Category Archives: Dave’s Corner

who’s to blame?

By David Hollen, Technical Engineer

Frequently a customer will state that they have short pump lives and immediately the blame is placed on the pump. However, often it is not a pump problem at all, but rather a system or operational problem.

Generally, when someone mentions this it is not uncommon to associate the problem with the hydraulic conditions. In fact, oftentimes the issue is not on the liquid side of the pump at all, but instead it is a problem with the air supply.

There are two types of common air supply problems; contaminated or dirty air and air starvation. Just as we need clean air to live, so does a pump. If the pump is clogged with dirt and debris it will be starved for air and not perform properly.

The best way to keep your pump clean from dirty air is to install a filter regulator (Figure 1). A filter regulator is easy to install and provides the precise pressure control necessary to optimize pump performance and efficiency, at the same time preventing airline contaminates from reaching your pump.

Figure 1: Filter Regulator

Yamada offers a wide selection of filter regulators specifically selected for optimal performance with your pump (see chart).

Filter Regulator & Yamada Pump Chart

Filter Regulator Pump Series
FR-1, FR-1A NDP-5/15/20
FR-3, FR-3A NDP-25/32
FR-4, FR-4A NDP-40
FR-5, FR-5A NDP-50/80
FRL-2, FRL-2A DP-10, G15
FRL-4 XDP-40
FRL-5, FRL-5A XDP-50/80
A = auto drain

The photo below (Figure 3) is a diagram of a proper Yamada pump installation.

Figure 3: Yamada Pump Installation Diaphragm

The second main air side problem, air starvation, can be caused by several factors; a dirty air filter, a partially closed valve, an undersized airline/fitting or an undersized compressor.

The best way to check if you are experiencing air starvation is to observe the air pressure gauge mounted near the pump. If there is not any swing in the gauge needle when the pump strokes, then you have a very good air supply. A swing of 10% is acceptable. If you get a wide swing, such as 70 PSI to 40 PSI, then the air supply may not be adequate, and the pump is starving for air.

Yamada Filter Regulator Video

If you are not receiving the proper air supply from your filter regulator, start by cleaning the air filter and check that the valve is clear of debris. Additionally, make sure you have installed the proper size airline, connections and air compressor.

If, after taking the necessary steps, you continue to have performance issues, contact your Yamada distributor for further assistance.

Dave’s Corner: DP-15 Pump vs. NDP-15 Pump

When someone asks me about a Yamada 1/2” pump, most people think about the NDP-15 series pump. However, there is another option called the DP-15. This pump uses the NDP-15 polypropylene liquid side, but uses the DP-10 air section.


The DP-15 is only pump available with a polypropylene liquid end and has the same elastomer options as the NDP-15 series pumps. Be advised: there is a significant difference in the maximum flow rates. The DP-15 series has a maximum flow rate of 7.4 GPM, while the NDP-15 series has a 13.5 GPM maximum flow rate.


While the NDP-15 series is good for higher flow rates, the DP-15 is ideal for low flow rates, extended dead head and dispensing applications. Both pumps share a common liquid end kit, but require different air motor kits. The DP-15 uses a K115-AM air motor kit and the NDP-15 uses a K15-AM motor kit.

Dave’s Corner: Shaft Cushions

Lately we have seen several pump failures due to improperly installed shaft cushions (p/n 770582). We have noticed that the problem occurs when a shaft cushion is installed in a pump that does not require it.

For instance, the shaft cushion is used on all NDP-40 and NDP-50 pumps with rubber diaphragms, including Santoprene® and Hytrel® elastomers. However, the shaft cushions are not to be used on NDP-40 and NDP-50 pumps with PTFE diaphragms or any NDP-80 series pump.

The purpose of the shaft cushion is to prevent the center disk from impacting the air chamber wall when operating at the far right of the performance curve. This isn’t an issue with the NDP-40 and NDP-50 pumps outfitted with PTFE diaphragms because the pumps are destroked and will not travel far enough to impact the chamber. This can, however, happen with the NDP-80 series pumps. A shaft cushion cannot be used because it will interfere with the center disk as it makes contact with the pilot valve.

Lastly, if you have a rebuilt NDP-80 pump and cannot get it to cycle, check to see if it was rebuilt (incorrectly) with shaft cushions. Below is a quick reference guide to follow when determining whether you can install shaft cushions in your pump.

shaft cushion

Dave’s Corner: AD Dampener Flanges

Often, we get a request for a Pulsation Dampener with ANSI Flanges, rather than the standard NPT port. Yamada only offers the ANSI Flange port option on the AD-25 and AD-40 series dampeners. We do not offer ANSI Flange ports on the AD-10 and AD-50V Kynar® series dampeners.
In addition, the ANSI Flange on the Aluminum AD-25 and AD-40 series dampeners is a threaded companion flange that is Loctited in place (see image).

flange dampener

All other available flanges will be fabricated. Please consult Yamada for pricing.

Dave’s Corner: Metal Finishing

In addition to our standard product line, Yamada offers a variety of surface finishes for our stainless steel pumps. These finishes are primarily used for food, pharmaceutical and high purity applications. Our FDA Series of pumps come with an electro-polished finish (reference figure A).

The process involves immersing the part in an acid bath, then an electric current is introduced to help pull out the in the stainless steel, removing surface contamination and leaving the part with a shiny finish.

Additionally, Yamada can also mechanically polish any stainless steel pump that is 1” of size or smaller. This process helps to remove the porosity from the stainless steel. Parts can be polished to either a 20 RA finish (180# grit) or a 10 RA finish (320# grit). The 20 RA finish is typically used in the food and pharmaceutical
industries; whereas the 10 RA finish is primarily used for semiconductor applications. Yamada pumps that are considered electro-polished are first mechanically polished.



  • Electro-polished – acid dip with electrical
  • Passivated – acid dip, no current applied
  • Mechanically polished – uses mechanical action to remove porosity from surface
  • 20 RA finish (180# grit) – food and pharmaceutical
  • 10 RA finish (320# grit) – semiconductor

Dave’s Corner: AD Dampener Control

Yamada makes an automatic pulsation dampener, known as the AD Series Dampener. The AD Series Dampener is self adjusting and runs off the same regulated air supply that powers the pump.

In most situations, the dampener does not need an air regulator of its own. However, there may be times when a separate air regulator for the pulsation dampener is helpful.

An example of this would be using an NDP-40BAN with an AD-40AN pulsation dampener. When running at 90 GPM at 50’ TDH (22 PSI) the air requirements are 100 PSI air pressure and 100 SCFM air volume.

dampener diagram

Running at that point on the performance curve generates a difference between the air pressure and the discharge pressure of 78 PSI. With the differential pressure being that high the dampener will consume more than the normal amount of air.

The solution to the pulsation dampeners high air consumption is to install an air regulator in the dampener air line (see Fig. 0.1). We recommend setting the dampener air pressure 10% above the discharge pressure. So with a discharge pressure of 22 PSI, adjust the dampener air pressure to 24 PSI.

Dave’s Corner: High Pressure Pumps

The installation of a Yamada high pressure pump is the same as a standard Yamada Air-Operated Double Diaphragm pump. The bottom port is the liquid suction; the top port is the liquid discharge, etc. The main difference is the pumps ability to generate twice as much discharge pressure as air pressure, a 2 to 1 ratio.

If using hose or light duty piping on the discharge of a high pressure pump, you must make sure that it will be able to stand up to the higher discharge pressure. High pressure pumps will generate more pulsation than a standard AODD pump. With this in mind it is recommended that a suction stabilizer and a pulsation dampener be used with any high pressure pump.

The sizing of a pulsation dampener for a high pressure diaphragm pump is different from a standard AODD pump due to the fact that a high pressure pump is a simplex pump, rather than a duplex pump. The working volume of a pulsation dampener for a high pressure pump should be 5-10 times the working volume of the pump. When using a high pressure pump, you cannot use an automatic dampener. You will need to use a manually adjustable or chargeable dampener on the discharge side and chargeable only on the suction side of the pump. In place of a pulsation dampener, a stand pipe may be used. Consult Yamada for help in selecting the proper dampener.

high pressure pump performance curve

High pressure pumps are available in metal only.
These pumps are available in the NDP-20 (3/4”) series size and larger. PTFE diaphragms are not available in the high pressure pumps and a shortened diaphragm life should be expected. For questions or technical assistance, please contact Yamada.

Dave’s Corner: XDP Pump with Cycle Counter

With the introduction of the XDP Series pumps we needed to use a proximity sensor other than the P1 and P2 sensors used on the rest of the Yamada product line, which sense the position of the C-Spool to count the cycles of the pump.

The P1X does not sense the air valve position. Rather, it senses the pressure shift that happens internally when the air valve in the pump shifts.

PIX sensor

Please contact Yamada technical services for further information.

Dave’s Corner: Diaphragm for NDP-20/25 Series Pumps

In August of 2008 the NDP-20 / NDP-25 series pumps came with a new style diaphragm which has an o-ring molded into the air side. This change was made for two reasons:

To prevent air leaks where the diaphragm contacts the air chamber. To prevent a diaphragm from pulling out of place if there is excessive air pressure.

On the thermoplastic diaphragms (TPO, TPE, PTFE), there is no o-ring molded in the diaphragm. Instead a separate o-ring is used to fill the o’ring groove in the air chamber wall.

The new style diaphragms cannot be used in the old style pumps, however the old style diaphragms can be used in the new style pump when used with the air chamber wall o-ring. The old style diaphragm will continue to be available for a few more years.

new diaphragm

Dave’s Corner: Proximity Sensor

Proximity Sensors can be provided on almost any Yamada pump. They are used to send a signal every time the pump completes a cycle. This signal can then be used to count cycles for preventative maintenance. It can also be used to monitor flow rate.

When used for one of these purposes the signal is usually sent to a basic digital counter that has no control capability. In addition to giving a totalized readout in cycles it will also be able to totalize in any engineered unit, such as gallons, cubic feet, cubic meters, liters, etc.

Most basic counters will also be able to give a readout in GPM, L/M, or other flow rates. When using a proximity sensor with a PLC and a solenoid in the air line you can also perform batch metering. In other words, you can pump to a predetermined amount and have the pump shut off at that predetermined amount.

The proximity sensor comes in two configurations. Please consult Yamada America for more information about proximity sensors and their use.

-P1 ISA 10-30VDC 3 wire unit
-P2 ISA 24-240VAC 2 wire unit

proximity sensor