Conducting a successful HAZOP session for a mining project

The hazard and operability (HAZOP) study was first used by Imperial Chemical Industries in the U.K. in the 1960s. The study gained industry-wide acceptance after an unfortunate disaster in Flixborough on June 1, 1974. Nypro Ltd. owned a chemical plant in Flixborough, U.K., to manufacture caprolactam, a raw material for nylon production. One of the reactors (reactor #5) at the chemical plant developed a crack. To minimize production loss, an ad hoc bypass line was installed between reactors #4 and #6 to transfer cyclohexane.The bypass line was not designed to mechanical safety standards. Uneven stress ruptured the bypass line, releasing 30 to 60 t of boiling cyclohexane at temperatures greater than 177 °F into the atmosphere. Cyclohexane is highly flammable and once the fumes found an ignition source, the chemical plant exploded. Twenty-eight employees were reported dead (39 percent of all employees present on June 1, a Saturday), while 36 (50 percent) were seriously injured. Had this been on a weekday, perhaps more fatalities would have occurred. After this unfortunate incident, the HAZOP study gained industry-wide recognition as a tool to understand the impact of process variation on equipment, process and people. The HAZOP study consists of a brainstorming session among employees from various departments. The group brainstorms on various scenarios of process parameters — such as high flow, low flow, high temperature, low temperature — and provides recommendations on ways to mitigate the hazard. Teams from Bagdad Mine and Bowman Engineering recently completed a HAZOP study on the water spray and dust collector systems on several conveyors in the crushing area. A few lessons learned from the study are: Size and composition of the group for the HAZOP brainstorming session — A group of 6 to 10 individuals from different departments is preferred to conduct the HAZOP study. It gives time for everyone to bring their concerns forward during the session. The group should have representation from operation, maintenance, electrical, instrumentation, engineering, safety, environment, industrial hygiene and planning department. End-users (operation and maintenance) must be involved in the HAZOP study — it is critical to have them dedicated to the session and not be pulled out for support during plant upset. Location of the HAZOP brainstorming session — HAZOP sessions should be conducted at a place not disturbed by operational upsets. A location away from the mine site is preferred. Timing of the HAZOP session — Due to the intense nature, it is better to start the meeting in the morning with breaks every one or 1.5 hours. Sharing the right documents — Piping and instrumentation drawings are generally shared for the HAZOP session. However, it is critical to share flow diagrams and 3D models before the session. Printed color-coded copies are likely to help the team visualize the new process. Walking the area — It is preferred to walk the area of the new process to help the team members understand relative location and surroundings. There is a possibility that some of the team members might not have been to the area before. The area walk should happen before the HAZOP session. Pictures of current layout and utilities connections must be readily available as HAZOP team members may not recall the area with accuracy if there is a gap between walk and HAZOP brainstorming session. Communication — An oval or rectangular type seating arrangement is preferred for better communication. Some attendees may join remotely; hence, it is necessary to ensure all network connections are available and reliable a day or two before the meeting. Once permission is granted, the session should be recorded. This will ensure that all comments are captured. Reliable scripter software can be used to auto-document the comments. Hazard matrix — Select the hazard matrix to be used in advance. There are many variations of hazard matrices available to conduct HAZOP, such as 3 × 3, 4 × 4 or 5 × 5. Ensure that all the team members understand the components of the hazard matrix before the meeting. Sharing the summary — Share the HAZOP findings with the team a day or two after the session. It will ensure that all the missed thoughts are captured soon after the HAZOP session. HAZOP brainstorming sessions are a great way to build safety in design rather than having it as an afterthought. Expertise from various disciplines is harnessed to create a safe design leading to a life-of-mine impact on personnel, equipment and production.

Conducting a successful HAZOP session for a mining project

Authored by: Jagdish Rawat and Ana Rios

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