ALARP systems

This system has proven to provide adequate levels of safety in the Gulf of Mexico and other similar areas where it is possible to abandon the location during a catastrophic event. In the North Sea where harsh environmental conditions exist, a different approach to safety has evolved which is based on developing a Safety Case and calculating an Individual Risk Rate (IRR) to show that the risk to any individual working in the facility is As Low As Reasonably Practicable (ALARP). 

For each substance that has a WEL, HSE will produce practical advice that will tell employers what they have to do to control for their use of the chemical. For chemicals that can cause cancer HSE s advice will explain what ALARP means in practice. Thus employers will not simply be left with a number, as in the present OEL system but will have information on what they have to do to comply with the law . 

The safety case concept requires that operators demonstrate that the systems and processes they have adopted ensure that their facility is sufficiently safe for all those people who are possibly impacted by their activities (workers and contractors at their facility, passengers and customers, people who live and work in surrounding areas). Most safety case regulations require the demonstration to take the general form of showing that risk is as low as reasonably practicable, or ALARP (or that risk has been reduced so far as practicable - SFAP). Clearly, safety cases are an example of the broad trend towards risk-based regulation (Hood et al. 2004). 

ALARP The system is safe as all risks are reduced ALARP... 

As we proceeded with our studies, we found that developing a distinct, perhaps statistical, universally applicable definition of acceptable risk that did not contain general and judgmentally interpretive terms is not possible. But, with a studied understanding of risk, and risk taking, and the concept of As Low as Reasonably Practicable (ALARP), I dare to offer a practical definition of acceptable risk that can be effectively applied when dealing with workplace hazards, risks, and deficiencies in safety and health management systems. 

The concept of ALARP helps with respect to the economic considerations necessary in risk decision making. A good and easily understood definition of ALARP may be found in the draft of MIL-STD-882E, the Department of Defense Standard Practice for System Safety ... 

Boidton D (2010) GALE or ALARP which to choose Safety Systems 20 1 1-3. Safety-Critical Systems Club... 

Management has to decide if the calculated level of risk is acceptable, and, if it is not, what actions need to be taken to reduce it. Some Safety Management Systems—in particular many Safety Cases—are built around the concept of a numerical value for an ALARP (As Low as Reasonably Practicable) value, as already discussed. If the risk lies above or below the predetermined ALARP value then corrective actions must be taken. 

ALARP concept basically comes from the British health and safety system (Act 1974)- It is not in true sense a quantitative method, although cost—benefit analysis is often used to get ALARP. It is a challenging subjective method, as it requires duty holders and others to exercise their judgment very carefully. In risk analysis, three factors play important role, viz. trouble, time, and cost. The breakeven point in... 

Fig. V/4.0.1-1B shows how one after another, IPL reduces the chances of risk and the system is brought back to ALARP region. A typical actual process example has been presented in Clause 1.1.2 (Fig. Vll/1.1-3) of Chapter Vll.

There is no system with zero risk. Safety functions are concerned with risk reduction. Developers need to assess EUC risk, tolerable risk, and residual risk. Residual risk shall be brought down to ALARP. 

The ALARP region lies between acceptable and intolerable, in which the system developer is required to reduce the risk to be as low as reasonably practicable (ALARP). lEC 61508 directs towards ALARP. Eor the concept of ALARP, refer to Chapter I. 

Overall safety instrumentation system (SIS) implementation. ALARP, as low as reasonably practicable IPL, independent protection layer. 

IPLs comprising SIS and non-SIS systems reduce the unacceptable risk levels to acceptable risk levels, which should be equal to or below the ALARP level. 

With initial assessment, all risks are listed and suitable IPLs are deployed. After this the entire system is reassessed. Because we are interested in SIS, in the final assessment only SIS is shown. After each assessment the IPLs and SIS are validated. After final assessment of overall safety requirements it is ensured that the risk level is at an acceptable level, as shown in the figure. This shall be a level equal to or below the ALARP level. In principle, what has been discussed here is more or less the same as discussed earlier, the only difference is that here the basic implementation process is shown. Similarly, SIS in the design phase is shown in Fig. XII/1.0-3. The reason for showing the figure is to recapitulate further details about SIS design. 

Design steps for a safe system. ALARP, as low as reasonably practicable BPCS, basic plant control system DCS, distributed control system IPL, independent protection layer PLC, programmable logic controller SIS, safety instrumentation system. 

ALARP seems to be an adaptation from ALARA. But ALARP has become the more frequently used term for operations other than atomic and it appears more often in the literature. ALARP is defined as that level of risk that can be further lowered only by an increment in resource expenditure that is disproportionate in relation to the resulting decrement of risk. The concept embodied in the terms ALARA and ALARP applies to the design of products, facilities, equipment, work systems and methods, and environment controls. 

The approach that is being widely promulgated in the UK is that the general form or framework for acceptability criteria should be represented as a three-tier system with (a) an upper bound on individual or societal risk levels, beyond which risks are deemed unacceptable (b) a lower bound on individual or societal risk levels, below which risks are deemed not to warrant concern and (c) an intermediate region between the previous two, where further individual and societal risk reduction are required to achieve a level deemed as low as reasonably practicable, the so-called ALARP principle. To achieve a wide consensus on the acceptable flood risk, it is indispensable that the various methods, rules, and tools to be developed in the advanced ALARP framework are robust and transparent. ... 

Where the instaiiation of such an independenf aufomatic overfiii prevention system at an existing tank is demonstrated to give rise to other more serious safety or environmentai risks eisewhere then other aiternative measures may be adopted to achieve the same ALARP outcome. 

Dutyhoiders wiii need to prepare a robust demonstration that aiternative measures are capabie of achieving an equivaient ALARP oufcome fo an overfiii prevention system that is automatic and physicaiiy and eiectricaiiy separate from fhe tank gauging system. 

The selection of any system is based on a combination of risk (to the environment and people), cost and practicality. Any consideration of improvements to lining systems for existing establishments where the risk is tolerable should be subject to an ALARP assessment. 

Within the PSLG Final Report, particular emphasis is given to overfill prevention as this is the primary means by which this major accident hazard can be prevented. In assessing what overfill prevention measures are required to reduce the risk to the environment to ALARP, the existing capacity of the bund and the tank level it was based on must be taken into account to determine the potential environmental consequences, eg whether the spillage is likely to be retained by the secondary containment system. If the overfill prevention system and the primary containment measures as a whole are in accordance with good practice, the risk to the environment is reduced. 

For SIL 1 safety requirements, improvements to existing systems may still be necessary to meet ALARP even in cases where it is not reasonably practicable to upgrade or replace existing systems to fully meet the requirements of BS EN 61511. The following issues should be addressed when considering what improvements are required ... 

Further to this, there is increasing effort to better imderstand the risks that rail organizations face and the risk management controls that are, and / or, need to be, put in place to manage these risks. In marty operations the human component is still a key defence against incidents and accidents occurring. We carmot eliminate the human from the system. Therefore, we need to be confident that our frontline personnel are equipped with the skills, knowledge and attributes required to be able to perform the required tasks safely. More specifically, we need to train our personnel such that we reduce the likelihood and consequences of human error to As Low As Reasonably Practicable (ALARP). 

A key development in system safety is the ALARP principle that states that the residual risk of a system shall be as low as reasonably practicable (ALARP principle) and was codihed through the UK Health and Safety at Work Act of 1974. The concept asserts that safety-critical systems and operations should be safe as far as reasonably practicable without risks to health and safety. This is important because it forces the overt decision to balance the realized safety benehts to the actual costs to implement in other words, residual risks are tolerable and thus do not need further mitigations. 

Central to the safety case is the hazard control and risk manag ent process, ensuring that risks are well managed. ALARP is used to determine how far you should go to control the hazard. The safety case process is very thorough and highly labor intensive and, if you are not careful, could become overly bureaucratic. It is just a snapshot in time of the safety of the system, so that means that it must be maintained to still be relevant. This is where bureauCTacy can take over if not careful. 

The probabilistic analysis supports the deterministic analysis by providing confidence that the safety systems used to control faulted conditions are tolerant to a single failure of an active component. The PRA also shows that the AP 1000 risks are likely to be less than UK targets, recognising that a formal demonstration is still to be presented. This forms a sound basis for the ALARP argument. 

The primary sampling system must be able to provide a representative sample of the primary coolant, whilst minimising operator doses to levels that are ALARP. 

Doses to the operator associated with the use of the primary sampling system ate ALARP. A delay coil of tubing is installed inside containment to provide at least 60 seconds of transit time for the sampling fluid to exit the containment from the hot leg. This 60-second delay is needed for N-16 decay. Control and instrumentation is provided for safe, reliable operation. Sample flow is routed to a grab sampling unit. This unit is in an enclosure, which controls the spread of contamination... 

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