Types of Reciprocating Pumps
- Single acting plunger pumps fill on the reverse stroke and exhaust on the forward stroke. The liquid end is sealed from the atmosphere by packing around the plunger. This type of pump is commonly called an “outside packed” pump. WGI manufacturers these pumps with either one, two, three, or five plungers/cylinders. This type of pump is horizontally operating.
- Single acting piston pumps exhaust only during the forward stroke of the piston, that is, during one half of the revolution.
- Double acting piston pumps fill and exhaust on the same stroke, one side of the piston facing the end of the cylinder being filled and the other side of the piston exhausting the other end of the same cylinder. This type of pump is commonly called an “inside packed” pump where the “packing” is a series rings or a set of rubbers which stop leakage from one side of the piston to the other. The piston rod diameter is relatively small compared to the diameter of the piston and is easily packed to avoid leakage. This type of pump is also horizontally operating.
Where Reciprocating Pumps are Used
- WGI reciprocating pumps are used in all applications requiring a combination of high differential pressure and relatively low capacities.
- a. Single acting plunger pumps for high capacities and high pressures at high rpm, low initial costs, and average lifetime.
- b. Double acting piston pumps for high capacities and moderate pressure, low rpm, moderate initial cost and extremely long life.
Sizing and Selecting a Reciprocating Pump
- In order to properly select and size a reciprocating pump, WGI requires the following information for most applications.Characteristics of the liquid:
- Liquid composition (including % and type of solids present)
- Outlet and inlet pumping temperature
- Specific gravity of liquid at outlet and inlet pressures & temperatures
- The corrosives and/or abrasives present
- Vapor pressure at pumping temperature
- Viscosity of liquid at pumping temperature
- Desired pumping capacity, at pumping temperature, in units of: gallons per minute, barrels per hour, or barrels per day.
- Whether a future or alternate capacity is contemplated for the pump(s).
- Pressure conditions required.
- Liquid pressure at the pump discharge.
- Liquid pressure at the pump inlet/suction (NPSHA).
- Whether a future or alternate pressure condition is contemplated for the pump(s).
- Electrical or other area hazard(s).
- Flange rating required for the operating pressures and temperatures, if other than standard.
- Preferred/specified metallurgy of major parts.
- Driver type, to include power characteristics; electrical voltage/phase/hertz or gasoline/diesel fuel.
- Space limitations/constraints.
- Site ambient temperature range.
- Indoor or outdoor location.
In order to prevent permanent damage to pumps which are placed in storage, the following procedures are recommended:
Short Term Storage
Recommended for period less than 6 months and a minimum requirement for any exported pumps or pump package units without customer procedures.
- a. Where possible, place pump in an enclosed storage facility. If enclosed storage is not available, cover the entire pump and associated exposed attachments with a heavy tarpaulin.
- b. Remove crankcase cover and fill the crankcase with lubricant (approved and specified on pump applications tag).
- c. Replace crankcase cover.
- d. Drain all fluids and remove; valve covers, cylinder heads, and inlet and discharge flange plugs.
- e. Apply a film covering of lubricant to all exposed parts.
- f. Remove cradle cover and coat plunger or rod surface with lubricant.
- g. Replace valve covers, cylinder heads and inlet and discharge flange plugs.
- h. Rotate crankshaft 10 complete turns and reapply liquid end protection, including plungers (as described in steps d, e, and f above), weekly.
- i. Check for oil leaks around pump and replace gaskets or seals immediately if necessary.
Refer to engine, motor, gear reducer, etc. manufacturer’s instructions for storage procedures.
Long Term Storage
Recommended for a period exceeding 6 months.
- The pump and parts should be stored in a clean, dry location, free from temperature extremes, in an approximately level position and without distortion.
- It is desirable to completely fill the power end (crankcase cavity, etc.) of the pump with the approved lubricant. Such a fluid level would ensure all parts within the power end are protected. To fill the power end, remove the hand cover and fill with lubricant. Be sure to replace the hand cover. Service the remainder of the pump as directed above in steps d-h.
- Inspect periodically for possible oil leakage and replace gaskets or seals immediately if necessary.
Caution: Before placing the pump, engine, gear reducer, etc. into service, fill the crankcase with the manufacturer recommended lubricant and check for proper lubricant level.
Caution: Double acting piston pumps, having steel or file hard steel piston rods, require special attention.
Remove liquid end stuffing box packing in pumps having piston rods in these materials as they are subject to chemical and atmospheric corrosion, if left in contact with the packing.
Exposed sections of these rod materials must protected by a coating of heavy grease or rust preventative.
Each time the pump is rotated during storage, this coating must be checked and reapplied, if needed.
A heavy coating of lubricant is also recommended immediately after servicing or recommissioning the liquid end.
Sizing a WGI Pump for High Inlet Pressure Conditions
- For double acting piston pumps, no derating is required.
- For a single acting plunger pump, where the rod load due to inlet pressure is less than 20% of full plunger/rod load, no derating required.
- For a single acting plunger pump (with standard bronze wrist pin bushings), where the rod load due to inlet pressure is greater than 20% of full plunger/rod load, derating is as follows:
- a. For triplex pumps, add two-thirds the inlet/suction pressure to the discharge pressure in selecting the pump maximum plunger pressure.
- b. For quintuplex pump, add two-thirds the inlet/suction pressure to the discharge pressure in selecting the pump maximum plunger pressure.
- 4. For a single acting plunger pump (with optional wrist pin roller/needle bearings), where the rod load due to inlet pressure is greater than 20% of full plunger/rod load, no derating is required if both of the following requirements are met:
- a.) inlet/suction pressure is less than 50% of the maximum plunger pressure rating
- b.) discharge pressure is less than the maximum plunger pressure rating.