mud pump pulsation dampener charge pressure free sample

At Sigma Drilling Technologies, we utilize out-of-the-box thinking and cutting edge innovation. From our revolutionary pulsation control systems, to our one of a kind performance boosting solutions, Sigma delivers unsurpassed technology. Helping businesses succeed by getting the most out their equipment investment is our goal. Let us partner with your team to help maximize your production output, enhance equipment investment, and place you at the forefront of industry advancements.

The Charge Free Dampening System™ is the first and only complete dampening system designed for maximum performance and cost savings. With the highest pressure rating at 10,000 psi, the CFD System far surpasses any pulsation control equipment in the drilling market today. Sigma’s system utilizes both appendage and flow-through technologies and yet still maintains the most compact design.

This multistage system utilizes several of Sigma’s advanced products that are proven to maximize efficiencies and upgrade operations of any reciprocating pumping system by themselves.

By protectively coating both inside and outside the system’s Charge Free Stabilizer™ and the Charge Free Dampener™, the system is entirely corrosion-resistant. The Charge Free Dampening System™ is easily the most protected pulsation equipment available.

The advantage of the CFD System’s small size, durability, and performance is combined with the fact the system requires no gas charging. The utilization of the Charge Free Conversion Kit® maximizes the dampening effects of the system without the need for nitrogen charging.

The Charge Free Dampening System™ is categorically the most sophisticated pulsation control available for your rigs’ pumping operations. With the introduction of the CFD System, Sigma Drilling Technologies proves to be the authority on state-of-the-art advancements in pulsation control technologies.

This device is designed to reduce pulsations (pressure fluctuations) that occur with systems that have a positive displacement pump.  Rubber bladder is pre-charged with nitrogen up to 50-60% of the system pressure.  As water passes by the pulsation dampener, it absorbs the pulsations that come from the movement of water in the system.  It is designed to protect pump equipment and piping in the system and can reduce pulsations down to 4%.

A Pulsation Dampener is an inline dampening device used to smooth out pulsations in a pump’s output. They are used alongside a pump as a mounted accessory to help achieve certain flow rates for an application.  They can be used with a variety of Positive Displacement Pumps which typically generate a pulsed flow (Diaphragm Pumps, Peristaltic Pumps, Dosing Pumps, Piston Pumps etc)

Pulsation Dampeners are required in some process applications when the customer needs smooth flow into the next phase of the production line, for example, to get an accurate reading through a flow meter or to fill a hopper consistently. On the flip side, Dampeners can be used to reduce water hammer effects through pipework. Water hammer is where the pump causes the pipes to vibrate and potentially fail, a smooth flow from a Pulsation Dampener reduces this.

For example, Diaphragm Pumps inherently produce a very turbulent discharge flow meaning that in some instances a Pulsation Dampeners are required to give a smooth pulse-free flow.

In the Tapflo UK range, we focus on Pulsation Dampeners for Diaphragm and Peristaltic Pumps, although we can also supply them for other pump technologies.

The Active Pulsation Dampener works by supplying an equal pressure to the pulsation supplied by the pump. The Dampener supplies this pressure during the low-pressure points of the pump’s operation, as the pressure drops between pump strokes creating a pulsating flow. The pressure supplied by the dampener decreases pressure variations, therefore producing a steady flow from your Diaphragm Pump. You can see the pressure drops and Pulsation Dampener benefits in action in the diagram below.

Tapflo supplied a 2” Air Operated Diaphragm Pump to a bleach factory, the customer used the T400 PTT for a couple of days and then called us to explain that the bleach line, running along the roof of his production facility, was shaking. Due to the nature of the product being pumped health and safety on site could not allow this to continue.

To support our Peristaltic Pump customers, Tapflo offers an in-line Pulsation Dampener for our PT and PTL Series’. They can reduce the pulsation of your PT Pump by as much as 90% to reduce the vibration and water hammer effects on pipework. Another benefit of this accessory is its ability to be installed on-site horizontally or vertically for flexible installation.

Mud Pump Pulsation Dampener is usually installed on the discharge line to reduce the fluctuation of pressure and displacement of the drilling mud pump.

Mud Pump Pulsation Dampener is a pneumatic device built into the outflow line of each UUD pump to dampen the pressure fluctuations resulting from the action of the pump. Although presented as a surge tank, this device is really a device that can be tuned to greatly diminish the output pulsations transmitted downstream from the mud pump. Unfortunately, the effectiveness of the pulsation dampener is a function of both output pump pressure and frequency of the pump pulsations.

This paper focuses on the operational experience that was gained during field test of the Hex Pump on a land rig in Jasper, Texas in October 2003. This field test showed that the pulsation frequency in the flow from the Hex Pump did not interfere with the MWD-measurements, providing a much cleaner signal to the directional driller. Also, the overall power consumption on the rig was reduced due to use of AC-motors.

My first days as an MWD field tech I heard horror stories surrounding what is commonly referred to as “pump noise”. I quickly identified the importance of learning to properly identify this “noise”. From the way it was explained to me, this skill might prevent the company you work from losing a job with an exploration company, satisfy your supervisor or even allow you to become regarded as hero within your organization if you’ve proven yourself handy at this skill.

“Pump noise” is a reference to an instability in surface pressure created by the mud pumps on a modern drilling rig, often conflated with any pressure fluctuation at a similar frequency to pulses generated by a mud pulser, but caused by a source external to the mud pulser. This change in pressure is what stands in the way of the decoder properly understanding what the MWD tool is trying to communicate. For the better part of the first year of learning my role I wrongly assumed that all “noise” would be something audible to the human ear, but this is rarely the case.

In an ideal drilling environment surface pressure will remain steady and all pressure increases, and decreases will be gradual. This way, when the pulser valve closes(pulses), it’s easily detectable on surface by computers. Unfortunately drilling environments are rarely perfect and there are many things that can emulate a pulse thus causing poor or inaccurate data delivery to surface. The unfortunate circumstance of this means drilling operations must come to halt until data can once again be decoded on surface. This pause in the drilling process is commonly referred to at NPT or non-productive time. For those of you unfamiliar these concepts, I’ll explain some of the basics.

A mud pulser is a valve that briefly inhibits flow of drilling fluid traveling through the drill string, creating a sharp rise and fall of pressure seen on surface, also known as a “pulse”.

Depending on if the drilling fluid is being circulated in closed or open loop, it will be drawn from a tank or a plastic lined reservoir by a series(or one) mud pumps and channeled into the stand pipe, which runs up the derrick to the Kelly-hose, through the saver sub and down the drill-pipe(drill-string). Through the filter screen past an agitator or exciter, around the MWD tool, through a mud motor and out of the nozzles in the bit. At this point the fluid begins it’s journey back to the drilling rig through the annulus, past the BOP then out of the flow line and either over the shale shakers and/or back in the fluid reservoir.

Developing a firm grasp on these fundamentals were instrumental in my success as a field technician and an effective troubleshooter. As you can tell, there are a lot of components involved in this conduit which a mud pulser telemeters through. The way in which many of these components interact with the drilling fluid can suddenly change in ways that slightly create sharp changes in pressure, often referred to as “noise”. This “noise” creates difficulty for the decoder by suddenly reducing or increasing pressure in a manner that the decoder interprets a pulse. To isolate these issues, you must first acknowledge potential of their existence. I will give few examples of some of these instances below:

Suction screens on intake hoses will occasionally be too large, fail or become unfastened thus allowing large debris in the mud system. Depending on the size of debris and a little bit of luck it can end up in an area that will inhibit flow, circumstantially resulting in a sudden fluctuation of pressure.

Any solid form of drilling fluid additive, if improperly or inconsistently mixed, can restrict the flow path of the fluid resulting in pressure increase. Most notably this can happen at the pulser valve itself, but it is not the only possible outcome. Several other parts of this system can be affected as well. LCM or loss of circulation material is by far the most common additive, but the least overlooked. It’s important for an MWD technician to be aware of what’s being added into the drilling fluid regardless if LCM isn’t present. Through the years I have seen serval other improperly mixed additives cause a litany of pressure related issues.

This specifically is a term used to refer to the mud motor stator rubber deterioration, tearing into small pieces and passing through the nozzles of the bit. Brief spikes in pressure as chunks of rubber pass through one or more nozzles of the bit can often be wrongly interpreted as pulses.

Sometimes when mud is displaced or a pump suction isn’t completely submerged, tiny air bubbles are introduced into the drilling fluid. Being that air compresses and fluid does not, pulses can be significantly diminished and sometimes non-existent.

Formation cuttings staying downhole can cause what is known as a pack-off of the anulus, which typically cause slower trends in pressure. A pack-off is less likely to cause significant decoding issues, but can.

Failed surface equipment such as transducers and transducer cables can occasionally allow current external to the circuit into the signal wire, resulting in what appears to be a pressure increase on the decoder. When experiencing poor decoding these are some of the first pieces of equipment to be replaced.

As many of you know the downhole mud motor is what enables most drilling rigs to steer a well to a targeted location. The motor generates bit RPM by converting fluid velocity to rotor/bit RPM, otherwise known as hydraulic horsepower. Anything downhole that interacts with the bit will inevitably affect surface pressure. One of the most common is bit weight. As bit weight is increased, so does surface pressure. It’s important to note that consistent weight tends to be helpful to the decoder by increasing the amplitude of pulses, but inconsistent bit weight, depending on frequency of change, can negatively affect decoding. Bit bounce, bit bite and inconsistent weight transfer can all cause pressure oscillation resulting in poor decoding. Improper bit speed or bit type relative to a given formation are other examples of possible culprits as well.

Over time mud pump components wear to the point failure. Pump pistons(swabs), liners, valves and valve seats are all necessary components for generating stable pressure. These are the moving parts on the fluid side of the pump and the most frequent point of failure. Another possible culprit but less common is an inadequately charged pulsation dampener. Deteriorating rubber hoses anywhere in the fluid path, from the mud pump to the saver sub, such as a kelly-hose, can cause an occasional pressure oscillation.

If I could change one thing about today’s directional drilling industry, it would be eliminating the term “pump noise”. The misleading term alone has caused confusion for countless people working on a drilling rig. On the other hand, I’m happy to have learned these lessons the hard way because they seem engrained into my memory. As technology improves, so does the opportunities for MWD technology companies to provide useful solutions. Solutions to aid MWD service providers to properly isolate or overcome the challenges that lead to decoding issues. As an industry we have come a lot further from when I had started, but there is much left to be desired. I’m happy I can use my experiences by contributing to an organization capable of acknowledging and overcoming these obstacles through the development of new technology.

The installation of properly sized pulsation dampeners minimize vessel costs while protecting the pump and piping system and improving process efficiency and accuracy.

A pulsation dampener reduces or eliminates the variations in pressure and flow produced by reciprocating pumps. In many applications, low frequency pressure waves cause problems within a given piping system and/or process. Eccentric, cam-driven pumps are probably the most commonly applied for services that require pulsation dampening, e.g., metering pumps and reciprocating (power) pumps.

Pulsation dampeners are found in a variety of designs, but for our purposes we will focus on only gas-charged pulsation dampeners, which rely on a calculated volume of compressed gas, usually Nitrogen, which is alternately compressed and expanded in synchronization with the pump plunger to reduce or eliminate pressure pulsations. This gas volume is normally separated from the process fluid by a flexible membrane. Common membrane designs include elastomeric bladders, PTFE diaphragms, PTFE bellows or stainless steel bellows.

Pressure waves or pulses are a consequence of the alternating acceleration and deceleration of fluid velocity corresponding to the travel of the piston or plunger. The pattern and amplitude of these pulses varies with pump configuration, specifically the number and size of pistons, as well as fluid compressibility factors.

It is precisely the fluid volume above mean on the discharge cycle of each stroke, which induces these pressure pulsations into a piping system. The number of pistons offered by the pump-given that all are of identical diameter and equally phased-displace a known peak volume above mean. These constants may be influenced by fluid compressibility, but for the purpose of this explanation we’ll assume none at this point. A pulsation dampener absorbs only that portion of piston displacement above mean flow, and then stores it momentarily before discharging it during the portion of the cycle below mean flow (on the suction stroke).

A simplex pump displaces a volume of fluid above mean that is equal to about 60 percent of total displacement. A duplex pump displaces a lower fluid volume above mean, approximately half that of a simplex pump. Pumps of three or more pistons of equal diameter, stroke length and proportionally phased will always present a very small fluid volume above mean to the piping system. A triplex pump, for example, produces about a 4 percent peak, as long as fluid compressibility factors and pump efficiencies are not at issue.

These smaller fluid volumes are accounted for by the crank angle of each of the cylinders. Triplex pumps are offset by 120-deg. Quadruplex pumps are set apart at 90-deg offsets; quintuplex pumps are offset 72-deg, and so on. It is the resulting overlap in pulses that yield the smaller fluid volumes above mean.

Fluid velocity gradients follow the same mechanical velocity gradients of the eccentric cam that drives the piston(s). Halfway through the piston’s forward travel (discharge stroke), fluid velocity between the discharge check valve and the pulsation dampener begins to decay. The corresponding drop in pressure causes the membrane inside the dampener to expand since the internal gas pre-charge pressure is now higher than the line pressure. The (stored) fluid now being displaced by the pulsation dampener maintains velocity downstream of the dampener thereby reducing, if not eliminating, any downstream pulsations.

Note: A pulsation dampener removes pulses only from the line downstream of the dampener-not upstream. That’s why it’s always recommended that discharge dampeners be installed as close to pump discharge nozzles as possible. In an application of a dampener for suction stabilization (reduction of acceleration head losses), it is the velocity gradient between the supply vessel and the suction nozzle that is minimized.

Let’s begin by defining the pump details required to properly size a pulsation dampener. We will use these values in a sample calculation to help clarify the process.

We recommend that the gas pre-charge pressure be set to 80 percent of system pressure. Lower pre-charge pressures may be specified elsewhere, but our experiences show that this is a low enough pressure to allow the membrane to move freely during operation while maximizing the gas volume. We will use 0.80 in the formula as the “% Pre-Charge” for 80 percent.

The result of the previous calculation is then divided by a constant. As noted previously, the constant is a function of pump configuration. We use a conservative 1.5 for simplex pumps, 2 for duplex pumps, and 7 for triplex pumps. Remember-if the fluid is compressible, then the constant may have to be adjusted downward.

Fluid volumes above mean are well within the range of these constants. The fluid pulse above mean flow from a simplex pump, for example, is about 60 percent. When we divide full stroke displacement by 1.5 the result is a conservative 67 percent. The divisor 7 that we use for triplex pumps allows for a nominal 14 percent fluid volume above mean. While 14 percent is far above the actual 4 percent produced by triplex pumps, the higher volume is an allowance for practical reasons, specifically size and nozzle limits. Otherwise, the result would be a very small dampener relative to pump size.

Ranges of (process) temperature and pressure must be considered in any sizing calculations for pulsation dampeners. Compensations must be made for temperature variations, which affect gas density, and dynamic variations in system pressure, since sizing is based on a set pre-charge pressure.

The objective is to select a dampener that is adequately sized to handle a range of operating pressures with a single pre-charge pressure. Remember that the gas pre-charge pressure should always be based on the minimum operating pressure as the pulsation dampener will have no effect when the system pressure is below the pre-charge pressure.

In instances of either (or both) temperature and pressure variation, we compensate by multiplying the result of our original calculation by the ratio of minimum and maximum temperature and pressure extremes.

Changes in ambient temperature can also influence gas density, but they’re generally disregarded for the purposes of pulsation dampener sizing. It is usually sufficient to make seasonal adjustments to pre-charge pressures, if necessary. Temperature and pressure calculations are recommended to be done using absolute values (Kelvin for temperature and BarA or PSIA for pressure).

Some fluids are highly compressible, such as cryogenics, olefins, liquefied gases, anhydrous ammonia, etc. In these instances, the benefit of lower pulsations from multiple piston pumps may be somewhat compromised. Fluid compression occurs during the leading edge of the (eccentric) crank angle. Given sufficient pressure and a high enough compressibility factor, there may be little or no overlap of pulses at all-in which case, adjustments have to be made and pulsation dampeners with larger gas volumes should be selected.

By installing a properly-sized pulsation dampener, users can reduce or eliminate pipe shake, vibration and noise. The result is a continuous flow of product which is required in many metering, mixing and spraying applications. Reduced pressure pulsations minimize long-term damage to instrumentation and pump components while improving the accuracy of many flowmeters and increasing pump efficiency.

The DA Series pulsation dampeners utilize a manual charge process, offer a flexible PTFE diaphragm that separates the liquid and compressed air chambers and can be installed in any position. Adjusting the inlet air pressure to the unit until the pump runs smoothly allows the dampener diaphragm to stroke at the same rate as the in-line AODD pump, effectively “dampening” the flow and discharge fluctuations.

DA pulsation dampeners are suitable for SANDPIPER ½" (S05) and ¾" (S07, S10) pump models and are available in polypropylene, PVDF, aluminum or stainless steel wetted housings.

The SANDPIPER TA Series pulsation dampener will self-adjust to application conditions by inletting or exhausting compressed air from the unit’s air chamber following application of full plant air (not to exceed 125 psi) to the tranquilizer. The pulsation dampener will automatically adjust to its optimum performance condition in order to maximize surge suppression, reducing both piping vibration and noise.

TA pulsation dampeners are suitable for SANDPIPER 1", 1½", 2" and 3" metallic pump models and are available in aluminum, cast iron and stainless steel wetted housings with various diaphragm (elastomer) options.