___ RPM
Displacement Specification
Theoretical Displacement
Displacement = Volume per revolution (cc/rev or L/rev)
Actual Flow = Displacement × Speed × (1 - Slip%)
DISPLACEMENT DATA:
Theoretical displacement: ___ cc/rev
At rated speed (___ RPM):
Theoretical flow: ___ L/min
Slip: ___ %
Actual flow: ___ L/min
Power Specification
Power Calculation
Shaft Power (kW) = (Q × ΔP) / (600 × η)
Where:
Q = Flow rate (L/min)
ΔP = Differential pressure (bar)
η = Pump efficiency (0.7-0.9)
POWER DATA:
Hydraulic power: ___ kW
Pump efficiency: ___ %
Shaft power: ___ kW
Motor rating: ___ kW
Service factor: ___
Cold start consideration:
Cold viscosity: ___ cSt
Starting torque requirement: ___ % of rated
Material Specification
Wetted Parts
| Component | Standard | Options |
|---|
| Casing | Ductile iron | 316 SS, Duplex |
| Screws | Chrome steel | Hardened SS |
| Wear rings | Bronze | PEEK, SiC |
| Shaft | Carbon steel | 17-4PH, Monel |
MATERIALS:
Casing: _______________
Rotors/Screws: _______________
Shaft: _______________
Bearings: _______________
Seals: _______________
O-rings: _______________
Special requirements:
□ NACE MR0175 (sour service)
□ Low temperature impact test
□ Material certificates required
Seal Specification
Seal Type Selection
| Service | Recommended |
|---|
| Standard | Single mechanical seal |
| Hazardous | Tandem or double seal |
| High temp | Cooled seal arrangement |
| Zero emission | Double seal with barrier |
API 682 Flush Plans
| Plan | Application |
|---|
| Plan 11 | Standard - discharge recirculation |
| Plan 12 | With filter - viscous fluids |
| Plan 13 | Return to suction |
| Plan 21 | External cooled supply |
SEAL DATA:
Type: Single / Tandem / Double
Arrangement: _______________
Flush plan: API 682 Plan ___
Seal face materials: ___ vs ___
Elastomers: _______________
Vendor Data Requirements
With Quotation
| Document | Required Data |
|---|
| Datasheet | All parameters filled |
| Performance curves | Flow vs speed, efficiency |
| GA drawing | Dimensions, connections |
| Sectional drawing | Internal components |
| Material list | All wetted parts |
| Curve | Data Points |
|---|
| Flow vs Speed | At operating viscosity |
| Flow vs Viscosity | At rated speed/pressure |
| Power vs Flow | At operating conditions |
| NPSHr vs Speed | If applicable |
Datasheet Template
=== SCREW PUMP DATASHEET ===
1. GENERAL
Tag Number: _______________
Service: _______________
Pump Type: Single / Twin / Triple
Quantity: ___ Operating + ___ Spare
2. OPERATING CONDITIONS
Rated Normal Min Max
Flow (m³/h) _____ _____ _____ _____
Discharge P (barg) _____ _____ _____ _____
Suction P (barg) _____ _____ _____ _____
Diff. Pressure _____ _____ _____ _____
Temperature (°C) _____ _____ _____ _____
Viscosity (cSt) _____ _____ _____ _____
3. FLUID PROPERTIES
Fluid name: _______________
Specific gravity: _______________
Vapor pressure at max T: ___ bara
Solids content: ___ % or ppm
Corrosive properties: _______________
4. NPSH
NPSHa at worst case: ___ m
NPSHr (vendor): ___ m
5. PERFORMANCE (Vendor to complete)
Displacement: ___ cc/rev
Rated speed: ___ RPM
Slip: ___ %
Efficiency: ___ %
Shaft power: ___ kW
6. MOTOR
Rated power: ___ kW
Voltage: ___ V
Frequency: ___ Hz
Enclosure: _______________
Area classification: _______________
7. MATERIALS
Casing: _______________
Rotors: _______________
Shaft: _______________
Bearings: _______________
Seals: _______________
8. SEALING
Seal type: _______________
Flush plan: API 682 Plan ___
9. ACCESSORIES
□ Relief valve (set at ___ barg)
□ Pressure gauge
□ Strainer (mesh ___)
10. STANDARDS
□ API 676
□ NACE MR0175
□ ATEX/IECEx