1 Introduction

Valve drive device is a device that uses external power to open and close the valve. The purpose of the valve using the drive device is to make the operation of the valve labor-saving, convenient, fast and reliable, or to realize automatic control and remote control. The basic requirements that the valve drive device meets are: torque or thrust can meet the opening and closing needs of the valve, the stroke and torque control is accurate and reliable, the selection of power is suitable for the site situation, the opening and closing action meets the control requirements, and the device itself is light and small. With the enlargement of valves and the automation of the production process, in addition to manual devices, pneumatic devices, hydraulic devices, electric devices, gas-liquid linkage devices, electro-hydraulic linkage devices, etc. are currently most used.

2 Common driving device and failure analysis of a gas field

2.1 Electric actuator

Electric actuator is a device that uses a motor to drive a deceleration mechanism to make linear or rotary motion to drive the valve. It is characterized by small size, large torque output, high safety and reliability, etc., suitable for remote control and automatic control, and is widely used. It is generally composed of a dedicated motor, a reduction mechanism, a remote control mechanism, a manual and electric switching mechanism and an opening indicator.

As of 2017, there are 447 electric actuators in use in a gas field. The main brands used are LIMITORQUE, ROTORK and BIFFI. The specific problems are shown in Table 1.

Failure analysis:

①The component pins on the circuit board are oxidized, and the circuit board itself is broken due to material and temperature changes, which will cause the electronic product to malfunction;                ②The product selection: product power is too small, and the operating torque cannot be Satisfy the valve starting needs; the product withstand voltage range is too narrow to meet the objective use requirements of gas field stations in special areas such as towns and towns; 

③Product manufacturing: individual product manufacturing accuracy is not up to the requirements, and the sealing is not strict; 

④Equipment operation, maintenance, and general troubleshooting skills need to be improved.

2.2 Pneumatic actuator

Pneumatic actuators are mostly composed of pressure cylinders driven by compressed gas. It is characterized by compact structure, rapid opening and closing, suitable for indoor or corrosive, flammable and explosive environment; its disadvantage is that the piping is more complicated and not suitable for remote control.

As of 2017, there are 40 pneumatic actuators in use in a gas field. The main brands used are ROTORK, BIFFI and BETTIS. It is mainly used as the driving device of the emergency vent valve supporting the ESD system of the station. This type of equipment usually only operates during debugging, and the main cause of failure is the aging of the accessories caused by the long service time.

2.3 Gas-liquid linkage actuator

Gas-liquid linkage actuator is mainly composed of poppet valve gas circuit control block, manual pump device, actuator, gas-liquid tank, spare gas source tank, limit switch, LINEGUARD control box and other parts. It is characterized by rapid action and large output, which can drive large-caliber valves.

As of 2017, there are 110 gas-liquid linkage actuators in use in a gas field. The main brands used are BIFFI and SHAFER. Most of the equipment is located in the line valve room, and the operating performance is relatively stable.

Analysis of the main causes of equipment failure:

①Long service time, the aging of some seals of the gas-liquid linkage actuator, coupled with the influence of temperament, the occurrence of malfunctions caused by gas flow in the controller, and the failure of the ball valve to open normally after closing the valve; 

②The seal of the gas path control part More, high sealing requirements; 

③some through holes are small, sensitive to particles and dust impurities, and easy to block.

3 Suggestions for improvement

①For aging, oxidized and easily blocked components, spare parts storage should be done, and targeted maintenance and troubleshooting training should be carried out for station employees to ensure that on-site problems can be dealt with in time; 

②Conscientiously carry out the initial stage of the project The review of technical specifications, the acceptance inspection of goods in storage, and the joint debugging and testing of on-site installation ensure that the product quality meets the requirements of on-site use and installation specifications.