Val-Matic 2-12 in. (DN 50-300 mm) Wafer Style Dual Disc Check Valve User Manual

Page 5

MAINTENANCE

Dual Disc

Check Valves require no scheduled

lubrication or maintenance.

INSPECTION: Periodic inspection for leakage can
be performed by listening for leakage noise from the
valve while the pump is shut down. If leakage is
heard, drain the pipeline, remove the valve, and
inspect the seating surfaces for wear or damage. If
the resilient seat is damaged, replace the valve or
return the valve to the factory for refurbishing.

TROUBLESHOOTING

Several problems and solutions are presented below
to assist you in troubleshooting the valve assembly
in an efficient manner.

· Valve Chatters or Vibrates: Verify that velocity is

at least 4 feet per second (consult the factory for
air service). A partially open valve will wear
prematurely. Verify that there are three diameters
of straight pipe upstream.

· Valve Leakage: Check gaskets and flange bolt

torque for flange leakage. Drain line, remove
valve, and inspect seating surfaces.

· Valve Does Not Pass Flow: Check flow arrow

direction on valve body. Verify that downstream
isolation valve is open and there is no line
blockage downstream.

· Valve Slams: Remove valve and inspect spring.

Heavier springs can be furnished for severe high-
head applications. Consult factory if the valve is
installed in a vertical pipe with the flow downward.

DISASSEMBLY

The valve should be removed from the pipeline for
disassembly. All work on the valve should be
performed by a skilled mechanic with proper tools.
Refer to Figure 3.

WARNING: The line must be drained before

removing the valve or pressure
may be released causing injury.

1. Remove the valve from the pipeline. NPS 10-12

(DN 250-300) valves are provided with a lifting
eyebolt to aid in this process. Lay valve on flat
surface or bench with the flow arrow facing
upwards.

2. Remove the retainer set screws (7) & (8) and the

rubber spheres (9). The retainer set screws are

metric and should be uninstalled using standard
metric hex drive bits or wrenches.

3. Drive out the pins (4 and 5) with a round bar or

punch while pressing down on the spring (3) to
prevent it from unwinding.

4. Lift discs (2) from body. Inspect pins and seating

surfaces for wear. The shaft diameter is normally
about 1/16 in. (1.5 mm) smaller in diameter than
the hole in the disc lugs. Some minor dents and
discoloration are normal. Wear areas in the
resilient seat will cause leakage and require valve
replacement or refurbishing at the factory.

5. Remove spring (3) and check for wear or cracks.

REASSEMBLY

All parts must be clean and the gasket surfaces
should be cleaned with a stiff wire brush in the
direction of the serrations or machine marks. Worn
parts, gaskets, and seals should be replaced during
reassembly.

1. Lay body on flat surface with arrow facing

upwards. Carefully place the two discs with the
machined sealing surfaces down on the body
sealing surface. Align the disc lugs with the pin
holes in the body.

2. Insert the disc hinge pin into the hole on one side

of the body, but not through the disc lugs. Install a
spacer (10) between the inside diameter of the
body and the disc lug. Push the disc hinge pin
further to engage the first disc lug.

3. Install a thrust bearing (6) between the first and

second disc lugs and push the pin further to
engage the second disc lug.

4. While holding the torsion spring (3) with one of the

ends facing you, wind the rear tab 180 degrees in
a clockwise direction and then press the spring
between the two sets of disc lugs. Engage the pin
further to retain the spring and the third disc lug.
The legs of the spring should apply a downward
force on the discs.

5. While pushing the pin further, install the second

thrust bearing (6) and the fourth disc lug, and then
the second spacer (10). The pin should now be
centered in the body and the disc should rotate
without binding.

6. Insert the disc stop pin (5) into the holes in the

body.

7. Insert a sphere (9) into each of the four pin holes.