High pressure regulating pneumatic valve the causes of loose screw 2)

event in October. High-profile MOE, unit overhaul #, #, stem the collapse of the head ( No thread here, but have a stop pin hole machining level, ф mm, L for mm) Transverse fracture occurred. Due to stop across the needle ( Cross-selling) Did not appear before the break, so the tone is not exceptional also # high stability.
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door head fractures. 。 Power. Long shot axial periodic exciting force to the valve, gate threaded portion easily fatigue damage of the connecting rod and head
. 。 And processing technology. Door and pin hole machining level after reaming drill bit, blades in the form of a typical stress concentration, the formation of cracks, hole edge will be rapid development, once the fracture.
。 。 And materials. Rod material CrNiMoWV, working under high temperature, in order to increase its resistance to high temperature oxidation, special surface nitriding process, formation. Mm of nitrogen, iron compounds of a thick layer of hardness, wear resistance, oxidation resistance significantly increased, the corresponding brittleness increases, the lower toughness.
。 。 Improper assembly process.
the steam factory assembly drawing requirements: high tone is cold installation, pole screw suite door, you need to leverage the torque N * M and feet, and then into the intersection. It was required to install the back door, the overall tension power guide bush, left gap is prohibited. Hot, for pneumatic valve rod set up in guiding internal temperature than the guide sleeve, the axial linear expansion than guide bush strengthen can still be guaranteed with pre-tightening force, higher. Therefore, when the door is running hot rod, bar by the axial vibration force valve, the force will be passed directly to the guide bush, pneumatic valve stem thread connection, whether the effect of vibration force, as a part of it is more likely to damage the connecting thread of stress concentration, so as to avoid the fatigue damage of the screw. That is not the case, six high tone in different degree, is not in conformity with the technical requirements of phenomenon exists, it is cold when install the back door of the torque rod applying N * M, pneumatic valve stem cross pin hole and guide hole dislocation cross-selling occurred the phenomenon of cross-selling sleeve can not successfully installed. In order to successfully install cross stitch, slight rotation shot her back towards the door, if the dislocation cross pin hole mm, rod connecting thread M expressway exit about * when the valve stem. , there is the calculation of the door head and guide sleeve. Mm gap, which is in conformity with the technical requirements do not conform to the pre-tightening force. If you ignore the maintenance personnel assembly technology requirements, efforts and plans to install, it will leave a safe hidden trouble. Keywords:
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