Choose the right safety valve
Safety valves ensure that overpressure does not occur in the system. VIMAB can help you choose and maintain your safety valves.
Safety first!
Keep an eye on the pressure
Safety valves are there to protect life and property. In the early days of industrialisation, it was not uncommon for boilers to explode, which led to the introduction of safety valves. The basic problem then is the same today - a pressurised system must be safe during operation.
The medium used in the process is not only pressurised, it can also be at high temperature and hazardous to health. It can, for example, be corrosive. The plant is designed to withstand a certain pressure that must not be exceeded. If a higher pressure occurs, it can be both dangerous and cause emissions that are harmful to the environment. High pressures can also damage the system and cause costly production stoppages.
The safety valve makes the plant safe by releasing part of the medium in case of overpressure. When the pressure returns to normal, the valve closes again.
The cause of overpressure can be a blocked outlet in the system, overheating leading to rapid expansion of vapour, uncontrolled thermal expansion of the medium, a chemical reaction in the medium, or a mechanical failure in the plant.
When are safety valves used?
The safety valve should normally never be used. It is a last lifeline to ensure that the plant does not break down.Therefore, it is important to periodically check that the safety valve is still working.
All industries with processes need safety valves. These include the oil industry, chemical manufacturing, pulp and paper, power plants, food and pharmaceuticals, to name just a few.A safety valve may also be referred to as a pressure relief valve, pressure relief valve or pressure safety valve.
How to choose the right safety valve?
Safety valves must be used to meet the legal requirements. In addition to meeting legal requirements, the valve chosen must of course also be suitable for the process requirements. In addition, the technical standards must be taken into account ? ISO if the process equipment is designed to European requirements or API/ANSI if they are American, as is often the case in the oil industry.
Choosing the right safety valve can be complicated. Please call us at VIMAB and tell us about your application, and we can help you choose the safety valve that best suits your process.
How to maintain safety valves?
Once the safety valve is installed, it must be ensured that it continues to function. In some applications, maintenance is needed more often than in others. This can happen, for example, if the medium is sticky, as can be the case with thick oil in oil refineries, or lye in paper mills.
It may also happen that a process changes. Since the plant was designed for a certain pressure, temperature and medium, the safety valve may no longer be suitable for the application. If there is a fault with the valve, or if it is incorrectly dimensioned, it may not open at the correct pressure. This can be dangerous.
Who is responsible for ensuring that the safety valve works?
It is the owner of the installation who is responsible for ensuring that the ongoing maintenance work is carried out. Ensuring the functionality of the safety valve is a collaboration between you as the plant owner; VIMAB as the service partner; and the inspection body, which must be accredited. VIMAB has extensive experience of working with accredited inspection bodies and can help to resolve any issues that arise.
The work carried out by VIMAB is inspected by the inspection body. The regulations can be found in AFS 2017:3 on pressurised installations. The safety valve can be exercised during operation to ensure that they still work. But this is associated with a certain risk and without training you can do more harm than good..Vimab has both the right knowledge and trained staff. VIMAB can also organise training for your staff.
Types of safety valves
High-lift safety valves are the most common type of safety valve. It provides a quick lift at a small increase in pressure. These are used for venting media that can be compressed, such as vapour and gas. They are designed to open as quickly as possible. The outlet is larger than the inlet, so that the medium has the opportunity to expand.
A proportional safety valve opens gradually as the pressure rises. It is used for hot water. Since liquid cannot be compressed, it does not need the same sensitivity as a gas system.
An additive-loaded safety valve provides faster and more controlled opening and closing. The additive consists of compressed air that controls a pneumatic actuator, which opens and closes from an external control cabinet. Because the valve is controlled very precisely, the operating pressure of the system can be close to the opening pressure of the valve.
The safety valve must be completely tight during normal operation. The material of the seal is selected taking into account the medium. There is a wide choice of polymer materials with different properties and resistance. If the medium is corrosive or very hot, such as steam, use a hard-sealing valve that seals metal to metal.