Email Enquiry

Subject:                  H2S Personal Monitors - Do All Personnel Have to Wear During TAR?

Date of Initial Email :  Thu 30/07/2009

Initial Email Detail:

Once again I am calling upon the JOIFF membership for some guidance - We are shortly heading for a major shutdown/turnaround, one of the questions raised was, should the wearing of H2S personal monitors be mandatory for all personnel, i.e. contractors.  Considering we will have approx 1,500 extra staff, obviously not all working on site, but predominately the bulk, the cost implications could be enormous.  Have any of our member refineries have any guidelines on this issue. 

Second Email:

I believe that if a specific need is identified in a balanced risk assessment, affected personnel should be required to wear appropriate personal monitors. This does not translate to blindly issuing 1500 units to people who probably have no idea what to do with them.

From more than 3 decades of refinery experience, I cannot think of too many parts of the plant that should qualify as necessitating a personal monitor. Certainly, the expectation I grew up with was that the plant had to be sweet on handover on Mechanical Day 1.

Areas that can resist even the most diligent sweetening activity include all parts of the blow down / flare systems, the amines units and deodoriser / sour water stripping facilities. Cracking processes, including FCCU, Visbreakers and Delayed Cokers, resist sweetening; in fact, most product accumulators and flash drums that have a sludgy residue that needs to be cleaned out will have H2S but of course, every one of these is subject to gas test before entry. As a rule of thumb, workers inside such vessels should be required to wear air lines until all the sludge is removed, so a personal H2S monitor is unnecessary. The sludge usually doesn’t continuously release H2S in volumes that pose a hazard to workers in the open air nearby, even if it is sufficient to cause a life safety threat in the vessel itself.

Some bad experiences with H2S:

• A team sent to insert blinds in the flare line was issued with SCBA but opted to not use it. One fitter lost consciousness but recovered
• A worker complained of dizziness where he was working without BA below a point where fitters were blinding the blow down line at unit battery limit
• A worker entered a CDU overheads accumulator without permission and was incapacitated; a rescuer entered without breathing protection and fell down inside the vessel; the rescue team was right there (he was the team leader at the time) and pulled both to safety

Even with such horrifying tales, one can say that if the risk assessment identifies potential exposure areas from an experience base, where ambient H2S can be anticipated, then you can limit the number of personal monitors to realistic levels – say in the amines recovery unit, the scrubbers and the vicinity of any flare surge drum that is to be opened. If the shutdown procedure and isolation protocols are adequately managed, migration of H2S from the blow down system into traditionally sweet units can be prevented – then periodically verified by the safety professionals. Of course, the work plan must ensure that where exposure risks arising from planned work can be anticipated (bullet 2 above), the area should be barricaded until blinding is complete and the flange tightened again.

Another consideration: instead of personal monitoring, one can use strategically positioned area monitoring devices near a potentially exposed work site. I think Crowcon used to have these tripod-mounted units. One device protecting parties of say 10 people may be more economical than policing multiple individual units.