More Troubleshooting Tips

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Here are some tips to keep the hammer going at the jobsite.

By LaTisha Shipman

In continuing with the troubleshooting tips from my March column &#;Troubleshooting Tips,&#; I recently had a call where someone&#;s brand-new hammer wouldn&#;t fire.

There was a lot of back-and-forth between me and the customer, and then between me and the hammer manufacturer as we tried to assess the issue and troubleshoot the problem.

I&#;m grateful to the customer for enduring the endless line of questioning, and the same with the manufacturer. I know it can be both difficult and frustrating for everyone involved when new products don&#;t work the way they were envisioned.

I want to share some of the questions that were asked in order to identify the problem. I think this is a good example of what to expect when calling in to troubleshoot a hammer problem. Remember, the complaint came in that the hammer doesn&#;t seem to fire.

My first question was, &#;Above the hole or in the hole?&#; to which the response was both; it wasn&#;t firing at all.

I asked if air was blowing through the hammer. Yes, it was blowing air, but wouldn&#;t fire. The reason for this question was to determine if air was exiting the hammer. If it isn&#;t, then we need to work our way backwards to see where the airflow is being disrupted. For example, it could be a blown hose.

I checked to make sure the bit he had on the hammer had a blow tube in it as this particular hammer requires a blow tube. His bit had the blow tube, but for good measure, he decided to change out the bit.

It is necessary when running foam to double the amount of rock drill oil that you use as the foam and water mixture negates the lubricity of the oil.

The next comment I got from him was that they had gotten the hammer to fire! It wasn&#;t ever a hammer issue at all, and it had taken someone else on their team investigating everything further.

I mention this because sometimes we overlook things. It&#;s just part of our human nature. When you are having issues with a hammer, you might consider having someone else on your team work on it with you. They just might catch something you&#;ve overlooked.

Now, here are some more DTH problems and tips.

Problem 1.

I&#;m running into high heads of water. What can I do to keep my hammer from stalling out?

The Cause

The pressure from the water outside the hammer creates backpressure for the air inside the hammer. We must increase air pressure to unload the water from the hole.

One (1) foot of water in the hole is equal to 0.434 PSI. If you have 100 feet of water in the hole, there will be 43.4 PSI of backpressure that we need to overcome to maintain the minimum operating pressure of the hammer.

What Can I Do?

If possible, it&#;s best to increase the air pressure, or consider adding a booster to continue drilling. You can also implement foam to assist in lifting the cuttings through the water.

Problem 2.

I don&#;t have enough air on my rig to run the hammer. What other options do I have other than buying a larger air compressor?

Possible Causes

Believe it or not, we get this question a lot!

Drillers sometime inherit hammers larger than what they have air to run the hammers efficiently. This can be due to project requirements on  occasion. Perhaps they need to set 16-inch casing. A 10-inch or 12-inch hammer would be required to do that, and the driller may only have a 350/900 compressor on the rig. In a project like that, we&#;re going to need to consider uphole velocity and run calculations for that.

An issue I address regularly is that the customer has a 200/400 compressor, and they are asking what hammer they can run with that. I always check the minimum air compressor requirements on the air consumption chart for the hammers to make sure it will operate at 200 PSI, and not just meet minimum requirements.

I prefer to see the hammer in the mid-range on the PSI requirements. If we start a hammer out on the minimum operating requirements, we can expect the hammer to drill slow. And as we drill deeper, we can expect to encounter the problem of not having sufficient air to bring the cuttings to the surface and the risk of burying the tooling.

What Are My Options?

You don&#;t necessarily have to have the biggest air compressor on the market to run your hammer, but it is important to match the hammer requirements with your air compressor as closely as possible. You may consider downsizing the hammer and running an oversized bit. There are multiple ways to tackle this issue.

If you have a hammer that uses a choking mechanism, we want to make sure you are using the correct choke for the amount of air pressure you have available. Choking the hammer properly can allow hammer pressure to build up inside the hammer, even in lower air pressure applications.

Secondly, you can implement drill foam or soap to help evacuate cuttings from the hole. Using a high-quality, heavy foam will allow for better hole cleaning. The consistency to look for is like shaving cream with small little bubbles. A lower-quality foam will break down quickly, and a lighter foam would have larger bubbles and the consistency of your wife&#;s bubble bath.

For more information, please visit High Pressure DTH Hammer.

Note: It is necessary when running foam to double the amount of rock drill oil that you use as the foam and water mixture negates the lubricity of the oil and any benefits to oiling the hammer are lost.

When running foam, it&#;s also important at the end of your drilling day to flush the hammer out with clean air and water as the foam is corrosive. You need to rinse the hammer clean to prevent premature wear on internal hammer parts.

When you know you are running with a lower air pressure than recommended, it&#;s important to keep the hole clean at regular intervals. Drill slow and steady.

Problem 3.

I hear squealing coming from the hole. What causes that?

Possible Causes

This is often due to a too high rotation speed. Faster isn&#;t always better. Rotating faster does not always increase penetration rates. Hammer and bit life is directly affected by rotation speed. Over-rotation causes scraping of the rock formation and not crushing as the DTH hammer and bit are designed to do, resulting in premature wear and possible failure.

What to Know

A good rule of thumb is RPM = ½ penetration rate per hour in feet. For example, if you&#;re drilling 60 feet/hour, RPMs should be around 30. Most 6-inch hammers will run between 12-40 RPM depending on drilling conditions, particularly the hardness of the formation you&#;re drilling in.

Drillers can learn to feel what the best RPM is for good penetration rate without sacrificing bit life. Ground conditions, formation hardness, and abrasiveness all must be taken into consideration.

Another cause of squealing can be a too low feed force. Recommended feed force for a 6-inch hammer is approximately to pounds. You will want to reference your hammer manual for the manufacturer recommendations.

Sometimes the squealing is due to difficult drilling conditions, and it is the formation that is causing the issue. In this case, just drill carefully. Make sure you follow the hammer manufacturer recommendations and flushing often.

A broken drill bit or broken carbide at the bottom of the hole can also cause odd sounds coming from the borehole. Check to see if the bit needs to be repaired or replaced. If you have lost buttons in the hole, you can try to extract them with a magnet. If you put a new bit on and haven&#;t extracted the lost buttons, you can ruin your new bit as well.

Problem 4.

I lost my chuck and drill bit in the hole!

Possible Causes

Normally, the first thing we ask when we get this call is, &#;Did you reverse rotate?&#;

If everything is engaged at the bottom of the hole and you reverse rotate&#;even inadvertently&#;you may unscrew the driver sub from the piston case. This will leave everything at the bottom of the hole: your bit, chuck, bit retaining rings, and bearing. Usually, the piston retainer ring will keep the piston from falling out, but even that is not always the case.

This is caused on occasion by hammering without rotating, which can wiggle everything loose over an extended period of time. Back hammering can also be the culprit. Over time, the threads can become worn, so you can encounter this more often with an older hammer or chuck.

What to Remember

Be careful to keep rotating to the right or clockwise while hammering and check threads often for excessive wear, and replacing at regular intervals.

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These problems as well as the ones recounted in the March column show there are countless issues that can happen and countless tips to remember. Hopefully, I&#;ve shared some tips that keep the downtime to a minimum at your jobsite.

Idea for a Column?

If anyone has a question or subject that they would like to see addressed, please contact me at

LaTisha Shipman is the Texas branch manager for Drilling Equipment Resources. She has more than 20 years of experience in the drilling industry, with most of that time spent working in manufacturing with DTH hammers and bits. She can be reached at .

Water, at up to 180 bar delivery pressure, is used to power the impact mechanism of the hammer at a high frequency rate. When the water leaves the hammer, it loses the pressure and keeps a low flush velocity. This however is still adequate to bring any cuttings to the surface and clean the borehole. Additionally, the hydrostatic column, which is created above the hammer, helps to keep the hole stable while preventing potential collapse. This also prevents water from being drawn into the borehole, which increases hole stability and prevents potential environmental issues.

Unrivalled performance

The piston in a DTH hammer always strikes directly on the drill bit. A top hammer, on the other hand, loses approximately 4-6 % of impact energy at each drill rod connection, as the percussion unit is located on the drill rig.

When comparing an air-powered DTH with a water-powered DTH, which, in principle, work the same way, there are significant differences. The energy per blow can be expressed as follows:

E equals the piston mass, m times the piston impact velocity, v squared and divided by 2.

The output power P equals the pressure p of the medium powering the piston, times the pistons pressurized area A, times the piston impact velocity v, all divided by 8.

The piston mass and the pressurized area are determined by the diameter of the hammer case and are therefore rather fixed. The impact velocity depends on the piston material characteristics and is therefore also a parameter which cannot be significantly improved. But the pressure of the medium powering the DTH hammer is a parameter that can be considerably increased/improved, for a hydraulic hammer.

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