Rupture Disk Valve

Rupture disc, also known as bursting disc/pressure safety disc/burst disc is a pressure relieving device used in Chemical, Pharmaceutical, Aerospace, Aviation, Defence, Railroad, Nuclear, Food Processing, Petrochemical industries. The main purpose of the disc is to release excess pressure and prevent any structural/functional damage to the instruments/machines.

Functionality:

A Rupture disc is fitted inside the pressure pipes/instruments & is designed to rupture/burst/tear at a pre-defined pressure. It can be calibrated for a pre-determined pressure (positive) or vacuum conditions.
When the disc is designed for vacuum conditions, the atmospheric pressure would push this disc into the system. Hence, a support device is used to prevent the atmospheric pressure from pushing the disc into the system. Thus, when the pressure rises, the disc ruptures and releases excess pressure thereby protecting the system from damage.

Uses:

1. As the name suggests, the rupture disc ruptures and thereby prevents a catastrophic damage that would otherwise be done to the structures/machines

2. The disc forms the weakest side of the system and prevents the other parts of the system from suffering pressure damage

3. A key feature of the rupture disc is that it is placed well away from the heavily traversed area of the factory. Thus, harmful chemicals/fumes are released away from the workers and can also be connected to discharge pipes which safely guide the exhaust fumes/fluids

4. Minimum maintenance costs

Limitations:

One of the biggest limitations of a rupture disc is that once burst, the entire system has to be shut down to replace the disc. The downtime on shutting down the entire system and then rebooting it can cost some heavy losses in price sensitive & highly competitive markets.
To overcome this disadvantage, designers were sent back to the drawing board for designing an improvised version of the rupture disc.

Relief Valve:

A relief valve serves the same purpose as the rupture disc but has the added advantage of not shutting down the system. The inlet is threaded and connected to the system. The outlet is threaded and connected to the exhausts. The system is embedded with a spring which controls the release of pressure.

The Rupture Disc was implemented by PANORAMA ENGINEERS at VERTEX PHARMACEUTICALS.

Process Safety Management

OSHA’s Process Safety Management

Unexpected releases of toxic, reactive, or flammable liquids and gases in processes involving highly hazardous chemicals have been reported for many years, in various industries using chemicals with such properties. Regardless of the industry that uses these highly hazardous chemicals, there is a potential for an accidental release any time they are not properly controlled, creating the possibility of disaster.

To help ensure safe and healthful workplaces, OSHA has issued the Process Safety Management of Highly Hazardous Chemicals standard, which contains requirements for the management of hazards associated with processes using highly hazardous chemicals.

Process safety management (PSM) is addressed in specific standards for the general and construction industries. OSHA’s standard emphasizes the management of hazards associated with highly hazardous chemicals and establishes a comprehensive management program that integrates technologies, procedures, and management practices.

OSHA has been busy when it comes to monitoring facilities with highly hazardous chemicals (HHCs). Since 2010, OSHA has issued more than 69 enforcement cases regarding Process Safety Management (PSM). The problem is, many organizations don’t understand OSHA’s PSM standard or realize if it even applies to them.

Why Did OSHA Develop PSM?

In 1991, to help ensure safe and healthy workplaces, OSHA issued the Process Safety Management of Highly Hazardous Chemicals standard (29 CFR 1910.119). This rule contains requirements of the management of hazards associated with processes using HHCs. Additionally, in January 2017, OSHA issued a new National Emphasis Program to further protect workers’ health and safety in certain industries that pose high risks to people and the environment.

To help minimize toxic occurrences, PSM was created. PSM aims to prevent the release of toxic, reactic, flammable, and explosive chemicals into the environment.

What Facilities are covered?

OSHA states that the PSM standard applies to “a process that involves a chemical at or above the specified threshold quantities (TQs) listed in Appendix A of the standard. The Appendix contains a list of toxic and reactive HHCs, which present a potential for a catastrophic event at or above the TQ. When evaluating chemicals on the list, it’s important to look at the TQ as well as checking and verifying the chemical abstract service number (CAS). This involves the entire chemical inventory, making an appropriate chemical inventory process crutial.

One important interpretation to note is that OSHA uses the phrase “on site in one location” in the standard to mean that the standard applies when a TQ of a HHC exists within an area under the control of an employer or group of affiliated employers. It also applies to any group of vessels that are interconnected or in separate vessels that are close enough in proximity that the HHC could be involved in during a potential catastrophic release.

Types of Industries Included

Any industry that processes chemicals could be included in OSHA’s PSM standard. Some examples of these industries include:

• Industrial organics and inorganics

• Paints

• Pharmaceuticals

• Adhesives

• Sealants and fibers

• Petrochemical facilities

• Paper mills

• Food processing with anhydrous ammonia over the TQ

Exclusions

A company is exempt from the requirements of PSM when:

• A TQ of flammable liquids is stored in atmospheric tanks or transferred without the benefit of chilling or refrigeration.

• Hydrocarbon fuels are used solely for workplace consumption as a fuel (e.g. propane used for comfort heating or gasoline for vehicle refueling).

• Fuels are not a part of a process containing another HHC covered by this standard.

Considering the severity of the consequences that HHCs pose to the environment and the past disasters that have occurred, we only see PSM continuing to become a stronger and stronger regulation.