When the handwheel torque rises above its normal value, the cause is usually friction on the stem threads, the stem guide, or the packing. Prompt treatment restores smooth operation and prevents stem damage or seizure.The main gate valve product names of China gate valve Network include:Electric Non-rising Stem Single Disc Wedge Gate Valve,Electric Rising Stem Single Disc Wedge Gate Valve,Electric Wafer Knife-shaped Gate Valve,Electro-hydraulic Wafer Knife-shaped Gate Valve,Electric Slurry Valve,Electric Flange Gate Valve,Fire Special Signal Relisient Seat Seal Gate Valve,Fire Special Rising Stem Resilient Seat Seal Gate Valve,Forged Steel Socket Welding Valve,Forged Steel Flange Gate Valve.

Diagnose the Source of the Torque

First, determine whether the stiffness originates at the stem or at the gate. If the handwheel is stiff throughout the entire stroke, the stem threads, guide, or packing are the source. If the valve turns freely until the gate approaches the seat, the problem is seat interference, debris, or over-closing, not stem lubrication. A gradual increase in torque over months of service is commonly caused by lubricant washout, moisture ingress, or process contamination that leaves a dry or gummy film on the stem threads. Stem corrosion, a bent stem, or misalignment between the bonnet and body can also raise torque and must be corrected before lubrication.

Select the Correct Lubricant

Lubricant selection must match the service conditions. For general water, oil, and steam service, a high-quality synthetic grease with good oxidation stability and water resistance is suitable. For high-temperature service, specify a grease rated above the maximum operating temperature, such as a fluorinated or graphite-based product. For oxygen service, only oxygen-compatible fluorinated grease may be used. The lubricant must be compatible with the stem and body materials and must not degrade the packing. Do not apply general-purpose grease to a valve handling aggressive chemicals without confirming chemical compatibility.

Lubrication Procedure

Isolate the valve and relieve all pressure before any maintenance. Clean the exposed stem threads with a compatible solvent to remove old grease, dirt, and corrosion products. Apply the lubricant to the stem threads and the stem guide path only. Do not lubricate the gate sealing face or the seat. For most gate valves, a thin, even film is sufficient. Excess grease attracts particles and can increase torque over time. If the packing is over-tightened, loosen the gland nut by a quarter turn before cycling the valve. Operate the handwheel through five to ten full open and close cycles to distribute the lubricant evenly along the thread engagement. Then check the operating torque and adjust the packing gland only enough to prevent leakage without adding resistance.

Prevention

The most effective prevention is regular lubrication at intervals matched to the duty cycle, clean and dry process media, and correct packing adjustment. For high-cycle or high-temperature service, a semi-annual lubrication interval is a practical baseline. Upstream filtration removes particles that contaminate the stem threads, and periodic inspection detects stem corrosion or bending before it causes seizure.

Summary

Gate valve high opening torque is most often caused by dry or contaminated stem threads and over-tightened packing. Treatment requires isolating the valve, cleaning the threads, applying a service-matched lubricant to the threads and guide only, adjusting the packing, and cycling the valve to distribute the lubricant. Correct lubricant selection and regular maintenance prevent recurrence and protect the valve from stem damage or seizure.Do you still need to know or purchase the following gate valve products:

• API Manual Lug&wafer Knife-shaped Gate Valve
• API Sprocket Lug&wafer Knife-shaped Gate Valve
• API Electric Lug&wafer Knife-shaped Gate Valve
• API Bevel Gear Lug&wafer Knife-shaped Gate Valve
• API Pneumatic Lug&wafer Knife-shaped Gate Valve