NOTE: If there’s anything on this page that you as a water hauler can use to train your new drivers, feel free to help yourself–as long as the manual you produce using my material gives me the credit and tells everyone where to find this page.
The number of likely scenarios in which a driver is required to blow off a load of water–i.e. unload his tanker under pressure applied by his truck-mounted vacuum pump–is impressive. A few possibilities include unloading into:
1. An open disposal pit.
2. An open reserve pit.
3. An open temporary storage pit.
4. A frac tank.
5. An upright (400 barrel) tank.
6. A manifold.
And one more: When the dirt roads are bone dry and the dust is a problem, you may use your tanker to spread a spray of water over those roads. That requires a special “spreader bar” and a bit of trial-and-error effort to accomplish properly–frankly, it’s more art than science–and won’t be discussed in detail here.
The other six situations, however, deserve a few words.
Blowing Off a Load into a Pit
There is one pit type which requires almost no instruction when it comes to blowing off a load of water. There are (or at least used to be) a few large disposal pit operations for produced water (commonly called production water) that can only be described as a pleasure to behold. All a driver needs to do at such a disposal site is the following:
The Super Accessible Pit
1. Back the tanker trailer onto the heavy, black, waterproof plastic (which lines the pit and extends out over the edges) until the rear end is literally hanging out over the edge. Naturally, you don’t want to back up so far that you the trailer tires are at risk, but in the proper position, any spillage from the valves will simply spill down the plastic and into the pit.
2. Chock the tires.
3. Uncap both discharge valves and open both valves so that water begins to gush out under “gravity feed”.
4. Start the vacuum pump in “push” mode to speed up the process.
5. Enjoy the show. Under a full head of pressure, the twin four-inch “water cannons” are absolutely fun to watch. It’s almost impossible to mess this up (stress on the word “almost”).
6. When the load has “blown off” to the extent that nothing but air is issuing from the valves, shut off the pump and open the blowoff valve to depressurize the tank. Not that there’s much pressure left at this point, but still.
7. Shut the water valves, replace the caps, pick up the tire chocks, and…done.
However, not every pit is so accommodating. More often than not, it’s impractical or impossible to safely position the tanker trailer with its valves hanging out over the edge. In more than a few cases, you may need to thread a hose through a barbed wire fence to reach the pit dropoff edge.
The Less Accessible Pit
1. Position the tanker trailer as close to the pit edge as possible. This can be a matter of just a few feet of separation between the dropoff and your rig…or, in extreme cases, a “reach” of sixty feet or more if it’s a tight location with lots of “clutter” blocking truck access.
2. Chock the tires.
3. Run at least one hose–usually a 4-inch version–from the trailer to hang over the pit edge.
4. Figure out how you’re going to secure the hose when it starts trying to whip around like a rabid rattlesnake under pressure from the vacuum pump. My preferred method at many locations was to open the discharge valve under gravity feed only to get things started. Then, after firing up the pump, I’d head back to either stand or squat on the hose until the water was all “blown off” and the hose (now pushing only air) was willing to settle back down.
5. Shut off the pump, load the hose back up on the side tray, get the caps back on the valves…starting to sound familiar?
6. HEY! You forgot to pick up your tire chocks! Just drove over them…AGAIN!
The Frac Tank (or Any Other Tank)
The focus on this section is on air pressure. You’ve read the first two chapters, so you know how to hook up to a frac tank. We’ll not repeat that here.
There is some ground to cover, though.
Okay, you’re ready to start blowing off your load into that tank.
First, head on up that ladder. Take your flashlight (NOT your BIC!) with you. Take a look inside that tank. The tank should be totally empty. After all, that’s what your best buddy just told you as he was leaving location to go get another load–nobody had started filling that particular tank. That’s what he said.
Uh-huh. Guess what. It’s not empty, is it? Nope. In fact, it’s full to within roughly two feet of the top!
Oh. That’s different, then. That’s very different. Because if it had been empty, you could have popped your load in there under full pressure, 15 psi or so, no problem, done deal.
Better watch the pressure gauge on your trailer for this one, especially as it gets toward the end.
Whew! If you’d blown your full 130 barrels into the top end of that 500 barrel frac tank, the surge-and-purge effect when the air hit all that water would likely have splooshed stuff right out through the top and onto the ground! AGH-H-H-H!
Can’t have that.
But you’re a cautious driver, so you keep an eye on things the right way. You hike up and down that ladder endlessly as the tanker delivers its load, making sure the whole load really will fit. You even open the screaming-loud vent valve on your tanker just enough to hold it down to 10 psi at first, 5 psi at the end.
Okay. Done. The load is off. You did let a little air run through, bubbling and surging things a tad but not too much, and then you shut off the frac tank valve first
What? Ah. Yes, we should mention that. By the numbers, then, for a frac tank or any other tank:
1. Before beginning to blow off a load of water (be it fresh water or frac water makes no difference), check the level of water already in the tank. This can be a problem (sometimes) with tall upright (fresh water) tanks if the tank gauge is busted and the rule on that location is that only rig crew members are allowed to climb up top to look, but you need to know.
2. If the water level in the receiving tank is anywhere near the top, reduce the psi used to push the water out of your tanker drastically, especially near the end when air will be following water through the hose. (This is usually done by partially opening the air vent on your tanker. Ear protection at this point is a really good idea.)
3. Open the trailer valve first (pressurizing the hose and thus preventing existing water in the receiving tank from climbing back toward your trailer) and close it last.
4. WAIT! You’ve gotten rid of your load of water. The frac tank (or upright tank) valve is once again closed. DO NOT DISCONNECT THE HOSE YET. There’s still pressure in there. Pop those tabs loose, and the steel-hard metal fitting at the end of that hose may explode right into your face.
Frankly, it could just…explode your face.
5. Turn off the vacuum pump and open the tanker’s bleedoff (vent) valve to let the pressure inside the tank bleed down to nothing–or close to it.
6. Snap the trailer valve full open for just a second or two and then slam it back shut. What this does is allow the pressure trapped inside the hose to burst into the now depressurized tanker, hopefully carrying with it any bit of water that hadn’t completely exited into the receiving tank. That slam-shut move is to keep what you blew back into the tanker from getting back to the hose.
7. NOW it’s safe to disconnect your hose and do all the other little things that wrap up the unloading process.
Huh? You forgot? Hey, reread the earlier–well, foo. All right, but I’m not saying it again: Get the hose back up on the side tray. Replace the travel cap over the trailer valve end and latch it down. Unscrew the frac fitting before you forget and drive off without it…again. Pick up the tire chocks.