The SIL Approach to Saving Money

1. Introduction
Most companies in the process industry perform Process Hazard Analyses (PHA) upon their assets. In some jurisdictions, PHA is mandatory, but even where it is not, companies have started to realize economic benefits from performing PHA. The most common PHA process is the Hazards and Operability Study (HAZOP) and this is being increasingly combined with Safety Integrity Levels (SIL). SIL as defined in IEC 61508, may be easily performed from HAZOP results combined with a risk graph. It is possible to use a SIL optimization process to suggest ways of improving protection against hazards that could have large economic penalties in plant operation.

2. Safety Integrity Levels
The term Safety Integrity Level comes from the International Electrotechnical Commission’s standard IEC 61508 “Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems (E/E/PE)”. Although SILs were first formulated with these systems in mind, the basic principles behind SILs can be applied to any system. IEC 61508 was intended for use by the manufacturers of E/E/PE systems. A second standard IEC 61511 was intended for the users.

3. Some Common Problems and the SIL Approach

3.1. Premature PSV Opening
Situations can arise where a high level or high pressure in a storage tank, which may not be dangerous itself, will trigger a premature opening of a PSV and a subsequent loss. SIL analysis of HAZOP deviations that lead to high levels or high pressure have shown that automating of specific block valves will reduce the frequency of premature PSV opening to a more tolerable level, at a relatively modest cost.

3.2. Defining/Reducing Test Frequencies for ESDVs
Test frequencies for ESDVs, and other safety related equipment, are often mandated or are defined with only previous practice as a guide. This means that testing can be disruptive, expensive and it sometimes wears out the equipment, before it is ever needed in reality.

The methods used to validate SILs, in practice, provide an opportunity to obtain evidence that less frequent testing will suffice to maintain the required SIL. Often, the test frequency, or test interval, is the most dominant factor in the calculation of the probability of failure on demand (PFD). Therefore, it is relatively easy to change the test interval and determine what is the lowest test frequency that will still satisfy the required SIL. In this way, a case can be made for easement of mandatory test frequencies, or to change established practice.

4. Conclusions
Using the SIL approach to follow up the results of a HAZOP or other PHA can help to reduce losses and operating costs at a modest expenditure of effort and money.

Training Workshop on Safety Integrity Level (SIL) - IEC 61508/61511
The International Electro-technical Commission (IEC) has developed guidelines as per Standards IEC: 61508/61511 on Safety Integrity Level (SIL). The standards deal with the Integrity/functional Safety of Instrumented Systems and present a systematic approach to Life Cycle Safety and Safety Management. It means that Safety Instrumented Systems (SIS) like Emergency Shutdown Systems (ESD) complete with sensors and final elements need to be designed and maintained to guarantee a certain Safety Level of the operation. The SIL represents the probability of failure on demand.
The IEC 61508 standard will increasingly act as a Global Industrial best practice Standard for Safety Management with a special focus on Safety Instrumented Systems. Derived from it is sector specific Standard IEC 61511 for the process Industry. The Regulators (OSHA in the case of PSM) expect that facilities will follow the relevant good engineering practices (GEP) or have an equivalent process in place that achieves the same level of safety. The Standard will guide Regulators/Insurers to evaluate Safety in a company. The Standard will enable to demonstrate that the Method is followed as an internationally accepted best practice for safety. This will even be more important in the cases of accidents and liability claims.
KLG Environment & Safety Sciences Ltd, a subsidiary of KLG Systel Ltd is conducting a two days workshop on SIL classification and verification at New Delhi and Mumbai which is the first of its kind being conducted in India. The core faculty for the workshop will include speakers from TNO Safety Solutions Consultants BV (TNO SSC)The Netherlands at doorstep, who are pioneers in advising implementation of, and compliance with the IEC 61508/61511 Standards and have run similar workshops in several European and Asian countries. The workshop is exclusive of its type and is designed to have a detailed insight into the understanding and compliance with the IEC requirements in relation to the “Classification of Safety Integrity Levels (SIL) and Verification”.
SIL Study helps to fulfill this objective and offers a high reliable system towards overall plant safety. The concept of SIL is already well entrenched and adopted in USA, CANADA, EUROPEAN and other developed countries. Participation in this workshop would be extremely useful for all management, project and safety personnel with responsibilities for Safety Management and Safety Instrumented Systems.

We have planned to conduct two SIL Workshops along with faculty from TNO Safety Solutions Consultants BV, The Netherlands during Nov 2004 as follows:
 

The per participant fees is Rs. 45,000/- (Rupees Forty Five Thousand Only) inclusive of all taxes, lunches/ refreshment etc. The course material/ certificate will be provided to all the participants.
Companies/ Organization to forward the names & address of the participants and place for training along with cheque for participant fees in favour of “KLG ENVIRONMENT & SAFETY SCIENCES LTD”. In view of limited availability of seats registration will be done on first come first served basis for this program. Substitutes would be welcome in case nominee is unable to attend.

For further feedback if any, contact.

V B Sarin
vbsarin@klgsystel.com
Mobile: 9810487379

CV of Herman Jansen
CV of ChrisMPietersen