Managing Health and Safety Risks of Harmful Gas Vapours – Part 2

Managing Health and Safety Risks of Harmful Gas Vapours – Part 2

Understanding and Mitigating the Risks

The risks posed by leaks of harmful substances are not always immediately obvious.

Beyond the acute dangers of exposure to toxic substances, smaller or frequent leaks can result cumulatively in long-term bad health, as well as environmental contamination and property damage. Systems need to be designed, operated, and maintained with meticulous attention to safety protocols.

Factors such as inadequate ventilation, equipment malfunction which does not failsafe for parts controlling any emissions, improper maintenance, inadequate or unskilled inspection, and human error can all aggravate the severity of the risk.

The recent HSE Safety Notice illustrates how, when all factors have not been appropriately considered, the failure of a single component can lead to the failure of the safety critical overfill protection. This highlights the importance of understanding the risk posed by the processes in place and ensuring safety critical protections are identified and are suitably managed and monitored

Role of Vapour Capture, Pressure Reliefs, and Overflow Valves

Vapour capture systems, pressure relief devices, and overflow valves are some of the critical safety devices used as engineered controls to mitigate the risks associated with harmful gas and vapour leaks.

In the incident which led to the HSE’s safety notice, the overfill protection of the VRU was linked with the basic process control system (BPCS), and when the BPCS failed it also caused the VRU overfill protection to fail leading to the unintended loss of containment.

Any critical safety system which acts to prevent or mitigate a hazard (e.g. release pressure before it exceeds the designed pressure of the process) should be independent of normal control systems such that any foreseeable failure of the control system would not cause the safety critical device to fail as well.

Safety critical devices such as Pressure Reliefs and Overflow Valves should also assist, when designed correctly, by safeguarding from overpressure and potential loss of containment scenarios. These mechanisms are designed to capture, contain, or divert the buildup of excessive pressure within containment systems, thereby reducing the likelihood of leaks or of catastrophic failures in the surrounding environment which might injure personnel.

In a recent matter in which Finch Consulting was retained to advise, the venting of ammonia to an area outside was occasionally required. This, however, was the same area to which persons evacuated when alarms were triggered. Following an alarm, the evacuated workforce consequently suffered a range of symptoms from the exposure, some needing hospitalisation.

Control measures need consideration:

  • individually
  • as part of the whole suite of measures, and
  • with an understanding of potential failures anywhere in the process, to understand how they may impact each other.

Continued in part 3.

Tristan Pulford | Sohail Khan | Sue Dearden

If you need further information or advice on the effectiveness of your engineered harmful substance controls please contact Tristan Pulford: [email protected] : 01530412777 

We can audit the controls in place in your workplace and assist in identifying where there are gaps in measures in place (as well as solutions).

Tristan is a chartered mechanical engineer and process safety engineer and is Finch Consulting’s Capability Director. Sohail is a chemical engineer experienced in process safety management. Sue is a Solicitor at Finch Consulting specialising in Health and Safety.

Finch is a leading risk management consultancy, working worldwide with blue-chip clients in multiple sectors.

As a “critical partner” to our clients, we provide confidence to be a better business by helping identify, manage and mitigate risks associated with engineering, health and safety, and regulatory compliance. This is delivered through three core areas: Asset Management, Health & Safety Management and Process Safety Management.

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