Choosing the Right Method
For flares exceeding 100 meters at an onshore facility, the decision is whether to use mobile cranes or a mechanical handling option. Nowadays, the choice is made during the EPC phase of the flare and is dictated by the future operator. Usually, the operator wants to keep both options available for future replacement requirements.
Why does the operator want to keep the replacement options open?
I am not sure. The operator might be under the impression that cranes will evaporate from the face of the earth, that somehow the existing cranes cannot be used, or the cranes are too expensive. He might want to force the handling method to be part of the CAPEX decision to overcome future operational expenditures.
Before breaking the choice down into its essentials, I will explain the mechanical handling method and the sub choices to be made.
The process of replacing flare tips using a mechanical handling method is based on small lifting structures. These lifting structures are either permanently installed, removable, or retractable. All of the mechanical handling options have different pros and cons.
- The permanently installed system requires the least number of mechanical parts. It is constantly exposed to the environment and the flare tips' heat.
- The removable handling system is stored in warehouse conditions. It can be tested prior to the shutdown and assembled at the flare tip access platform during the shutdown. Conbit shows many examples on their website using davit and gantry-type systems.
- The retractable system is located below a heat shield, which is typically installed at the flare tip access platform. It is erected once the shutdown has started.
All systems allow keeping the lifting winch at ground level. The winch is fixed to a foundation while the winch wire is reeved to the lifting system at the top.
The permanently installed and the retractable systems are often of the davit type. They are both exposed to weather conditions. The retractable system is less exposed to heat radiation.
All mechanical handling systems will require a load test in their operating condition. If the load test fails, the system needs to be rectified before the actual lift can take place.
As a rule of thumb, all the items installed permanently at the top of a flare tower need to be load tested and provide a risk to your shutdown or turnaround planning. In case the component fails, there is a need to conduct corrective maintenance, which is taking place at a very remote location.
Crane vs. Mechanical Handling Method
Several factors influence the decision to replace flare tips with either a crane or a mechanical handling system.
- Elevation and location: The elevation and the location of the flare structure are important. For onshore flares below 100 meters, a crane is often available that can reach the flare structure relatively easily.
- Crane availability: The availability of cranes is not the same in many parts of the world. For a maximum of 100-meter-tall flares, we have noticed cranes always available near chemical and petrochemical sites.
- Shutdown days: The number of shutdown days should be considered for selecting the method. If the asset owner plans long shutdowns, he might consider installing a permanently installed or retractable lifting system. In the event the lifting system fails the inspections, there is sufficient time to rectify it within the shutdown duration.
- Investment: Another reason is of an investment nature. In some projects, the future asset owner will require as much of the costs in its CAPEX investment, rather than having all kinds of operational costs during asset’s lifetime. In that case, the lifting system will be part of the EPC contract for constructing the flare.
- Cost-effectiveness: Mobile cranes are almost always more attractive for flares below the elevation of 100 meters.
When using a crane, the following are required:
- A lift plan
- Solid ground conditions
- Access to the flange of the flare tip (2 persons)
- Rigger/signaler at ground level
- Crane and crane driver
When using a mechanical handling system, the following are required:
- Extensive engineering
- Dedicated inspection and test regime
- Access to the flare tip access platform (3-4 persons)
- Winch + foundation at ground level
- Load test before use of lift system
- The crew of 4-5 persons
To compare duration for both options:
Crane Mechanical handling system
Mobalization: 2 weeks 3 days
Lifting operation in shutdown: 2 days 5-6 days
Demobilization: 1 week 2 days
The duration does not include the engineering and project preparation. The engineering time for the mechanical handling system is between 4-6 months. On the other hand, engineering for a crane operation is limited to one week.
We have studied the budget requirements for both alternatives and can share the results of this study with our clients. Please invite us to be part of your internal discussions.
Conbit works in the field of mechanical handling of flare tips. We have replaced flare tips on different elevations. Over the years, we have found that for onshore flare tips below 100 meters, a mechanical handling method is almost never the preferred option. Globally, there are suitable cranes near chemical and petrochemical plants available, which are always more cost-effective than this method.
Conbit has been performing many flare tip replacements. For shorter flares in onshore facilities, it is advisable to rely on mobile cranes because of the following reasons:
- The cranes are used every day, and risks are known.
- The inspection of the crane is routine work, and the flare owner does not need to organize it.
- The budget required for the operation is less than with a mechanical handling method.
- The CAPEX can be reduced because no lifting provisions are required to be installed on the flare structure.
- No permanent components that are used for lifting are exposed to weather and heat radiation.
- The engineering and project preparation required is very limited.
By: Adityo Utomo is a lifting specialist. He is a trusted advisor to maintenance and inspection managers of chemical and petrochemical facilities. He is one of those young professionals who really want to make a difference for his clients. Adityo works from the Jakarta sales office to be close to Conbit’s clients in the region.