The HSE "theme" for 2009 for Top Tier COMAH sites is Process Safety Performance Indicators, PSPIs. These are high-level statistical or numerical indicators which show whether a Major Accident could be caused or not. It applies to all Top Tier sites, even if you're only warehousing hazardous substances.

The HSE have a document explaining this, called HSG 254, Developing Process Safety Performance Indicators - see http://www.hse.gov.uk for details.

This is my personal explanation on how PSPI indicators may work in practice, it may be useful if you are having difficulty with the HSG 254 definitions.

Please note that PSPIs are site-specific and process specific, and need to be assessed by professionals who know and understand your operations.


What PSPIs are trying to do

A brief explanation is that PSPIs are a few, relevant overview statistics you can take to the MD or the board to show that the safety hazards are running reasonably smoothly.

There are three types of indicator you can use:

• leading indicators,
• real-time indicators (if you monitor process variables using a good computerised process control system)
• lagging indicators

The leading and real-time indicators are the most useful because you have a chance to use them to prevent incidents.

Example for choice of PSPIs

If you were to consider PSPIs for company money, the Board might need to know:

• the amount of cash in the bank (realtime indicator),
• your conservative cashflow projection for the next quarter (leading indicator, at what point you run out of cash, assuming nobody pays you on time)
• your bank statements for the previous quarter (lagging indicator, how your cash levels fluctuated)

If you just relied on the lagging indicator of the company bank statements, you can run out of money and be out of business before you really know what is happening. So the two most important parameters are cash in the bank, and when you could run out of money.

If things are running smoothly, the Board does not generally want to know all the gory details eg that your clients Glacially Slow* are in arrears again, or that your suppliers Costem Loads* have only been partly paid because you are disputing their bill.

But if you only have £20 and a brass button in the bank, and your cashlow projection shows a large electricity bill due in a fortnight, the Board will probably want to know who is phoning Glacially Slow* to get your money off them, and who is negotiating longer credit terms with all your suppliers, and which Board member is going to grovel to the bank for an overdraft so you can keep trading.

As with leading cashflow indicators, so with potential major accident leading PSPIs - if you define them sensibly, you can start to analyse how they are caused, and try to ensure that you don't get into the area where they may occur.


More sophisticated PSPIs

The HSE like to consider PSPIs in pairs ie leading and lagging – but in real life, there may be one leading and two lagging indicators, or vice versa.

The important thing is not how many PSPIs are chosen, but that they show plant managers and senior management when you are out of the “safe” zone and in an area where incidents become more likely.

Other thoughts on PSPIs

My personal opinion is that leading and current indicators, particularly in combination, are much more useful than lagging indicators.

Lagging indicators are very useful for investigating “near misses” and consequence analysis – last month, two customers didn’t pay us on time, and we got very close to going under – how can we prevent it happening again?

But it’s not as useful as giving insight into what’s going to happen, and what’s going on right now, which leading and real-time indicators can provide.

J Murfin, TT Environmental Ltd, April 2009

* these company names are fictional, for the purposes of illustration only, and are not intended to represent any existing business.