ATEX pneumatic motor for vent valves

12 mars 2018

MOT_EN_applications

Vent valves are used in the gas or petrol production industry when the gaseous fumes, given off during the production, treatment, transport or storing of gas or petrol, are transmitted to a device to be dispersed into the atmosphere.

In this particular application, the stopcocks on the gas pipelines have to be opened and closed from a safe distance.

Context

When carrying out maintenance on sections of a gas pipeline, the gas - which is subject to a pressure of 80 bars - must be evacuated from the pipe section in question so that the operators can work in safe conditions. To do this, bypass terminals, with vent valves installed, are positioned along the gas pipeline at regular intervals. The decompression of the gas during evacuation via these vent valves generates noise levels close to 150 decibels (double protective hearing gear must be worn), as well as considerable vibration to the overall facility and causes the air to be saturated with gas.

All of which makes for very dangerous and restrictive conditions for operators intervening close to the gas vent zone.

Working in such conditions, it is better to use a pneumatic motor as opposed to a hydraulic motor which is much heavier and takes a long time to set up. In addition, pneumatic motors are ATEX certified – they are particularly recommended for use in dangerous environments where there is a risk of sparks or high temperatures causing fire from explosive gases, dust or vapours. As there is no electrical component in a pneumatic motor, there is no chance of causing a spark or explosion in air saturated with inflammable gas.

Requirement

So that the vent valves can be activated in total security, operators need to be able to carry out the procedure from a distance so they are safe from the gas emissions and also from the noise and vibration produced by opening the stopcocks.

At the same time, any proposed appliance must be simple to set up and easy to transport from one site to another.

It must also be capable of providing and maintaining a high torque during the evacuation process because the strong vibrations could cause the valve to close at an inopportune moment.

Finally, given the dangerous working environment, the complete solution provided must be certified Atex II 2.

Solution - A remote air motor !

Our team carried out an initial on-site test using a reversible pneumatic motor mounted on a gearbox selected from our MT30 range.

The motor with 490W power is able to limit air consumption, which means it can operate on a relatively low air source. The motor runs up to a set calibration level so that the valve can be maintained in an open position.

The MT30 gearbox, meanwhile, allows you to lower the motor’s speed sufficiently to be able to open the valve slowly, thereby limiting vibration levels. The gearbox design also means the appliance can withstand a torque in excess of 600Nm.

To keep the motor in place, our design department came up with an ingenious modular torque retention system, which is part of our Portable Valve Actuator range. It involves a telescopic bipod and strap that takes no time at all to set up – with this system, the torque reaction is easily deflected to the ground (in bipod configuration) or to channels above and below the valve. It comes with a belt system that ensures the torque retention stays fixed in position during use.

So that operators can keep their distance, the motor is piloted by an Atex SATbox which is mounted, for this particular appliance, with a 4-way valve to facilitate varying the rotation direction. The SATbox is a safety device that protects both the user and the equipment. It is integrated into the FRL unit and fitted with safety features, including an emergency stop button, an automatic circuit cut-out, a pressure dip detector and automatic feed closure. The SATbox is connected to the motor by 20m flexible pipes.

Following the on-site test which proved successful in terms of functionality, the client also asked us to add:

  • 1 exhaust outflow limiter, which makes is possible to regulate the motor’s rotation speed for better control of the vent valve’s opening speed.
  • 1 angle-position indicator attached to the motor which allows the operator to visualise the position of the stopcock (open or closed) from a distance.
  • 1 waterproof transport trunk to help transport, stock and set up the unit.

Conclusion

We have recently delivered the first set of equipment and trained the client’s staff in how it should be used and serviced. Always ready to listen to our clients’ needs, we made a final modification to the system to make it more stable on loose soil.

Since their training, the operators have greatly appreciated the fact that they can now work in total safety, using a solution that is perfectly adapted to their needs and yet is sufficiently multi-functional to use whatever the configuration and position of the valve.

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