Engineering Advancements in the Free Stand Service or Workover Rig
In the past, Service Rigs (Workover Rigs) were called “guyed rigs” because they had load transmitting cables going from the top of the derrick to the ground to help stabilize the rig. These load lines were anchored so they could handle a substantial load and still be capable of keeping the rig really stable. Relatively recently, this style of rig was abandoned in favor of the free standing rig that uses outriggers or load beams for support instead of cables. This shift in equipment came primarily because of safety concerns with drilling an anchor into the ground in order for the guyes to attach to. However, with the new rig design there was additional challenges because the tall, slender derrick of the free stand was self-supported and had to stay erect even in high winds. Sparta addressed these safety concerns and the Sparta Free Stand is now a faster, safer and a more efficient rig.
The 8 Main Components of a Free Stand Service Rig:
- Mast: For use with any of the Sparta designed masts.
- A-legs: Our “fan brace” a-leg structure made using the same design principles of the mast. It utilizes light weight, high strength material and a self-jigging plate steel design. No sealed structural tubing involved.
- Bumper: High capacity rear bumper with integrated tow lugs and cylinder mounts.
- Leveling jacks: Two SJ-900 leveling jacks provide a clear primary load path to the load beam.
- Center Load beam: High tensile plate steel center load beam with arched design.
- Turn buckles: Turn buckles have aluminum barrel and steel lugs for the perfect blend of strength and weight.
- Load beam wings: Lightweight fold up high tensile load beam wings with wellhead rake.
- Engineered Tow Lug: Engineered tow system integrated into the bumper.
Advantages of the Sparta Free Stand Service Rig
All of Sparta’s rigs are free standing and have been carefully designed and optimized to perform better in the field. They also offer several key advantages:
- Quick set-up and tear-down time: The Sparta Free Stand Service Rig boasts one of the quickest deployment times in the industry and includes a hydraulically driven folding beam that retracts and folds up for transport. On this free stand, the center section of the beam is solid and the outer wings fold up and in by actuating the hydraulic cylinders and retracting the leveling jacks. The video below shows some action from our prototype folding system. The system shown below also automatically folds up or deploys the driller’s platform.
- Unique Arch Design: Arches have been a part of engineering since the beginning of time and can be seen on structures ranging from ancient architecture to space ship design. The beautiful part about the shape is an arch transmits stress to the ground in a highly efficient manner while spanning difficult terrain. Through our design process we concluded that the force entering the beam is very localized to the area around the jacks. This is where we distributed the most material. The area of beam in between the jacks is just there to tie everything together. This is where we focused on weight reduction. The other reason for moving to an arched design over traditional load beams is this new system will be much more forgiving on uneven ground or planking beneath the beam.
- Material: Our load beams started their life as aluminum structures. Originally, we did this because we wanted to reduce the weight the field guys had to move around every time they set up or tore down the rig. There are two major problems that we had with using aluminum in such a critical location. The first, during construction you start with 6061-T6 material which is heat treated aluminum with pretty good mechanical properties. As you build the load beam, you introduce a substantial amount of heat from welding causing a reduction in the effectiveness of the heat treatment. What was once 6061-T6 material becomes something like 6061-T0 in the heat affected zones which effectively drops the yield strength of that material to one quarter of what it was in the original material. Aluminum is also very susceptible to fatigue and cracking problems so it was common place to put a restrictive life span on these aluminum beams. After a few years of producing aluminum load beams we switched over to QT-100. By reviewing the design and utilizing the higher strength material along with the techniques such as the archway we were able to maintain a marginal increase in weight over the aluminum one while providing superior lifespan and a superior product.
- Integrated & Engineered Tow Points: Each free stand bumper comes with two engineered tow points integrated right into the structure of the rig. Rated to move up to 80,000lbs these two lugs are right in line with the frame rails and cut right into the flange of the bumper.
The Future of Free Standing Packages:
Free standing service rigs are on the verge of changing dramatically. The latest version of the API 4F 4th Edition code which governs mast and derrick design, has significantly increased the requirements for the mast to resist wind. The traditional free standing package that most people are currently working with will not qualify under these new guidelines. We expect there will be a general shift away from the traditional free stand package towards something new and unknown. Sparta is currently working on an API 4f fourth Edition. Send us a note to request more information or signup for our e-newsletter for the latest announcements from Sparta.