Zhejiang Weiguang Valve Manufacturing Co., Ltd.
Current Position:Home > News > What are the common faults of valve?
What are the common faults of valve?
author:admin  source:weiguang   time:2014-11-19 16:35:20  

1, the gland leakage

This is run, run, drip, leakage of the main aspects, often seen in the factory.


Causes of stuffing box leaking in any of the following points:


1) packing and working medium corrosion resistance, temperature, pressure does not adapt, (2) the packing method is wrong, especially packing hovering in the root, the most easily produce leakage; (3) stem machining accuracy and surface finish is not enough, or have ovality, or have a notch; (4) stem pitting corrosion has occurred, or due to a lack of protection in the open air and rust; (5) stem bending; 6 packing used for too long, has been aging; All landowners operation too strong.


In addition to the packing leakage elimination method is: (1) correct choose packing; (2) according to the correct loading; (3) stem processing is unqualified, to repair or replace, minimum surface roughness to achieve del 5, more important, to achieve del 8 or more, and no other defects; (4) to take protective measures to prevent corrosion, erosion has to change; (5) the valve stem to bend straightening or update; 6 packing use after a certain period of time, to replace; All landowners must pay attention to the steady operation, slow slow close, to prevent the temperature change or medium shocks.


2, close a leak


Usually called gland leakage were leaked, called shut down a drain. Close a leak, inside the valve, it is not easy to find.


Close a leak, can be divided into two kinds: one kind is leak sealing surface, another kind is seal leak root.


Lead up the reasons of leakage are: (1) sealing surface grinding well; (2) the sealing ring and valve seat and valve disc with no tightness; (3) the disc and stem connection not prison *; (4) stem bend torsion, make up and shut down a wrong; (5) shut down too fast, sealing surface Bad contact or already damaged; 6. Improper selection of materials, cannot endure the corrosion of the medium; All landowners will stop valve, gate valve used for adjusting. Seal face cannot endure the erosion of the high-speed flow medium; Today, some media gathering cooling after valve is closed, the seal face in thin seam, also can produce erosion phenomenon; Pet-name ruby some sealing surface and USES threaded coupling between the seat, disc, easy to produce the oxygen concentration cell, loose corrosion; Attending for welding slag, rust, dust and other impurities embedded into, or mechanical parts in the production system off plug valve core, the valve cannot be locked.


Preventive measures are:


1) before use must carefully test leakage, found that the sealing surface leakage or seal leaking roots, to deal with again after use; (2) to check the valve parts in advance, can not use stem bend torsion or disc and stem connection not * valves; (3) the valve shut to make steady effort and don't make MengJin, found between the sealing surface contact is bad or if there is any block, should immediately open a bit, let the debris flow, and then carefully shut; When choosing the valve (4), not only want to consider the corrosion resistance of the valve body, and to consider closing a corrosion resistance; (5) according to the structure characteristics of the valve, the correct use, need to adjust the flow components regulating valve should be used; After 6 to close the valve of cooling medium and the temperature difference is bigger Conditions, then the valve shut up after cooling; 7) the seat, disc and seal ring adopts screw connection, can make thread between packing with ptfe tape, make it no gap; Was likely to fall into the impurities of the valve, should add filter in front of the valve.


3, the valve stem lift failure


Stem lift failure reasons are: (1) conduct operations, thread damage; (2) lack of grease or lubricant failure; (3) stem bend torsion; (4) surface finish is not enough; (5) fit tolerance, biting too tight; 6. Stem nut tilt; All landowners improper selection of materials, such as the stem and stem nut for the same material, easy to bite; End of thread is medium corrosion (non-rising stem valves or valve stem nut on the bottom). Pet-name ruby open valve a lack of protection, the stem thread covered in dust sand, or corroded by rain and dew frost and snow.


The method of prevention:


(1) operation carefully, don't make MengJin when closed, open when not in top dead center, open enough back to handwheel after one or two laps, make thread or upper, lest medium to promote stem upward shocks; (2) check the lubrication condition, maintain the normal lubrication state; 3. Do not use long lever open and close the valve, used to use the short lever workers must strictly control hard discretion, in case of twisted stem (refers to the handwheel and direct connection of valve stem); (4) improve the quality of processing or repair, meet the specification requirements; 5) material to corrosion, to adapt to the working temperature and other working conditions; 6. Stem nut do not use the same as the valve stem material; Plastic make stem nut, all landowners to check strength, cannot consider only good corrosion resistance and low friction coefficient, must also consider the strength, the strength is not enough, do not have to use; Today in the open air valve to add a protection to the valve stem; Pet-name ruby normally open valve, turn the handwheel, regularly in order to avoid the valve stem rust.


4, other


Gasket leaks: the main reason is that no corrosion, don't adapt to the working temperature and working pressure; And the temperature change of the high temperature valve. Prevention methods: adopt to adapt themselves to the working conditions of the gasket, the new valve to check whether the gasket material is suitable for, such as unsuitable should be replaced. For high temperature valves, when use tight the bolt again.


The body cracking: generally due to freezing. The day is cold, the valve should have heat preservation heat tracing measures, otherwise after shutdown valve and connecting pipe should be in the water is clean (such as bottom plug valve, drainage) can open the plug.


The handwheel damage: caused by impact or long leverage against operation. As long as the operator and other relevant personnel pay attention to, can be avoided.


Packing gland fracture: compression strength uneven when packing, or gland (typically cast iron) is flawed. Compress packing to symmetrically rotary screw, not twisted. Manufacture should not only pay attention to the bulk and key-module, also pay attention to the gland elements such as time, otherwise affect use.


The valve stem and valve plate connection failure: gate valve stem oblong head and ram T slot connection form is more, T slot sometimes not processing, so that the valve stem oblong head wear quickly. Mainly from the aspects of manufacture to solve. But use the unit can also fill the t-slot processing, make it has a certain roughness.


Double ram disc of the valve pressure can't close the cover: the tension of double ram is * wedge, some gate, poor roof wedge material (low grade of cast iron), use soon wear or broken. Top is a small wedge, the material is not much, use the unit can be made of carbon steel on its own, replace the original cast iron pieces.

Copyright © 2014 Zhejiang Weiguang Valve Manufacturing Co. Ltd. All Rights Reserved. Technical support:lianke