Showing posts with label Kunkle. Show all posts
Showing posts with label Kunkle. Show all posts

Wednesday, March 7, 2018

Combining Rupture Discs With Pressure Relief Valves

pressure safety valve
A safety valve protects closed systems from excessive pressure
Image courtesy Kunkle Valve Division - Pentair
Safety and pressure relief valves are common elements of any pressurized system. Their general purpose is to provide a positive means of preventing system pressure from exceeding a preset value, avoiding uncontrolled events that could result in damage to personnel, environment, or assets. Their operating principle and construction are comparatively simple and well understood.

Long term exposure of a relief valve to certain types of process media can result in corrosion, material buildup, or other conditions which may shorten the useful life of the valve, or worse, impair its proper operation. This excessive wear will increase the ongoing cost of maintaining or replacing a prematurely worn valve. One other aspect of relief valves can be the reduction in their seal integrity or force as the system pressure approaches the setpoint. This could possibly lead to fugitive emissions, an undesirable condition.

An effective approach to mitigating some of the effects of exposure to the process media is to install a rupture disc upstream of the safety valve inlet. Isolating a relief or safety valve from the process media through the installation of a rupture disc upstream of the valve inlet eliminates exposure of the costly valve to effects of the media. It is necessary to establish proper rating and selection for the rupture disc to avoid any impairment of the overall operation of the relief valve, but the selection criteria are not complex. A number of benefits can accrue with this concept.

  • Rupture disc isolates the valve from the media, allowing application of less costly valves fabricated of non-exotic materials.
  • Rupture discs are leak free and bubble tight, eliminating possibility of fugitive emissions from the safety relief valve, especially when system pressure may approach valve setpoint.
  • Relief valve inventory can be evaluated for reduction.
  • Longer valve life.
  • Less downtime.

The additional cost for the rupture disc enhancement can have a reasonable payback period, with all factors considered. In any case, the rupture disc protection makes for a cleaner relief valve installation. Rupture discs and holders are available in sizes and materials for most applications. Share your ideas with a valve specialist, combining your process knowledge with their product application expertise to develop an effective solution.

Tuesday, January 5, 2016

Pressure Relief Valves - Safety Sentry

Gas fired industrial steam boilers
Industrial processes involve hazards. Thoughtful engineering
and design minimize risk and mitigate damage.
Danger and hazards are an integral part of industrial processes. The mitigation of these dangers and hazards, as well as reducing the probability of their occurrence, is the primary charge of industrial process engineering. Every product intended for use in a process control setting has safety and protection included in its design criteria. Pressure relief valves fall in that category of products designed and intended solely for safety purposes.

Manufacturers of what most generally refer to as pressure relief valves break the genre down into two distinct groups, relief valves and safety valves. One manufacturer, Kunkle (a Pentair brand), distinguishes the two valve types in their "Safety and Relief Products Technical Reference"...
Relief Valve: A spring-loaded pressure relief valve actuated by the static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. A relief valve is used primarily with incompressible fluids (liquids).
Safety Valve: A spring-loaded pressure relief valve actuated by the static pressure upstream of the valve and characterized by rapid opening or pop action. A safety valve is normally used with compressible fluids.
The difference between the two valve types is found in their response to an excessive pressure condition. The relief valve, according to the definition, responds proportionally to the pressure increase, whereas the safety valve provides a non-proportional rapid response. Note also that the relief valve is generally intended for use with liquids (incompressible) and safety valves are commonly applied to compressible fluids, which would include steam and air.

Pressure relief valves are found anywhere pressure is contained, be it a piping system, vessel, even a
Pressure relief valve spring loaded
Spring loaded pressure
relief valve
Courtesy Kunkle
household pressure cooker. The purpose of the relief or safety valve is to protect a pressurized system or vessel, should the system pressure exceed the maximum allowable working pressure. Simply put, keep it from breaking apart.

Because of the potentially catastrophic nature of a pressurized system failure, there is a high level of scrutiny, regulation, and testing focused on pressure relief and safety valves. The proper sizing and selection of the valves is also critical to providing proper function.

I have included a technical reference bulletin from Kunkle with this article. Browse through it. You are bound to discover something you did not know about safety and relief valves and their proper application. You can also contact the specialists at Mountain States Engineering for assistance in proper valve sizing and selection.