The NAPCO rotary gear pump will eventually lose operational efficiency as a result of wear of the moving parts. A bearing housing/side cover can be easily removed in order to observe the condition of the gears and inner pump chamber and determine whether any parts need replacement.

Whenever a bearing housing/side cover is removed and/or shafts and gears are replaced, it is extremely important, when pulling out or re-inserting the shafts, that care be taken that the shaft ends do not nick, damage or dislodge the seals and bearings in the bearing housing/side covers. Any such damage or movement will cause the pump to leak and quickly fail. NAPCO has tapered the ends of the shafts to facilitate their removal and insertion through the seals and bearings. Napco also recommends that a lubricant be applied to the tapered end of the shaft to further facilitate moving it through the seals and bearings. (See the “Repair/Installation Procedure” section below for further guidance on repair and maintenance.)

NAPCO Repair Kits

Individual pump spare or replacement parts can be ordered from NAPCO or its authorized distributors (See the “Spare Parts Identification Drawing and Chart” at the end of this brochure). NAPCO also offers “repair kits” that include all the moving or wear parts in a NAPCO pump typically needing replacement. A NAPCO Repair Kit contains:

  • (1) drive gear assembly and one
  • (1) idler gear assembly - both with gear mounted on hardened shaft.
  • (4) roller bearings.
  • (4) high pressure seals.
  • (4) low pressure seals.
  • (2) .016 inch thick center case gaskets.
  • (3) .008 inch thick center case gaskets.

A NAPCO 2” pump (PA200C ductile iron pump or PA200S stainless pump) will require a PK200C (for ductile pump) or PK200S (for stainless pump) repair kit. A NAPCO 3” pump (PA300C ductile iron pump or PA300S stainless pump) will require a PK300C (for ductile pump) or PK300S (for stainless pump). If a customer has ordered a ductile iron pump modified to contain stainless steel shafts , that pump will require a stainless steel pump Repair Kit.

The following diagram illustrates the position of these replacement parts in the NAPCO pump:

NAPCO Repair Kit Diagram

Repair & Installation Procedure

Periodic Inspection of Internal Working Parts

Periodically, or upon indication of loss of performance, pump can be easily opened, inspected and cleaned by following steps 2.1 and 2.2 below.Follow the applicable steps under 2.3 to reassemble pump.

  • Quick internal inspection and pump cleanout

    • Close valves, lock out drive.
    • The non drive bearing housing/side cover may be removed to remove blockages and/or inspect for damage.

Inspection and/or repair of pump


  • Remove non drive bearing housing/side cover.Bearing housing/side covers have 2 bolts with washer & O-rings.Note location for reassembly. Caution, do not damage gaskets.Note how many on each side.
  • Remove top idler gear, pull by hand.
  • Remove drive gear.Take care during shaft removal not to damage seals with sharp keyway.
  • Unbolt and remove drive side bearing housing/side cover. Take care not to damage gaskets.
  • Remove bearing grub screws and bearings.
  • Remove high and low pressure seals, note orientation for correct reassembly.

Clean and inspection:

  • Clean all pump parts of product and old grease.
  • Inspect all parts, particularly:
    • Gear rubber for excessive wear or damage.
    • Bearings, seals, gaskets, grease nipples for rust, wear, damage


  • Install 4 bearings: insert from external side of bearing housing/side cover using bearing tool NAPT0001.Secure with set screws with loctite 222 on threads, then back off set screws 1⁄4 turn.
  • Install 4 low pressure seals: grease seal OD and ID and insert from pump side of bearing housing/side cover using tool NAPT0003 till seal seats on lower shoulder.Be sure that open side of seal faces away from tool. Pre stretch seal ID with tool NAPT0005.
  • Install 4 high pressure seals: grease seal OD and ID and insert from pump side of bearing housing/side cover using tool NAPT0002 until flush with upper shoulder.Be sure that open side of seal faces tool.Pre stretch seal ID with tool NAPT0005.
  • Fit 1 x .016” or 0.4 mm. drive side gasket by adhering to bearing housing/side cover with grease. Note: bearing housing/side covers can be oriented to provide best access to grease nipples with pump in service.
  • Fit drive side bearing housing/side cover, align with aligning pins, secure housing cover with 12 bolts tightening evenly to 35 ft/lbs. or 48 Nm. Remember that the two recessed bolts have washers and O-rings. Install gear assemblies. Grease both sides of shafts. Take care not to damage seals when inserting shafts through the seals in the bearing housing/side covers --particularly with sharp keyway edges.
  • Adhere 2 x .008” (0.2mm.) gaskets to remaining bearing housing/side cover, locating over alignment pin.
  • Mount the remaining bearing housing/side cover by sliding cover onto the protruding gear shafts.Take care not to damage seals, particularly with sharp keyway edges.
  • Secure bearing housing/side cover to the pump center case with 4 equally spaced bolts, torque to 35 ft/lbs. or 48 Nm. Important: set the gap between gears and pump bearing housing/side covers to .006” to .008” or 0.1524mm. to 0.218mm. ie a small amount for gear free play. This is achieved by forcing each gear to one side by tapping the gear shaft, set depth gauge to ‘0’ then forcing gear shafts to the other side and note length of travel.Adjust free play by adding or removing gaskets.
  • Fit bearing housing/side cover when free play is correct and secure all 12 bolts to 35 ft/ lbs or 48 Nm.
  • Grease all bearings (one stroke) and seals (7 strokes) with high quality bearing grease.Evidence of grease should be present in the weep hole and around the bearing seal.
  • Rotate gears by hand. They should not bind.
  • Important: ensure any drive coupling has free play to provide gear free play within the pump and the drive does not force the gear to one side.
  • Fit any guards.

Prime and test pump:

  • Run the pump and ensure prime. It may be necessary to use the air bleed valve to achieve initial prime.
  • Check for any abnormal noises or sound of gears rubbing or slapping which would indicate the pump having run dry or without product.

Video on Rebuilding a pump