Always make sure that isolation or lock-out procedures are followed.
If an electrical contractor needs to access some wiring, they should follow a procedure of isolating or
de-energizing the circuit.
Electrical contractors should have written procedures they are supposed to follow, but many people (often non electricians) will skip isolating a circuit to do something that is simple of quick. Although this often seems ok and often works, there is a high risk of injury or damage to circuits.
Unpluging a power supply, isolating a circuit etc should always be done. Otherwise an accident will eventually happen.
If a valve should not be used, it should have a lock-out tag put on it. Especially if it is to be left unattended or if it contains dangerous or contaminated material (eg chemicals, sewage).
It is a good idea to carry a lock-out tag with you on site inspections, commissioning, or any site work you do. If you need to turn off a valve to open a pipe or equipment, you can easily put your lock-out tag on it for the few minutes you are doing the work. This reduces the risk of someone inadvertently turning the valve back on.
As a project manager you should not practice lazy or “save time” habits that others may often use. You are in charge of the project. You should set a good example, but also insist on proper procedures. This reduces risks, potential liability, and increases professionalism.