vent & drain

Abhijit, You wrote:
Lines are tested together with equipment connected. Which also means, the line which is starting with vessel A to vessel B may not have hydrotest vent & drains as the connected equipment will have it & can be used for the required purpose.

So let's consider the situation. "Lines are tested with equipment connected" This means the lines AND the equipment will be tested together. Correct? If this is correct, then there may or may not be any high points or low points in the piping. If there are no high points or low points in the piping then you do not need vents or drains in the piping. This means that the equipment on the high end must have a way to vent out any air in the system. It also means the equipment on the low end must have a way to drain out the hydrotest fluid. This brings us to the equipment. Do they each really have a way to vent and drain the system. Do they also have a way to fill the system?

- Are you really going to test through the equipment?
- If you are not going to test through the equipment then how are you going to isolate the piping from the equipment?
- How are you going to fill the piping with hydrotest fluid?
- What size are these specific lines (connected to the equipment)?

Abhijit,
Thank you for the sketch. It helps a lot.
The way I see things, you have two options:
Option #1 - Hydrotest the piping on the ground before you install the piping. Get two Blind Flanges and install a valved connection (hole in the BF, O-Let fitting , Nipple and valve) in each Blind Flange. Arrange the piping on the ground so there is only one high point and one low point. Install the valved blind flanges and fill the piping with water and do the test.

Option #2 - Install two small valved outlet connections minimum distance from each end flange of the line. Install the line complete with the Spec Blinds. Use the two new branch connections to fill the line and bleed out as much air as possible. Do the test making allowance for the fact you do not have a completely full line. After the test open the valves to drain out most of the water then open the flanges to remove the Spec Blinds and drain out the rest of the water.