Pressure and/or vacuum relief valves are used on liquid storage tanks and other process vessels or systems to prevent structural damage due to excess internal pressure or vacuum.

Storage tanks are pressurized when liquid is pumped in and compresses the existing vapour or when increasing temperature causes increased evaporation or expansion of existing vapour. Conversely, a vacuum may be created when pumping out or decreasing temperature. To prevent damage, vapour must be allowed to escape or enter the tank at a specified pressure or vacuum. The volume rate of venting depends upon the tank size, volatility of the contents, the pumping rate, and the temperature. See API Standard 2000 for the procedures to determine venting requirements.

Pilot Operated Relief Valves serve the same primary purpose as pressure/vacuum relief valves, but with better performance characteristics than weight or spring-loaded valves. Lower leakage and better flow performance make a pilot operated valve the solution when the focus is product conservation, expanded tank working band, and reduced fugitive emissions. A pilot operated relief valve provides the maximum available leakage control technology as specified in the Clean Air Act of 1990.

The pilot-operated relief valve has two principal advantages over standard types of relief valves:

  1.  it is bubble-tight to set pressure, and
  2.  it is fully open at less than 10% above the set pressure.

These characteristics permit an operating pressure nearer to the maximum allowable working pressure of the tank. High operating pressures reduce evaporation and total venting volume, thereby reducing product loss and cost of processing emissions.

 Relief Valves – Pilot Operated

Related pressure and vacuum safety-relief products

Seminar

If you or your team want to know more about Tank Venting or get up to speed with the latest changes to API2000 we will be happy to run a technical seminar or lunch and learn session for you. We make no charge for the sessions for end users or groups of 5 or more people.

Some of our customers testimonials


Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech- pilot operated pressure relief valves service and calibration

After conducting a Third Party Witness Inspection, I was most impressed with Ewart and his team, their professionalism, and product knowledge I found to be excellent.

Ian Johnston

Director, RAK Inspection


Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech- Geodesic Dome Installation

Assentech were subcontracted to assemble and install a 25m geodesic dome for Shaft G on the Lee Tunnel project. My experience with Assentech from pre-contract through to assembly has been very positive. Unlike other subcontractors I have experienced on this project, Assentech had a very positive attitude to producing the level of documentation required for a project of this scale. Leading to a high quality pre construction packaged approved in a timely manner. The communication regarding the manufacturing process was first class allowing us to easily plan our works and prepare the site. Dome assembly was carried out very efficiently and completed to programme. The task was correctly resourced and well supervised. The work force had a positive attitude and carried out the task safely. In summary from my perspective it has been a very easy subcontract to manage with a high quality finished product.

Robert Colthorpe

Site Agent – Lee Tunnel Project, Morgan Sindall


Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech wins supplier excellence award from Eastman Chemicals

We were extremely pleased with the level of service and professionalism demonstrated by Assentech, right from our initial enquiry, through delivery and post installation. As a recipient of only two of these awards made by Eastman Chemical Company in the UK, based on performance in 2014, Assentech are rightly proud of their achievements.

Robert Dodgson

TH3 Project Procurement Lead, Eastman Chemical Company


Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech-IFR Installations at Vopak, Teesside

As you said “you delivered what it said on the tin”. On time and on budget.  Your up front engineering to determine the suitability of your product for our application was second to none, i have not seen anyone else in the industry pay as much attention to detail before you get the purchase order number as Assentech.

Garry Lee

Project Manager, Navigator (formerly Vopak Limited)


Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech-IFR Installations at Navigator Terminals

Assentech have supported our Navigator Terminal (formerly known as Vopak Teesside) on two important projects by providing technical assistance and supplying and fitting a total of 11 Internal floating roofs. Both projects have been completed on schedule and on budget. Assentech have provided an excellent level of experience and front end engineering support with high quality drawings and documentation. Their specialist on site labour have worked collaboratively with us and Assentech have proven to be open, honest and flexible partners.
We have experience of both their Heavy Duty Pontoon type and Full Contact IFR’s and we continually monitor operation and performance of all lFR units Installed on site and consider the Assentech supplied Matrix brandto be the best in the market with exceptional build quality and rigidity. Our clients have inspected the installations and have always remarked upon the build quality and have been impressed with their strength in fully supporting up to four people without noticeable deformation. The design and construction of their stainless steel shoe seals continue to prove to operate excellently with no noticeable reduction in performance or flotation ability over the time since Installation.
Assentsch have proven to be extremely competitive on price and their installation and inspection activities have always been thorough. Navigator therefore have no hesitation in recommending Assentech to other companies considering their services.

Brian Beddow

Project Manager, Navigator Terminals Seal Sands