Appendix 1 Vents Drains
Appendix 1 Vents Drains
Appendix 1 Vents Drains
3.0 INSTRUCTION
Hydrostatic vents and drains, used for the hydro testing of piping systems, are
positioned by Piping. These vents and drains do not need to be added to the P&IDs.
Whenever possible the vents and drains should be grouped together, i.e. on the same
easting or northing coordinate, and at the edge of modules for ease of use by
Operations. Vents are to be placed at ALL high points and drains are to be placed at
ALL low points within a PIPING SYSTEM.
A PIPING SYSTEM is defined as the complete routing of the line and any branches.
Piping does not provide vents or drains on the high or low points of a module unless this
is the high or low point of the system. Vents and drains at module high and low points for
shop hydro test are the responsibility of the module fabricator. For example, Piping will
detail a high point vent on a rack loop and a low point drain if required, but may not
include them on lines rising out of the rack as that may not be the highest point of the
SYSTEM. Sketch 1.
Any valved instrument connection at a high point, such as a PI, is an acceptable
alternative to a vent. However, “cracking flanges” at vessel nozzles is not acceptable. In
these cases a vent is required prior to the nozzle. In a fitting to fitting situation, i.e. elbow
and flange, use an elbolet. Please request elbolets as required from Material Control.
Hydrostatic vents and/or drains are also required on both sides of a spec break. Sketch
2.
Hydrostatic vents and drains are not required on Instrument or Utility Air systems.
Hydrostatic vents and drains are permanent installations. Valves are not removed and
reused elsewhere after testing.
A type of vent is the “bleed connection”, such as those used at a tie-point. These will be
¾” in all cases. Do not tap blind flanges for bleed connections. Use hub flanges. Sketch
3.
Auto Air Vent location to be determined by direction of flow. See sketch below.
4.0 SKETCHES
4.1 SKETCH 1
SKETCH 1
4.2 SKETCH 2
SKETCH 2
4.3 SKETCH 3
SKETCH 3