Safety Valve Of Mechanical Pump

1. How does the safety valve work?

The safety valve is a valve that automatically opens and closes according to the working pressure of the medium. When the working pressure of the medium exceeds the specified value, the safety valve can automatically open the valve disc and discharge the excess medium (gas). When the pressure returns to normal, the valve disc can automatically close again.


2. What are the requirements for valve assembly?

1) Assembly conditions:

After all valve parts are cleaned, inspected, repaired, or replaced, their dimensional accuracy, mutual position accuracy, smoothness, material properties, and mechanical properties such as heat treatment should meet the technical requirements before they can be assembled.

2) Assembling principles:

In general, dismantle first and then install, and those who disassemble first install first, clarify the nature of the fit, avoid violent knocking, and operate in order, first inside and then outside, bottom-up, first easy and then difficult, first Parts, components, mechanisms, back cover pressure test.

3) The effect of assembly:

Proper fit, correct connection, complete valve parts, tight bolts, flexible opening and closing, accurate indication, reliable sealing, and adaptation to working conditions.


3. What inspection methods are there for valve quality?

1) Visual inspection

2) Dimensional inspection

3) Assembly inspection

4) Disassembly inspection

5) Pressure test inspection


4. How many types are valves divided into according to their structural characteristics?

1) cut-off shape
2) gate shape
3) Cock shape
4) Butterfly
5) Spin-up shape
6) Slide valve shape


5. What are the basic parameters of the valve?

1) Nominal diameter of the valve
2) The nominal pressure of the valve
3) The relationship between the working pressure of the valve and the working temperature
4) The medium used for the valve


6. What are the characteristics and uses of gate valves?

1) Advantages:

The sealing performance is better than that of the stop valve, the fluid resistance is small, the opening and closing is less labor-saving, the sealing surface is less eroded by the medium when fully open, and is not limited by the flow direction of the medium. It has double flow directions, the structural length is small, and the application range is wide.

2) Disadvantages:

The overall size is high, the opening needs a certain space, the opening and closing time is long, the sealing surface is easy to be eroded and scratched during opening and closing, and the two sealing pairs bring difficulties to processing and maintenance.

3) Uses:

Gate valves are generally used in pipes and equipment with a diameter of DN15-1800mm. It is used in a large amount, mainly for cutting off, and is not allowed to be used for throttling.


7. What are the functions of the valve?

1) Opening and closing function
2) Regulation
3) Throttling effect


8. What should be paid attention to when installing the stop valve?

1) Due to the asymmetry of the inlet and outlet of the stop valve, the medium should flow through the valve port from bottom to top during installation, that is, low in and high out, so that the valve is opened with less effort and the packing is not easy to leak. It really plays the role of cutting off and adjusting pressure and flow.

2) If the stop valve is installed in the opposite direction, the inlet pressure will exert pressure on the middle flange base packing of the valve body. The design pressure of these two parts of the valve is low, which will cause leakage at the middle flange and packing of the valve body.


9. What are the general requirements for valve installation?

1) Before the valve is installed, the inside of the pipeline should be cleaned to prevent iron oxide chips, welding slag, hard particles, or other foreign matter from scratching the sealing surface of the valve. At the same time, carefully check the model and specification of the valve, and carefully check whether the valve is closed tightly.

2) Pay attention to the installation direction of directional valves, and do not install them backward.

3) Due to the left-right asymmetry of the valve cavity of the stop valve, the fluid flows through the French port from bottom to top after installation.

4) The gate valve should not be inverted, otherwise, the medium will stay in the valve cavity for a long time, and it is easy to corrode the valve stem. The rising stem gate valve should not be installed underneath to avoid corrosion of the wheel post.

5) There are two types of check valves: lifting type and swing type. The lift check valve can only be installed horizontally, and the swing check valve must ensure that its shaft pin is installed horizontally. Swing check valves can be used on horizontal and vertical pipelines.

6) Generally, it should be installed in a closed state.

7) When installing or replacing heavy doors, the lifting lock should not be tied to the handwheel or valve stem, but should be tied to the valve body, so as not to damage the handwheel or valve stem and other parts.

8) When the pressure-reducing valve is installed, cut-off valves and pressure gauges should be installed before and after the valve, and a safety valve should be installed behind the valve.


10. What are the directional valves?

Directional valves generally include globe valves, throttle valves, pressure-reducing valves, check valves, etc.


11. How about the strength test process (hydraulic test) of the valve?

1) After the valve is filled with water, the internal air is discharged.
2) The valve is open.
3) Slowly increase to the test pressure.
4) After reaching the test pressure, keep the pressure for more than 5 minutes, and there should be no leakage at the packing valve cover of the shell.


12. How should the safety valve be transported to the site for installation after calibration?

After the safety valve is calibrated, add a lead seal, keep it in an upright position during transportation and installation, and strictly prohibit collision with other objects to ensure the calibration accuracy of the safety valve.


13. What tests should be carried out during valve testing?

First, carry out the hydrostatic strength test, and then check its airtightness.


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