Pressurized Grease Delivery for Valve Stem Thread Lubrication
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Solution Overview
Problem
Existing valve stem and stem nut designs, particularly in motor-operated valves, often lack internal grease paths, making it difficult to effectively lubricate mated threads without actuating the valve or exposing the threads, leading to inadequate grease coverage and maintenance challenges.
Innovation Solution
A method involving a thread lubricator and adapter nut that pressurizes one end of the thread interface with grease, allowing it to flow and displace old grease without actuating the valve, using a device with a bore for pressurized grease reservoir and a seal to ensure effective lubrication without an internal grease path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If valve stem threads are exposed for manual grease application, then grease can be applied to the threads, but the valve must be actuated which causes liquid inventories to flow
Solution Approach 1:
A grease delivery device is introduced as an intermediary between the grease source and the thread interface. The device includes a body with a bore that receives the valve stem, a grease fitting for introducing pressurized grease, and delivers grease directly to the thread interface between the stem nut and valve stem, eliminating the need to expose threads by actuating the valve
Solution Approach 2:
Pressurized grease is used to deliver lubrication to the thread interface. The grease is introduced under pressure through a grease fitting into the bore, where it flows along the valve stem to the thread interface, using fluid pressure rather than manual application methods
2Productivity
If valve stem moves through short stroke, then valve operation is efficient, but valve stem threads are not sufficiently exposed for effective manual grease application
Solution Approach 1:
The grease delivery device serves as a mediator that brings the grease source to the thread interface without requiring the valve stem to move. The device remains stationary while delivering grease directly to the mating threads, maintaining both short stroke operation and effective lubrication
Solution Approach 2:
The grease delivery device is designed to remain attached to the valve housing and automatically deliver grease to the thread interface during normal operation. The device includes a bore that receives the valve stem and delivers grease continuously or periodically without requiring manual intervention or valve actuation
3Ease of manufacture
If grease is applied to exposed valve stem threads, then threads are lubricated, but stem nut rotation wipes grease from the stem reducing coverage
Solution Approach 1:
Grease is delivered to the thread interface in advance of stem nut rotation. The grease is introduced under pressure directly at the interface between the stem nut and valve stem, ensuring the threads are lubricated before contact occurs, preventing grease wiping during rotation
Solution Approach 2:
Pressurized grease delivery ensures adequate grease coverage at the thread interface. The pressure forces grease into the mating threads, ensuring complete coverage that can withstand the wiping action during stem nut rotation without compromising lubrication
4Ease of operation
If internal grease path is included in stem nut, then grease can be delivered to mated threads, but device complexity increases
Solution Approach 1:
A separate grease delivery device acts as an intermediary, eliminating the need for internal grease paths within the stem nut. The device includes a body with a bore that receives the valve stem, a grease fitting for introducing grease, and delivers grease externally to the thread interface, keeping the stem nut structure simple
Solution Approach 2:
The lubrication function is separated from the stem nut structure. Instead of integrating a grease path within the stem nut, the grease delivery is handled by a separate device that attaches to the valve housing and delivers grease to the thread interface, simplifying both components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method ensures thorough lubrication of mated threads without valve actuation, collects old grease for analysis, and maintains lubrication during normal operation, addressing the limitations of existing designs by providing consistent and efficient grease distribution.
Implementation Method 1
pressurizing with pressurized grease one end of the thread interface defined by the mating threads with pressurized grease. The threaded grease flows into the one end of the thread interface and flows towards the other, opposite end of the thread interface
Implementation Method 2
the thread lubricator compressing a resilient seal against the face of the stem nut
Data Source
AI summary
A method for greasing the mated threads of a valve stem and a stem nut of a motor-operated valve without the need to actuate the valve and without the need for an internal grease path within the stem nut includes pressurizing one end of the thread interface defined by the mating threads with pressurized grease. A device for carrying out the method may include a thread lubricator that has a bore that receives the free end of the valve stem and an adapter nut that attaches the thread lubricator to the valve housing. Pressurized grease flows into the thread lubricator and to the one end of the tread interface.