Forward acting rupture disc

Forward acting describes the direction in which the process pressure loads the disc. The pressure acts on the concave side of the dome, the hollow side. That puts the metal in tension, much like the skin of an inflated balloon. When the tension exceeds what the membrane can carry, the disc tears open. This is the classic rupture disc design and still one of the most widely used. The opposite type is the reverse acting disc, where the pressure acts on the convex side. In our range, the STRIKO forward acting metal discs are designed for high pressure environments. We pair them with forward acting holders for accurate and reproducible performance.

High burst accuracy is one of the main strengths of this design. Because the disc fails in tension, its burst pressure depends on material strength, thickness and dome geometry. Those properties can be controlled closely during manufacturing. The tolerance, meaning the permitted variation around the set burst pressure, is determined by material properties and production. STRIKO keeps that tolerance under control with its philosophy of testing, evaluating and recalibrating. The holder plays its part too, because an uneven clamping load can shift the actual burst pressure. Our forward acting holders are built with tight tolerances and a consistent bolt load for that reason. Accuracy is therefore the result of disc and holder working together.

Yes, forward acting discs are suited for both gas and liquid applications. That is one of the qualities our forward acting holders are known for. A typical liquid case is a pipe section that can be blocked in between two valves. When that section heats up, the liquid expands and the pressure rises quickly. Liquid holds little stored energy, so the disc must open reliably without a large gas volume behind it. A disc that fails in tension handles that duty well. We still check the complete relief case, including temperature and possible back pressure. Send us the medium and the scenario and we will confirm the right combination.

The most common cause is fatigue from repeated pressure cycles. A forward acting disc is stretched with every pressure peak and relaxes again afterwards. When the operating pressure regularly approaches the burst pressure, that repeated stretching can weaken the material. Damage during handling or installation is another cause, since even small defects can affect the burst pressure. An uneven or incorrect bolt load in the holder can also shift the burst pressure. Vacuum or back pressure that pushes the dome the wrong way is a third possibility. If a disc keeps opening early, we look at the pressure trend, the installation and the holder together. Often a reverse acting disc or vacuum support solves the problem for good.

X and C shaped cuts in the dome give a controlled bursting action. They define the lines along which the disc opens. That produces a specific and predictable opening pattern. This is useful where the shape of the opening matters for the relief flow. It also helps where downstream equipment should not receive loose pieces of the disc. Domed discs with X or C cuts are part of the metal disc range we supply. Which pattern suits your position depends on the medium, the pressure and the layout of the discharge line. We select the pattern together with the disc material and the holder.

Only if the disc can see pressure from the wrong side. A forward acting dome is shaped to resist pressure on its concave side. Vacuum in the vessel or back pressure in the discharge line pushes the dome the other way. Without support, the disc can flip over or be damaged, and the burst pressure changes. Vacuum support holders prevent that and are essential in batch processes and cleaning cycles. Vacuum suitable discs and double discs are available for systems that face both overpressure and underpressure. Tell us whether vacuum can occur during emptying, cooling or cleaning. We then include the right support in the proposal.

Metal rupture discs can be clamped directly between flanges in systems with straight pipe sections. That is a simple and compact solution for suitable positions. For pulsating pressure, cyclic loading or where process integrity matters most, a holder is the better choice. A holder protects the disc during installation and applies a reproducible clamping load. It also makes it possible to integrate burst detection and leak detection ports. The holder is designed for long term reuse, so only the disc is replaced after an opening. We advise per position which route fits best. In many critical services the holder is what makes the burst pressure truly reproducible.

Consider switching when the process cycles heavily or runs close to the burst pressure. Those are the conditions in which tension loading leads to fatigue. High process temperatures are another reason to look at reverse acting. Reverse buckling designs offer higher resistance to pressure cycles and better performance at high temperatures. They also allow a higher ratio between operating pressure and burst pressure. If your pressure trend is steady and well below the set point, forward acting usually remains the logical choice. A disc that repeatedly opens too early is a clear signal to review the choice. We are glad to compare both options against your process data.