Centrifugal pumps use a rotating impeller to increase fluid pressure and move it through a central piping system. Centrifugal pump mechanical seals add a necessary buffer to shield the pump's shaft when packing material proves insufficient. Mechanical seals have a rotating component secured to the pump shaft and an idle component secured to the pump casing. The polished sealing surfaces of each component form a seal that prevents leaks along the pump's shaft. Installing a centrifugal pump mechanical seal requires adequate experience in industrial mechanical service.
Things You'll Need
- Braking fluid
- Stainless steel bolts
- Adjustable wrench
- Mounting screws
- Phillips screwdriver
- Tape measure
- Pressure gauge
Clean the centrifugal pump parts with braking fluid to remove grease. Inspect the pump parts for signs of wear. Replace the pump's shaft, sleeve, o-rings and Teflon connections if necessary. Remove all obstructions, such as burrs that would cut seal connections or interfere with good starting bevel.
Align and thread stainless steel bolts through the guide posts between the stuffing box back plate and the centrifugal pump frame. Torque fittings with an adjustable wrench. Lubricate the shaft sleeve with oil and install it on to the shaft. Secure mounting screws through the impeller and on to the shaft sleeve to firmly hold it into position. Torque until firmly tightened with an Phillips driver.
Trace a line across the shaft sleeve on the stuffing box face with a pencil. Dislodge the stuffing box locking nuts and bolts and remove the stuffing box plate.
Measure the mechanical seal's operating length with a tape measure. Position the shaft gland on a clean surface area with the stuffing box facing up. Install the stationary seal with the gland's secondary seal and use gasket tape to secure the fittings. Adjust the gland gasket's alignment until properly positioned. Turn the rotary unit face-down against the stationary seal face.
Measure the gland gasket's distance to the top of the seal while at free height. Conduct a compression test measuring the required 1/8-inch compression for springs with less than 2 inches in diameter with a pressure gauge. Test for 3/16-inch compression for mechanical seals with multiple springs larger than 2 inches in diameter. Subtract the proper compression figure from the determined seal's length.
Trace a second line on the shaft sleeve's impeller end with the determined distance as measured in Step 5. Place the stationary seal gland and gasket on the pump shaft. Position the rotary unit on to the shaft sleeve and slide it to the rotary's rear on the second traced line. Mount the rotary unit to the shaft sleeve with a Phillips driver and screws. Insert bolts into the stuffing box plate and into the pump's frame. Torque until fully tightened. Use the new impeller gasket to install the impeller.
Compress the shaft gland against the stuffing box plate. Test seal compression between the gland gasket and the stuffing box plate. Torque the gland studs until flush. Rotate the shaft to free of existing binds.