Industrial Utility Efficiency    

Universal Air & Gas Products Engineers NGV Refueling Stations

CABP: Good morning. Thank you for taking the time to discuss natural gas fuel systems.

UAPC: Glad to do it. Universal Air & Gas Products Corporation (UAPC) has decades of experience in gas compression, storage, dispensing, regulation and controls for natural gas fuel systems. We have been designing and manufacturing natural gas fuel systems through the many “roller-coaster” market cycles related to natural gas fuel systems.


CABP: Your firm certainly isn’t a typical “air house”. Please describe UAPC’s focus on designing and manufacturing gas packages.

UAPC: Since 1962, UAPC has worked with air or gas compression, filtration, drying and precipitation systems. These custom-engineered systems range from 0.002 Torr vacuum to 6000 psig. This is truly a “knowledge market” where clients value (often with their lives) our years of experience designing and building systems.

An example of this is breathing air systems. We supply SCBA refilling stations for fire departments and also support many SCUBA applications at 3000 to 6000 psig for OSHA Grade E breathing air. We also provide OSHA Grade D low-pressure breathing air systems ranging from 60 to 200 psig. Each situation is unique and demands customized engineering and high-quality fabrication.

Universal Air and Gas NorfolkLocated in Norfolk, we have long supported our military with a wide range of projects. Most are custom projects to support a unique application. We have a rental fleet of air compressors, for example, customized for the military. When a submarine docks for maintenance, the Navy requires a high-pressure, dockside, pier-power air compressor ready to be used in an explosion-proof environment. We have technicians working on military ships and submarines worldwide. For this, both UAPC and some of our technicians have been prequalified and have different secrecy clearances depending upon the project. In addition to our rental air compressors, we also have a fleet of CNG compressors available for long-term rent for the CNG refueling market.

This history led us naturally into other custom-engineering markets like medical compressed air, vacuum and blower systems complying with NFPA-99 standards. The alternate fuel compression systems market has also gotten us heavily involved with biogas, digesters, hydrogen, landfill gas, syngas, and wastewater applications.


CABP: The stories you could tell (but sometimes can’t)! Please describe UAPC’s overhead commitment required to support so many market segments requiring custom engineering.

UAPC: Sure. We’ve been called a “design and build” engineering firm. We’ve also been called a “Boutique Engineering” firm. We have seven engineers on staff. Many of us have strong backgrounds in chemistry and metallurgy. We work with our team of 3D CAD designers to meet customer needs in these unique packages. Once the client signs off, this software output goes to the production floor.

UAPC has a significant investment in manufacturing; we build everything in-house except for the ASME pressure vessels. We do all the fabrication in-house in our 51,000 square foot warehousing and manufacturing plant located in Norfolk, Virginia. Here we can cut, bend, weld and paint all the custom components engineered for each job. Our assembly area then puts all the components together as a complete package. Our engineers also program and build the PLCs and controls for each unit. If our customer needs a HMI panel with certain information displayed, we design it here in-house. Our systems are supported with SCADA with remote adjustment capability as an option.

A lot of companies subcontract this kind of work. It’s unique to UAPC that we do all this work under one roof. There is an advantage to having a “gas guy” designing the controls and building a PLC – specifically for a gas package.


CABP: Let’s talk about natural gas.

UAPC: Where do you want to start? We design 30 psi high-volume applications feeding co-gen engines, 600 to 1200 psig packages for shale gas, landfill gas, individual plant systems like a 275 psig system at a steam plant. In addition, we have many decades of experience designing and building natural gas vehicle refueling stations with pressures ranging from 3000 to 6000 psig.


CABP: OK. Let’s start with the macro situation. How do you view the future of the Natural Gas Vehicle (NGV) market?

UAPC: We’ve been involved with the compressed natural gas (CNG) market roller coaster ride for twenty years now. Historically, this market has been driven by government grants, causing the market to surge and then fade away. For UAPC, we’ve always had a certain volume of CNG business, but this is our third such surge in CNG activity.

This time, however, we believe is different. Now, we are seeing the vehicle and truck OEMs make great strides in vehicle reliability. They are also investing unprecedented amounts in NGV vehicle and truck design and manufacturing lines. This is in response to the extraordinary demand for energy independence in the U.S. This has contributed to a new (and we believe permanent) commitment to compressed natural gas by gas producers, infrastructure developers, vehicle OEMs, and consumers. We still have a long way to go, but we think NGVs are here to stay.

Beyond energy independence, CNG is a win/win for air quality, job creation, and business finances. For example, Waste Management recently announced they are converting their entire fleet of garbage disposal trucks to CNG. They say a typical garbage truck is saving $200 per day on fuel – that’s a huge financial impact for a company of this scale – and there are greatly reduced emissions. It’s a bonus for everyone.


CABP: What topics are on the minds of your customers investing in the NGV infrastructure build-out?

UAPC: To provide the anticipated build-out of NGV refueling station infrastructure, industry experts are projecting a remarkable growth rate of forty percent per year for the next five years.

We work with two very distinct buyer groups -- municipalities and private investors. Municipalities operate fleets of school buses and garbage trucks. Private investors are building convenience-store or stand-alone NGV refueling stations. They have different motivations and challenges.

Municipalities operating school buses and garbage trucks have a defined demand for fuel that is easy to forecast. Here we deal with a municipal-fleet manager who remembers seeing his fuel budget disappear when diesel and gasoline prices spike. Many municipal-fleet managers we speak to talk about 2009 when their yearly fuel budget had been depleted by the month of May. They want to reduce fuel costs but even more importantly, they want a stable fuel cost. They believe the advancements and expansion of natural gas exploration--in the U.S.--will provide them with a long-term, low-cost, stable fuel supply situation they can budget for.


Refueling System

Twin 125 horsepower compressor packages with inlet desiccant dryer for large time-fill NGV Refueling System for Refueling Transit Buses.


The second distinct buyer is the private investor building NGV refueling stations into existing convenience stores or building stand-alone NGV stations. This is where the ROI scenario is important. If you are a fuel retailer, natural gas is attractive to sell due to higher profits per gallon. These guys are used to making a nickel ($0.05) profit per gallon sold. With natural gas, profits are said to average $0.75 cents per gallon equivalent. This provides the motivation to invest.

A big challenge and risk area for these investors, however, is to forecast demand. You hope to have anchor fleets using your station, but this isn’t guaranteed. In a convenience store, how many NGVs will pull in to refuel? This is a tough question for forecasting. UAPC works with investors on their forecast models, and then we help them design the “supply-side” NGV station that best match this forecast. This is a highly consultative process, often requiring several years.


CABP: Please describe the time-filled NGV refueling stations you design.

UAPC: Our philosophy is to help customers design NGV refueling systems able to satisfy their current demand – but that are modular so that when demand grows they can easily add capacity to their system. This is often the most efficient use of their capital. Many times we talk to clients who have been told by others to design for maximum future demand. Our position is that until these larger stations reach full utilization, their ROIs will fall short of investor expectations.



Twin-hose fill-posts for overnight refueling of a gas utilities' NGV service fleet.

There are two fundamental types of NGV refueling systems. One is a time-filled system, and the other is a fast-fill system.

Time-filled (also known as “slow-fill”) systems use a simple fill-post and are for anchor-based fleets. A municipality or private-fleet operator with garbage trucks may have twelve hours available to refuel overnight. That’s simple to do, as they have a defined demand and refueling time period. We do help these fleet operators answer questions such as, “What are the conversion (to CNG) costs for the trucks? How much fuel does each vehicle hold? How much does each truck consume per day? How much fuel will be required during refueling per truck? How much time is available for refueling?” These questions will drive system characteristics including inlet gas pressure, discharge pressure, gas storage and throughput required.


CABP: What are fast-fill NGV refueling systems, and what are some of the design considerations?

UAPC: A normal gas station or convenience store will use a fast-fill NGV refueling station. Cars and trucks pull in to refuel and are on their way. Time is of the essence for these customers, so we have to focus on delivering sufficient flow and pressure of natural gas-on demand. A fast-fill system, allowing customers to fill their tanks in three or four minutes, uses a low, medium and high-bank storage system feeding into the dispenser. The gas dispenser looks just like a regular dispenser, except it’s a “smart” dispenser that knows which storage bank to pull gas from. As the vehicle fills, the dispenser knows to change supply pressures by switching supply banks. The target pressure is normally 3600 psig. When gas flows slow, and we are below our target pressure of 3600 PSIG, the dispenser switches to the higher-pressure storage bank to reach our target pressure in a timely manner.

An important factor here is storage. You can install smaller compressors (and spend less capital) if you have space for storage. Many convenience stores, however, do not have space, so they need a larger flow compressor to maintain the required fill time.


Gas Storage

Compression, storage and drying equipment supplying CNG fuel for a public access station.


As an added service, UAPC offers our customers a fully enclosed compressor. This option provides gas stations and convenience stores a way to protect their equipment against hot summers and cold winters. We design enclosures with both ventilation and freeze protection. Other important reasons to consider enclosures are noise suppression, increased safety and protection against vandalism (with locked access doors). Most of our customers choose enclosures that are design-neutral, while others have developed special designs to highlight their CNG service. Better than half the systems we design are fully enclosed.


CABP: Please discuss temperature compensation and sequencing controls in NGV fueling stations.

UAPC: Two primary NGV fueling system control components are temperature compensation and sequencing controls. Gas will expand or contract depending upon the ambient temperatures. Fast-fill stations are subject to tremendous temperature swings during the fall and spring each year. UAPC controls imbed programming, which is constantly reading ambient temperatures and calculating what variations in pressure need to occur. The software will calculate, at a given temperature, what our fill-pressures should be.

Sequencing controls determine which bank is filled first, second and third. Natural gas station storage tanks are generally rated for 5500 psig. Our systems provide for a 1000 psig buffer because we can easily see a 500-600 psi swing in pressure due to changes in ambient temperature. The last thing we want to do is to over pressurize the storage vessels. Nobody wants to see (or hear) a relief valve actuate at these high pressures!


CABP: Motor drives and controls--what are the design drivers with NGV fueling systems?

UAPC: Some clients want electric drives while others want natural gas engines. Most use electric drives if they have available power. A key thing to remember here is that this unit will most likely be, by far, the biggest power consumer on site. A convenience store has some refrigeration compressors and a municipal warehouse may have an HVAC system with fan motors. However, these don’t compare to larger horsepower motors on the CNG compressors! In eighty percent of the cases we see, the natural gas compressors are the biggest energy consumer--by far.

One of our main design objectives, therefore, is to minimize the peaks in power demand when the compressors start. Peak demand on two 50 hp motors, for example, can total 350 amps--similar to what is seen in small manufacturing plants. This kind of in-rush spike can really impact a facility’s energy bill. We have a customer in South Carolina who owns a landfill and operates a fleet of 17 CNG trucks. He has a time-fill system. They plug in at the end of day, and in the morning they are full and ready to go. The owner called saying his local electric utility was about to implement a change, making his peak demand period between 3 and 8 p.m. This meant his demand charge was going to occur exactly when his consumption was the highest. Our solution was to modify the PLC controlling the compressors so they wouldn’t turn on and begin the refueling process until after 8 p.m.


Refueling Station

Public access NGV fast-fill refueling station.


On fast-fill systems, you want the compressor to give all you can - as fast as you can get it. Case specific, our designers will use Wye delta starters and/or variable speed drives to avoid the demand peaks when you start the motor.

Another thing we do to control power consumption is to use a modular approach. Other suppliers will put in one large motor with one large compressor. We break it up into smaller modular systems using, for example, twin 50 hp compressors with staggered starts to reduce the inlet rush (using Wye delta starters) instead of one large 100 hp compressor. Most suppliers will size the gas compressors based upon a theoretical peak demand level and put in one unit able to satisfy the demand, disregarding peak energy consumption concerns.


CABP: How do you control moisture levels in natural gas?

UAPC: Gas quality is an important factor when designing a system. Depending upon the age of the pipeline, gas can be a lot wetter in some areas of the country than others. Saturated (laden with water) natural gas on the suction (inlet) side of a gas compressor can cause breakdowns and problems with the vehicle’s fuel delivery system. Dry gas is a must for a reliable NGV refueling station.

As noted, the moisture content of inlet gas will vary. Because gas moisture content can change, gas dryers are required to ensure a predictable high quality gas to the vehicle. Typically, you can get the gas company to give you a gas analysis to size a gas dryer properly. The specification for municipal gas is seven lbs. of water per million cubic foot. That’s pretty dry. In ninety percent of cases, the dryer isn’t doing much work. The gas quality is pretty good--normally.

On lower flow machines (75 cfm and below) we often use cartridge type dryers using molecular sieve adsorbents. These cartridge-type dryers are installed on the high-pressure discharge of the compressor. On larger systems, we typically use suction side low-pressure dryers that are placed just after the gas meter coming into our system. The gas is then dried before coming into the compressor.


CABP: What are some challenges facing the NGV Industry?

UAPC: The lack of predictability and long-term visibility with federal regulations and government tax incentives. For example, the automotive industry looks long-term at things like the 2015 Emissions Standard, which is the current standard. However, if you are Ford, and are thinking of new CNG vehicles and production lines, you want to know what the Emissions Standard will be in 2025.

The 3800 series of federal tax incentives were set to be discontinued--but then on the last day of the year, they were continued. We lost a whole year because they didn’t reinstate the tax incentive until December 31st, and investors decided to hold off until they knew what the future looked like.

Another challenge facing private investors interested in investing in NGV infrastructure is the competition from natural gas companies. Some of these companies have installed their own refueling stations and are selling natural gas at very low prices so that they can secure gas-supply contracts. Selling gas at $1.18 (an equivalent gallon) is not something on which a private investor can make a decent ROI, and this is impacting investment in some geographies. There are a couple of gas companies that have gotten into the dispensing business. They will finance the whole site construction, with a “take-or-pay” contract, which can be a high risk for the investor.

Despite the challenges, the future is clear. Our country’s thirst for energy independence, which supports job creation, a strong economy and our national security, has never been higher. Universal Air and Gas is at the forefront of this critical change to an abundant, low-cost alternative fuel.


CABP: Thank you for your insights.


For more information please contact Universal Air & Gas Products Corporation at tel: 800-326-8406,

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