Design of direct-acting safety valve - heading

Contents

Terms of Reference

Introduction

1. Select a design diagram and describe how it works

1.1 Purpose of the structure

1.2 Description of the structure

2. Basic Design Parameter Calculations

2.1. Definition of main parameters of the main valve

2.1.1. Determining the forces to move the main valve

2.1.2. Calculation of main valve spring

2.2. Determining the main parameters of the control valve

2.2.1. Liquid reaction to control valve

2.2.2. Calculation of hydraulic resistances

2.2.3. Calculation of control valve spring

3. Basic Strength Calculations

3.1. Calculation of bolts for strength

4. Basic Characteristics Calculations and Graphs

4.1 Mathematical model of indirect valve

Literature

Application

Introduction

Safety devices are responsible units which shall ensure safe operation of the plant under pressure of gas, steam or liquid.

In equipment operating at high pressure, damage to safety devices can cause serious consequences and production difficulties during operation. Many disadvantages in the operation of safety valves can be explained by the choice of valves without taking into account their design features and characteristics!

The most difficult issues are the force of the flow on the valve disk. Effective patterns in the operation of safety valves can best be expressed using the principles of the theory of physical similarity of processes.

1.1 Purpose of the structure.

Control hydraulic devices change pressure, flow rate and direction of oil flow by partial opening of working flow section.

Such devices include pressure valves that limit, maintain or control the pressure in the hydraulic system.

Pressure valves are used to maintain pressure in hydraulic lines by continuous or occasional drain of working fluid. Depending on the functional value, it is customary to divide them into safety and overflow valves, despite the identity of the structures.

Safety valves are pressure hydraulic valves designed to protect the volumetric hydraulic drive from pressure exceeding the set one by draining liquid at the moment of pressure increase. They only operate in emergency situations as opposed to overflow valves designed to maintain a given pressure by continuously draining oil during operation.

At low oil flow rates and operating pressures, direct relief valves are used. With an increase in flow rate and working pressure, the dimensions of the valve spring increase sharply, therefore, in hydraulic systems, non-direct devices are often used, in which a small auxiliary valve controls the movement of the overflow spool connected to the pressure and drain lines.

Safety valves shall keep the set pressure as constant as possible over a wider range of oil flow rates passing through the valve. In dynamic modes, speed is required to prevent the occurrence of a pressure peak with a sharp increase in flow rate.

Increased speed often causes a loss of stability, accompanied by noise and pressure fluctuations. Thus, the design of the valve should provide an optimal amount of damping; the pressure peak usually does not exceed 1520%.

For such valves, it is especially important to consider not only static Pk = f (Q), but also the dynamic characteristics of pressure change over time Pk = f (t) at a given time interval of flow change Q. The main requirement for the static characteristic of the valve is a slight change Pk in a wide range Q. For its implementation, a flow part of a special shape is used.