For any valve maintenance regimen, there are four easy steps to follow:
1.Safety first. Disconnect the power source and depressurize the system before repairing a valve. Also, be sure to properly and safely handle the unit based on the fluid it controls.
2.Coil. Inspect the coil for cracks. In wet or humid environments, moisture might penetrate the coil and cause valve failure. While reviewing the coil, check its connections for damage or corrosion, which can also affect valve performance. When powering up an AC coil, ensure the coil is properly installed on the valve’s sleeve or stem. Otherwise, the resulting influx of current might result in a coil burn-out.
3.Pressure Vessel. When the coil is removed, the remaining unit is called the pressure vessel. Its sleeve will have a feature that accepts a sleeve removal tool like a wrench. Try to avoid clamping onto the sleeve tube, as this may cause the tube to dent or bend. Once you have removed the sleeve, the valve body will expose the internal components of the valve operator, including the plunger with a seal, the plunger return spring, an O-ring, the sleeve and operator body. Systematically examine each for damage or wear, and replace as needed:

• Take a look at the seal for any signs of swelling, cracking or deterioration.
•  The spring should be inspected for worn or broken coils.
•  The body orifice itself may have been nicked or the crest worn.

When the plunger lifts, it normally makes contact with the sides and stop of the sleeve. As a result, the top of the plunger and the inside of the sleeve may show wear as well. For more complex solenoid valve types utilizing diaphragms, pistons, spools and levers, follow the manufacturer’s instructions for maintenance.
4.Reassembly. Once all necessary parts are replaced and the valve is cleaned of build-up and grime, reassemble the pressure vessel according to manufacturer directions and reattach the coil. Then, reinstall the newly assembled valve back into the application. Once the parts are accurately installed, power up the valve again.