Overview of Volumetric Hydro-Testing

Volumetric Hydrostatic Testing

July 17, 2007

By Charles Grenci, President

1. The Basics:  A condensed primer providing an overview of the procedure and equipment.

Do you remember when Jaws lost its appetite when a SCUBA cylinder failed the gunfire test? The myth busters demonstrated that what happened to Jaws could happen to anything or anyone in proximity to a compressed gas cylinder when it suddenly fails to contain the pressure inside. If the cylinder failure is in proximity to other pressurized cylinders, a domino effect can create multiple powerful explosions. It may be helpful to have some kind of information about just how much energy is contained in a compressed gas cylinder to give people an appreciation for the value of testing them periodically.

Fortunately compressed gas cylinder accidents are rare in most places.  We at Galiso Incorporated are thankful that we have had the opportunity for 45 years to participate in the process of testing compressed gas cylinders around the world. People use the equipment that we make to verify that gas cylinders can safely contain the pressurized gas that the cylinder provides. The equipment we make is used to verify that a cylinder is safe to use by measuring the growth characteristics of a cylinder that is pressurized beyond its normal working pressure.

Compressed gas cylinders are designed with a safety factor that is measured by our equipment in the following way. A compressed gas cylinder is pressurized with water to a pressure that is higher than its normal working pressure where the cylinder may: A) do nothing which is the best case, B) stretch slightly within the required tolerance, which is acceptable, C) stretch beyond the tolerance, which fails the cylinder from service, or D) explode inside the test jacket. The test jacket is designed to safely contain the force of the hydrostatic explosion. The force of a hydrostatic explosion or burst is minimal compared to a pneumatic explosion due to the use of water, not air as a pressure medium. This is due to the minimal compressibility of water vs. the highly compressibility of the gas that the cylinder normally contains.

Cylinders should receive a complete external and internal visual inspection prior to a volumetric hydrostatic test.  A typical volumetric hydrostatic test (VHT) is comprised of the following steps:

1. De-valved and filled with water
2. Connected to a test jacket sealing apparatus and placed inside a test jacket that is full of water.
3. The temperature of the water inside the cylinder and outside the cylinder in the test jacket should be verified to be within 4 degrees F of each other, or the test results will be affected.
4. The expansion zero value is established (fig 1).

Figure 1 VHT Zero Point

5. The pressure inside the cylinder is raised to the required test pressure for a required time, causing the cylinder to grow in size. The cylinder expansion at test pressure is then recorded (fig 2).

Figure 2 VHT Pressure Hold / Total Expansion

6. The pressure is released and the cylinder should return to a required percentage of its original size. When the de-pressurized cylinder expansion is stable, a permanent expansion value is recorded (fig 3).

Figure 3 VHT De-pressurized / Permanent Expansion

7. The cylinder is drained of water and dried.
8. The cylinder is then re-valved and stamped.

The amount of water forced out of the test jacket as a result of the cylinder's growth during the pressurization is measured in an expansion measuring device and compared to the amount of water left in the expansion measuring device when the cylinder is depressurized. The amount of water left in the expansion measuring device corresponds to the amount that the cylinder was permanently deformed by the test pressure. Generally, if the cylinder returns to within 10% of the amount it expanded while pressurized, the cylinder passes the test.

Cylinders that pass both the visual inspection and the hydrostatic test may be stamped with the re-qualification marks, and can be charged and offered for transportation for 3-10 years depending on the type of cylinder. The pass/fail criteria for some cylinders differ. As an example most composite cylinders must return to within 5% of the amount they expanded.  However, the new carbon fiber composite cylinders fail based on their elastic expansion. When a cylinder exceeds the expansion limits for the retest, it indicates that the cylinder has yielded, and the cylinder must be condemned.

This type of test procedure is often referred to as "hydrostatic testing" or "hydrotest". Technically there are many types of hydrostatic test applications that are unrelated to the cylinder test described above so for the purpose of this article we will refer to this type of testing as "volumetric hydrostatic testing" or “VHT”.

 2. The Benefits: Why choose volumetric hydrostatic testing vs. ultrasonic testing (UT)?

The answer to this question is multi-faceted and so we will attempt to answer this question in more than one way.

First, in many applications VHT is required by government or industry regulations so there is no choice. There are regulations that apply to cylinder manufacturing that require 100% of all manufactured high pressure cylinders that are greater than two inches in diameter to be tested by VHT to meet Department of Transportation (DOT) regulations.

Second, there are certain types of cylinders that ultrasonic equipment cannot test for defects at the present time. Composite cylinders are a fast growing segment of the cylinder business in applications like self contained breathing apparatus cylinders, medical oxygen cylinders, aviation cylinders, CNG and Hydrogen fuel cylinders, paintball gun cylinders etc.  Light weight is a primary advantage of composite cylinders. There are ultra-light type 4 CNG cylinders that are constructed from a thin plastic bladder with a small metal gas connection boss and then wrapped with carbon fiber. In a composite cylinder, the fiber wrap does most or all of the work of containing the force of the internal cylinder pressure. Trying to find a flaw in the composite structure with UT would be like trying to find a needle in a haystack. This is an example of a cylinder application where VHT is required for both manufacturing and re-qualification testing.

Some readers may want to know why Galiso does not offer UT equipment for testing cylinders. The answer to this question is multi-faceted as well. Shortly after my father, Carl Grenci, passed away in 1980, I came back to work at Galiso. My father was very involved in CGA and my mom and dad were involved in IOMA, NWSA and NAFED. At the age of 21 I was able to sit in for my dad at CGA meetings with some guys that were pillars in the industry like Ralph Tribolet of Union Carbide, Milt Hillegas of Air Products, etc. I also began attending IOMA meetings with my mom, La Nora. At one of the first IOMA meetings that I attended with her in Palm Springs, one of the speakers gave a presentation on how acoustic emission (AE) testing would replace volumetric hydrostatic testing as the preferred method of testing compressed gas cylinders. One of this speaker's main points was that pressurizing a cylinder to 5/3 of its service pressure damages the cylinder. So we loaded up the bus and headed to this man's company to see if we could offer this kind of equipment that would replace volumetric hydrostatic testing.

It would be interesting to find out how many companies there are that have an exemption to test cylinders with AE today. It is also noteworthy that there are many cylinders that are still in service from the early 1900's, so his comment about 5/3 test pressure damaging a cylinder might be questionable.  We responded to a later IOMA call for speakers and I was able to present "Automating the Process of Hydrostatic Testing" at the Maui meeting. The video version of the presentation is available at our web site. Later, Galiso became involved in producing automated gas filling equipment for
ultra high purity (UHP) semiconductor cylinder gases and these developments led to another IOMA presentation, "Visual Information Technology," about the use of computer graphics in gas industry applications. The work that we did in this area led to our involvement in the semiconductor wafer fabrication industry and many of the control concepts and capabilities that the Recortest 4 (R4) systems have came out of this work.

Later in the early 1990's UT came on the scene as a potential replacement for VHT. FIBA obtained an exemption to perform UT on cylinders and began offering licenses to customers who were interested in the potential cost savings that UT can provide. Airco, Dapco, and Galiso submitted a joint application for exemption to DOT and were rejected. Dominic Pagano of Dapco is the inventor of the liquid filled wheel that is used to perform UT on railroad rails. This was the second time we tried to get on board with a technology that was going to replace volumetric hydrostatic testing. Things got real interesting when the DOT sent up a test balloon saying that VHT would no longer be an acceptable method and all cylinders re-qualification would be UT. In a real life "Mr. Smith goes to Washington" Darrell Garton went to Washington and pretty much single handed slew Goliath. In his wonderful way, Darrell confronted the powers that be with some basic facts that they were not able to legitimately address.

Having been rejected by DOT, Galiso sat on the sidelines of the UT playing field and watched FIBA and others run their plays. The first "real" machine that I saw for performing UT on cylinders was created by a pair of guys named Mike Gorman and Steve Ziola of Digital Wave. They created a very viable UT machine and then sold the rights to a company called SCI (not the cylinder maker) which made a real mess of things, and now I believe that Mike and Steve have bought back the rights to the product and are back in the cylinder re-qualification business. If Galiso ever does offer a UT product, I hope it is in cooperation with Mike and Steve. It is noteworthy that they are experts in both AE and UT. Their site address is www.digitalwavecorp.com.

We nearly partnered with Digital Wave, when an opportunity came along to provide Thunderbird Cylinder in Phoenix, which already had an exemption to test cylinders with UT, with a Rec4 system. This was an opportunity to see if we could achieve higher throughput and overall efficiency with VHT in what I believe is the best potential application for UT, medical aluminum cylinders. One criticism of VHT is that it will not find a crack that does not propagate during the test. There are many medical aluminum cylinders that were made with an inferior alloy that have neck cracks. UT can spot these cracks if the equipment is set up to do so, but I think that most UT equipment is still only configured to check the cylinder side wall. We were able to create a system that is capable of completely processing 80 medical aluminum cylinders per hour with 4 test operators. With our latest adaptation of this configuration I believe that we will be able to test 60 cylinders per hour with 2 test operators. It will be interesting to see how this compares with best-of-class UT systems.

UT is not an actual strength test. In the case of heat treatment damage this is a major problem because sometimes cylinders are in fires or people use baked paint finishes that destroy the heat treatment properties of the cylinder. UT and Eddy current will not catch a soft metal problem which is one reason why VHT is required in manufacturing to check the performance of the heat treatment operation.

Perhaps this analogy is appropriate. You need someone to lift 100 pound boxes so you A) send him in for a UT test and the results show that he has muscles that are big enough and are free from any detected flaws. The problem is muscle mass and muscle power are variable and with any imaging equipment some flaws go undetected. The same size vs. strength issue is true of materials like steel and aluminum, or B) ask him to lift a 160 pound box and he can..... this Very Heavy Test proves they can readily lift 100 pound boxes as long as they are not injured lifting 160 pounds.

UT is accepted as a replacement for VHT by exemption only. UT is not an approved cylinder test method even after over 10 years in the exemption phase which is noteworthy. 

3. The Position VHT and UT occupy in the market

The U.S. DOT currently lists 34 facilities that are performing UT out of 2411 re-testers. UT has some tremendous cost savings potential for the cylinder industry. The problem is that UT does not actually strength test the cylinder to establish a safety factor. Not having to de-valve, then fill, then test, then drain and dry, and then re-valve is a significant advantage of this technology over VHT. 

There are some applications where UT really shines, like specialty gas cylinders where the contents are dangerous and the process of VHT is impractical. The statistics above show that UT has not become widely accepted as a method of cylinder re-qualification. It is noteworthy that UT has been in the exemption phase for over a decade with a low number of facilities performing this type of test.

4. New innovations: Our company’s latest technical developments.

We are in the beginning stage of introducing the Recortest 4 series as a standard product. We have been developing this product series with beta customers for two and a half years and the recent Rec4 installations in Japan demonstrated to us that the products are now ready for a wider audience. Final development aspects that are now complete are:  A) the database for machine settings and test results, B) operator interface standards to display information for the variety of test operations that the Rec4 is able to control, C) screens for calibration, test cylinder data entry, pressure and expansion graphs that can rewind and display history, system diagrams with instrument values and valve status, and a pre-test data entry form allowing for entry of visual inspection information and Pass/Fail of “Eddy Current” test results (figs 4-10). For safety, system interlocks and EMO are standard features of the Rec4 control.

Figure 4 Rec4 VHT Calibration Screen

Figure 5 Rec4 VHT Data Entry Screen

Figure 6 Rec4 VHT Pressure & Expansion Graph Screen

Figure 7 Rec4 VHT Results Screen

Figure 8 Rec4 VHT Diagram of System Status Screen

Figure 9 Rec4 VHT Visual Inspection / Eddy Current Test Screen

Figure 10 Rec4 VHT Mfg Cylinder Weights Screen

The Galiso programmable logic controller (PLC) network control, working with the Galiso operator interface that runs on Microsoft Windows XP operating system, leverages the communication capabilities of the internet (figs 11 & 12). When connected to the internet, the Rec4 offers remote support capability. We are able to operate, service, and support networked R4 systems from our office in Montrose, Colorado USA. This capability has allowed us to provide a higher level of software support than ever before.

We are often able to accommodate a software change request from our customers in one day. In the beta development cycle this capability has allowed us to report bugs on a foreign installation and have them fixed while we sleep, thus enabling our technicians to be ready to test when they arrive to work the next day. The video camera on the Rec4 allows users to make free video calls to other camera-equipped computer users worldwide. This free communication medium has been a real asset in building meaningful customer relationships. The quality of video calls has improved steadily during the Rec4 beta timeframe. The Rec4 offers bar code capability, thereby allowing easy entry of cylinder information to increase the accuracy and speed of data entry.

Figure 11 Galiso Network PLC Control for Lam PTX Alliance

Figure 12 Galiso Network PLC Control for Lam PTX Alliance up close

Automatic email and verbal communications, test results, and error messages are automatically generated and sent to a distribution list. Automatic emails make it easy to keep track of system operations.  Messages are also announced on the Rec4 sound system as verbal messages. The voice of our programmer, John Okulski, is becoming well known with Rec4 users worldwide who are learning, among other things, that the Rec4 knows when they try to start a test with missing cylinder information.  Alternate verbal messages can easily be recorded on the Rec4 system in the test operator’s native language. Test results are simultaneously recorded in a local database and also in a remote database. The remote database can be any valid network location. This allows test information from multiple test shop locations to be automatically recorded in a central location.

We have employed 3D solid modeling software in the design and development of the Rec4 control console and test station options (figs 13-16). We hope to offer many advanced service features with the solid models to our customers, such as enhanced training images to help them understand system operation and function, and also 3D Solid model parts identification for repair and maintenance. Models are easily viewed from any angle or magnification.

Figure 13 Recortest 4 Control Console 3D Model

Figure 14 RSP-10DA VHT Pressurization Module and RSP-25DA Burst Pressurization Module

Figure 15 Automated VHT Station for Small Cylinders

Figure 16 HFP-8k Cycle Test Pump Module

5. Growth areas: New applications and geographic targets.

Our traditional product line is focused on the needs of cylinder re-testers worldwide, and this still remains a primary market segment for our company.  However, there have been significant orders from cylinder manufacturers around the world for the Rec4 PLC-controlled systems due to the Rec4's ability to provide multiple hydrostatic, cycle, and burst test modules that can operate simultaneously, providing increased efficiency and productivity.

Airline servicing centers worldwide that wish to service airlines under the jurisdiction of the Federal Aviation Administration (FAA) must test according to U.S. DOT regulations. Therefore, most of the world's airlines are a primary target market for VHT.  In this market segment, we have a truly global market wherever reliable air transportation is involved.  We hope that the network control capabilities of the Rec4 will be desirable in this market where quality documentation of testing procedures and results is an important requirement.

We have VHT systems in over 100 countries worldwide, and this existing customer base is a target market for those customers wishing to upgrade their existing systems to incorporate Rec4 technology and capabilities into their current testing stations. We plan to introduce Rec4 PLC-controlled upgrades this summer to customers all over the world. The Galiso Recortest 3 generation of VHT technology was first released in the 1980's, so we hope that the Recortest 4 series of hydrostatic testing products will provide significant benefits to our customers, and that there will be good demand for Rec4 systems and upgrades to both new and existing customers worldwide.

As we have mentioned earlier, composite breathing air cylinders come under regulations that require VHT testing, so VHT is the testing standard for these types of cylinders. We have a new automated loading system that provides for simultaneous testing of four cylinders, including automated filling and drying stations that are all enclosed in a multiple filtered water recirculation station. This all-inclusive automated system is in operation at three cylinder manufacturing sites and is providing great efficiency gains and high throughput with reduced labor requirements. One operator can test between 35 and 40 manufactured cylinders per hour using this new automated system. The VHT for composite cylinder manufacturing requires an autofrettage pre-test.  We are looking forward to testing the throughput of this testing station with medical aluminum cylinders, and we estimate that in this application a single operator can VHT re-qualify an estimated 50-60 cylinders per hour.

6. Current key company initiatives and programs

The key company initiative at the present time is trying to discover ways to enhance the quality of our work experience, which is very important to me at this stage of my life. I love that we are moving toward an environment where it is understood that people make mistakes, where finger pointing is discouraged, and where lending a helping hand to a fellow colleague to overcome a mistake or problem is encouraged. I am thankful to be working in an environment where God is working miracles in our relationships with our suppliers, customers and each other. We are enjoying the combination of leisure activities like poetry, music, and art with our business activities. Jonathan is a very gifted poet, and it is wonderful to have the experience of writing poetry with him to capture some of our experiences traveling together.

His son Joel, age 13, wrote this poem last year.  I quote it often because I hope to live this way:

The Credibility of Time  

Credible, credible cried the clock as the hours ticked like chimes

If I'm not mistaken every second taken is lost to the plots of time.

So don't be preempted by Time's cruel plot

Discontent in disarray,

Rather be credible, enjoy what you've got

If not Time will take it away.  

We have had some wonderful experiences with our initial Rec4 customers that have been life-changing for us and for them. We have also had some involvement with elementary school classes that has been a real blessing. Our hope is to leverage technology to enhance our relationships, and it amazes me that we can video call anywhere in the world for free. Jonathan's brother Dan works with us, and he recently coined the term "Rec4 connect" when we were on a video call talking about how meaningful relationships are becoming our primary goal. Here is a summary of what we hope that "R4 connect" will combine into a life giving experience for all involved: 

• Meaningful connections with the people we interact with in business
• National and global strategies for upgrading testing centers for gas supply companies worldwide
• Development of customer-tailored Rec4 hydrostatic retest stations
• Galiso corporate/educational partnerships, internships, and career training
• Increased web-based customer support and global servicing using Internet technology

My father believed that time was more valuable than money and that money is a reward for well used time.  I would say that another significant corporate initiative is well used time.  We hope to replace corporate profitability with meaningful personal connections as the top objective of our corporate mission.  We still have profitability and technical excellence as key goals, but the Rec4 connect approach highlights the personal and relational nature of our business by elevating meaningful human interaction and personal connections as a premier corporate priority in all aspects of our business.  As a result of this, our personnel will be encouraged to view working colleagues, vendors, and customers as people who have hopes, fears and dreams and as potential life-long friends. We are hoping to stop perceiving them as necessary business intermediaries to achieve economic goals.  We hope to use web-cams and internet technology to enhance interpersonal communications with traveling personnel and customers worldwide and become a tangible example of how the R4 connect approach can be implemented technically to enhance relationships meaningfully.  A benefit of doing business this way is that it is more fun and more rewarding for everyone when we connect.  

So far the Rec4 connect approach has been well received by our customers and has yielded both tangible and intangible results. The international market has been growing steadily for us over the years and now represents about 40% of our revenues and has contributed to an approximate 24% increase in total sales.  Due to the need for volumetric hydrostatic testing systems wherever high-pressure gas cylinders are manufactured or re-qualified according to DOT or equivalent standards, the marketplace for our testing systems and products is growing worldwide.  With customers in over 100 countries worldwide, we are thankful to be in a position of leadership in volumetric hydrostatic testing systems.  In the last year, over 90% of the new Rec4 systems have been installed in foreign countries, and it has been both challenging and rewarding to serve the global marketplace.

During this time we have enjoyed increasing personal relationships with school classes and educational partners.  We hope to have increased involvement in situations where academic data and knowledge are acquired and transmitted in real-life, work experiences where learning becomes fun, relevant and part of a life-long process.  This educational interchange includes the company:

1)  Adopting grade school classes for the school year

2)  Participating in school-to-career exchanges

3)  Offering work internships for high school and university students

4)  Writing white papers with input from collaborators around the world

We have also been able to provide a relational work environment that helps individuals in recovery to rebuild their lives with human connections that are vital to personal health.  As a community employer, we have been able to offer employment opportunities to individuals who are faced with challenging personal addictions or difficult personal histories.   In this way, we are hoping to provide opportunity to hurting people in our community at large.

  7. Examples: Exciting new customer installations

MCS Dinslaken Germany:

MCS, formerly Mannesmann, is one of the world’s oldest cylinder manufacturers.  MCS currently manufactures some of the most advanced light weight type 4 composite cylinders for automotive CNG fuel and breathing apparatus applications. They are the first Rec4 VHT customer and recently installed a second R4 system with high volume electric pumps for cycle testing and a 25,000 psi RSP pump for burst testing.

The first Rec4 installation at MCS was a conversion upgrade of an existing Recortest 3 system that was not able to perform a reliable automated pressurization of the 190 liter type 4 composite cylinders that MCS produces (fig 17). Type 4 cylinders are plastic containers with metal gas connections that are fully wrapped with carbon fiber and as such have pressurization behavior that is quite different from all other cylinder types. It was in response to this problem that the decision was made to try the same Galiso PLC that we use to control the Galiso HGS process on semiconductor etching tools, along with some valves and miscellaneous parts to see if we could solve the problem that MCS was having and to establish a common control platform that leverages the work we've already done in the semiconductor industry. 

When we arrived in Dinslaken Germany, we set up a development lab in our hotel rooms and started the final phase of development to convert the existing control to PLC. The owner of the hotel saw what we were trying to accomplish and gave us the downstairs two bedroom apartment that was not being used at the time for use as our lab, free of charge (fig 18).

Figure 17 Rec4 VHT #1 Type 4 Large Composite - MCS International

Figure 18 Rec4 Beta #1 development "Lab" Dinslaken Germany

The three week conversion installation took place in December of 2004, and the first night we were there we walked into a restaurant for dinner where the man behind the counter welcomed us in perfect English. The restaurant proprietor, Henry Lindenau, has become a good friend and we have enjoyed some wonderful times with Henry and Stefan Limke, who is the engineering manager for MCS.

This conversion installation was performed by Rick Wright, Chris Hinchey, and Chuck Grenci. Chris Hinchey is a distributor for Galiso products located in Sussex, England. The installation was very challenging with many problems and thankfully many solutions. We could not have had a better customer contact to work with on the first Recortest 4 development than Stefan, and it is wonderful to look back and see the progress that has been made on subsequent Rec4 installations including the second Rec4 cycle and burst system that MCS purchased.

On the day that Rick returned to the U.S. we were picked up by a cab driver who had a station wagon big enough for all the boxes from the “lab”. We asked him to take us to Mannesmann thinking that he would relate better to the old company name. He replied, “You mean MCS International,” and proceeded to drive us though a back company entrance through the factory and right up to our equipment inside the factory. The MCS factory is about the size of 3 football fields, and as it turned out our taxi driver was a former employee of Mannesmann.

Thunderbird Cylinder, Phoenix Arizona:

Thunderbird is one of the larger cylinder re-qualification facilities in the U.S. Thunderbird obtained an exemption for UT testing and purchased a machine to UT test cylinders, but later opted to use Rec4 VHT for testing small aluminum cylinders (fig 19). This is noteworthy in that small aluminum cylinder testing is one of the best applications for UT. Their Rec4 VHT is able to test 80 cylinders per hour with 4 test operators. This includes de-valve, inspection, fill, test, dry, stamp, and re-valve.

Figure 19 Rec4 VHT #2 Medical Aluminum - Thunderbird Cylinder

Giant Bicycle Company/Compositech, Taichung Taiwan:

Giant Bicycle is one of the world's largest bicycle manufacturers and has developed a specialty in manufacturing light weight composite structures. They are working to produce carbon fiber wrapped cylinders for the paintball industry. This was the first Rec4 station to provide control for multiple test stations (fig 20).

Figure 20 Rec4 VHT/Cycle/Burst - Giant Bicycle Ctech Division

Scuba Service, Antwerp Belgium:

Scuba Service is using Rec4 VHT to test composite self contained breathing apparatus cylinders (SCBA) and steel self contained underwater breathing apparatus (SCUBA) cylinders. The company is owned by Ronnie and Peggy Desmet. The test shop is located behind their home and is a unique example of a Rec4 VHT in use by a small family owned business (fig 21).

Figure 21 Rec4 VHT - Scuba Service

Advanced Material Systems, Taipei Taiwan:

Advanced Material Systems is another Taiwan cylinder manufacturer that is working toward the production of DOT approved carbon fiber wrapped cylinders for the U.S. paintball market. The Rec4 configuration at AMS includes an automated loading small cylinder water recirculation station, a cycle test station, and a burst test station (fig22).

Figure 22 Rec4 Automated VHT for Small Composite Cylinders - Advanced Material Systems

Asahi Seisakusho, Iwatsuki Japan:

Asahi Seisakusho is a cylinder manufacturer in Japan that has three Recortest systems in operation, the original Recortest 3 that they purchased from Galiso in 1991, the first Recortest 4 automated water recirculation station for their FRP composite cylinder manufacturing line, and the newest Rec4 installation at the time of this article for retesting cylinders in Japan to DOT regulation. This system is installed in their test shop opposite of the 1991 Rec3 station (figs 23 & 24).

Figure 23 Rec4 VHT Automated Small Composite Cylinder Test Station - Asahi Seisakusho

Figure 24  Rec4 VHT Asahi Seisakusho Test Shop

Abdullah Hashim, Jeddah Saudi Arabia:

Abdullah Hashim in Saudi Arabia is a longtime Galiso customer who is evaluating the upgrade of existing Recortest3 test stations to Rec4. They are an industrial gas supply company that has been very successful in their market (fig 25).

Figure 25 Recortest 3 Components Being Replaced by Rec4 - Abdullah Hashim Industrial Gases

Crossfire Paintball, Kalamazoo Michigan:

Crossfire Paintball is the oldest manufacturer of valves for paintball guns and operates a DOT certified CFFC (carbon fiber, full wrap, composite) manufacturing facility. They use a Rec4 VHT automated 4-station system to VHT qualify the cylinders that they manufacture.

Ragasco, Raufoss Norway:

Ragasco is perhaps the most advanced manufacturer of composite cylinders for LPG and CNG in the world. They operate a fully automated production facility that is state-of-the-art. They are using a Rec4 cycle and burst station for testing CNG cylinder designs in preparation for high production manufacturing.

Japan Airlines, Narita Japan:

Japan Airlines Airtech is one of the newest Rec4 installations and is designed with stainless steel test jackets for testing aircraft cylinders. Working with JAL- Airtech is a great opportunity to explore the potential advantages of the Rec4 platform in Aircraft service applications (fig 26).

Figure 26 Rec4 VHT Airline Service System - Japan Airlines - Airtech Division

At the time of this article, 12 Rec4 systems are in operation - 3 in Japan, 2 in Germany, 2 in Taiwan, 2 in the United States, 1 in Belgium, 1 in Saudi Arabia, 1 in Norway.

8. A look ahead: A glimpse of our R&D efforts and our vision for the future of hydrostatic testing.

We hope that the flexible Rec4 network PLC control and operator interface that we have written for the windows operating system combined with a growing number of standard stations for VHT, cycle, and burst testing will allow us to respond quickly and competitively to a variety of opportunities in the testing of compressed gas cylinders. We would like to explore hydrostatic pressure applications outside the cylinder industry like washing cars and oil rigs.

We desire to employ the concepts that we have developed for automated movement of small cylinders through the VHT process to stations for large cylinders. Using the high output electric pumps that we have engineered and supplied for cylinder cycle test applications in volumetric hydrostatic test applications, we hope to increase test throughput for large cylinders where pressurization time is a significant factor.  The Rec4 has the ability to test four cylinders simultaneously compared to the Rec3's two (in limited custom configurations). This capability provides increased VHT throughput for customers who need it. Machines that work well can be rewarding and fun to operate, and we hope to refine and fully apply the various capabilities of the Rec4 to make cylinder testing an easy, reliable and enjoyable experience for our customers.

Overall, it is our hope to integrate our new technologies within the framework of our "Rec4 connect" approach to plant and water relationships with suppliers, customers, and employees...and then look for God-given growth. The cultural impact of the "Rec4 connect" approach on daily operations is that corporate resources are directed at accomplishing meaningful relationships that will provide a better foundation to build upon than profitable business exchange.

Weight Expansion Measurement System

WEIGHT EXPANSION

MEASUREMENT SYSTEM

1.0  The weight expansion measurement system (WEMS) incorporates the methodology of volumetric expansion by measuring the weight (rather than the volume) of water displaced in a volumetric expansion test.   The WEMS uses a siphon tube instead of an open top burette tube to measure the weight of the water displaced.   The WEMS is based upon the scientific correlation between the volume of water and the weight of water: 1 cubic centimeter of water weighs 1 gram of water (at 4 degrees Celsius).   Therefore the WEMS simply measures the weight of water displaced by using a weigh container on a digital weigh scale or load cell, and then determines the expansion of water displaced.

1.1  The weight expansion measurement system has certain practical advantages over the burette system.  Most importantly it eliminates any possibility for operator interpretation error during burette meniscus expansion readings.  Second, the expansion volumes can easily be determined with great precision and then communicated to operators or to computer-controlled automated testing systems.  In addition, WEMS eliminates the need for fragile glass burette tubes and plumbing to multiple burette tubes.

1.2  However, there are several factors that must be addressed to ensure the accuracy of the WEMS: temperature, the buoyancy effect of the siphon tube, the effect of water column height, and the accuracy of the weight measurement device.  All of these factors may affect the accuracy of the weight expansion readings unless adjustments are made to account for their impact on the readings.

1.3  The effects of water column height change and buoyancy of the siphon tube can be easily determined by pouring a known quantity of water into the expansion measurement container when the device is open to a test jacket.  The weight measurement device can be easily tested and verified by using a calibrated reference weight to determine its accuracy.  Water density changes due to temperature can be corrected mathematically using known water density values at various temperatures (See Appendix B). 

1.4  In a hydrostatic testing system, the above factors can operate inversely such that the aggregate impact of all effects combined has a negligible impact on the accuracy of the expansion values derived.  Various tests have been conducted to verify that such combined effects do have a very minute effect on expansion values at ambient temperatures around 22 Centigrade.  

1.5  The accuracy of a weight measurement device is tested by placing a calibrated reference weight upon it to verify its accuracy.  Next, 100 cubic centimeters of water at ambient temperature is weighed into a container using another calibrated digital scale with a resulting weight of 99.7 grams (see Appendix B for resulting weights at different temperatures).   The 100 cubic centimeters of water are then poured into a 3 liter square expansion container that rests on the expansion measuring weigh scale.  Expansion weight values are then recorded.  The process is repeated in 100 cc increments with expansion weight measurements being recorded respectively at each 100 cc volume level. 

The following expansion testing data and graphs clearly portray the minute and negligible impact resulting from the combined effects of temperature, buoyancy, and water column height.  

  APPENDIX A:

APPENDIX B:

Expansion Measurement By Weight

Open Letter Re: Calibration

Greetings from Galiso Incorporated

This letter pertains to the recent changes to the calibration values for your calibrated cylinders. Galiso technicians have found this to be necessary on many Recortest 4 installations and upgrades. The reasons that the cylinder values are no longer correct are thinning of the cylinder walls due to corrosion and or incorrect previous calibration.

Calibrating a cylinder on site with the installed / upgraded machine requires a check of each of the 4 calibration accuracy issues to establish that the cylinder calibration values that are done on site are accurate. When there is a discrepancy in prior calibration values to present ones, a check of each of these four calibration accuracy issues is important to prove the new calibration data is correct.

These issues are:

1. Accuracy of pressure measuring device . . . verified with master gauge.

2. Accuracy of expansion measuring device . . . verified with test weights

3. Temperature . . . measured to determine the weight of water during calibration

4. Buoyancy . . . checked with the a pour test and adjusted for temperature.

Regarding issue 1, the Recortest 4 uses a digital pressure transducer that is a high accuracy, traceable pressure standard suitable for calibration of cylinders. Because the .02% accuracy of this transducer is better than the .25% accuracy of the master gauge the master gauge is used to confirm that the transducer is functioning properly but we do not calibrate the digital transducer to the gauge. This we believe is a major factor in the need for us to re calibrate cylinders during Recortest 4 installations and upgrades. Prior to the installation / upgrade it was possible to adjust the pressure transducer to match the expansion values. We also verify that the pressure circuit comprised of the high pressure pump, valves and tubing, hoses, test head, and cylinder are not leaking.

Regarding issue 2, in most cases the load cell weigh bowl assembly is replaced by the digital Recortest 4 weigh bowl scale. The accuracy of this digital scale has proven to be very stable over time and eliminates the need for frequent calibration.

Regarding issue 3, When the ambient temperature is 4 degrees c / 39 degrees f, one cc of water weighs 1 gram but at 40c/104f room temperature, one cc of water weighs .992 grams which is a accuracy loss of negative .8%. By determining the ambient temperature we can correct its effect on the weight of water when we perform a pour test to verify the accuracy and leak integrity of the complete expansion circuit comprised of the weigh bowl, siphon tube, plumbing and valves, test jacket, test head and cylinder.

Regarding issue 4, We determine the effect of siphon tube buoyancy on the system that will be used to create calibration cylinder values. To do this we open the expansion circuit to the weigh bowl with the cylinder to be calibrated in the test jacket. Then we pour 100cc of water into a cup on a separate scale by using the weight of water at ambient temperature. For example if the ambient temperature is 20 degrees c / 68 degrees f, then we would pour 99.8 grams of water into the cup. Next we pour the water out of the cup into the weighbowl of the Recortest 4 that is connected to the test jacket with the calibrated cylinder. This test is performed several times to verify that the complete expansion circuit is accurate and stable.

We then run repeated tests at each calibration pressure to gather the expansion data for each pressure point. Finally we check the linearity of all calibration points and then create a certificate of expansion values for the calibrated cylinder. If you have any further questions about this work please feel free to contact our service team anytime.

Thankfully yours – The Galiso team