In this short guide, we will take a look at the ANSI ISA S84 standard.
What is ISA S84.01?
This is the Functional Safety standard published by ISA (International Systems and Automation Society)’s S 84 committee. This is applicable to functional safety in the process industries. The standard was initially published as ANSI/ISA S84.01:1996 and was recognized by OSHA as a “generally accepted good engineering practice” via their letter to ISA.
Some Historical background about ISA S84.01
Here’s some history about this standard, so that hopefully things become clearer. While the ISA S84 committee was working on this standard, at the same time, the International Electrotechnical Commission (IEC) was also developing a Functional Safety Standard IEC 61508, which was released in 1999. This was not specifically for the Process Industry sector, but for any industry that wanted to implement functional safety and Safety Instrumented Systems (SIS).
Incidentally, the IEC has 60 full member countries of which the US is a member. Other notable members include Canada, France, Germany, Japan, China, India, Australia, South Korea, UAE, Saudi Arabia, UK, Netherlands. There are further 87 affiliate countries, which are not yet full members, but on the path to becoming full members. Thus the IEC standards can be considered as global standards.
What is ISA 61511? ISA 84 vs IEC 61511
The IEC 61511 standards committee was formed to have a process industry specific standard based on IEC 61508. These efforts came to fruit sometime around 2003, when this was released as a standard. This became popular all over the world. This standard was then adopted by the ISA committee (with one modification) and published as ANSI/ISA S84.00.01-2004 (which was referred to as IEC 61511 Mod). After the second version of IEC 61511 was released in circa 2016 the ISA committee accepted IEC 61511-1 as ISA 61511-1 in 2017.
Finally ANSI approved the new standard and it is now known as ANSI/ISA 61511-1:2018
Where can I get the ISA 84 standard pdf?
The old ISA 84 standard is now obsolete and you should use IEC 61511, which you can get from the IEC website. On the ISA website, you can get some Technical Reports as guidance documents in implementing IEC 61511. Thus there are several useful TRs (Technical Reports) available such as :
1. ISA TR 84.00.02- SIL Vertification of Safety Instrumented Functions
2. ISA-TR84.00.03-2019, Automation Asset Integrity of Safety Instrumented Systems (SIS)
3. ISA-TR84.00.04-2020, Part 1, Guidelines for the Implementation of ANSI/ISA-61511-1-2018
4. ISA-TR84.00.04-2005 Part 2: Example Implementation of ANSI/ISA-84.00.01-2004 (IEC 61511 Mod)
5. ISA-TR84.00.05-2009, Guidance on the Identification of Safety Instrumented Functions (SIF) in Burner Management Systems (BMS)
6. ISA-TR84.00.08-2017, Guidance for Application of Wireless Sensor Technology to Non-SIS Independent Protection Layers
7. ISA-TR84.00.09-2017, Cybersecurity Related to the Functional Safety Lifecycle
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Where can I learn about Safety Instrumented Systems?
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ISA S84 versus IEC 61511
There are many questions as to whether one should use ISA S84 or IEC 61511? These questions are no longer valid as both are essentially the same now as ISA S84 has now evolved to be ISA 61511. However if you were earlier following the older version of ISA S84, you should now be migrating to the latest version.
Is ISA S84.01 mandatory in the US?
In the US, OSHA has regulatory powers of enforcement. OSHA Regulation 29 CFR 1910. 119, requires the identification and management of instrumented systems for safe operation. OSHA recognized ANSI/ISA S84.01:1996 as good engineering practice.
If you have an existing SIS, then you may make use of the “grandfathering” concept, which means if you have a SIS was built to earlier standards that were considered good engineering practice at that time and it still has sufficient safety integrity, then you may use it “as-is”, until the user determines that the equipment is no longer meeting the safety or integrity requirements. However, there are several things that you need to do, you cannot just give a simple declaration that the SIS is good enough. You need to prove that your Functional Safety Management system works, you need to gather data that supports your assertion and prove that the equipment remains “fit for use”.
For details on what data and procedures are to be followed please refer to ISA TR 84.00.04-2020 Part1.
For new installations, you should follow ISA 61511 (which is the same as IEC 61511).
What are general Safety Instrumented System requirements?
You can read about Safety Instrumented System requirements here in a short guide.
Disclaimer: Nothing that is stated above can be deemed to be safety, financial or legal advice. You need to carry out your own due diligence that applies to your own situation. The information given above is just a broad guideline that may help you understand functional safety standards.
