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In this post I compare three of the most common service rig (workover rig) pump truck designs – The Winch Pump Truck, The Trailer Mounted Pump Truck and Hook Lift Units.
Pump Trucks in the News
A recent fatality in Alberta involving a young employee operating a pump truck has caused the industry to question the safety of this piece of equipment. The rumor (unconfirmed) is that the employee slacked off the winch on the truck with the tank half on and half off. When the tank slipped off, the operator was hit with the cable causing death. This tragedy has caused a number of companies to explore alternative ways of loading a mud tank onto a pump truck in an effort to increase safety. The following review explores three common options and lists the pros and cons of each.
If you are not familiar with what a service rig pump truck is you can review specifications and pictures here: Sparta Engineering Pump Truck
Pump Truck #1 – Review of the Winch Design:
This style of truck is probably the most common. On this unit, the operator will use a deck-mounted winch situated approximately half way down the truck. This includes 100ft of cable on the drum to drag the tank off the ground over the live roll at the rear and onto the truck. The operator then chains the tank down securely for transport. This design resembles the oilfield winch truck or bedtruck, which are specifically designed to move around skid-mounted equipment.
This setup has excellent maneuverability and flexibility for field operation. With the standard equipment, the truck has good weight balance and since its just one unit, it is easy to maneuver onto lease and into position. The winch is very flexible and forgiving on alignment and environmental conditions compared to other systems. This allows the operator to maneuver the tank and truck into position in less time and with less need for precision.
The downside to this design is that when the winch fails, they are unpredictable and dangerous. This unfortunately creates safety concerns for people in the radius of the cable. This design also relies on a single point of contact with the winch so there is no ability to stop the tank from sliding sideways. This can be a problem when there is frost on the deck and the truck is on a hill. The operator may find the tank sliding off the side during loading. This is especially critical on a winch truck as there is very limited contact with the tank and the truck during different stages of loading. Lastly, there are safety concerns with operators around the tank and winch during loading (to secure it for transport). With this design, the operator has to get close to and possibly under the overhand of the tank in order to chain it down for transportation.
What I would Change: As with any design there is always room for improvement. What I would personally suggest implementing into this design is an automatic guide and lock system to the top of the deck and the bottom of the tank. The guide would keep the tank perfectly straight coming onto the deck and the lock would use an air cylinder to over cam a positive lock on the tank. This would remove the need for someone to chain the unit down for transport but also helps to keep the tank straight during loading.
Pump Truck #2 – Review of The Trailer Mounted Design:
Trailer mounted mud tanks were more common before winch trucks became popular. Trailer mounted units are exactly what they sound like. The mud tank is pulled behind the pump truck via the pintle or 5th wheel. The biggest advantage (and disadvantage) you have with this design is that you are adding extra axles to the system. This allows you to haul a lot more stuff but also increases the cost substantially. Some efficiencies are gained since a structural member is required under the tank even if it is skid mounted so attaching a set of axles to it doesn’t really add any weight or any additional material cost. This design also frees up the 20ft of deck where the mud tank sits on the winch-mounted version for other purposes such as eliminating or at least supplementing the equipment truck. This setup also has a lower center of gravity and is further from the maximum legal height that the DOT sets. The biggest downfall to the trailer mounted version is that it is difficult to get around the lease site with a trailer and that it ends up being a fairly long unit when it needs to pull a 20ft tank. Historically people have complained about this style of tank sinking into the mud and being difficult to get out.
What I Would Change: I really like the trailer mounted system and I think there are a lot of possibilities with the design. The first thing I would do to address the safety issue is design a system where the truck does not have to detach from the trailer and eliminate the sinking problem. With the correct angle on the tank and a hitch that hinges I think it would be possible to get the tank to lay flat on the ground when on site. This would eliminate the need for as much structure below it and take care of the sinking issue.
Related Content: Curious about Pump Truck options? Contact Us
Pump Truck #3 – Review of The Hook Lift Design:
A hook lift pump truck has the usual pump and manifold mounted behind the cab but the rear 20ft or so is the hook lift system. A hook lift uses a mechanical arm that folds down off the deck and grabs the mudtank by a specially made lifting point and drags it onto the deck. The mechanical arm can either be manufactured locally or purchased from any of the large crane manufacturers such as Palfinger. The benefit of a hook lift system is that there are fewer degrees of freedom during the lift so it ends up being more controlled and safer. Also, there are usually built in hooks that provide securement for traveling so there is no need to chain or strap the load down. This is a long proven way of loading and unloading equipment. The main downside to a hook lift truck is the increase in price and weight over a winch. Sparta Engineering generally produces a tandem drive and single steer pump truck and there isn’t any spare weight for a hook lift system. Expect to run either a single tri or tand-tand configuration depending on setup. These trucks are also moderately less forgiving in the field than a winch since you have to be close and lined up properly to load it.
What I would Change: A slight variation of the hook lift system is the roll off system. I like this system as it provides a solid guide for the tank to roll up but has a better mechanical advantage then a hook lift system. See: Palfinger’s Roll off trucks
Have a different idea for a pump truck? I would love to hear about it.