Preface

We have written this book to help provide you, the user of a WGI reciprocating pump, with the knowledge of how a reciprocating pump works and guidance in your selection and operation of a reciprocating power pump. For specific recommendations which are not covered within, please contact our applications department and provide them with all pertinent information regarding your pumping application.

Thanks to all the persons and companies who have provided reference material used in this book. Our further thanks and acknowledgment is extended to the "Hydraulic Institute", for their section on Hydraulic Institute Standards - Reciprocating Pumps, Power (Types, Nomenclature, Ratings, and Applications).

We sincerely hope this book will give you some insight into how your reciprocating pump works and why reciprocating pumps are still one of the most efficient and effective way of transporting liquids of all types.

Although all the information in this book generally applicable to all reciprocating pumps, the specific data within applies only to WGI pumps.

Tulsa, Oklahoma, USA

Updated 10-10-96

Introduction

We believe the commonly accepted conventional nomenclature and descriptions of liquid supply systems for reciprocating pumps is often misleading and provides an inaccurate description of the pumping action. This nomenclature often describes attributes of the pump which do not exist. Intellectually, we all understand the conventional notations and descriptions, however the concept of the pump being a machine which takes action on a liquid often confuses and deceives the intellect into believing that the pump has control over the amount of liquid being introduced into the pump.

The pump relies upon outside forces to push the liquid through the inlet manifold and inlet valve into the liquid chamber of the pump. The pump cannot pull the liquid into the liquid chamber as there is no tensile strength to the liquid. The pump merely creates a partial vacuum in the liquid chamber which is then filled by the forces acting upon the liquid on the inlet side of the pump.

Also, please remember when reading this manual, that liquids remain liquids only so long as outside pressure remains high enough to keep the liquid from boiling. If the pressure on the liquid is reduced below the pressure at which the liquid boils at the pumping temperature, the liquid changes to its vapor state and is no longer a liquid. It is the responsibility of the liquid supply system to provide liquid to the pump inlet at sufficient pressure to keep the liquid from boiling during the pumping cycle. Doing this will prevent many dollars from being spent on repair of the pump, the supply system, and the discharge system.

This manual is not intended to solve all the problems which come up in applications involving WGI reciprocating pumps. We do hope it does provide enough insight to allow the reader to place the action of a reciprocating pump in its proper perspective.

Table of Contents

I. Warnings and Precautions Before and After Starting a WGI Reciprocating Pump 1

II. Fundamentals of Operation 4

III. Pump Material Selection 13

IV. Pump Applications 17

V. Supply System Considerations 21

VI. Installation Suggestions 39

VII. Trouble Locating of Reciprocating Pumps 41

VIII. Appendix

ix. index & Bibliography ix1..ix4

You will want to look your pump over very carefully and get acquainted with the pump prior to starting. Also refer to "Operating Instructions and Maintenance Suggestions" or "Operators Manual" published by WGI for the specific pump type and model.

I. WARNINGS AND PRECAUTIONS BEFORE AND AFTER STARTING A WGI RECIPROCATING PUMP.

A. Safety Precautions

1. Never start or operate a pump against a closed discharge line. Catastrophic destruction of piping or pump will promptly occur.

2. Avoid starting against a full discharge load. Bring pump up to speed using a bypass, then gradually place pump on line.

3. Bleed air from pump and piping before starting pump.

4. The cradle cover must be in place while pump is running.

5. Stand clear of pump while operating under pressure.

6. Do not operate pump above "maximum design pressure" indicated on metal tag. Operating above the maximum design pressure will result in damage to pump, person or property. Notify WGI at the first sign of a suspected malfunction.

7. Contact WGI immediately if operating conditions or type of service change. Upon request you can receive recommendations to meet the new specifications and a new application tag can be sent.

B. Warnings

Before starting a WGI reciprocating pump.

1. Packing for piston and plunger pumps:

a. Piston Pumps - Piston pump stuffing boxes are not packed when shipped from the factory. These pumps must be packed before starting. If the pump is to be placed in storage before use, the piston rods should be coated with grease to prevent rusting. See the Pump Storage section for other steps to take before placing pump in storage.

b. Plunger Pumps - These pumps are packed prior to shipment for immediate service. If temporary storage is intended, the plunger must be protected by taking the following steps: rotate the crankshaft slightly more than one revolution, and apply a film of oil to each plunger surface as the plunger moves out of and into the stuffing box packing. Change the position of the plungers periodically/or at least once a week and reapply oil onto each plunger. These steps will help prevent pitting of the plunger from chemical reactions between the packing and the metal surface of the plunger, during periods of inactivity. See Pumps Storage section for more information.

2. Crankcase has been drained by WGI before shipping pump to you. Fill with lubricant as recommended by operating instructions to ensure proper lubrication of gears, chain, crossheads, connecting rods and shaft bearings. Then rotate the crankshaft by hand at least once a week until starting in order to avoid rust formation from water condensation on unpainted internal parts. Shaft bearings requiring a separate oil bath have been filled at factory with recommended lubricant but should be checked for proper oil level before starting. Check oil levels daily. Change lubricant at least every six months. Drain and thoroughly flush the crank case and bearing housings when making this change.

3. Pump must set level for proper lubrication and alignment.

4. Read Operating Instructions and Maintenance Suggestions or Operator Manual for the specific pump model. If misplaced or lost, please contact your nearest WGI distributor or contact WGI direct for a copy.

5. A pressure relief valve must be installed in the discharge piping between the pump and any other pipe fittings. See page 40 set pressure suggestions.

6. All belt and coupling guards must be firmly in place.

7. Be sure that all pipe joints and fasteners are definitely tight before putting the pump into operation.

8. Check connecting rod bearings for proper adjustment - according to operating instructions.

9. Check main bearings for proper adjustment - according to operating instructions.

C. Warnings

After starting a WGI reciprocating pump.

1. New non-adjustable lip type packing rings (plunger pumps only) may be expected to leak slightly for a day or so, but will gradually seat. The packing gland must be retightened and periodically checked after the packing has seated.

DO NOT attempt to adjust packing while pump is running.

2. Piston pump packing is available in several different configurations. All are adjustable type packing. Care must be taken to ensure that this packing is not overtightened. On most installations, a very slight drip is desirable to aid in lubrication and as visual proof that the packing is not too tight.

3. After Two (2) Hours Operation (also refer to Appendix I)

a. Check all the crank end connecting rod bearings for proper adjustment. Check connecting rod bolt nut torque and adjust if necessary.

b. Check lubricant level and pressure gauge (if forced lubrication system is furnished).

II. FUNDAMENTALS OF OPERATION

A. How a reciprocating pump works

A reciprocating pump is a positive displacement mechanism, liquid discharge pressure being limited only by the strength of the structural parts. Liquid volume or capacity delivered is constant regardless of pressure, and is varied only by driver speed, speed reduction, and/or plunger/piston size changes.

Reciprocating motion is imparted to a plunger/piston by a slider crank linkage which results in a piston motion closely approximating simple harmonic motion, as shown in Appendix B. This reciprocating motion alternately lowers the pressure in front of the plunger/piston when filling the pump, and increases the pressure when emptying the pump. The incoming liquid opens the suction/inlet valve. At the same time the discharge valve is held closed by the downstream line pressure. Outgoing liquid closes the inlet valve and opens the discharge valve. This simple mechanism provides high volumetric efficiency, approximately 95 percent, for most incompressible liquids.

Characteristics of a WGI reciprocating pump are;

(a) positive liquid displacement

(b) high pulsations caused by the sinusoidal motion of the plunger/piston

(c) high volumetric efficiency

(d) high mechanical efficiency

(e) low pump maintenance cost

B. Plunger or Piston Rod Load

Plunger or piston rod load is an important power end "design" consideration for WGI reciprocating pumps. Rod load is the force caused by the liquid pressure acting on the face of the plunger/piston. This load is transmitted through the adapter or piston rod to the crosshead, then to the crosshead pin, wrist pin bushing, connecting rod, crank shaft, main bearings and power frame. This load is directly proportional to the discharge gauge pressure and the square of the plunger/piston diameter.

Occasionally, allowable liquid end pressures limit the "allowable" rod load to a value below the "design" rod load. It is important that liquid end pressure DOES NOT exceed WGI's latest published recommendations.

Rod loads are not generally used when "applying" the pump. They are used to establish the power frame design - not to determine the allowable pressures, in most cases, for each size plunger/piston.. Also see the Sizing pumps in high inlet pressure conditions section.

C. Calculations of Volumetric Efficiency

Volumetric Efficiency (E_V) is defined as the ratio of actual pump capacity to ideal pump displacement. The E_V calculation depends upon the internal configuration of each individual liquid end cylinder, plunger/piston size, and the liquid being pumped. Given full details regarding differential pressure, pumped liquid mixture, and expected temperature rise on the discharge stroke - WGI can calculate this efficiency.

1. Calculating E_V for Water

See TABLE 4 Page A31 for the water compressibility chart. An example of volumetric efficiency calculation for water is also shown.

2. Calculating E_V for Hydrocarbons

See TABLE 6 Page A34 for the physical properties of hydrocarbons. For compressible liquids such as these, horsepower calculations are slightly more complex than for incompressible liquids. However, the magnitude of the horsepower required will be slightly less than if calculated for the full displacement.

3. Displacement Table