AODD Pump Pulsation Dampener Design Guide

Pulsation Fundamentals

Why AODD Pumps Pulsate

AODD pumps produce inherent pulsation due to:

• Reciprocating (back-and-forth) action
• Alternating discharge from two chambers
• Air valve shift creates momentary flow gap

Flow Pattern Without Dampener:

Flow
Rate
  │    ╱╲    ╱╲    ╱╲    ╱╲
  │   ╱  ╲  ╱  ╲  ╱  ╲  ╱  ╲
  │  ╱    ╲╱    ╲╱    ╲╱    ╲
  │ ╱
  └────────────────────────────► Time
    Peak   Valley   Peak   Valley

With Dampener:
  │  ─────────────────────────
  │         Smooth flow
  └────────────────────────────► Time

Pulsation Characteristics

Effects of Pulsation

Dampener Types

Bladder Type

┌───────────────┐
│   Gas (N₂)    │
│   ┌───────┐   │
│   │Bladder│   │ ← Flexible bladder
│   │       │   │    contains gas
│   └───────┘   │
│    Liquid     │
└───────────────┘

Characteristics:

• Gas contained in bladder
• No gas-liquid contact
• Better gas retention
• Fast response
• More maintenance (bladder replacement)

Applications:

• General purpose
• Where gas contamination is concern
• Higher pressure applications

Diaphragm Type

┌───────────────┐
│   Gas (N₂)    │
├───────────────┤ ← Diaphragm
│    Liquid     │
└───────────────┘

Characteristics:

• Diaphragm separates gas/liquid
• Robust construction
• Lower maintenance
• Slightly slower response

Applications:

• Heavy-duty service
• High temperature
• Where maintenance is difficult

Bellows/Membrane Type

┌───────────────┐
│   Gas (N₂)    │
│   ╱╲╱╲╱╲╱╲    │ ← Convoluted membrane
│    Liquid     │
└───────────────┘

Characteristics:

• PTFE or metal bellows
• Excellent chemical resistance
• Wide temperature range

Applications:

• Aggressive chemicals
• High purity
• Extreme temperatures

Type Comparison

Dampener Sizing

Basic Sizing Formula

For 90% Pulsation Reduction:
Dampener Volume ≥ 10 × Stroke Volume

Stroke Volume Calculation

Step 1: Calculate Stroke Volume

GPH ÷ 60 = GPM
GPM ÷ SPM = Gallons per stroke
V (cubic inches) = Gallons per stroke × 231

Example:
Flow = 60 GPM
Stroke rate = 120 SPM
Gallons per stroke = 60 ÷ 120 = 0.5 gal
V = 0.5 × 231 = 115.5 cu.in. per stroke

Minimum dampener = 115.5 × 10 = 1155 cu.in. ≈ 5 gallons

Pre-Charge Pressure

Pre-charge Pressure = 80% × System Pressure

Example:
System pressure = 100 psi
Pre-charge = 0.80 × 100 = 80 psi

Sizing Table (Quick Reference)

Detailed Sizing Steps

DAMPENER SIZING WORKSHEET

1. Determine Pump Data:
   Flow rate: ___ GPM
   Stroke rate: ___ SPM
   System pressure: ___ psi

2. Calculate Stroke Volume:
   Gallons/stroke = GPM ÷ SPM = ___
   Cubic inches = ___ × 231 = ___

3. Determine Dampener Volume:
   Minimum = Stroke volume × 10 = ___ cu.in.
   Convert to gallons = ___ ÷ 231 = ___ gallons
   Select next size up: ___ gallons

4. Set Pre-charge:
   Pre-charge = System pressure × 0.80 = ___ psi

5. Verify Selection:
   □ Volume adequate
   □ Pressure rating sufficient
   □ Material compatible
   □ Temperature rated

Installation Guidelines

Location

Best location: Immediately downstream of pump discharge

Correct Installation:

PUMP ─→ [DAMPENER] ─→ Discharge piping
        ↑
        As close as possible to pump

Why location matters:

• Closer = more effective
• Captures pulsation at source
• Reduces stress on downstream piping

Orientation

Correct:                Incorrect:
┌───────┐              ┌───────┐
│  Gas  │              │Liquid │
├───────┤              ├───────┤
│Liquid │              │  Gas  │
└───────┘              └───────┘
Gas above liquid       Gas below (won't work!)

Mounting

Operation and Maintenance

Initial Setup

1. Install dampener with gas chamber up
2. Drain liquid from gas chamber
3. Set pre-charge to 80% of system pressure
4. Start pump and verify operation
5. Check for leaks

Pre-Charge Verification

Pre-Charge Check Procedure:

1. Isolate dampener from system
2. Drain liquid from dampener
3. Check gas pressure with gauge
4. Adjust to 80% of system pressure
5. Reconnect to system

Frequency: Every 3-6 months

Maintenance Schedule

Common Problems

Automatic Dampeners

Self-Adjusting Dampeners

Some AODD-specific dampeners feature automatic pre-charge:

Automatic Dampener Features:
- Uses pump air supply for pre-charge
- Automatically adjusts to system pressure
- No manual pre-charge needed
- Lower maintenance

Products:

• Blacoh AODDampener series
• Sandpiper TA Series (self-adjusting)

Benefits of Automatic

Sizing Examples

Example 1: Chemical Transfer

Application:
- 1-1/2" AODD pump
- Flow: 100 GPM
- Pressure: 60 psi
- Stroke rate: 150 SPM

Calculation:
1. Stroke volume = 100 ÷ 150 = 0.67 gal/stroke
2. Min dampener = 0.67 × 10 = 6.7 gallons
3. Select: 8 gallon dampener
4. Pre-charge = 60 × 0.8 = 48 psi
5. Material: PVDF (chemical service)

Example 2: Food Processing

Application:
- 2" AODD pump
- Flow: 150 GPM
- Pressure: 80 psi
- Stroke rate: 200 SPM

Calculation:
1. Stroke volume = 150 ÷ 200 = 0.75 gal/stroke
2. Min dampener = 0.75 × 10 = 7.5 gallons
3. Select: 10 gallon dampener
4. Pre-charge = 80 × 0.8 = 64 psi
5. Material: 316 SS (sanitary)

Specification Template

=== PULSATION DAMPENER SPECIFICATION ===

Service: _______________
Tag: _______________

PUMP DATA:
Pump size: ___ inch
Flow rate: ___ GPM
Stroke rate: ___ SPM
System pressure: ___ psi

SIZING:
Stroke volume: ___ gallons
Minimum dampener: ___ gallons
Selected size: ___ gallons

DAMPENER TYPE:
□ Bladder  □ Diaphragm  □ Bellows  □ Automatic

MATERIALS:
Housing: □ SS □ PP □ PVDF □ Other: ___
Bladder/Diaphragm: □ Buna □ EPDM □ PTFE □ Viton
Connections: ___ size, □ NPT □ Flange

OPERATING CONDITIONS:
Pre-charge pressure: ___ psi
Max pressure: ___ psi
Temperature: ___ °C

ACCESSORIES:
□ Isolation valve
□ Drain valve
□ Pressure gauge
□ Mounting bracket

INSTALLATION:
Location: □ Pump discharge □ Other: ___
Orientation: □ Vertical (gas up) □ Horizontal

Summary

Key Points

1. Size for 90% reduction: Dampener volume ≥ 10 × stroke volume
2. Pre-charge at 80%: Set gas pressure to 80% of system pressure
3. Install close to pump: Effectiveness decreases with distance
4. Gas chamber up: Proper orientation essential
5. Check pre-charge regularly: Every 3-6 months