Always follow standard safety procedures when working on a valve. The valve should be welded onto the line with the wedge in the fully closed position. Leaving the valve even partially open can cause distortion and leaking. Verify the drawings to make sure that the valve has bi-directional sealing capability. If the valve only has unidirectional sealing capability, make sure it is installed into the pipeline in the correct orientation. Single direction sealing gate valves have a nameplate on the side of the valve that has a relief hole or pressure equalizer. This should be the high pressure side when the valve is closed.