Valve failure, you know how it is produced
- Nov 22, 2017 -

Stuffing box leaked

This is the main performance of run, risk, leak, often seen in the site, factory. There are several reasons for the stuffing box leak:

 

1, filler is not suitable for working medium corrosive, temperature and pressure;

2, the filling method is wrong, especially the entire root filler into the spin-off, the most prone to leakage;

3, stem machining accuracy or surface finish is not enough, or oval, or scored;

4, stem pitting has occurred, or due to lack of protection of the open rust;

5, stem bending;

6, the filler used for too long has been aging.

7, the operation is too hard.

 

Closure parts leaks

Usually leakage stuffing box is called outer leakage, the closure of the leak is called inner leakage, closing pieces of leakage, inside the valve, not easy to find.

Closure pieces can be divided into two categories: one is the sealing surface leakage; the other is the root seal leakage. Causes of leakage are:

1, sealing surface grinding is not good;

2, seals and seat, with the valve is not tight;

3, disc valve stem connection is not solid;

4, stem bent, so that the upper and lower closure is not aligned;

5, close too fast, poor contact surface or already damaged;

6, improper choice of materials, can not withstand the corrosion of the medium;

7, the globe valve, gate valve is used for regulating, sealing surface can not withstand the impact of high-speed flow medium;

8, some media, gradually cooling after the valve is closed, so that the sealing surface of the slit, will produce erosion phenomenon;

9, some seals and the valve seat, the valve between the use of threaded connections, prone to oxygen concentration of the battery, corrosion loose;

10, due to welding slag, rust, dust and other impurities embedded, or the production system has mechanical parts off plug spool, so that the valve can not be closed.

 

Valve stem failure

Valve stem failure, the reasons are:

1, excessive operation to thread damage;

2, the lack of lubricant or lubricant failure;

3, stem bending and torsion;

4, the surface finish is not enough;

5, with the tolerances are not allowed, too tight bite;

6, stem nut tilt

7, improper choice of materials; for example, stem and stem nut for the same material, easy to bite;

8, the thread corroded by the medium (referring to the dark rod valve or stem in the lower part of the valve);

9, the lack of protection of open valves, stem thread sticky dust, or rain and snow rust.

 

other

Body cracking: usually caused by freezing. When the weather is cold, the valve should have thermal tracing measures, otherwise the valve should be shut down after the shutdown and the water in the pipeline (if there is a plug at the end of the valve, you can open the plugging drainage).

Damage to the handwheel: Crash or long lever caused by violent operation. As long as the operator or other relevant personnel pay attention, can be avoided.

Packing gland fracture: Uneven packing force, or gland flaws. Compression packing, to the symmetry of the rotating screw, can not be skewed. Manufacture should not only pay attention to the main body and key components, but also pay attention to gland and other minor parts, otherwise affect the use.

Valve stem and gate connection failure: Gate valve stem square head and gate T-slot connection in the form of more, sometimes not processed T-slot, so the stem square head wear faster. Mainly from the manufacturing side to solve. But the use of units can also be T-slot for additional work, so she has a certain finish.

Double gate valve gate can not compress the sealing surface: double gate tension is generated by the top wedge, some gate valve, wedge material poor (low grade cast iron), the use of wear or break soon.