Many filter systems operate under the threat of a sudden influx of contamination that plugs the filter elements. Recently, water-absorbing elements have added to this concern. If no one is watching the differential pressure gauge at the time, you can burst the elements, with the dirt and debris going downstream and possibly into the aircraft. We designed the Gammon DP-Pilot so you can forget about element bursting or deck plate damage with any type of element, even the water absorbing elements.

In 1995, we wrote GamGram 44 showing that high differential pressure concerns could be erased by a unique mounting of a rate of flow control pilot valve. The solution is simple and elegant. The pilot senses the pressure drop on a vessel and, if that pressure drop exceeds a set limit, the pilot takes over, lowering the flow rate. Because pressure drop decreases as flow rate decreases, the elements can never burst.

We have now designed an all stainless steel pilot specifically for this purpose, and we are proud to offer the Gammon DP-Pilot. The DP-Pilot field test was performed at a US Air Force facility in early 1998. Their primary concern was that water-absorbing elements could rupture or the deck plate in the vessel could deform or tear. As a result of that test, this pilot was designated as required equipment on all US Air Force refueler vehicles.

We ran the test starting at full flow rate. The DP-Pilot had no detrimental effect on the system. We then added water to plug the water-absorbing elements in this truck’s filter vessel. As the differential pressure increased, nothing happened until it reached 20 psid (differential), our set point (this is adjustable). At 20 psid, the DP-Pilot took over, slightly lowering the flow rate. This kept the differential pressure from exceeding the set point. As we added more and more water, the pilot dutifully closed the main control valve more and more, lowering the flow rate and maintaining the 20 psid pressure drop. At the end of the test, the meter was barely moving, less than 1 gpm, yet the pressure drop never exceeded 20 psid!

Will it work with prefilters and filter separators?
Yes. Any filter vessel in a system that has an in-line control or slug valve if it has a pilot circuit can accept a DP-Pilot. You can even add two DP-Pilots to a slug valve downstream of a prefilter and filter separator combination. One pilot protects the prefilter and the other protects the filter separator.

What pressure drop ranges are available?
Our standard set point is 20 psid. On the basic model, this is adjustable from 15 to 35 psid. Other springs are available for ranges from 1 to 50 psid.

What is the maximum working pressure?
We recommend the maximum working pressure of this pilot to be 450 psi. There is no minimum pressure, minimum flow rate, or maximum flow rate. The maximum temperature is 250°F.

What brands is it compatible with?
The Gammon DP-Pilot works with Cla-Val, Whittaker, Brooks, Oil Capitol, Smith, Haar, Avery Hardoll, or any other brand of piston or diaphragm in-line control valve if it has a pilot flow circuit.

How is it installed?
Call us with your valve make and model number for an installation schematic.

When drawing a visual sample of fuel from the filter separator sump, you learn immediately whether or not there was any water in the fuel supply. If the fuel is hazy, the filter separator is not functioning properly. If it is clear and bright but liquid water is found in the closed circuit sampler, you can reason that the filter separator is coalescing the water, but you surely will want to check the source of the supply. Dirt particles indicate that the coalescers are not filtering properly.

Installation

In most sampler installations, the sample is taken directly from the flow stream after the filter separator or monitor. A light located behind the sampler is very useful at night. The condition of the fuel just before it enters the aircraft provides the operator with immediate information. Alternatively, some operations may prefer to check a sample of fuel from the filter separator sump to learn immediately if any water or particulate contamination was in the fuel supply.

Fuel enters the sampler tangentially at the bottom, creating a clockwise swirl to force particles and water to the center of the coned-down, white epoxy chamber bottom. Any contaminants are then easily seen. After inspection or testing, simply open the outlet valve to release the contents to the dump or slop tank.but the range has been reduced so they will fit in the Aljac sampler.

Hydrometers and Thermometers for Closed Circuit Samplers

Standard length ASTM hydrometers and thermometers are too long to fit the holders if it is desire to leave these instruments in place with the lid closed. For customers who want to leave them in place, we offer special short models as follows.

These hydrometers have shorter scales than are required for standard ASTM models. For example, in the metric models, the graduations are 2.14 mm apart for 1 kg instead of 2.59 mm for standard hydrometers. These thermometers have the same graduation spacings as for standard ASTM thermometers such as 12°C and 12°F but the range has been reduced so they will fit in the Aljac sampler.

See Bulletin 61 for product information.

In presenting all 33 colors and the 9 particle photographs on one 8.5×11” chart, our model SGTP-3940 provides convenience that has never before been achieved. Particle assessment is a requirement in section 2-17 of ATA-103, along with color rating. Particle rating is also specified in Section FO-6 of the United Airlines “Fuel Operations Manual.”

The color rating presenting is unique in that oblong windows of adjacent colors are provided so that the technician can more easily compare shades and colors. The filter membrane is placed under the chart, allowing the operator to see four different colors at one time for comparison.

The official ASTM color rating booklet, model GTP-1074-1, which we also produce, was designed so that it could be kept closed to protect the colors from soiling and contamination. This new chart is not provided with such a means of protection so it must be kept in a notebook. Standard 3-ring punchings are provided. For more information on the color rating book, see Bulletin 80.

Made entirely of stainless steel, these couplers are fully interchangeable with Flight Refueling models, as well as those available from A. Searle & Co.. Because we make the caps of aluminum, there is no possibility of thread galling as in other brands when the coupler is also aluminum. We used the Gammon tapered gland O-ring seal principle that has proven to be astonishingly reliable for the last 50 years in the Jet Test QD®.

In addition to the two basic models, we also offer each one with either BSP or NPT threads for installation on fueling nozzles. Refer to the chart below.

Jet fuel particulate contamination testing is performed to ASTM D2276 and IP-216. Conventional equipment on the market is not suitable for high pressures. This is because the plastic monitor is only rated for 100 psi. We have found a way to design a housing which allows testing using standard plastic monitors at up to 450 psi.

For replacement membranes and backup pads, see Bulletin 73.

For testing at pressures below 100 psi, see Bulletin 8.

The three-lug adapter is manufactured in accordance with MS-24484-2 and will accept any aircraft refueling nozzle made by Whittaker, Carter, Zenith, or Avery Hardoll. It will also receive 2 1/2” bottom loading couplers made by these firms but it is not available to accept the product selection feature. It will also receive any U.S. military refueling nozzle that is manufactured to MIL-N-5877.

The connection has a 3” NPT female thread and is made of type 6061 aluminum with an anodized finish.

A pressure sealing cap is included.