Posts Tagged ‘safety’

Why it pays to pay more for safety (Part 2)

February 19, 2014

In our last blog, we looked at the real costs that can arise where safety takes a back seat and explained some of the factors behind the higher costs of specialised instrumentation and control equipment for safety applications.

In this blog, we’ll be looking at the parameters that define the overall effectiveness of a safety loop and will show why opting for higher integrity equipment can save money in the long term.

Let’s start by looking at the required Safety Integrity Level (SIL), as defined by IEC 61508. IEC 61508 is the “mother” standard that spawned corresponding “daughter” standards for the process industries (IEC 61511), nuclear facilities (IEC 61513) and machinery (IEC 62061). It is not a legal requirement for British businesses, but HSE accepts it as good practice.

Confusion can often arise when it comes to designing a safety system as it’s not as simple as just applying a blanket SIL to cover an entire process. Instead, operators must first consider the individual safety instrumented functions (SIF) within a process, these being the functions of a given device that are necessary to protect against a hazardous event. This can then be used as the basis for designing and engineering the safety system solution, consisting of the inputs, the logic solver and the final elements, including instrumentation.

As a general rule, it is almost always better to design risk out of a process before installing specialised systems to control it. This will often reduce the required SIL and therefore the cost of the safety systems needed to deliver it.

Next is the average probability of failure on demand (PFD). The acceptable PFD of a system varies depending on the required SIL as well as the required mode of operation of the safety instrumented function, which is the frequency with which a safety instrumented system will be used. For a safety function operating in a low demand mode of operation, the PFD ranges from ≥10-2 to ≥10-1 for SIL1 to ≥10-5 to ≥10-4 for SIL4.

The overall PFD is calculated by combining the PFDs of all the individual components in the loop. For example, a transmitter designed for safety will typically offer a lower PFD than a standard transmitter, bringing down the overall PFD of the system and potentially raising the SIL.

Other factors that determine whether an individual instrument is suitable for a particular SIL are the safe failure fraction (SFF) and the hardware fault tolerance (HFT).

The SFF is a function of the number of safe failures, the number of dangerous undetected failures and the number of otherwise dangerous failures that can be rendered safe by being detected, for example, by installing self-diagnostic capabilities.

The HFT indicates the number of faults that need to crop up within a device before a safety failure occurs. For instance, the failure of a standard transmitter might result in the output from a transmitter freezing on its last setting, but a transmitter designed for safety might revert to a prearranged fault setting, which could in turn trigger an alarm. Built-in redundancy can also raise the HFT from 0 to 1.

The integrity level provided by a given combination of SFF and HFT varies depending on whether the overall safety system is a well-proven Type A or less well-understood Type B, according to the IEC 61508 standard. The other key factor to be considered is the systematic capability. This relates to factors such as the methodology, techniques, measures and procedures used in the design and engineering of the element itself and the integration of elements to form the safety system.

The other thing to look out for is the quality of documentation available from the equipment supplier. Are their instruments certified by independent testing bodies? Have they got a sufficiently strong track record for the user to be confident that the equipment is “proven in use”?

Savings soon add up

Independent tests and extra paperwork may not sound like a cheap option, but there are several ways in which opting for higher integrity equipment can save money in the long term.

The first is that the safety systems do not need testing as often to check that they are still working properly. The required proof test interval can be extended significantly if equipment can demonstrate a higher HTF and a lower frequency of dangerous undetected failures. This will deliver lower operating costs for any user, but the difference is likely to be especially significant in industries such as offshore or nuclear, where gaining access to the systems can be difficult and expensive. It might, for example, mean the difference between sending inspectors out to an oilrig by helicopter every three months or once a year.

The second area where savings can be made is in insurance. In fact, some insurers now insist on complying with particular safety integrity levels before they will agree to provide cover.

However, it is the prevention of accidents that still offers the biggest potential financial savings, not just in terms of financial penalties, but also the impact that an accident or incident can have on a company’s share price and reputation. Add to this the imperative to protect personnel and be a good neighbour to the surrounding community and the case for excellence in safety systems is compelling – whatever the state of the economy.

Why it pays to pay more for safety (Part 1)

February 10, 2014

Quite apart from any moral considerations, skimping on safety can be an expensive mistake. The right safety instrumentation can deliver long-term security and a lower life-time cost.

If the Buncefield and Deepwater Horizon disasters prove anything, it’s that safety can never be taken for granted. Aside from the devastation they caused to their surrounding environments, both disasters also resulted in multi-million dollar damages for the operators involved.

While most industrial safety breaches have less spectacular and expensive consequences, they are sadly all too common. The Health and Safety Executive prosecuted 973 offences in 2013 and achieved 849 convictions. The firms in question collectively received fines of £12.9 million, equating to an average fine of £15,153.

When it comes to safety, fines are just one aspect of the costs of getting it wrong. Material damage, personal injury claims and the damage to a company’s reputation and subsequent sales can all send the price of poor safety sky high.

With companies facing considerable pressure to cut costs in every possible area, even areas as critical as safety find themselves subject to tightening budgets. Moreover, as the standards currently accepted as good practice are not actually legal requirements, there is an obvious temptation to skimp on safety systems. As can be seen from the potential consequences of failure mentioned above though, this is unlikely to prove a cost-effective strategy in the long run.

Higher standards

When it comes to specialised instrumentation and control equipment for safety applications, it’s true to say that you get what you pay for.

Compared to a normal process control loop that is operating most of the time, a safety system will typically kick in only when there is a problem. This sporadic operation means it’s quite possible for a transmitter or other component within the safety loop to malfunction without being detected. However, if it fails when needed then the consequences can be dire.

Making sure a safety system doesn’t fail demands good quality equipment that has been extensively tested and analysed. It may also mean building in a level of redundancy and a self-diagnostic capability far outstripping that required for non-critical systems. All this pushes up the price.

The second point is that safety is a niche application. A refinery might easily have 900 control loops distributed around the site but fewer than 100 safety loops. This more specialised market for safety equipment simply doesn’t benefit from the same economies of scale as the mass-market in standard controls.

Lifetime savings

Rather than looking for the cheapest option, it’s important to look for instruments and systems offering the optimum combination of security and cost-effectiveness over their lifetime. It’s a complex area, and users hoping to find the best solution can benefit from getting to grips with some of the terminology surrounding safety.

In our next blog, we’ll explain the parameters that define the overall effectiveness of a safety loop and will show why opting for higher integrity equipment can save money in the long term. Look out for it this time next week. If you can’t wait that long, then please email moreinstrumentation@gb.abb.com for the full article, ref. ‘The price of safety’.

ABB level transmitter helps Robinson Bros keep the lid on explosive chemical

August 7, 2013

Thanks to our AT100 magnetostrictive level transmitter, Midlands-based manufacturer of speciality chemicals, Robinson Brothers, are now able to meet strict safety standards regarding the storage of highly reactive carbon disulphide (CS2).

CS2 is so reactive that it has to be stored under a layer of water to prevent it from igniting, and the level of the interface between the water and CS2 requires constant monitoring. Therefore it is essential that any associated measurement devices is safety-critical.

Level measurement was previously achieved using a very simple magnetic float-based device that provided a local indication of the level but didn’t link in to any wider control system. However, an ongoing programme of improvements at the plant called for updated state-of-the-art innovative solution fully enabled for the latest communications.

This [float] principle of measurement had given many years of faultless service in what is a demanding application. In simple terms, magnetostrictive systems can be thought of as a “float on a stick”. The “stick” is actually a sensing tube wrapped around a wire that receives regular electrical pulses. Each current pulse interacts with the magnetic field created by the magnetic float to produce a torsional stress wave in the wire. This stress wave travels at a fixed speed along the wire to a patented piezo-magnetic sensing element in the transmitter assembly. The transmitter measures how long it takes for the wave to reach the sensor, which indicates how far away the float sits as it moves up and down the sensing tube in step with the liquid interface.

As CS2 is so volatile and prone to ignition, it’s one of the few chemicals that requires instrumentation to be certified to the most extreme, ATEX Exd IIC T6, protection standard. It can also be used in safety instrumented systems to meet the tough SIL1 performance ratings.

Thanks to official ABB WirelessHart distributor, instrumentation specialist ICA Services’ partnership with ourselves, ICA was able to recommend our AT100 magnetostrictive level transmitter, which meets both these criteria, providing process signals which output to both our local and site monitoring systems and meeting our own internal requirement of SIL1-capable instrumentation. As such, Robinson Brothers has purchased four additional AT100 transmitters for use on its other CS2 process systems.

AT100 transmitters provide continuous level indication, and transmission of an analog and/or digital signal for monitoring or control. The unique design boosts the resolution of the device to more than 100 times greater than a conventional reed switch-type device.

For more information, email moreinstrumentation@gb.abb.com ref. ‘magnetostrictive level’ or visit www.abb.co.uk/measurement. Alternatively, for more about ICA Services and Robinsons Brothers, please visit www.icaservices.co.uk or www.robinsonbrothers.co.uk.

ABB confirms its position as number one supplier promoting functional safety in oil and gas industry

May 15, 2013

With the final Safety Execution Centres (SECs) in our global network set to be TÜV-certified within the next 18 months, we are proud to confirm our position as the number one supplier promoting functional safety in the oil and gas industry. To date, some eleven SECs out of our 20-strong global network are already certified.

Working closely with colleagues within the company’s Product and Consulting businesses, the SECs play a key role in helping ABB deliver total safety-assurance for customers operating high-risk process installations. The Centres design and engineer Safety Instrumented Systems (SIS) to support effective functional safety throughout the entire lifecycle of process and functional safety solutions.

Recent incidents are focusing companies’ attention towards adoption and compliance to safety related industry good practice standards with increased project spend to achieve the correct level of functional safety to these standards to ensure sustainable operations. ABB’s experience and tried and tested systems and procedures help to ensure that companies achieve complete functional safety with a high level of pragmatism without paying more than they need.

Many operators and contractors within the oil and gas industry do not have access to specialist functional safety resources in-house. ABB’s support can ensure that safety is designed into projects properly from the start, avoiding the potentially catastrophic consequences of underspecifying safety systems, as well as the added costs of overspending on unnecessary equipment.

All the Centres work to deliver SIS that comply with the latest industry standards (IEC 61511 and IEC 61508, edition 2). The SECs in India, Argentina, Denmark, Germany, two in Italy, Singapore, the United Kingdom, Mexico, Brazil and two in China are already certified by TÜV as the independent accreditation body in line with the standards, while Canada, Colombia, US, Korea, Taiwan, Thailand, Australia, Hungary, Czech Republic, Ukraine and Slovakia are currently in the process of achieving certification.

The SECs design, engineer, integrate and configure SIS using ABB third-party certified elements and subsystems from the various Product Groups, to IEC 61511/IEC 61508. They offer the full range of systems, up to and including SIL 3 for the most hazardous duties.

They also provide consultancy on functional and process safety, working with the Consulting Group, Control Technologies and Consult IT businesses within ABB. Competency is a key issue within functional safety, and the SECs complete their all-round support for clients by working with the ABB University to provide training.

Key engineering personnel at all 20 SECs have achieved either TÜV Rheinland Functional Safety Engineer or Exida Certified Safety Engineer and ABB has access to a number of “Expert” status consultants under the same competency schemes.

For more information about ABB’s range of functional safety services, email oilandgas@gb.abb.com or call 01480 475321 ref. ‘Functional Safety’.