How to Control Tightening Torque for Instrument Threads?

Instrument pipelines in complete sets of chemical and automation projects adopt a large number of precision stamped connecting fittings. The thread fastening quality of stamped fittings directly determines the safety and stability of the whole pressure measurement system. Improper torque control of industrial fasteners may cause pipeline medium leakage and shutdown in mild cases, or equipment damage and safety accidents in severe cases.

Some customers receive our stamped fitting samples with qualified dimension, flatness and thread go/no-go gauge test. However, leakage, insufficient gasket compression or thread stripping occurs half a year after installation. Failure analysis shows that in most cases, the issue is not the precision of stamped parts themselves, but improper on-site assembly process — especially thread tightening torque.

Three Typical On-site Failures Preventable via Torque Control

1. Leakage Caused by Inadequate Gasket Compression Workers only hand-tighten several turns. Copper gaskets are not plastically deformed, and medium seeps from gasket edges after startup. The correct operation is to follow torque values according to fitting specs and compress gaskets to the designed compression rate.

2. Stamped Body Cracking from Over-tightening Excessive force on thin-wall stamped fittings creates invisible circumferential cracks at ports. No leakage is found during pressure test, but temperature cycling expands cracks and triggers leakage after 1~2 months of operation. Rework cost for such faults is extremely high, often requiring pipe cutting and fitting replacement.

3. Thread Insert Spinning Out For plastic / aluminum alloy stamped fittings with copper inserts, assembly torque exceeding insert holding torque will rotate inserts together with nuts and scrap the whole fitting.

Recommended Tightening Torque for Stamped Instrument FittingsPrecondition: Stamped stainless steel / copper fittings + copper or aluminum gaskets + sealant; normal temperature working conditions

Extra Notes for Stamped Part Assembly

1. Single-use Gaskets: Copper and aluminum gaskets are plastic sealing components and must be replaced after disassembly for maintenance. Reused gaskets cannot guarantee sealing specific pressure.

2. Check Flatness of Stamped Surfaces: Visually inspect stamped sealing surfaces for stamping scratches and indentation before installation. Minor defects can be polished with fine oilstone; deep scratches mean scrap.

3. Correct Wrench Operation for Fittings with Thread Inserts: Hold the fitting body and only turn the nut. Do not twist both ends simultaneously, otherwise inserts may loosen.

4. Regular Calibration of Torque Wrenches: On-site torque wrenches should be calibrated every 6~12 months. Uncalibrated wrenches make torque control invalid

Jiaxing Aoke Trading can supply precision stamping parts, instrument connecting fittings and supporting industrial fasteners. Custom stamping processing is available, and non-standard stamping connectors can be produced according to drawings. Besides product delivery, we also provide assembly technical consultation to help customers standardize on-site thread assembly procedures, improve the assembly quality of instrument pipelines, reduce the risk of leakage faults in later project stage, and help the stable commissioning of chemical and automation projects.