September 2014 • Rubber Lining

Modern Cad systems can be problematic for rubber liners….

1 Cad people may not take into account the rubber gasket on the face.

Normally when an engineer lays out the piping system they choose many different ways for the software to dimension the Isometric.

Long run dimensioning – Dimensioning from intersection to intersection, this is ok if you let the fabricator interpret the spool lengths. Generally the pipe lengths get indicated but the rubber lined face gaskets are not taken into account, groove type gaps or the fitting dimension are incorrectly setup. The other common mistake to this style of dimensioning is that the travel exceeds the physical manufacturing limitation of the spools in between.

Spool dimensioning -Dimensioning to the center of all the joints- This is by far the best method if the model is setup correctly. Grooves should be modeled not just specified, as the tolerance of this should be taken into account (1/8″ rubber on the face of the groove as well). The biggest challenge becomes when people use stock grooved libraries for non rubber lined product for a rubber lining system. The addition of the face rubber increases the fitting dimensions.

2 Descriptive modelling

As most modern advanced Cad systems such as Bentley, Aviva, Integraph or Microstation are very ridged and are provided with a standard parts library. For example many rubber lined systems end up being a coupled system. When using auto routing for piping, rules are set for spool lengths and gaps. A common cheat is to describe the piping as piping with grooves and to download the spool separations to the manufacturing. The result is that most spools in this case will have to be redrawn by the manufacturer as opposed to processed using Spoolgen for example. The redrawn spools may not always conform to the design dimensions making drawing checking and receiving of final product very difficult.

3 Libraries built for a steel only system.

All cad systems in the market are built to accommodate steel fabricated systems. So there are always compromises when it comes to descriptions and dimensions. As a rubber lining supplier it is very cost prohibitive to create libraries for all the engineering systems. Currently some coupling system companies have up to 23 different software catalogues built so that engineers can use their products.

4 Specifications do not always contain the compounds or thicknesses.

When processing Isometrics a specification a line class is usually provided. Some time these are very well laid out for rubber. Other times it is a combination of pipe sizes, service and line class that will determine the lining. The lining information is often not contained on the Isometric itself. Depending on your cad team this can be a difficult item to interpret from the information provided.

Conclusion

The sooner you can get involved in a project the better. Working with the engineering firms, understanding their challenges and concerns will help you find common grounds. Working with both the EPCM and end users will reduce processing errors, reduce the overall project lead times and cost.

Soluble Salt testing is becoming the latest inclusion into EPCM specifications for quality requirements.

What are Soluble Salts and Sulphates?

Soluble Salts and Sulphates are the most dangerous forms of contaminants for paints and coatings. When they are painted over they have the power to draw moisture through Osmosis and cause blistering, detachment and accelerate corrosion of the underlying metal. When steel is repainted, rough or pitted areas are visible after dry abrasive blast cleaning. These may contain soluble salt contamination, especially in the base of the pits. Dry abrasive blasting does not remove these salts. It is wise to check for the presence of soluble salts with specially designed field test kits before painting and if they are present in detrimental amounts, to take additional cleaning steps to remove the salts.

How can you test for Soluble Salts?

The common tools used to test for soluable salts are the Chloride Iron Test Kit for Surfaces. This test looks for remaining chloride levels on a sub-straight prior to painting. The second tool is a Salt contamination Meter. This tests for soluble salts on the substrate surface prior to painting by absorbing distilled water soaked filter paper and then testing it.

How do Soluble Salts Occur?

There are many ways your steel can be exposed to soluble salts and sulphates. The most common way is through transportation. Pipe and steel travelling at sea can accumulate contaminants during travel to the fabricators. The other method is when trucking materials during the winter. Road salts can easily be distributed on to steel during the transportation process.

Is checking for Soluble salts necessary?

Soluble salts became an additional test required and recommended by Nace. As engineers attempt to cover off as many concerns with their specifications as possible, it is becoming a popular addition. The method of testing and the frequency required by this code make production volume of pipe spooling and steel testing costly and difficult. Most pipe from mill come with mill varnish helping protect the surface during travel. New steel will generally not be pitted, where a good sandblast profile will easily eliminate any surface contaminants. There are situations where you are on an oil platform, recoating old steel, in the middle of the ocean where this specification is highly advisable but for most steel processing this is considered over processing. The short answer is where required.

Soluble Salt in relation to rubber lining.

Generally speaking in a rubber lining application, the internal liner will fail far sooner than the steel or coating will deteriorate. Rubber lined product is generally considered a wear product. Warranties are difficult as process flow, materials configurations are always changing. Unless adamantly specified this specification should be avoided.

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

Month: September 2014

Rubber Lined Piping Systems and your Cad System

Soluble Salts Testing

Storing Rubber Lined Equipment

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