Showing posts with label rupture disc. Show all posts
Showing posts with label rupture disc. Show all posts

Wednesday, October 31, 2018

Overpressure Protection Devices

Fluid pressure exerts force on any surface area it contacts, as described by the formula F = PA. One practical consequence of this fact is that process vessels and pipelines may catastrophically burst if subjected to excessive fluid pressure. If subjected to excessive vacuum, some vessels and piping may implode (collapse in on themselves). Not only do these potential failures pose operational problems, but they may also pose severe safety and environmental hazards, especially if the process fluid in question is toxic, flammable, or both.

Special safety devices exist to help prevent such unfortunately events from occurring, among them being rupture disks, relief valves, and safety valves. The following subsections describe each of these protective devices and their intended operation. In a P&ID, rupture disks and relief valves are represented by the following symbols:
Overpressure Protection Devices

A rupture disk acts like an electrical fuse for overpressure protection: when the burst pressure is exceeded, the disk ruptures to let fluids escape through it. Safety and relief valves work like self-resetting circuit breakers: they open to relieve pressure, then re-close to seal the process system once more.

Two common causes of process overpressure are piping blockages and overheating caused by fires. Although it may sound ridiculous, a number of fatal industrial accidents have been caused by something as simple as shut block valves that should have been left open. When fluid cannot escape a process vessel, the pumping forces may exceed the burst rating of the vessel, causing catastrophic failure. Fires may also cause overpressure conditions, owing to the expansion of process fluids inside sealed vessels. Overpressure protection devices play a crucial role in such scenarios, venting process fluid so as to avoid bursting the vessel. It should be mentioned that these two causes of overpressure may have vastly differing protection requirements: the required flow rate of exiting fluid to safely limit pressure may be far greater in a “fire case” than it is for a “blockage case,” which means overpressure protection devices sized for the latter may be insufficient to protect against the former.

Overpressure protection device selection is a task restricted to the domain of process safety engineers. Instrument technicians may be involved in the installation and maintenance of overpressure protection devices, but only a qualified and licensed engineer should decide which specific device(s) to use for a particular process system.

For more information on overpressure protection devices, contact Flow-Tech by visiting https://flowtechonline.com or by calling 410-666-3200 in MD or 804-752-3450 in VA.


Reprinted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.

Tuesday, January 31, 2017

Safety and Performance Through Proper Installation and Maintenance of Rupture Discs

rupture discs
Increase safety with proper installation
and maintenance of rupture discs.
Rupture discs are fixed setpoint devices designed to provide failsafe performance in venting gases or liquids in the case of excessive pressure. The precision made and certified disc is contained within a holder specially designed for the disc and to facilitate proper inspection and maintenance.

An integral part of the inclusion of a safety device in a process system is the manner in which it is installed. Documented product performance, upon which the user is depending, is predicated upon installation in a manner which duplicates the rating condition. Varying from the manufacturer's installation procedure or instructions can have an impact on the performance of almost any process measurement and control product, but adherence to procedure is especially important when safety devices are concerned. The video below demonstrates the proper procedure for installing Fike rupture discs.

Fike provides certified rupture discs to meet all applications for process industries including isolating pressure relief valves from corrosive materials, reducing involuntary emissions, insuring pressure relief in critical applications, rupture discs for sanitary/pharmaceutical processes.

Share your over-pressure safety requirements with a product specialist and select from the complete line of cost-effective rupture discs, holders and custom pressure relief devices which are compliant with global code regulations and designed to meet or exceed industry requirements for performance, reliability and quality.

Wednesday, August 31, 2016

Rupture Disc Sizing Technical Bulletin

rupture disc
Rupture disc (Fike)
The objective of this bulletin is to provide detailed guidance for sizing rupture discs using standard methodologies found in ASME Section VIII Div. 1, API RP520, and Crane TP-410. To assist in the sizing process, contact Flow-Tech at 410-666-3200 for help.

Overpressure Allowance

When sizing pressure relief devices, the Code defines the maximum pressure that may build up in the pressure vessel while the device is relieving. This pressure varies depending on the application of the device. The following table defines the various overpressure allowances.

Rupture Disc Sizing Methodologies

There are 3 basic methodologies for sizing rupture disc devices:
  • Coefficient of Discharge Method (KD) — The KD is the coefficient of discharge that is applied to the theoretical flow rate to arrive at a rated flow rate for simple systems.
  • Resistance to Flow Method (KR) — The KR represents the velocity head loss due to the rupture disc device. This head loss is included in the overall system loss calculations to determine the size of the relief system.
  • Combination Capacity Method — When a rupture disc device is installed in combination with a pressure relief valve, the valve capacity is derated by a default value of 0.9 or a tested value for the disc/valve combination. See technical bulletin TB8101 for specific application requirements when using rupture disc devices in combination with PRVs.

Sunday, January 31, 2016

Explosion Detection and Suppression Systems

explosion detection system
Explosion detection system (by Fike)
A typical explosion detection sequence begins when a spark or other ignition source ignites particulate in a vessel. The resulting deflagration grows at an exponential pace as the material burns. The pressure front preceding the deflagration expands, reaching the pressure detector connected to the explosion protection control panel, which processes 4,000 data points per second. The system alarms at a preset pressure level, and activates the gas cartridge actuators on the suppression and isolation devices. The system maintains a history event for future reference.

The gas cartridge actuator drives the piston on the isolation valve, closing the slide gate and provides mechanical isolation which prevents the propagation of the explosion through the duct work to interconnected vessels. The actuator opens a rupture disk on the suppressor bottle, that uses nitrogen pressurized to 900 PSI to drive suppressant into the vessel, filling the entire cavity and extinguishing the advancing deflagration.

It is also necessary to isolate the deflagration, preventing the transmission of the flame into interconnected vessels. The system simultaneously opens a rupture disk on an isolation container that uses 500 PSI of nitrogen to drive suppressant into the ductwork, providing a chemical isolation barrier that prevents the propagation of the explosion. Fike’s explosion protection system effectively saves lives and property from explosion damage.