Anti-leakage Measures for Long-term Use of Internal Thread Plugs
2026-06-01 09:50:58
Injection Molds
Internal thread plugs are basic sealing components widely applied in injection molds, hydraulic systems, cooling and heating circulation pipelines and industrial pressure vessels. Most on-site faults including water seepage, oil leakage, poor pressure holding and pressure relief are caused by sealing failure of thread plugs. Thread leakage rarely occurs suddenly. Instead, it is accumulated by multiple factors such as long-term vibration, alternating temperature, aging of sealing components, non-standard assembly and wear of thread fits. To realize long-term zero leakage of internal thread plugs, comprehensive standardized management shall be carried out in terms of sealing material selection, assembly technology, working condition adaptation, hidden danger rectification and daily maintenance.
Root Causes of LeakageLeakage of internal thread plugs is not simply caused by insufficient tightening. There are inherent fitting gaps between threads, and conventional thread structures cannot achieve complete sealing. Micro penetration will occur under long-term pressure. Continuous vibration during equipment operation loosens thread plugs gradually and damages the original sealing state. Repeated thermal expansion and contraction of metal threads under alternating high and low temperatures enlarge sealing gaps.
Meanwhile, many irregular operations exist in actual production, including mismatched sealing materials, repeated use of gaskets, residual iron scraps and oil stains on thread surfaces, and thread damage caused by forced tightening. As service time goes by, sealing components harden and age, threads wear and slip, and threaded holes deform slightly. Eventually, minor seepage develops into obvious leakage, which affects equipment pressure holding and production stability.
Scientific Selection of Sealing Materials for Long-term Working Conditions
Selecting proper sealing materials is the core of long-term leakage prevention, and materials shall be matched with specific working conditions. For ordinary low-pressure water pipelines at room temperature, thickened PTFE tape can be adopted. Wind 2 to 3 layers of tape starting from the second thread, and reserve several threads at both ends without wrapping to prevent tape debris from blocking flow channels. It should be noted that PTFE tape is only suitable for low-pressure and normal-temperature scenarios, and cannot be used for equipment under long-term high pressure, high temperature and severe vibration.
Anaerobic thread sealant must be used for high-pressure oil circuits, high-temperature water pipelines and vibration-intensive equipment. Liquid sealant fully fills micro gaps between threads and forms high-strength sealing layers after curing. It integrates sealing, anti-loosening, oil resistance and temperature resistance functions, and thoroughly eliminates hidden dangers of long-term micro seepage. Gaskets or FKM O-rings must be installed on the end face of thread plugs. Metal gaskets such as copper and aluminum gaskets have good ductility, which fit tightly under pressure and resist aging. FKM parts adapt to oil, water, high temperature and corrosive media. All gaskets are disposable consumables and must be replaced with new ones during each disassembly and assembly. Reuse of deformed and aged old gaskets is strictly prohibited.
Standardized Assembly Technology to Eliminate Hidden DefectsNon-standard assembly is the major human-induced factor leading to later leakage. Before assembly, thoroughly clean threaded holes and plugs to remove residual sealant, iron scraps, oil stains and rust, and keep thread fitting surfaces clean and dry. Impurities remaining on threads will cause incomplete engagement and poor end face compression, resulting in sealing failure and seepage soon after operation.
Violent tightening is forbidden during assembly. The misconception that tighter fastening means better sealing prevails in many workshops. Excessive force will stretch and damage threads, crack mold holes and crush gaskets. Although no leakage can be seen in the short term, loosening and seepage will happen easily under vibration later. Operators shall use torque wrenches for uniform tightening according to standard torque values, to ensure full thread engagement and even compression of end face gaskets. If thread sealant is applied, sufficient curing time shall be reserved. Water and pressure shall not be applied before complete curing, otherwise the sealing layer will crack and fail.
Rectification and Optimization Measures for Worn Threaded Holes
Threaded holes of long-serving old equipment usually suffer from wear, shallow thread profiles and excessive fitting gaps, which cannot be solved by conventional sealing methods. For slightly worn threads, enhance sealing effect by applying extra sealant and matching metal gaskets. For severely worn holes with large gaps, adopt thread repair technology or install oversized thread plugs to restore normal fitting precision.
Additional anti-loosening measures shall be taken for equipment in severe vibration environments, such as using anti-loosening thread sealant or lock washers to prevent thread loosening caused by long-term vibration. Ordinary rubber gaskets shall be replaced with metal gaskets or high-temperature resistant FKM parts in high-temperature working conditions. Corrosion-resistant sealing materials are selected for pipelines conveying corrosive media to slow down aging of sealing components.
Establishment of Regular Maintenance SystemLong-term leakage prevention relies on regular maintenance. Sealing components are wearing parts with natural aging cycles. All sealing accessories are recommended to be replaced every 1 to 2 years regardless of leakage status, to avoid sudden failure caused by hidden aging. Enterprises shall establish regular inspection systems, and check all thread plugs on oil and water pipelines quarterly to detect minor seepage, loosening, rust and indentations at an early stage.
Standard operating procedures shall be followed during daily disassembly and maintenance, including thread cleaning, gasket replacement, standardized sealing and torque tightening. Unified assembly quality is guaranteed to avoid hidden dangers left by human errors.
ConclusionLong-term leakage of internal thread plugs is a common equipment problem in production workshops, involving material selection, assembly quality, working condition loss and aging maintenance. To achieve stable zero leakage for a long time, relying on forced tightening or temporary leakage repair is not feasible. A complete management system consisting of condition-based material selection, standardized assembly, rectification of worn holes and regular maintenance must be implemented. Standardized management thoroughly solves problems such as thread micro seepage, pressure relief, oil and water leakage, protects molds and equipment structures, reduces failure downtime, and improves equipment operation stability and production efficiency.
