| 1.0 |
PURPOSE
The purpose of this document is to provide general specification and guidelines to improve reliability of Hose of Teflon® assemblies and provide a method of consistency in product specified. This guideline can be used for all transfer hose types, including rubber, metal, plastic, silicone etc. |
| 2.0 |
SCOPE |
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2.1 |
This standard describes guidelines to choose flexible hygienic, high purity, sanitary and processing hoses of Teflon®. |
| 2.2 |
This standard provides procedures for selecting qualified fabricators / assemblers based on a distributor qualification procedure. |
| 2.3 |
See Resistoflex Engineering Standard RX2000, "Hygienic Purity Hose Specification" for general guidelines for hose of Teflon®. |
| 2.4 |
If a hose is used as a permanent installation, then a documented design analysis should be completed. |
| 3.0 |
DEFINITIONS |
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3.1 |
Core Manufacturer - facility that manufacturers the core Teflon® liner, bulk product to the fabricator/assembler or completed assemblies. |
| 3.2 |
Components - core, over-braid, and end fittings (e.g., stub ends, flanges, threaded couplings). |
| 3.3 |
Fabricator/ Assembler - facility that assembles components to form a hose assembly. The components are supplied by the Manufacturer, and components cannot be mixed to form an assembly unless authorized by the Manufacturer. In some instances the component manufacturer will supply the fully assembled hose. The same qualification is required for both the field fabricator and the manufacturer. |
| 4.0 |
CONSTRUCTION - HOSE OF TEFLON® |
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4.1 |
There are 4 major components of a Hose of Teflon®: |
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4.1.1 |
Inner-Core Liner is a tube of Teflon® PTFE T-62 on all smoothbore and convoluted series except TRC-FEP, which is Teflon® FEP. |
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CAUTION: If the word TEFLON® or PTFE is used generically, you will NOT be guaranteed to receive DuPont resins as specified and tested. Please refer to Teflon® PTFE literature for information concerning differences in resin materials. |
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4.1.2 |
Exterior Braid or Rubber Cover. |
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4.1.2.1 |
Metal Over-Braid Construction - The metal over-braid construction is usually 316 Stainless Steel, but in some cases such as SBT series smoothbore, the braid is 304 Stainless Steel as a standard. Monel® 400, Hastelloy® C276 and the specific grade of Stainless Steel should be called out. Some hoses offer both a single woven braid and a double woven braid for increased flexibility and working pressures. |
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CAUTION: If the correct metal braid material is not called out, you could receive a lower grade Stainless Steel instead of 304 or 316 SS. Please refer to DM2002 for details on specific grades used for each hose material. |
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4.1.2.2 |
Non-Metallic Over-Braid Construction - Non-metallic braid comes in a variety of colors and materials. Polypropylene is normally blue and is designed with a UV inhibitor to avoid premature failure in applications in direct contact with ultra violet sun rays or light. Not all polypropylene braids offer this, so it must be specified. Kynar® is normally white in color. |
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CAUTION: If the correct non-metallic braid material is not called out, you could receive a polypropylene braid without UV inhibitors or different thicknesses. Please refer to DM2002 for details on specific grades used for each hose material. |
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4.1.2.3 |
3 Rubber Reinforced, Bonded Construction - There are many issues with TRC (rubber covered Teflon® hose) that can be wrongly substituted as an equal. The rubber carcass should be multiple layers of EPDM, reinforced with two layers of polyester tire cord. A dual helix carbon steel wire should be imbedded into the rubber for increased flexibility, crush resistance and increase vacuum rating. The liner thickness should be .030" or thicker and made of Teflon® PTFE T-62 or Teflon® FEP. |
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CAUTION: If the word Teflon® or PTFE is used generically, you will NOT be guaranteed to receive DuPont resins as specified and tested. In the case of rubber covered Teflon® hose, you could receive FEP, PFA, Tefzel® or a generic PTFE as a wrongly substituted equal. Please refer to Teflon® PTFE literature for information concerning differences in resin materials. |
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4.1.2.4 |
TMH Dual Containment Construction - TMH series hose is made of three components. (1) Liner, (2) Corrugated metal hose carcass, (3) Braid. The metal hose carcass is welded jointly to the braid collar, fitting and braid, then the Teflon® PTFE T-62 liner is drawn down to a smaller size to fit into the hose carcass. The lined assembly is then placed into an oven at a set time/temperature to Thermalok® the liner into the hose by allowing it to swell and lock into the convolutions of the metal hose. This process allows the liner and metal hose to expand and contract with pressure and temperature equally, unlike lined hoses that just place a liner inside a metal hose. A 1/8" vent hole is drill into each metal fitting before lining to allow any trapped permeation or pressure to escape without collapsing the liner. Resistoflex is the only hose manufacturer that does this complete process. The metal carcass, braid and fittings are 316 Stainless Steel, Monel® or Hastelloy®. The vent hole is standard. |
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CAUTION: TMH series hose MUST be thermally locked into place to avoid liner movement inside the metal carcass. If the liner shrinks faster than the metal hose, the flares with break off (liner suck-back). If the liner grows faster than the metal hose, the liner will buckle causing catastrophic failure. A loose lined hose will fail much quicker because of these two reasons. Refer to the DM2002 for more details on TMH hose. |
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4.1.3 |
Fittings - Fittings materials and styles are many.
As with metal braiding, the exact material must be called out. Stainless Steel fittings could mean many different grades. Exotic metals such as Monel®, Hastelloy® and others must specify which grade.
Solid plastic fittings are manufactured in polypropylene, Kynar®, PEEK and other exotic plastics. Pressure ratings will vary with plastic fittings and should be tested at the maximum temperature requirement before specifying.
Encapsulation of metal fittings has three issues. (1) metal material, (2) type of Teflon® used, (3) locking mechanism to bond the metal and plastic together. Encapsulated fittings should NOT have holes in the hose shank to accomplish the task of locking the plastic and metal. The holes become the failure point after crimping occurs. The plastic is forced to create stress cracks by the crimping process. See Figure 1 for Correct and Incorrect design. These fittings should use only high purity PFA Teflon® to avoid cracking due to shrinkage. Fittings should be able to withstand a full vacuum test up to 500°F. |
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CAUTION: If the word Teflon® or PTFE is used generically, you will NOT be guaranteed to receive DuPont resins as specified and tested. If Teflon® encapsulated fittings are specified without stating "no holes in hose shank design", premature failure will likely occur. |
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Figure 1: Correct vs. Incorrect Encapsulation Design  |
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4.1.4 |
Hose to Fitting Attachment Mechanism - Crimp collars and fitting inserts should be designed to work together. Since the Teflon® liner is very thin, incorrect crimping collars, or over crimping will cause the fitting to cut into the liner and eventually leak product. Under crimped collars do not bite into the liner and external carcass causing fitting blow-off. An integral system called a "braid lock" allows the collar and fitting to become one. This system, when done correctly allows the perfect amount of bite into the liner which stops any possible weeping between the hose shank and the liner. The braid lock actually lock the fitting insert to the collar avoiding fitting blow-off and acts as a go-no go gauge avoiding over-crimping or under-crimping of the fitting. |
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CAUTION: Each end of the hose shall be checked with a caliper to determine correct crimping has occurred. This should be documented under each serial number and controlled. |
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4.2 |
Design and Construction Details - |
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4.2.1 |
The inside diameters of the liners shall not be less than 95 percent of the nominal size of the assembly. |
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4.2.2 |
Metal flange retainer (stub ends) must have a phonographic spiral finish to grip and bite into the gasket materials to be used. This reduces flange weepage and leaks. |
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4.2.3 |
All flanges used with the assemblies shall conform to ANSI B16.5 standard for flange dimensions and drilling. |
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4.2.4 |
Any hose assembly that does not vent automatically (braiding) shall have a vent hole or pin pricked cover on rubber covered hose so that gases will not be trapped between different layers. This also provides a means of detecting early leaks. |
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4.2.5 |
All carbon steel fittings shall be completely coated with a corrosion resistant coating, primer or plated. |
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4.2.6 |
Any welded fittings or metal hose shall be full penetration welded. |
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4.3 |
Liner and carcass properties - |
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4.3.1 |
Manufacturers literature shall include the following information for each diameter: |
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4.3.1.1 |
The liner nominal thickness and tolerance. |
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4.3.1.2 |
Maximum working pressure at the maximum temperature range and all pressures and temperature in between. |
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4.3.1.3 |
Minimum bend radius. |
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4.3.1.4 |
Vacuum rating based upon test data. |
| 5.0 |
100% TESTING OF FINAL HOSE ASSEMBLY PRIOR TO SHIPMENT |
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5.1 |
Hydrostatic Pressure Test
If hose is to be hydrostatically and pneumatically tested hydrostatic test will be performed first. If hose will not fit in test tank only hydrostatic test will be performed.
- Attach appropriate test cap.
- Attach test caps to quick disconnect to fill hose.
- Start test using keypad of test apparatus.
- Observe for any leaks. (Any leaks are cause for rejection).
- Upon passing completion mark hose with blue dot.
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5.2 |
Pneumatic Pressure Test
If hose is to be hydrostatically and pneumatically tested pneumatic test will be performed second.
- Attach appropriate test cap.
- Place hose in test tank.
- Attach test caps to quick disconnect to fill hose.
- Start test using keypad of test apparatus.
- Observe for any leaks. (Any leaks are cause for rejection).
- Upon passing completion mark hose with yellow dot.
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5.3 |
Electrostatic Test
Hose shall be tested for grounding.
- Use heavy duty ohm meter.
- Attach node to each end of hose.
- Reading must be below 5 ohms to pass test.
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| 6.0 |
QUALIFICATION TESTING / HOSE & FITTINGS
Hoses lined with Teflon® shall be capable of passing qualification tests designed to demonstrate the hose's ability to withstand severe operating conditions. Once a hose design has passed qualification testing, re-testing is not required. If the manufacturer changes the hose design, however, the new design must be re-tested. Purpose of qualification testing is to validate manufacture's performance claims. The hose manufacturer shall make hose qualification tests reports available upon request. Qualification testing is as follows: |
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Burst Testing Subject hose to destructive burst test to determine allowable operating pressure and proof test pressure.
- Install hose on test stand designed to allow internal pressurization of hose with hydraulic fluid.
- Introduce hydraulic fluid into hose, purge all air.
- Pressurize at an approximate rate of 100 psi/sec. until hose fails.
- Record burst pressure.
- llowable operating pressure is defined at 25% of burst pressure for a 4:1 safety factor.
- For Chlorine Transfer Hose, allowable operating pressure is 20% of burst pressure for a 5:1 safety factor.
NOTE: Allowable operating pressure is also known as "rated working pressure" and "working pressure".
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Steam-Cold Water Cycling Subject representative Teflon® lined hose samples to steam-cold water cycling to determine the ability of the lined hoses to withstand rapid temperature changes. Procedure is as follows:
- Install hose on closed-loop test stand and circulate saturated steam at 125 psig (50 psi for TRC) until the skin temperature varies no more than 2.5°F for 10 minutes. Temperature shall be measured by a thermocouple attached to the crimp collar.
- Close off the steam and immediately circulate water a maximum temperature of 77°F until the skin temperature reaches 122°F.
- Vent and introduce air to purge the test hose for a minimum of one minute to completely drain hose of water.
- Repeat steps 1-3 for a total of 100 cycles.
- During the 100 cycles, leakage is cause for rejection.
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Impulse Testing Subject hose assemblies to rapid and frequent pressure cycling to determine hose assembly's ability to withstand long-term pressure cycling. (Note: impulse testing is not required for TR or TMH).
- Install hose on test stand designed to internally pressurize hose with hydraulic fluid.
- Pressurize hose to 125% of rated working pressure, return to ambient pressure, return to 125% of rated working pressure. This is defined as one cycle.
- Continue cycling at a rate of approximately 70 cycles/min. until 50,000 cycles have been completed. (100,000 cycles for rubber covered Teflon®).
- During the test, any leakage is cause for rejection.
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Vacuum Testing Subject representative hose assemblies to vacuum conditions to determine rated vacuum conditions for hose at a given temperature.
- Seal assembly ends with modified fittings to draw a vacuum in the hose interior. Place assembly in an oven and heat until the desired temperature is reached.
- Reach the desired vacuum level and hold for 48 hours.
- At the end of the 48 hours, turn off the oven and allow the hose to cool to ambient temperature while still under the same vacuum level.
- Turn off the vacuum and observe the hose for buckling or collapse of the liner. Any buckling or collapse of the liner shall be cause for rejection.
- If no collapse or buckling has occurred, the vacuum and temperature shall be considered acceptable.
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| 7.0 |
DISTRIBUTOR / FABRICATOR / ASSEMBLER QUALIFICATION
Qualification of fabricating distributors is important, as they are the main contact and provider for hoses on a daily basis. |
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7.1 |
Distributor Qualification
Each fabricating distributor must pass qualification/certification testing directed by the manufacturer. Information regarding specifics of the qualification can be found in the Distributor Approval Documents. |
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7.2 |
Distributor Fabrication Guidelines
Each fabricating distributor must assemble hoses per the Distributor Fabrication Guidelines provided by the manufacturer. |
| 8.0 |
RECERTIFICATION of IN-SERVICE HOSE
Hose of Teflon® in service for extended time should be recertified periodically to ensure the safety and reliability of the assembly. |
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8.1 |
Visual Inspection
Hose should be visually inspected before taken from service. Items to look for include any leakage, kinks, or damaged covering. Upon removal of service, the hose should be rechecked for items mentioned previous as well as inspection of fittings and liner for deterioration or other faults. Any leakage or other faults is cause for rejection. |
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8.2 |
Cleaning
If a hose passes visual inspection it should be cleaned before any other testing is performed. This prevents any mixture of fluids that may be used for test and ensures safety of testing personnel from contact with in service chemicals. |
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8.3 |
Pneumatic Test
A pneumatic test under water should be performed prior to a hydrostatic test. The pneumatic underwater test should be a leak test and the pressure should be no greater than 15 psig. Any signs of leakage is cause for rejection. |
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8.4 |
Hydrostatic Test
A hydrostatic test should be performed with an equal pressure of the original fabrication hydrostatic test pressure and held for a minimum of 5 minutes. This test should be performed for fitting blow-off and leakage. Any signs of leakage or bulging is cause for rejection. |
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8.5 |
Record
Any hose failing all or any portion of sections 8.1 - 8.4 should be removed from service. Hoses passing all recertification tests should be tagged with information regarding date and pressure of retest, along with date to remove and/or retest again, and can be returned to service. A written record of this certification should be kept. |
| 9.0 |
HANDLING & SHIPPING |
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9.1 |
End Fittings
All end fittings should be protected by plastic caps, wood covers, or other suitable covers to prevent damage to flares, threads, or other sealing properties. These covers should only be removed during inspection and installation. |
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9.2 |
Packing
Hoses should be packed in suitable containers that are crush and weather resistant to protect during handling, shipping, and storage. |
| 10.0 |
PURCHASING |
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10.1 |
Proper Purchase Order
Each purchase order should consist of at least the following information:
- Full Description (Figures 2 & 3 show improper and proper hose descriptions).
- Quantity.
- Ship to address.
- Ship to instructions.
- Pricing for each line item and total line items.
- Delivery Requirement.
- Part number (if available).
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| Figure 2: Improper Description |
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1" x 10' Teflon hose, stainless steel braid, stainless steel male pipe by encapsulated flange. |
| Figure 3: Proper Description |
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1" x 10' PTFE T-62 Teflon® Natural Convoluted liner, 316 Stainless Steel single braid, 316 Stainless Steel Male NPT one end, High Purity PFA Encapsulated Flange Retainer with 150# Carbon Steel Epoxy Coated Flange one end. |
Document revised July 2002
This document may be used and reproduced only with permission of Resistoflex.
The information contained herein is provided only as a guide for the use of Resistoflex products and does not constitute an express warranty of any kind. Resistoflex specifically disclaims the implied warranty of merchantability and fitness for a particular purpose.
Confidential |
