What should you do before opening the tank valve of an oxygen cylinder connected to a cutting torch?

Before opening the tank valve of an oxygen cylinder connected to a cutting torch, it is essential to turn the diaphragm screw all the way in. This action ensures that the regulator is properly closed and will not allow oxygen to flow until it is intended to be used. If the diaphragm screw is not fully seated, there could be an uncontrolled release of oxygen, which could be dangerous and lead to a fire hazard when using a cutting torch.

It's important to recognize that taking this precaution helps establish a safe environment for operating the cutting tool. By securing the diaphragm screw, you ensure that the system remains in a controlled state until you are ready to proceed with the task at hand. Proper handling practices and safety measures, such as this, are critical in maintaining a safe working environment when dealing with flammable materials and high-pressure gases.