Rubber Archives • Rubber Lining

Inspection of Rubber Lined Vessels

Posted on June 1, 2015 by Dan Chamberland

An inspection of a rubber lined vessel should be conducted once per year and never delayed. A close check should be maintained on operating procedures and conditions at all times. If a problem is going to occur with a rubber lining, generally it will happen within the first 3 months of service, which is why it is important to check a lined vessel after the first 3 months of service.
This is likely to be true whether the problem is caused by workmanship or by misapplication of material choice.
In some cases, the solution for which the tanks were originally lined for will have little detrimental effects on the rubber while the increase of a few percentage points in the service condition (added heat, less of more concentration, introduction of new chemical) may have a definite deteriorating effect of the rubber.
The tank must be clean, degassed, and dried before a proper inspection can be made.

A full visual inspection should be conducted, being aware of:
– Any loose seams
– Blisters
– Cracks
– Cuts
– De-lamination of the sheet surface
– Discoloration or suspicious areas

Notes of the date of the inspection should be entered within a log book which is kept on each rubber lined tank and should be updated each time the tank is inspected. The areas which were described as suspicious on the previous should be identified by some means of a reference of a location and rechecked with each additional inspection.
***Note: On entering a rubber lined tank, workmen MUST wear smooth sole shoes (no contamination is acceptable) and be very cautious not to drop sharp or heavy tools onto the lining or place hot electrical lights against the rubber linings. Ladders MUST have padded feet (both top and bottom) and placed gently inside the tank.

Any questions on inspections of rubber lined vessels or repair procedures please consult

Buck Meadows / Rubber Technologist

RubberSource at 519-620-4440.

Compressed Air Blotter Test for Rubber Lining and Painting

Posted on March 3, 2015 by Dan Chamberland

Compressed Air Blotter Test

What is it checking for?

The background behind this specification, which is becoming more and more prevalent in engineering documentation, has to do with the presence of oil and water in the air stream. As you can imagine having oil sprayed onto a surface prior to painting would be terrible. It would immediately create fish eyes, lack of adhesion and all types of terrible things for the paint. Water is just as bad as flash rusting can occur.

Rubber and hydrocarbons for the most part don’t get along. So the presence of oil on a surface will definitely have a negative impact on the adhesion and longevity of rubber on a steel sub straight.

Why would water be in the air line?

Humidity (water molecules suspended in the air) is found in the air all around us. When compressed the moisture forms into water. Most compressors are equipped with a water separator. But water separators are not all created equal. Based on the volume of blasting or painting, your air water separator may not be able to process the volume of water. Winter is a good gauge of if your water air separator is working for your setup. If your lines freeze in winter yours is not adequate for your work load.

Why would oil be in the air line in the first place?

Not all compressors are made the same. Piston compressors are more prone to oil in the air than screw compressors. Although all compressor designs offer various risk to oil in the air lines, there are many inline solution to capturing any residual oil left in the air.

How is the testing done?

You can use a 4″ X 4″ clean cotton cloth. Spray for a duration of 1-5 minutes and look to see if you any oil or water. This only needs to be done once per shift as objective evidence for your client if required. Otherwise it’s good practice to monitor your compressor air as well as you oil separation for long term performance issues.

For the exact specification the standard would be according to ASTM D 4285

The net result of good clean air!

A clean well blasted metal with no surface impurities will enable you to create a perfect adhesive bond that will ensure a rubber coating will last forever.

Good process equals good results…

Bends and Rubber Lining

Posted on February 9, 2015 by Dan Chamberland

Bends and Rubber Lining

The use of bends in a designed piping system is critical to managing wear in piping directional changes.

In short the longer you can make the directional transition, the less wear you will ultimately have in your elbow. Induction bent elbows provide engineers and designers an infinite degree of adjustment and allows the elbow to have any sweep dia, limited only by the sweeping arm of the induction bending machine.

Although there are very little limitation of what can be fabricated as an elbow, lining these elbows with rubber can be a challenge.

Here are some general rules of thumb.

Positive: Larger diameters elbows are easier to line as you can reach the inside to stitch and work out possible air pockets.

Negative: Large diameter tubes are very heavy and hard to manage, sometimes difficult not to create wrinkles

Negative: Small diameter long swept bends are challenging as you cannot manually adjust the tube in the swept section. Difficult to stitch in corners.

Negative Small long swept bends can hide bubbles and wrinkles as they can be hidden in the inside radius which is impossible to see with the naked eye.

Positive: Small diameter tubes are generally easy to handle.

Thick liners in small diameter bends are difficult, due to the tube not wanting to turn the corner and kinking when folded in half. The liner has tendencies to create large wrinkles.

New trends is to have thick liners in pipe and elbows. Engineers are using the additional rubber thickness in order to match flow calculations and standardize pipe size. An example of this would be using a 30″ dia. pipe and lining it with 2″rubber. The engineering design recommended 28″ pipe for the flow. But 28″ pipe is not common and 28″ flanges and valves are not commonly stocked and are very expensive. Using 2″ rubber would accomplish the reduction in interior diameter.

Other times the belief is that a thicker liner will make the elbow last longer, this is inaccurate. If using the correct compound for the fluid with particle size and flow taken into consideration than 1/2” rubber sub-straight is ample for best performance.

Lining with 2″ thick material is extremely in-practical. The weight of the tube would exceed the tear strength of the silk required to pull the tube through the elbow. The tube would weight in the area of 700 lbs. The other challenge with such a thick liner, the sag created in the material during the vulcanization process will create an uneven liner. The top of the part would thin and the lower section would increase dramatically. An uneven liner generally created uneven wear.

From a designing perspective, 3D bends should generally have a minimum 1D tangent. Anything less and the end of the pipe will result in an elliptical form. An elliptical end will create challenges with the termination, flanges and grooved ends. This generally doesn’t affect rubber lining but 1D tangents are good design practices.

Pro Tip.

-Although 6 D bends are great for wear, the most common swept bend ordered are 3D 45’s and 90’s. These are common and stock in most location have a 1D tangent. Even if the site has a 1 deg slope try to standardize all bends to normal standard angles for ease of replacement and interchangeability.

-3D Bends 8″ and below 1/4″ liners

-3D Bends above 8″ 1/2″ Liners.

-3D Bends above 16″ if required 1″ liners are possible

-On cyclone under-flows where the material if very coarse like 3’/4″ ,minus allow for the longest possible Radius such as a 5D or 6D elbow.

What elastomeric lining material is appropriate for what service?

Posted on October 31, 2014 by Dan Chamberland

Rubber selection can be intimidating as there are a number of engineered high performance linings which can have several different applications. I will list a few different elastomers and durometers as a general guideline.

There can be many different formulations of the compounds listed below with different physical properties than what is listed.

Soft Natural Rubber, 30-60 Duro Shore A, Temp Limit 160 Deg F, Resistance to Hydrocarbons Poor

Typical Uses: Acid Storage depending on concentration, Transportation equipment, Abrasive Services, Sulphur dioxide scrubbers.

Semi Hard Natural Rubber, 80-85 Duro Shore A, Temp Limit 180 Deg F, Resistance to Hydrocarbons-Fair

Typical Uses: Chemical Processing and Plating

Hard Natural Rubber, 90-100 Duro Shore A, Temp Limit 200 Deg F, Resistance to Hydrocarbons-Fair

Typical Uses: Chemical Processing, High temperature nickel-copper plating, steel pickling, vacuum service.

Graphite Loaded Hard Rubber, 90-100 Duro Shore A, Temp Limit 212 Deg F, Resistance to Hydrocarbons-Fair

Typical Uses: Special lining for wet chlorine gas, in chlorine cells and associated equipment. High wear applications.

Three-ply (Soft, Hard, Soft) 40-50 Duro Shore A, Temp Limit 230 Deg F, Resistance to Hydrocarbons-Fair

Typical Uses:Steel pickling lines, Phosphoric Acid

Neoprene 40-70 Duro Shore A, Temp Limit 230 Deg F, Resistance to Hydrocarbons-Very Good

Typical Uses: Chemical or abrasive services with oil present, best for strong bases, good weather resistance, fire retardant.

Nitrile, 60-90 Duro Shore A, Temp Limits 200 Deg F, Resistance to Hydrocarbons-Excellent

Typical Uses: Aliphatic hydrocarbons, kerosene, animal, vegetable and mineral oils.

Butyl, 50-75 Duro Shore A, Temp Limits 225 Deg F, Resistance to Hydrocarbons-Fair

Typical Uses: Oxidizing acids, 70 percent hydrofluoric acids, super phosphoric acid, best water resistance, good for alternative service.

Chlorobutyl, 40-60 Duro Shore A, Temp Limits 200 Deg F, Resistance to Hydrocarbons-Fair

Typical Uses: Much the same as butyl but easier to apply and faster curing, sulfur dioxide scrubbers.

EPDM, 40-60 Duro Shore A, Temp Limits 180 Deg F, Resistance to Hydrocarbons-Poor

Typical Uses: Hypochlorite bleach, ozone and weather resistant.

Feel free to ask about applications and we can suggest compounds.

Rubber Lined Piping & Engineering Manufacturing Procurement Process Challenges

Posted on October 10, 2014 by Dan Chamberland

Doing a large project for engineering firms can be rewarding and challenging depending on the contract at the same time. Here are some of the process challenges with rubber lined piping and piping projects in general.

The most common way to price many short lead, large scope projects is to bid a Bill of Material. These BOM’s are generally generated form a snapshot of their CAD system model. The CAD bill of materials unfortunate provides the first challenge such as how to price 10,000 feet of pipe when you don’t know the individual lengths? How many termination are there, how many branches are there, supports etc…? The descriptions of the piping will say rubber lined grooved. So to determine the quantities of grooves you must sometimes estimate based on the coupling count.

Some of these challenges have been overcome by providing welding rates, cutting rates, branch rates etc… This method of pricing does not provide the purchasing groups a clear cost on the project. As many of the welds and cuts do not get rolled up or counted into the price. The preferred alternative is to price a- la cart. This style of pricing would mean that any flange price listed for example in the BOM would include all the shop processes required to fasten a flange for example to any piece in the system. This provides a transparent all in fabrication price.

Assuming your prices are competitive and you won the contract, the next challenge is that generally the fabrication drawings are not complete. Hopefully the purchasing people will allow you to purchase the BOM as it stands, as waiting for drawings can delay projects, while the drawings are being completed you can purchase and stage your materials for fabrication. Next arrives the drawings and they pose their own problems as discussed in my blog on cad challenges.

Now you fabricate your rubber lined piping. When you ship your project to site you are not shipping flanges pipe and a branch separately. You are shipping a spool that contains all the materials listed in the BOM. Reconciling the original PO is extremely difficult as the original PO is based on a BOM. Depending on the purchasing team a backup document containing the price breakout of the spool may becomes a useful tool to reconcile the billing on the spool i n order to eventually consolidate the project purchase order at the ends

Keeping these interesting challenges in mind and discussing the challenges with an agreement ahead of time, before the issue of a purchase order will ensures a smooth trouble free contract.

Storing Rubber Lined Equipment

Posted on September 3, 2014 by Dan Chamberland

ALL-WEATHER STORAGE

1. Rubber linings should never be exposed to direct sunlight or direct outdoor weathering, for periods longer than a few days. All other linings should be protected from sunlight. If no other alternatives are possible, linings should be periodically painted with Age Guard.

SUMMER STORAGE

1. If possible, store in shaded areas away from direct sun exposure.

2. Paint outside of tanks with aluminum or white paint, or cover with a tarpaulin.

3. Closed tanks should be kept ventilated.

4. Tanks to be stored for long periods after having been in service, should be partially filled with a diluted solution of the chemical they were designed to contain (a 1-3% concentration probably will be sufficient).

5. For piping, the ends to be capped at all times before going to service. Helps protect against the weather and damage that may occur on site

WINTER STORAGE

1. Equipment should be protected as much as possible from the elements by covering with tarpaulins, erecting temporary shelters, etc.

2. Tanks containing solutions must be emptied if temperatures drop below the freezing point (of the solution contained therein).

3. Equipment should be handled very carefully and protected from subjection to external forces (sudden blows, flexing, twisting, etc.). Sudden temperature changes also are to be avoided. These precautions are most important for linings with a hard durometer.

IDLE OR STANDBY EQUIPMENT STORAGE

1. Idle or standby equipment (especially semi-hard lined) should be protected against excessive drying out and temperature changes. The best way to accomplish this is to fill the tanks with a 1-3% solution of acid, preferably H2S04, and hold at ambient temperature. This will help keep the lining more flexible and minimize the expansion and contraction problem as well as decrease the possibility of thermal shock when the equipment is put back into service.

2. If the diluted solution is not optioned, then apply Age Guard to the rubber linings once per year the lined equipment is idle.***Note: All idle equipment should be inspected prior to being put into service.

Any questions please contact RubberSource @ 519-830-0546 / buck@rubbersource.ca

Buck Meadows / Rubber Technologist

Technical Sales Manager

RubberSource

Shelf Life Of Uncured Protective Rubber Linings

Posted on June 16, 2014 by Dan Chamberland

In determining the shelf life of uncured rubber linings, several instances but be understood:

The level of heat memory built into a compound (ex. Synthetic Rubber takes more heat to break down than a Natural Rubber)
The lower the storage temperature, the longer the rubber lining will be useable.

As a rule of thumb the average uncured rubber linings (NR, IIR) will have a shelf life of approximate shelf life of 9 to 12 months if stored at a temperature of 10°C (also out of sunlight). If the linings are stored at a lower temperature the rubber lining will much longer the 12 month period. Please note that Neoprene (CR) and Nitrile (NBR) compounds have a typical shorter shelf life than the above mentioned compounds. In dealing with these compounds a great of caution is to be used as they can cure much faster. If storing rubber at a lower temperature that the recommended 10°C the rubber may become frozen, if this was to happen the roll will need to be unrolled and left at an ambient temperature for 2 weeks to thaw the rubber. After the 2 week interval the rubber will need to go on a hot table to help facilitate any shrink that might of occurred during the freezing process.

Any Questions please contact RubberSource @ 519-830-0546.

Buck Meadows / Rubber Technologist

Technical Sales Manager

RubberSource

General Call for Rubber Lining Industry Suppliers Articles!

Posted on June 2, 2014 by Dan Chamberland

Rubber Lining.org is a site dedicated to being the repository of knowledge for the rubber lining industry.

We welcome articles from professionals in the rubber supply, rubber lining, piping, engineering and wear industry. We will publish all articles related to rubber lining and associated information as long as they are written by rubber lining industry professionals who wish to contribute to this knowledge base and given that the articles are non-partisan.

If your company contributes an article you will get credit for the information as well as get listed under one of the vendor tabs at no cost.
If you wish to submit an article please e-mail it to.

Dan.chamberland@Rubberlining.org

Thanks

Bromobutyl Rubber Linings

Posted on June 2, 2014 by Dan Chamberland

Bromobutyl is a derivative of the halobutyl family, which is structurally similar to chlorobutyl rubber and produced through the same halogenation process: Brominated (BIIR) to Chlorinated (CIIR). By using the brominated process allows the same workability in the lining as a chlorobutyl. The Bromobutyl polymer will exhibit stronger physical characteristics over Chlorobutyl. Bromobutyl Linings are either blended with Natural Rubber for ease of application or made pure in polymer content, which means there is no other polymer in the formulation which gives the lining stronger permeation and heat resistance.

Advantages

• Tight knitting of the molecular cross link which results in an extremely low permeability rate.

• Low glass transition temperature

• Wide vulcanization versatility

• Fast cure rates

• Higher Heat Resistance

o Other Bromobutyl linings have a maximum heat resistance to 121°C as to the pure bromo can run at a constant temperature of 127°F and handle spikes up to 150°C

• Stronger bond strength to substrates

• Excellent Oxidation / Ozone Resistance

• Good Abrasion Resistance

Common uses of Bromobutyl linings are:

– Scrubber Towers

– Piping,

-Storage Vessels

– Chutes

– Thickeners / Clarifiers

Any questions on our Bromobutyl linings please feel free to contact

Buck Meadows / Rubber Technologist

RubberSource

Ph# (519) 620-4440

Email: buck@rubbersource.ca

ASTM specs and what they mean for rubber.

Posted on May 20, 2014 by Dan Chamberland

There are many standards used to qualify rubber. ASTM, NACE as well as others which attempt to define and standardize the industry.

I will attempt to simplify and clarify some of the standards and usefulness.

Some specifications are valid as a key performance indicators for wear, while others are simply elemental, the physical characteristics.

ASTM D297 or Specific gravity is a good example of an elemental specification. The fact that rubber has a specific gravity less than one is a good indicator that it will float. Floating does not necessarily indicate that the rubber will perform better or worse in a slurry application.

In the old days this was used to determine the actual content of natural rubber. Adders and filler like clay and carbon’s can affect the buoyancy of rubber they can also affect it’s wear characteristics most times in a positive way. Material science has gone a long way since the floating test.

Cut and Chip The best indicator for how rubber sheet will perform in a real world application is the “Cut and Chip” resistance. This test is used to measure the performance of a rubber in a wear application. This test was originally devised by the tire companies to evaluate service life of tires in various conditions. This is a much better indicator of how a compound will perform in a wear application and much less an elemental test, describing the physical properties.

ASTM D2240 or Hardness Shore A although this is a very popular way of describing rubber. Effectively this is another elemental specification. People will argue that the durometer of rubber aid in different wear characteristics and they would be right. But it is still not a final indicator of how it will wear. It simply defines it’s hardness.

ASTM D412 This one covers Tensile and Elongation this is an interesting specification because elongation and tensile are very good when describing rubber for track. Let’s take a snowmobile track for example. The moment you spin a track, you want the rubber to have enough elongation to absorb some of the initial inertia. In a rubber lining application it is somewhat irrelevant. When bonding a rubber sheet to steel sub-straight the elongation will never really come into play for wear.

ASTM D624 Tear Die C another elemental indicator. In rubber lining, the force at which the rubber sheet will tear is not good wear resistance indicator. When building a tire, snowmobile or tank track this is a great indicator. Adhered to steel tearing it is the least of your concerns. Ultimately all these factors only help to describe how this material could perform. The forces required for an adhesive pull test is 25lbs to pass ASTM and Nace pull tests are very low compared to most sheet listed tear specifications.

ASTM D7121 Rebound and Resilience Although rarely listed in a rubber sheet or specification, the ability of a rubber to return to it;s original shape is important especially when defending against rocks, slurry and wear.

ASTM D5963 Wet and Dry Abrasion loss This is a good indicator of if your rubber will last in a wear application. This test directly measures wear. The best wear resistant rubbers will have good wet and dry abrasion properties mixed with excellent cut and chip resistance.

ASTM D573 Heat Aging Depending on the application this is a good test to evaluate rubber longevity. As rubber is generally a cocktail of materials how they perform over time and temperature will vary. This test monitors the physical changes of rubber with aging. This elemental test will give indication of how the rubber will perform over time.

Rubber wear characteristics are complex and understanding what the specification mean will help you in the long term choice for the various applications.

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