15th March 2010
Written by: Dr Julian Hought
Published in: Storage Terminals Magazine
Would Your Process Plant Pass its MOT?
By Dr Julian Hought, Managing Director of leading process safety and risk experts, HFL Risk Services
Every twelve months, the motorists amongst us are required to put our vehicles through an
In order to keep our motors running smoothly, a service is also recommended, usually every six or twelve months, where tyres and brakes are checked, oil is changed, filters replaced and fluids topped up. This is not so that garages and car dealerships can squeeze some extra income out of us, but for the sake of our own safety.
You might wonder why I’m talking about motor vehicles in a publication about the storage and distribution of chemicals, but my point is this: If we treat our cars in this manner, then why aren’t we taking similar steps to ensure the safety of our chemical plants? If we don’t examine and service our cars regularly, sooner or later they will fail. The same is true for plant and equipment if you don’t have sound procedures in place for operation, maintenance and modification.
Effective Process Safety Management (PSM) systems should be the lynchpin of a company’s safety policy. Operators should be able to identify the critical layers of protection required to prevent an accident from occurring and/or mitigate the consequences to people and the environment if it does.
The plant itself should be designed to appropriate standards, competent operating personnel should be employed and good procedures followed. Maintenance personnel should be equally competent and instructed to follow strict procedures. The process hazards and associated risks should be understood by all.
Over time there has been a shift in emphasis by the Competent Authorities from examination of the physical layers of protection to overall systems management, but both are vital for operational peace of mind. One cannot work effectively without the other.
As far as the management systems are concerned, those responsible should be asking themselves whether their procedures are appropriate. Let’s take equipment as an example – do your inspection and maintenance procedures cover all of your equipment? As a bare minimum, do you know which pieces of equipment are critical to safety? This is vitally important. You simply cannot afford to run certain items of equipment to destruction, whereas others can run their natural course. Distinctions need to be made. If we take the car analogy again, we know that the safety of the vehicle will not be compromised if the CD player gives up the ghost, but it is an entirely different matter if a wheel falls off or the brakes fail.
Sadly there is no ‘
The closest thing we have to a process systems
It is fair to say that the HSE is also concerned with the inspection of pipes and non-pressure equipment. However, rather than inspecting the equipment themselves, they are intent on examining the way in which the equipment would be inspected – the theory of the inspection rather than the practicality of it.
Why is mechanical integrity so important? The answer is simple. Loss of containment due to lack of mechanical integrity can cost companies dearly - much more than the cost of routine inspection itself. BP’s Grangemouth petrochemicals plant found this to their cost following a major accident in June 2000. The organisation was fined nearly £1 million when a redundant 7cm branch to the main transfer line between two distillation columns failed during start-up in the fluidised catalyst cracking unit. 1.3 tonnes of highly flammable naphtha was released, which subsequently ignited and caused considerable damage to the plant. In addition, asbestos contamination occurred, due to damage to insulation in the vessel and the pipework. The branch failed because of progressive vibration fatigue, itself the result of inadequate support and a prolonged period of service that saw a greater number of start-ups than normal, putting increased pressure on the system.
Statistically speaking, the most likely route for hazardous substance release is via piping or pipework elements. Even if the substance contained does not pose a threat in itself the effect of its release on adjacent equipment and to a process could prove disastrous.
Regulations such as the Pressure Systems Safety Regulations (PSSR 2000) do go some way to guarding against major accidents, but they are principally concerned with the risk of release of stored energy through system failure whereas the chemical hazards on many high hazard sites present a much greater potential for harm.
There is concern that on a large number of installations, inspection of vessels and process equipment that falls outside of the scope of the pressure systems legislation is lacking and in some cases does not take place at all. As a consequence, if nothing is done, this lack of inspection will in all likelihood translate into a loss of containment incident.
Should a tank containing toxic material fail, it is likely to kill or injure people or cause significant damage to the environment. Companies often fall into the trap of assuming that they already have an effective inspection and maintenance programme in place. The reality is that, more often than not, they are doing sufficient to comply with specific legislation, but are falling short in other areas not covered by it. Knowing what, when, where and how plant should be inspected is the key to an effective integrity management programme, which should be:
- tailored to the process fluids and materials of construction in use;
- designed to ensure that all foreseeable risks/failure modes are identified, addressed and -where necessary - maintenance plans developed;
- sustainable in terms of resource and competency; and
- robust enough to reassure stakeholders that the asset remains safe to operate.
We are all aware that the 2005 Buncefield explosion was attributed to the overfilling of a tank. However, all the improvements concerning design and operation recommended by the Major Incident Investigation Board (MIIB) following its investigation rely on reducing the likelihood of the overfilling event by ensuring that the integrity of a number of layers of protection is maintained - the Swiss cheese approach. The more layers of holey Swiss cheese are present between the cause and effect, the less chance there is of the holes lining up and the event occurring.
I mentioned earlier the importance of identifying safety critical items of equipment and the fact that pipes and pipework are common sites for release, but almost every element of the containment system is susceptible to deterioration or damage. For example, storage tanks can suffer from either internal or external corrosion due to process and/or environmental conditions. This can cause the walls to become thin with an increased risk of failure. Similarly, functional safety devices, the very devices that are designed to protect against overfill, over-pressure, etc., are not immune to failure and can be affected by condensation, fouling and calibration inaccuracies, so they should also form part of an inspection regime.
It is not just plant degradation that can cause major accidents and a host of other concerns must be addressed, including human factors in design, operation and maintenance; and the need to maintain the design intent through effective management of change to ensure the risk profile is not unintentionally adversely affected. Those involved in management of risk, from senior managers to frontline operatives, must understand why particular tasks are undertaken and in which order, and how the smallest deviation can undermine safety.
The Process Safety Leadership Group (PSLG), comprising a number of industry bodies including the Tank Storage Association,
This is all sound thinking in terms of what the industry needs, but it is nothing new. For example, the CCPS has been active in this area for some time and has issued some excellent guidance on risk based process safety, covering:
- commitment to process safety;
- hazard identification and risk assessment;
- management of risk; and
- learning from experience.
Those involved in auditing PSM systems would do well to consider this guidance. PSM audits should be undertaken by a knowledgeable and skilled auditor and should consider each aspect in turn. As a minimum they should focus on maintaining the design intent, i.e. the approach to hazard identification and risk assessment; managing the integrity of plant and equipment; the methods of operation; the competence of the workforce; management of change; and emergency response.
In my experience, many company audits simply look at compliance against existing procedures and never question standing against recognised good practice in these areas. To continue operating plant in a safe and responsible manner, companies need to take a more holistic view of operations and constantly question what more can be done. In most cases this can be achieved through a marriage between good risk assessment and effective management systems geared around the key risks. But like every marriage, this relationship needs boundaries, constant attention and work to ensure a happy future, but when lives are at risk, it must surely be worth the effort.
