What is Automatic Line Break Control / Low pressure shutoff?

What is Automatic Line Break Control?

Automatic line break control is a safety device which closes the main pipeline in case of considerable loss of pressure in the pipeline that means in case of leakage detection.

Automatic line break control is an important device used in the gas pipeline where gas leakage will be highly explosive or untraceable and costs high.

The reliability of this system makes the Automatic Line Break System pressure drop safety combined with low-pressure shutdown protection from the preset pressure sensor.

How an Automatic line break control works?

The low pressure shutoff portion of the control functions as follows:

Sequence 1:

The low pressure shutdown feature control elements include an adjustable air relay valve (X) and an ESD poppet valve (N).

Pressure from the pipeline is ported to the air relay valve (X) sensing section holding it in the open position. The low pressure falling trip point is created by way of the flexible spring.

Sequence 2:

If the mainline pressure drops below the air relay valve (X) fixed point level, the valve shifts to the closed position venting the pilot pressure from the front side of the piston (O) to the ESD poppet valve (N), shifting the poppet (Q), blocking the exhaust port and allowing power gas to shift the shuttle valve (M) insulating the secondary control (A).

Power gas pressurizes the closing gas hydraulic tank (K), forcing high pressure hydraulic fluid into the operator causing the valve operator to close quickly. The resident fluid in the operator is forced into the opening tank (L). As the valve and shuttle valve (W) shifts and selects the high pressure side of the valve as a power source for the operator.

Sequence 3:

When the valve operator reaches the end of stroke, the mechanical actuator ®, which is connected to the operator rotor, mechanically shuts the ESD poppet valve (N) pressing the poppet (Q) into the power seat, causing the gas hydraulic tank and operator pressures to neutralize.

The user is now in a lost role in emergency. The valve remains closed, allowing repairs to be made by isolating the damaged pipeline segment.

Only after the pipeline pressure has risen high enough to open the air relay valve (X) can the valve operator be opened. This pressurizes the ESD poppet valve pilot (N) and no longer requires a hydraulic actuator ® to keep the ESD poppet valve (N) closed. The valve operator can be opened by using poppet control (A) or manually hand-pumping.