Created on:2022-03-30 13:17

Analysis of common faults of diaphragm accumulator

Analysis of common faults of diaphragm accumulator

1. Introduction

Accumulator is a commonly used auxiliary device in hydraulic system. It mainly plays the role of storing and releasing pressure energy in hydraulic system. It can also be used as a device to absorb and eliminate pressure pulsation. There are many kinds of diaphragm accumulators. Compared with piston and bladder accumulators, diaphragm accumulators have the characteristics of small volume, light weight and fast response, so they are widely used. With the development of industry and the improvement of working frequency, the requirements for diaphragm accumulator are higher and higher, so the accumulator is also easy to fail due to failure.

2. Working principle and common fault analysis

The assembly drawing of diaphragm accumulator is shown in Figure 60. The top of the accumulator is a charging valve, and the lower oil hole is a hydraulic oil inlet hole. The working principle of the accumulator can be described by the following formula;

img1

Where V0 -- charging volume of accumulator;

Δ V -- working volume of accumulator, △ v = V1-V2;

P1, V1 - minimum working pressure of accumulator and gas volume under this pressure;

P2, V2 - the maximum working pressure of the accumulator and the gas volume under this pressure;

P0 -- inflation pressure;

N -- absolute thermodynamic index.

Before working, the accumulator shall be inflated according to the requirements of inflation pressure pill (generally nitrogen). In the working process, the accumulator constantly stores and releases oil, so the pressure and volume in the accumulator chamber are constantly changing. This change is completed through the deformation of diaphragm rubber cup. When the rubber cup fails, the accumulator fails. According to the application experience, the common faults of its diaphragm accumulator are diaphragm breaking and air leakage.

The diaphragm breaking phenomenon often occurs for the accumulator under high-frequency operation, and some breaking phenomena are that the accumulator breaks immediately as soon as it is used. The main reasons are as follows: ① poor elasticity and low tensile strength of rubber; ② The wall thickness of rubber diaphragm changes unevenly; ③ Influence of inflation pressure; ④ Rubber aging, long-term storage by the manufacturer.

Air leakage mainly occurs in two places; One is the poor sealing of the inflation valve, and the other is the metal riveting at the bottom of the rubber diaphragm, respectively at positions a and B shown in Figure 60.

The main reason for gas and gas is that after the accumulator works for a period of time, because the accumulator is always in the alternating process of filling and discharging liquid, coupled with the pressure impact of the working mechanism in the system, vibration inevitably occurs, which makes the threaded connection or riveting of the above two places loose, resulting in the decline of sealing capacity.

60、61

3. Improve design

We have improved the design of the manufacturer's diaphragm accumulator. First, the rubber diaphragm is improved, as shown in Figure 61.

It can be seen from figure 61 that its wall thickness changes evenly, especially at the place easy to break, which can not cause stress concentration. Secondly, nylon is added to the rubber material to improve its tensile strength,

As shown in Figure 61, the bottom of the rubber diaphragm changes the original metal riveting to the embedded structure. This improved structure has no air leakage problem at all.

For the air leakage at the inflation valve, the thread locking device is mainly added. In order to prevent the thread from loosening, the sealant is also used to seal, so as to prevent the occurrence of air leakage.

The improved diaphragm accumulator has been tested for 3.6 million times with a working pressure of 14 MPa. It is in good working condition without diaphragm breaking and air leakage.

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