# Presentation: 727581

## FUNDAMENTAL PRINCIPLES OF SLURRY PUMPS AND SEDIMENT PUMPING

- R. E. Randall
- Director, Center for Dredging Studies
- Ocean Engineering Program
- Texas A&M University
- College Station, Texas

## LARGE DREDGE PUMP

## DREDGE PUMP

## WHEELER DREDGE PUMP

## DREDGE LADDER PUMP

## JACKUP BOOSTER PUMP

## PUMP, INLET, CASING, IMPELLER

**PUMP, INLET, CASING, IMPELLER**

## DEFINITIONS

**SG = specific gravity**
*** ************ *****= slurry specific weight***** ***
********* *****= SG ********water**
**H = pump head **
******p = pressure change across pump **
**H = ******** p /******
**WHP***** *****= power delivered to the slurry (water horsepower)**

-  **WHP = ******** Q H**
**BHP = T******
***BHP***** = power required to drive the pump (brake horsepower)**
********  ****= angular rotation**
***T***** = shaft torque**
******= WHP/BHP**

## PUMP AFFINITY LAWS

**CONSTANT IMPELLER DIAMETER****	****CONSTANT ROTATIVE SPEED****	****	****	****	****	****	****	**
**	****	****	****	****	****	****	**** ****	****	****	****	****	****	****	**
**	****	****	****	****	****	****	**** ****	****	****	****	****	****	****	**

## EFFECTS OF SOLIDS ON PUMP PERFORMANCE

- Discharge, m3/s

- Hm

- BHP

- Eff

## BOOSTER LOCATION

## GAS ACCUMULATOR FOR GASSY SEDIMENTS

- SLURRY

- GAS

##  PUMP CAVITATION 		

- Liquid pressure is reduced below water vapor pressure causing vapor filled cavities.
- Dredge pump cavitation results in noisy operation, reduced efficiency, vibration and with time damage to pump.
- Cavitation effects are commonly characterized with the term net positive suction head (NPSH).
- Cavitation effects on dredge pump performance are usually determined experimentally (NPSHR).
- NPSHA < NPSHR Cavitation
- NPSHA > NPSHR No Cavitation

## DREDGE PUMP WEAR, LINING,& CLEARANCE

- Dredge pumps are designed to allow large particles to pass through pump (e.g. 6 inch sphere)
- Dredge pump clean out capability usually located at suction intake.
- Most dredge pumps are lined to minimize abrasion and wear.
- Wear is a function of design, material hardness, slurry concentration, size, velocity, weight of solids, median grain diameter, and angularity
- Wear is proportional to the velocity cubed.

## SYSTEM CURVE SUPERPOSED ON PUMP CHARACTERISTICS

**HEAD**

**SYSTEM HEAD CURVE**

**OPERATING**
**POINT**

## PIPELINE

- Material
- Steel
- Plastic
- Location
- Floating
- Shore
- Submerged

## PIPELINE AT DREDGE

## PIPELINE DISCHARGE

## TYPES OF SEDIMENT-WATER FLOWS

- Non- settling Flows
- Fine grained material (silts & clays)
- Settling Flows
- Sand & Gravel

## FLOW REGIMES

- Flow as a homogeneous suspension
- Heterogeneous flow with all solids in suspension
- Flow with a moving bed, saltation(with or without suspension)
- Flow with a stationary (fixed) bed

## SLURRY CONCENTRATION

## CRITICAL VELOCITY

## PUMP, SYSTEM, & CRITICAL VELOCITY CURVES

- Input pump curves
- Input system data
- Calculates system curve
- Calculates critical velocity
- Show pump system curves

- System Curve

- Head Curve

- Critical Flowrate

## 24 IN DREDGE,W/ LADDER & BOOSTER PUMP

## PUMP-PIPELINE SYSTEM

## SUMMARY

**Pump**
**Ladder pump needed to avoid cavitation**
**30 -24 inch suction & discharge diameter**
**5-6 ft impeller diameter**
**3-5 impeller blades**
**Pump liner**
**Are sediments gassy?**
**Solids effects**
**More power**
**Reduced efficiency**
**Reduced head**
**Booster pumps needed for long pipeline.  Placement critical**

**Pipeline (Cutter Suction or Hopper Dredge)**
**Critical velocity for settling flows**
**Dredged Material properties (insitu SG, d50, d85, etc)**
**30-24 inch pipeline diameter**
**Calculate pressure drop along pipeline**
**Position booster pumps**
**Cavitation (ram off)**
**Avoid shutting valves fast**
**Distribution at end of pipeline**
**Production = 0.297*C****v***** Q* DE**
**Steel pipe usually preferred to plastic pipe**
**Wear is function of velocity cubed**

## QUESTIONS