30 Rubber & Plastics News ● October 1, 2012 www.rubbernews.com

Technical

Defining pathways to test hydraulic hose and fittings By Chris Jorge

Haidar Inc.

Burst Test is defined by SAE, ISO orany other specification and in its majori-ty, these standards request for newhoses with fittings attached.

For instance, SAE J3431 defines atime interval for a hydrostatic pressurebe applied at constant gradient.

During that proposed time interval, ahose under test should pass or fail theburst test.

The two most common solutions avail-

Executive summaryBurst Test is defined by SAE, ISO or any other specification and in its major-

ity, these standards request for new hoses with fittings attached. The two most common solutions available in Burst Testers are based either

on an air-driven pump or a different technique which controls pressure x time,providing a more constant pressure ramp up .

A company searching for a Burst Test should examine these approaches toattain the most consistent and accurate results possible.

able in Burst Testers are based eitheron an air-driven pump or a differenttechnique which controls pressure xtime, providing a more constant pres-sure ramp up .

A company searching for a Burst Testshould examine these approaches to at-

tain the most consistent and accurateresults possible.

Test stands based on air-driven pumphave been around for a number of yearsand many companies feel comfortablebuilding their own tester.

We have seen many home-made orsmall testers provided by companies andthe majority of these air-driven BurstTesters, especially for medium and big-ger hose diameters, fail to complete thetest in the time interval requested bySAE.

The tester must reject/pass hose sam-

Fig. 1. Air-driven pump comparisons.

Fig. 2. The stroke of air-driven pump makes pressure reading less accurate.

Fig. 3. Burst Tester with LVMD length variation measuring.

TECHNICAL NOTEBOOKEdited by Harold Herzlichh

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Rubber & Plastics News ● October 1, 2012 31www.rubbernews.com

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Technicalples when they are tested between theproposed time interval.

If the equipment is used to define andconfirm burst pressure it should followthe determinations and protocol de-signed by SAE.

If no other solution is available andone has to use an air-driven pump to an-alyze burst pressure, the following crite-ria has to be met:

● SAE or other specification’s time in-terval requirements.

● Robust, safe to operate, protectingusers and the environment.

● No trapped air inside the hose (itmost likely will affect accuracy of re-sults)

Although air-driven pumps are relative-ly simple and low cost, they do not providean accurate reading of the pressure, whichcan be influenced by many variables, in-cluding readings on the top/bottom of thepump’s stroke. When comparing to othermethodology, see Fig. 1.

For an accurate pressure reading, aBurst Test with a controlled ramp up(pressure x time) will provide much bet-ter results.

In this case, the pressure ramp is ap-plied in a straight continued pressure

line that meets many standards. In summary, when designing your

own homemade solutions or acquiringa Burst Test at very low cost, andwhen accurate measurement resultsare desired, we strongly recommendstaying away from solutions designedwith air-driven pumps to do a BurstTest.

To meet current international specifi-cations such as ISO, SAE or MIL, espe-cially when testing all size hoses, werecommend a Burst Test with controlledramp up pressure to obtain more accu-rate and usable results.

European manufacturers and someU.S. customers are currently using thismethodology.

The Burst Tester should also accom-modate a measuring device to verifychange in length.

Proof testing, flushing, drying a hose Hoses should be clean and dry after a

Proof Test and before packing for ship-ment.

To shorten and speed up this process,a combination of proof and flushingequipment can do the task.

At the end of the test, the proof testmachine uses a special solution toclean the hoses at high pressure andthen dries them out at the end of thecycle.

Running many tasks in one uniqueunit maximizes the testing process, re-duces labor, time and expenses, and alsoprovides an excellent level of cleaningon the final product.

Cleanness level, as defined by ISONAS standards, can easily be achieved.

Hydraulic fluid considerations The importance of using a clean fluid

in a hydraulic circuit is widely knownbecause fluid contamination accountsfor most of the failures in a hydraulicsystem.

Despite appearances, a hydraulic flu-id from a new drum is not necessarilyclean.

Typically, hydraulic fluid from adrum will have a cleanliness level thatcan be classified by ISO CleannessCode.

For instance the digits following theISO Code determine a range of sizes andquantities of particles encountered permilliliter of fluid.

A typical 19/14 or 19/16 ISO Code (2)represents a fluid with a measurablequantity of impurities and if we continu-ously run several gallons of fresh, newoil from a drum, we would collect fewpounds of sediment.

A test stand must incorporate the cor-rect filtration methodology and properfiltration configurations to work moreeffectively and to present less downtime.

In summary, in addition to an ade-quate selection for filtration method, thetest stand must have a satisfactory fil-tration element with capacity to removeparticles and sediments.

Fig. 5. Proof test and flushing separated units.

Fig. 4. Burst Tester for hoses without fittings to test rubber material.

Fig. 6. Proof test and flushing com-bined unit.

Fig. 8. A self-contained impulse teststand capable of running multiplewaveforms.

Fig. 7. Volumetric expansion test.

Fig. 9. Combined test of multiplehoses.

See Hose, page 32

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Technical

Although simple, it is an importantfactor in many systems that have elevat-ed failure of pump, valve and other vitalcomponent.

Hydraulic circuit considerations The most common mistake when de-

signing a hydraulic circuit is heat gener-ation from inside the equipment.

It usually gets multiplied when ex-posed to heat generated from outsidesources.

The heat generated inside the equip-ment usually occurs as a result of inex-perience in designing proper hydraulicsystems (reservoirs, accumulators, valve

sizing, pump unloading). A poor design of the hydraulic circuit

usually leads to expensive remedies. For instance, when a company designs

an impulse machine or buys one on themarket that has a poor design it canlead to generation of excessive internalheat.

The power consumed to run a testwould be too high, thus incurring con-tinued losses if not corrected.

This issue can be remedied either in-ternally or externally.

An internal modification on the ma-chine’s design will most definitely incuradditional costs and time lost.

A less preferable remedy is to reducethe room temperature where equipmentis installed during warmer days to com-pensate the heat.

This palliative action only perpetu-

ates excessive costs to run a test. Selecting an equipment of poor de-

sign, because the investment is al-ready done, becomes more difficult torevert.

These are unfortunate steps that mostlikely should be avoided.

The same excessive expenses (or loss-es) happen with equipment in poor oper-ating conditions (leakages, inefficien-cies, lack of proper maintenance).

It can happen with new poorly de-signed equipment or when running “old”equipment.

For example, an old piece of equip-ment will require much more mainte-nance and will be less efficient thannewer designs.

Additionally, the fluid used today hasreceived a number of upgrades in thepast 30 years.

These upgrades provided quite a fewimportant characteristics changes onthe fluid and for equipment designedmany years ago these factors most cer-tainly were not considered.

Impulse testing When designing and building an im-

pulse test stand for hoses and fittings,

there is a range of methodologies and so-lutions that can be employed on the hy-draulic circuit.

A design which is too simplistic maylead to many issues and consequentlysystem failures.

For example, if filtration is poorly de-signed it can cause excessive heat, leak-ages and other issues that usually causedowntime.

If a hydraulic circuit is over “dimen-sioned” for the task at hand, by selectinga bigger pump and other elements, itusually results in a machine with highenergy consumption rates.

Testing equipment today has to fit thecompany’s testing requirements but atthe same time use less energy, producelower noise and deliver outstanding per-formance while working in a friendlyand greener lab environment.

Today, there are many specificationsdefining impulse test waveform andpressure ramp for applications such asaerospace, machinery, gas and petrole-um, automotive, construction equipmentand mining, etc.

The most frequently used specifica-tions can be divided into many cate-gories but for this study we will config-ure them into two groups.

1. Impulse with static manifold(or fixed manifold): Specificationssuch as SAE J343, ISO 6803, ISO 6772,AS 603, Hitachi peak, MIL, are the mostcommon for square or peak waveformwhere both manifolds are fixed and thehose is stressed by a number of cycleswith impulse pressure.

2. Impulse with dynamic manifold(or moving manifold): specificationssuch as SAE J1405, ISO 6802, UL 1405,MIL, which are largely used by compa-nies supplying hoses for machinery, con-struction equipment and other fieldswhere hoses are submitted to constantmovement.

In this case, in addition to the impulsepressure, hoses under testing are alsosubmitted to rotational or flexing forcesor just a horizontal travel provided bythe moving manifold.

For example, a flexing hose is general-ly subjected to a higher stress when itcomes in contact to an over sheaves as-sembly such as the ones used in fork-lifts, booms, aerial lifts, cranes andmany other applications.

In these cases, the impulse test asso-ciated with a dynamic movement of thehose under testing will greatly improvethe testing results because it moreclosely duplicates real-time perform-ance.

Impulse test with climatic cham-ber: To more closely advance to a realworking condition, a test lab can includetest stands with climatic chamber tem-perature, where in addition to control-ling the temperature of the fluid, the airtemperature inside the chamber canalso be controlled.

By setting negative/positive tempera-tures, one can simulate extreme hot andfreezing temperatures.

This type of test with controlled airtemperature will better represent work-ing conditions of hoses and other compo-nents designed for use in airplanes,cars, tractors, machinery, sub-sea um-bilicals (Petroleum) and others.

A test stand with a climatic chamberdetects issues in hoses designed to workin extreme temperature conditions.

SAE standards updates The SAE website shows most current

WIP (work-in-process) taking placeamong standards’ committees debatingthe required adjustments to some speci-fications.

Fig. 10. Square waveform and respective test report.

Fig. 11. Horizontal flexing movement.

Fig. 12. Rotational and flexing move-ment.

HoseContinued from page 31

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Rubber & Plastics News ● October 1, 2012 33www.rubbernews.com

TechnicalFor this section, visit the SAE website

to check the latest discussions.

A greener hydraulic test lab The following are some “best prac-

tices” to establish a greener hydraulictesting lab:

● Preventing and controlling an acci-dental spill.

—Properly containing fluid from a hy-draulic circuit

—Lessening the lab’s floor moppingand draining

● Preventing fluid from dispersinginto atmosphere

—Maintaining cleaner air environ-

ment ● Consuming less energy and generat-

ing less noise —Utilizing more efficient compo-

nents—Utilizing a better overall design ● Increasing operation efficiency —Protecting or shielding sources of

heat, energy consumption and noise ● Lessening the number of interven-

tions because of unpredictable mainte-nance

—Selecting filter elements, designand methodology

—Proper sizing of motors and pumps —Avoiding fluid contamination

References1. SAE J343 Revision Jan 2004 2. ISO 4406 1999 Code Chart, Particle Code Chart 3. Lightning Reference Handbook Eighth editionRev 2 July 2001

4. Society of American Engineers www.sae.org 5. BIMAL s.r.l 6. Other References and publications consulted: Na-tional Fluid Power Association NFPA, TribologyMagazine, Donaldson Co. Inc.

Fig. 13. Climatic temperature chamber to set above and below zero degrees.

The authorChris Jorge has more than 20 years of experience in testing solutions and

methodologies for aerospace, automotive, electronic, hydraulic components andassemblies.

Jorge has participated in design and development of test labs as well end-of-the-line testing systems for manufacturers of transmission drivelines, filters,steering units, valves, hoses and many other components.

He has been involved in implementation of customized testing solutions infactories around the world.

Jorge is business unit director at Haidar Inc. and can be reached by email atchris@haidar-inc.com.

ProductsDow Polyurethanes launcheshigh-performance polyol

Dow Polyurethanes, part of DowChemical Co., has launched a polyetherpolyol, Voranol 223-060LM, which itsaid is an effective, high-performancepolyol that can replace select traditionalpolytetramethylene ether glycol applica-tions.

It has the additional advantage of eas-ier processing as a result of its low vis-cosity, Dow said.

Voranol 223-060LM is a polyurethanethat forms the backbone for a wide vari-ety of adhesive, sealant and elastomerformulations.

Market applications include trans-port, construction, packaging, electron-ics and more.

Visit www.dow.com/polyurethane formore information.

Elastocon expands clearmedical-grade TPEs

Elastocon TPE Technologies Inc. hasseveral new grades of clear, SEBS-basedthermoplastic elastomers designed formedical products.

The newly expanded CLR series offerslow formulations, with some formula-tions being completely oil-free.

The expanded grades now include abroader range of hardnesses, from 15Shore A to 75 Shore A, Elastocon said.

The company said the TPEs are odor-less, can be extruded or injection mold-ed, utilize materials that are FDA com-pliant, give the end product a good (nottacky) feel, have exceptional tear resist-ance, offer high resilience, high strengthproperties, and can be easily color tint-ed.

For more information, call 888-644-8732 or visit www.elastocontpe.com.

NuSil releases silicone inkcolors for health care use

NuSil Technology L.L.C. has launcheda series of heat-cure colored inks calledMED-6613-X.

The newly released colors—red, white,

green, bright blue and dark blue—ex-pand the company’s color palette, NuSilsaid.

NuSil’s inks feature a long work timeand non-volatile content of about 60 per-cent, the company said.

Depending on the ink color, viscositiesrange from 800 to 3,000 cP and can bedecreased through dilution via compati-ble solvent.

These two-part, addition-cure inkscan be used in pad-printing and silk-screening processes for marking or col-oring silicone rubber parts, such ascatheters, NuSil said.

The company said because the cure isaccelerated with heat, the inks are suit-able for applications requiring a rapidcure time.

The suggested cure schedule is fiveminutes at 150°C.

The line of silicone inks was a collabo-rative effort between NuSil Technologyfor silicone development and C.I. Med-ical Inc. for application feedback.

Ashby Cross releases adhesive dispensing machine

Ashby Cross Co. has introduced a ful-ly automatic meter, mix, dispense ma-chine for epoxies, silicones and ure-thanes that produces small shots andstores up to 15 shot sizes.

Ashby Cross Model 1125 Variable Ra-tio IDS is a PLC-based automatic meter,mix and dispense machine that handlesfilled or unfilled epoxies, silicones andurethanes, with ratios from 1:1 to 6:1 byvolume, the company said.

The system features a touch-screeninterface with menu-selectable shotsizes from 0.3 to 160 cc, depending uponratio. It stores up to 15 user-definedshot sizes, and provides ±1 percent byvolume accuracy and repeatability, Ash-by Cross said.

It is suitable for low- to mid-volumeproduction and R&D, and it utilizes pis-ton-cylinder metering, standard staticmixers, handles viscosity up to 100,000cps, has a compact 18- x 12-inch foot-print, and operates on 110 VAC and 100psi air, the company said.

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