The Pressure Vacuum valve (PV valve) – a marine & offshore industry workhorse

The purpose of Pressure-Vacuum (PV) valves is to protect cargo tanks from excessive over/under pressure. Due to unavoidable pressure rise during loading  as well as temperature changes during transport, changes in internal tank pressure will occur.

A PV valve facilitates the flow of small quantity vapour during Breathing/transport as well as higher flow rates during loading, thereby allowing tank atmosphere pressure to stay within a preset level.
In case of over-pressure, the High velocity valve type opens directly to the surrounding atmosphere to ensure venting at high velocity vertically, while in the case of a pressure drop below atmospheric (under-pressure), the vacuum side of the valve will draw air into the tank.
The in-line P/V valve type will in the same way keep a pre-set and stable pressure range in the cargos tanks, but will vent to and from a Flame arrester placed in a mast riser.

Full range of PV valves

PV valves from Bay Valves cover the full range of equipment needed for handling the gas side of loading, storage and off-loading i.e. PV valves and high velocity valves for use on floating storage units like FPSO, FSO, oil and chemical tankers and their service vessels – shuttle tankers and PSV.

For different vessel types, and for different cargo classifications, the exact requirements for PV valves may differ. At Bay Valves, we are always ready to advice clients on the optimal PV valve solution for the individual case.
For some key customers, we have developed more specialized solutions which we are happy to present at any given opportunity. Please use the contact page to see what we have done for others, and discuss how we may assist you.

PV Valves custom-made to your specifications

While Bay Valves PV valve innovations meet general marine industry challenges, practically all of them have originated from a specific need brought to our attention by a costumer. We remain ready to co-develop custom-made solutions be it pressure-vacuum relief valves, breather valves or other types of P-V valves.

For instance, the characteristics of FPSO and FSO systems vary significantly from those of traditional oil tankers. Further, loading and un-loading rates are not always in the same range.

The major causes of variation in required venting rate are:

High gas evolution factor:

  • Loading commences in empty tanks.
  • Temperature difference between oil and inert gas.

Variation in loading rate:

  • Oil field production decreases over time.
  • Unloading to shuttle tankers at high rate compared to production rate.

PVRV Valves. Certified for FPSO vessels

Keeping your valves working safely and efficiently is as important as ensuring your FPSO vessel operates smoothly with no interruptions. Our straightmounted, flame arrester-integrated pressure-vacuum relief vent (PVRV) valves enable all of that. And more.

With its high capacity, low pressure drop, and in-situ maintenance, you can reduce downtime significantly compared to traditional pressure-vacuum (P/V) valve designs.

And they’re ATEX-certified to ensure the most effective flame passage prevention, strict regulatory compliance and complete vessel safety at every level.

Key PVRV valve solution features & benefits:
  • Adjustable negative pressure drop and flexible customerspecified closing pressure, with a maximum 0.5 kPa pressure drop over the valve.
  • Adjust settings without removing the valve from the system, reducing downtime, improving efficiency and promoting greater earnings.
  • Maintain valves by using a valve cradle for vacuum side removal, all whilst keeping the valves operational. Ensuring uninterrupted pressure side operation, minimal downtime and greater profitability.
  • Vacuum side near cargo oil tank (COT) to reduce pressure drop during unloading, especially for FPSOs with high cargo transfer rates.
  • Dedicated trolly-sized valve cradle for safe transportation to maintenance workshops.

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