Safety in the Plant Upstream isolation of
pressure relief valves Overpressure in manufacturing processes may be the result of a wide variety of causes, from runaway reactions and failed regulators, to operator mistakes and faulty equipment. Overpressure can have serious consequences, not just damaging equipment and systems, but also potentially leading to personal injury and even loss of life.
So, pressure relief valves are widely seen as the primary safety solution. However, sometimes an issue that can be overlooked is that these valves themselves are also in need of protection to maintain the intended level of safety.
Most often pressure relief valves are spring loaded and are set to open at a specified pressure. When pressure rises to an unacceptable level, they are pushed open and pressure is released. Once the pressure level has normalised, the spring forces the valve closed, and the process is resealed.
So, what do the pressure relief valves need protection from? The media itself. The valves are used in almost every industry so there is a wide variety of process media that they can be exposed to. Even where the media seems relatively benign, corrosion and wear & tear are always a risk since we are dealing with mechanical moving parts. The risks are obviously much higher with more corrosive, sticky or viscous media.
The three main issues which can affect PRVs are: A build-up of product media inside the pressure relief valves, corrosion and leakage.
Build-up A build-up of product media means there is a risk of blockage or reduction of the orifice. A complete blockage is not the only hazard. In many situations, the build-up of pressure is very rapid so the relief of pressure needs to be at a very high flow rate with a high volume and at high speed. In this scenario, even a small reduction of free-flowing through the orifice may mean the valve cannot relieve pressure effectively enough, leading to damage of the processing equipment.
Corrosion Corrosion affecting the PRV needs to be considered in relation to specific media, especially where non-standard materials of construction for the pressure relief valve may be required. The corrosion can either lead to the valve leaking at an increasing rate, or it can cause it to fail to lift when required, so it cannot relieve pressure as intended.
Leakage Where leakage is concerned, there are two separate issues. Firstly, a small amount of process media that leaks through can lead to an unexpected build-up of product on the downstream side, creating the same risks as addressed
WHO PROTECTS THE PROTECTION? WE DO.
To extend the life of your Pressure Relief Valves, use Fike® Rupture Discs. They create a barrier that isolates the valve from process media, preventing chemical corrosion and leakage. That means less maintenance, fewer fugitive emissions and a reduction in the cost of ownership.
Our industry-leading technical support, excellent customer service and global presence make Fike® the perfect choice to protect your business.
www.fike.com
ENQUIRY NO. 41 MARCH/APRIL 2018
www.reviewonline.uk.com 41
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