We have also found it necessary to re-classify the rig mat designs according to their bridge strength, rather than how many longitudinal rails they have in the mat, which really doesn’t tell you how strong the rig mat is. Although the number of longitudinal rails is related to the bridge strength, we are classifying our mats by the total weight of the longitudinal beams in a rig mat per foot. Therefore, we have classified rig mats as a Level 1 mat up through a level 5 rig mat. No other manufacturer builds a rig mat stronger than the level 2, which is the typical 4-rail rig mat. The 4-rail rig mat worked just fine most of the time, until the onset of the heavier walking rigs we have today.
Level 1 is characterized by the stock 3-rail rig mat which typically is manufactured with three 15 lbs 6”x6” wide flange beams. The total weight of longitudinal beams is therefore 45 lbs per linear foot. The mangled mats in photo 2 were used under a very heavy walking rig, running lengthwise with the sub bases and on an unseasoned soft location. Essentially, the walkers were running down the middle of the mats on only one I-beam, the center beam. The 3-rail mats nowadays are more appropriate for the backyard of a walking rig and not even that if the backyard is on walkers too.
Level 2 is characterized by the stock 4-rail rig mat with four 15 lbs 6”x6” wide flange beams. Total linear weight, 60 lbs per linear foot. This is where the stock production market stops. Level 2, 4-rail rig mats are fine with the smaller walking rigs if they are used correctly. We highly recommend that these mats be built in a smaller size, 8’x12’x6” is what is pictured here. Place them crossways to the sub bases and the walkers will always be walking on at least 4 rails. The extra width also gives the rig room to maneuver while walking down the mats, much easier than trying to stay in line on an 8 foot wide runway. I have never seen a level 2 rig mat used by setting up long ways under the walkers that wasn’t bent up. Usually, they need to be flipped over often to keep them usable and eventually replaced. The level 2 rig mat should always be set sideways under the walkers.
Level 3 is only made here at US Mat Systems. It can be a 5-rail rig mat with two ½” outer channels and three 15 lbs wide flange beams inside the glulam beams, or a 4-Rail rig mat with two ½” outer channels and two ½” wide flange beams inside the glulam beams. Linear weight per foot is in the 85 lbs/ft range. We believe that the 4-rail version with the ½” wide flange beams are stronger than the 5-rail design with the lighter wide flange beams. We have some of these Level 3 mats in the 4-rail, heavier ½” wide flange beam configuration, in the wild mixed in with their stronger Level 4 rig mats and they seem to be doing ok, but when the operator orders more mats, they always ask for the Level 4’s, not wanting to take any chances. These mats have always been used crossways under the largest of the walking rigs.
Level 4 is also only available from US Mat Systems and it is the rig mat we recommend for the heavier walking rigs. It is a 5-rail rig mat with two ½” outer channels and three ½” inner wide flange beams. Linear weight per foot is around 110 lbs/ft. The 8’x40’x6” 5-rail rig mat weighs in at just under 10,000 lbs each. They are a beast and we have never had one damaged by the heaviest walking rigs. That being said, thus far, they have always been placed crossways to the sub bases. The walking weight of your rig, the quality of location you are given and of course the weather will dictate what level mats you will need for your walking rigs. If you are in remote country it would be prudent to choose heavier rather than lighter. The 8’x12’x6” 5-rail Level 4 mat is a very strong mat, yet easy to transport. We also have a linking system that will be available soon that can link your walking mats together, or even to link the entire location together. The links actually transfer the moment from a rig mat to its neighbors and therefore will be an option for drilling without building an expensive gravel location in many environments.
Level 5 is also only available from US Mat Systems. It is an even more radical 6-rail rig mat with two ½” outer channels and four ½” inner wide flange beams. Linear weight per foot is about 145 lbs/ft. We have built small mats in this configuration as outrigger pads for the larger mobile cranes. We also have manufactured this mat as an engineered mat to be used in the well servicing industry. We are going to develop the Level 5 further as portable bridges and linked platforms suited for solving unstable ground difficulties in aid of heavy industrial construction projects.