Umbrella gear gate valve is a type of valve that controls the flow of pipeline media through mechanical transmission. Its core structure includes a gate (wedge-shaped or parallel), a valve seat, a valve stem, and an external umbrella gear device. When working, when the handwheel is manually operated to rotate, the power is transmitted through the umbrella gear set to reduce speed and increase torque - the small gear drives the large gear to rotate, converting higher speed into greater torque output to the valve stem. This design allows the operator to overcome fluid pressure and sealing friction with less force, pushing the valve stem to move in a straight line along the axis: when the valve stem rises, the gate plate disengages from the valve seat channel, allowing the medium to pass smoothly; On the contrary, when the valve stem descends, it forces the gate to tightly adhere to the sealing surface of the valve seat, cutting off water flow or other media.

Unlike ordinary handwheel connected gate valves, the key role of bevel gears is to optimize the efficiency of force distribution. Due to the accurate transmission ratio of gear meshing (usually multi-stage reduction), even under high-pressure conditions (such as PN16~PN40 levels), the required operating torque can be reduced through the lever principle, while ensuring the accuracy of the switch in place. In addition, some models will also incorporate bearing support structures to reduce friction losses and further enhance operational stability.

To ensure the long-term stable operation of umbrella gear gate valves, the following rules must be strictly followed:

1. Installation specifications

-Directionality: The flow direction of the medium must be consistent with the arrow on the valve body (usually "low in, high out"), otherwise it may cause uneven force on the gate and seal failure;

-Support and fixation: Large caliber valves require independent brackets to avoid the weight of the pipeline being borne by the valve (especially flange connection types), and to prevent deformation from affecting the seal;

-Cleaning the pipeline: Clean the welding slag and impurities inside the pipeline before installation, and install temporary filters if necessary to prevent debris from getting stuck on the sealing surface.

2. Operation taboos

Prohibit long-term operation with half open and half closed: Gate valves are designed for full open/full close operation. When partially opened, high-speed fluid flushing can accelerate the wear of the sealing surface and even cause vibration damage to components; If it is necessary to adjust the flow rate, a globe valve or a regulating valve should be selected.

Avoid rapid opening and closing: Sudden pressure impact may cause valve stem bending, sealing ring extrusion, or valve seat cracking; Especially for high-voltage systems, it is recommended to operate slowly (stay for 2-3 seconds per lap).

Overpressure use is strictly prohibited: The actual working pressure should not exceed the nominal pressure (PN) indicated on the valve, and the strength reduction caused by material creep should also be considered under high temperature conditions (such as allowable stress reduction for carbon steel above 400 ℃).

3. Key points of maintenance and upkeep

Lubrication and maintenance: Apply high-temperature lubricating grease (such as molybdenum disulfide base grease) to the umbrella gear pair and valve stem threads every quarter to prevent rust and blockage; Apply anti rust paint to protect exposed metal parts during outdoor use.

Sealing replacement cycle: Rubber fillers are generally inspected once every 1-2 years and replaced promptly after aging and hardening; If scratches appear on the metal sealing surface, they can be repaired by grinding (using specialized grinding paste).

Regular activity inspection: Valves that have been idle for more than one month should be manually turned 2-3 times before use to confirm that there are no blockages before formal operation.

4. Response to special working conditions

High temperature medium: Select heat-resistant materials (such as chromium molybdenum steel) and equip them with heat sinks or cooling jackets to avoid valve stem locking caused by thermal expansion; Slowly cool down after shutdown to prevent thermal stress cracks caused by rapid cooling.

Low temperature environment: For situations below -40 ℃, austenitic stainless steel or low-temperature steel should be used, and the lubricating grease should be of low pour point type (such as silicon-based grease) to prevent freezing failure.

Corrosive medium: Choose lining (rubber, ceramic) or corrosion-resistant alloy (Hastelloy) according to the properties of the medium, and shorten the maintenance cycle.