double block and bleed installation, pad gas pressure and double block and pad installation

[zolot_o]

трудности перевода:

All safety shutoff valves must be proven closed on all fuels and process feeds to the combustion zone and
a. the respective vent valves proven open for a double block and bleed installation
b. the pad gas pressure proven higher than fuel supply pressure for a double block and pad installation.

Речь идет об оборудовании с огневым подогревом

Помогите, пожалуйста, с переводом словосочетаний
double block and bleed installation,
pad gas pressure,
double block and pad installation

[zolot_o]

double block and bleed installation - не надо