Structural FRP Tanks

The ideal choice for residential and light commercial water treatment applications that require flexibility. Improve your water treatment system with Structural FRP Vessels. Easy to handle and install, our FRP tanks are available in standard polyester or chemical-resistant vinylester construction depending on your needs.

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Features and Benefits

• Standard polyester or chemical-resistant vinylester construction
• Easy to handle and install
• 10-year warranty for 6" to 13" vessels (softener/filtration applications)
• 5-year warranty for 14" to 16" vessels (softener/filtration applications)
• 2-year warranty for vinylester vessels (deionization applications)

Specifications

Pentair

• Safety factor: 4:1
• Minimum burst at 600 psi
• Tested to 250,000 cycles without leakage

NSF

• Safety factor: 4:1
• Minimum burst at 600 psi
• Tested to 100,000 cycles without leakage

Residential tanks 6"-16" in diameter are Certified to NSF 44. Commercial tanks 18"-63" in diameter are Certified to NSF 61.

• Maximum operating pressure: 150 psi
• Maximum operating temperature: 120° F - polyester, 150° F - vinylester

Certifications

• Vessels Tested and Certified by NSF International to NSF/ANSI Standard 61 for material and structural integrity requirements.

Colors

• Black
• Blue
• Natural

The FRP (Fibre Reinforced Plastic) Vessels have become a very popular alternative to the conventional pressure vessels made out of MSRL (Mild Steel Rubber Lining) and SS (Stainless Steel). The popularity of the FRP avtar of the vessels is due to,

-         Light Weight

-         Low Cost

-         Zero Corrosion

-         Requisite Strength to be used in RO / Softeners / DM Plants etc.

-         Operating pressure of 10 Bar

-         Burst Pressure of 40 Bar

With all due to respect to these advantages, the FRP vessels have a major process limitation. This limitation is its capacity to handle negative suction pressure (or) vacuum. Most commercial manufacturers worldwide limit the vacuum pressure that these vessels can handle as 5&#; HG column or 0.17 Bar. This means that the FRP vessels would be susceptible to failure if the negative vacuum pressure rises beyond 0.17 Bar. It sounds quite difficult to believe that a vessel which would not burst under a high positive pressure of upto 40 Bar, could fail at a negative pressure of 0.17 Bar. It is this irony that tempts many system developers to overlook this and end up into problems.

Manufacturing Process of FRP Vessels:

In order to understand this limitation, it is necessary to first get familiar with the manufacturing process of the vessel. The FRP vessel has an inner liner (inner base vessel) made up of a thermo-plastic material, the most popular being Polyethylene.

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This liner vessel is strengthened by winding continuous strands of Glass Fibre around it in a cross-lap weave format. During the winding process, suitable binders and resins are used which allow the glass fibre to adhere strongly over the vessel.

Nature of Failure due to Vacuum:

When the vessel is under operation and experiences vacuum pressure, the inner liner tends to be sucked inside. It pulls the winding along with it. Such a repetitive action causes a severe wear and tear and ultimately cracks the inner liner. The water inside the liner enters the cracks and flows in the gaps and crevices between the liner and the winding. Wherever it finds an opening, it sprinkles out of the vessel. An inexperienced user would mistake this as a pin hole in the vessel. However, the cause for this is a liner crack due to vacuum.

Under certain cases of high vacuum pressure (probably due to a high capacity pump), the suction force can crack open the liner and also rupture the outer winding.

Reasons for Vacuum in an R.O. (Reverse Osmosis) System:

The below gives a schematic representation of a basic R.O. System. 

A vacuum pressure could be created in the line due to various reasons. Some of them are as below,

(1)   Its quite common that the source of water is an underground well or an underground sump. In such cases, the raw water pump (as shown in line drawing) is most probably a vertical submersible pump that lifts water upwards into the main line of the R.O. System. When such systems are switched off, the water recedes backwards as it naturally goes back to the source of water which is at a lower level. This will happen in case of a non-return valve. When the water pulls backwards it draws all the air in the line and creates a negative suction pressure. Beyond acceptable limits, it cracks the liner of vessels as explained earlier.

(2)   In absence of a low pressure switch in the R.O. System, it would continue to run even when there is no water left in the source sump or well. In such cases the high pressure pump will run dry and pull all the air in the line towards it. This would cause a very high suction pressure in the line. This vacuum pressure is sufficient to damage the liner of the vessels.

(3)   If the sand filter is not regularly backwashed and maintained, there is a possibility that it is completely choked. There would be no water in the line after the vessel which is installed as a sand filter. Once again the demand of the high pressure pump would not be met and it would run dry. This will cause a vacuum in the line and damage the vessel.

Prevention of failure due to Vacuum

·      Continuously evolving technology is bringing in new material for the inner liner that are stronger and less susceptible to failure due to suction pressure.

·      A fully automated system with a lot of control points and pressure switches can be designed to automatically cut of the power to the system in case of negative pressure.

·      The most economical and popular solution is the use a of a modest &#;vacuum breaker&#;. This is a simple &#;normally closed valve&#; that can be installed in the line immediately after the vessel. Under negative pressure, the plastic component lifts upwards and allows atmospheric air to enter the line, thereby breaking the vacuum. 

GSE Filter Pvt Ltd is a leading supplier of high quality FRP Tanks, under its brand name ATLANTIC PLUS.

For more information, please visit GFRP Pipe.