How to Evaluate Screw Pump Vendor Quotations - TBE Guide
Complete technical bid evaluation guide for screw pumps including scoring methodology, critical parameters, common deviations, and red flags for Equipment Engineers.
API 676
TBE Evaluation Categories
Weighted Scoring Matrix
| Category | Weight | Key Evaluation Points |
|---|
| Technical Compliance | 40-50% | Flow, pressure, viscosity range |
| Performance Verification | 15-20% | Curves, efficiency, slip |
| Materials of Construction | 15% | Chemical compatibility |
| Vendor Experience | 10% | References, track record |
| Delivery Schedule | 10% | Project alignment |
| Documentation Quality | 5-10% | Completeness, clarity |
Technical Compliance Evaluation
Flow and Pressure
| Parameter | What to Verify | Acceptance |
|---|
| Rated flow | Meets specification | ±3% tolerance |
| Differential pressure | At rated flow | ≥ specified |
| Maximum pressure | Relief valve setting | ≤ 110% operating |
| Flow tolerance | Per ISO/DIN | ±3% typical |
Viscosity Verification
| Condition | Check | Why Critical |
|---|
| Operating viscosity | Pump efficient at this | Normal operation |
| Maximum viscosity | Can start/run | Cold start |
| Minimum viscosity | Slip acceptable | Hot operation |
| Temperature range | Full range covered | All conditions |
Critical Check:
Cold Start Verification:
- Viscosity at minimum ambient temperature: ___ cSt
- Motor torque adequate for cold start? □ Yes □ No
- Soft start or VFD required? □ Yes □ No
Slip and Efficiency
| Parameter | Target | Red Flag |
|---|
| Slip at rated | < 5-10% | > 15% |
| Volumetric efficiency | > 85% | < 80% |
| Overall efficiency | > 70% | < 60% |
Required Curves
| Curve | Purpose | Must Show |
|---|
| Flow vs Speed | Capacity verification | Linear relationship |
| Flow at multiple viscosities | Range verification | Full viscosity range |
| Power vs Flow | Motor sizing | At worst case |
| NPSHr vs Speed | Suction verification | If applicable |
Curve Analysis Checklist
□ Curves provided at specified viscosity
□ Rated point clearly marked
□ Operating range within capability
□ Power curve shows motor margin
□ Slip characteristic provided
□ Efficiency stated at rated point
Warning Signs in Curves
| Issue | Risk | Action |
|---|
| Curves at different viscosity | Performance uncertainty | Request correct viscosity |
| Non-linear flow vs speed | Design problem | Investigate |
| Power exceeds motor rating | Motor failure | Reselect motor |
| No NPSHr data | Cavitation risk | Request data |
Materials Evaluation
Wetted Parts Verification
| Component | Required | Offered | Compatible? |
|---|
| Casing | ___ | ___ | □ Yes □ No |
| Rotors/Screws | ___ | ___ | □ Yes □ No |
| Shaft | ___ | ___ | □ Yes □ No |
| Bearings | ___ | ___ | □ Yes □ No |
| Seals | ___ | ___ | □ Yes □ No |
| O-rings | ___ | ___ | □ Yes □ No |
Material Deviation Analysis
| Deviation Type | Risk | Evaluation |
|---|
| Alternative equivalent | Low-Medium | Accept with data |
| Downgrade material | High | Usually reject |
| Upgrade material | Low | Accept |
| Different coating | Medium | Verify performance |
Scoring Methodology
Scoring Scale
| Score | Definition |
|---|
| 5 | Exceeds requirements, no deviations |
| 4 | Fully compliant |
| 3 | Minor deviations, acceptable |
| 2 | Significant deviations, needs clarification |
| 1 | Major gaps, marginally acceptable |
| 0 | Does not comply |
Sample Evaluation Matrix
| Criteria | Weight | Vendor A | Vendor B | Vendor C |
|---|
| Flow/Pressure compliance | 20% | 4 | 5 | 3 |
| Viscosity range | 15% | 5 | 4 | 4 |
| Slip/Efficiency | 10% | 4 | 4 | 3 |
| Materials | 15% | 4 | 5 | 4 |
| Bearing life (L10) | 10% | 5 | 4 | 3 |
| References | 10% | 5 | 3 | 4 |
| Documentation | 5% | 4 | 4 | 3 |
| Delivery | 10% | 4 | 5 | 4 |
| Commercial | 5% | 3 | 4 | 5 |
| Weighted Score | 100% | 4.20 | 4.30 | 3.60 |
Common Deviations
| Deviation | Risk | Guidance |
|---|
| Slightly lower efficiency | Low | Accept if within 5% |
| Higher slip | Medium | Verify flow still meets spec |
| Different speed | Low | Accept if flow met |
| Lower NPSHr margin | Medium | Verify system NPSHa |
Design Deviations
| Deviation | Risk | Guidance |
|---|
| No relief valve | Critical | Reject or require |
| Different seal type | Medium | Verify API 682 compliance |
| Alternative bearing | Medium | Verify L10 life |
| Longer delivery | Commercial | Negotiate |
Documentation Deviations
| Missing Item | Risk | Action |
|---|
| Performance curves | High | Request before evaluation |
| Material certificates | Medium | Accept as clarification |
| Reference list | Medium | Request minimum 3 |
| Deviation list | High | Cannot properly evaluate |
Red Flags
Critical Red Flags (Potential Rejection)
| Red Flag | Why Serious |
|---|
| No performance curves at specified viscosity | Cannot verify performance |
| Relief valve not included | Safety requirement missing |
| Cold start not addressed | May not start |
| Slip not specified | Efficiency unknown |
| L10 life < 15,000 hours | Below API 676 requirement |
| No references | Unproven design |
Warning Signs (Require Clarification)
| Warning | Questions to Ask |
|---|
| Significantly lower price | What’s excluded? |
| Very short delivery | Proven design? |
| Incomplete datasheet | Request completion |
| Vague deviations | Request specifics |
Vendor Experience Evaluation
Reference Requirements
| Criterion | Minimum | Preferred |
|---|
| Number of references | 3 | 5+ |
| Similar viscosity | Within 50% | Same range |
| Similar pressure | Within 20% | Same or higher |
| Operating duration | 1 year | 3+ years |
Questions for References
- Operating viscosity range vs design?
- Any cold start issues?
- Actual slip vs quoted?
- Bearing/seal replacement frequency?
- Vendor support quality?
- Would you purchase again?
Lifecycle Cost Considerations
Cost Components
| Component | Typical % | Notes |
|---|
| Initial purchase | 10-15% | Higher than centrifugal |
| Energy | 35-40% | Efficiency dependent |
| Maintenance | 30-35% | Seals, bearings |
| Downtime | 10-15% | Reliability dependent |
| Spare parts | 5-10% | Long-term availability |
Comparison Factors
| Factor | Lower Cost | Higher Cost |
|---|
| Efficiency | Higher efficiency pump | Lower efficiency |
| Seal type | Single seal | Double seal |
| Materials | Standard | Upgraded |
| L10 life | Longer life | Shorter life |
TECHNICAL BID EVALUATION SUMMARY
Project: _______________
Tag Number: _______________
Date: _______________
VENDOR RANKING:
1. Vendor ___: Score ___/5.0
2. Vendor ___: Score ___/5.0
3. Vendor ___: Score ___/5.0
KEY FINDINGS:
- Technical leader: Vendor ___ (reason)
- Commercial leader: Vendor ___ (reason)
- Best value: Vendor ___ (reason)
CRITICAL DEVIATIONS:
1. Vendor ___: [deviation] - [resolution]
2. Vendor ___: [deviation] - [resolution]
CLARIFICATIONS REQUIRED:
□ Vendor ___: [item needed]
□ Vendor ___: [item needed]
RECOMMENDATION:
□ Award to Vendor ___
□ Award with conditions (list)
□ Re-bid required
□ Further clarification needed
Prepared by: _______________
Reviewed by: _______________
Approved by: _______________