Functions of Membrane Housing in Water Treatment System

Three kinds of RO pressure vessels with different materials.

RO system pressure vessel: FRP, stainless steel and PVC membrane housing

Membrane housing is a pressure vessel for loading membrane elements in a reverse osmosis water treatment system. Currently, there are three types of membrane housings with different materials for water treatment on the market: FRP (fiberglass reinforce plastic), stainless steel and PVC. However, in recent years, more and more reverse osmosis water treatment systems have chosen to use FRP membrane housing. This is because the FRP membrane housing has a strong advantage in terms of pressure bearing capacity, design size, material properties and operating temperature compared to stainless steel and PVC membrane shells.

High Pressure Capacity

As is well-known, reverse osmosis system relies on pressure to achieve the purpose of purification or concentration. While the membrane housing is the vessel that bears this kind of pressure. In a reverse osmosis system, the higher the concentration of raw water, the greater the pressure that needs to be applied. Table 1 shows the pressure range for FRP membrane housing, stainless steel membrane housing and PVC membrane housing. Obviously, the FRP membrane housing has higher pressure capacity than stainless steel membrane housing and PVC membrane housing. It means that FRP membrane housing can be used in more types of water treatment systems.

Table 1: Comparison Table of Pressure Range
TypeFRP Membrane HousingStainless Steel Membrane HousingPVC Membrane Housing
Pressure150–1200 psi≤ 600 psi≤ 200 psi

Larger Design Size

The larger the size and quantity of membrane elements, then the larger the water yield and the higher the working efficiency of the reverse osmosis system. The most common reverse osmosis membrane elements diameters are 2.5", 4", and 8". Table 2 shows that the common design sizes of the three kinds of membrane housing on the market. Although both FRP membrane housing and stainless steel membrane housing can be loaded with these types of membrane elements, it is clear that the FRP membrane housing can be designed to be longer and load more membrane elements. Therefore, large-scale water treatment projects mostly adopt FRP membrane housings.

Table 2: Common Design Sizes of Various Membrane Housings
Standard Membrane Element SizeLoad Number of Membrane Housings
DiameterLengthFRP Membrane HousingStainless Steel Membrane HousingPVC Membrane Housing
2.5”14”/21”/40”1/1/11/1/11/1/1
4”40”1–61–31–3
8”40”1–81–3

Strong material property

Substances produced by membrane housing corrosion are one of the main sources of RO membrane contaminants and water treatment projects tend to be a long-term. Therefore, the corrosion resistant performance and service life of the membrane housing are very important. FRP is highly resistant to almost all chemical solvents and it has a long service life. It is hardly aging. So FRP membrane housing is suitable for almost all water treatment projects. Compared with the FRP membrane housing, the stainless steel membrane housing is difficult to resist the corrosion of the chlorine-containing medium. In addition, FRP membrane housing has higher strength and impact resistance, which means it is more difficult to damage during transportation and installation.

Wide operating temperature range

FRP membrane housing, stainless steel membrane housing and PVC membrane housing all can work at room temperature. But in some severe cold areas, only FRP membrane housing can be adopted. Because the material properties of the FRP membrane shell will not be affected by low temperature. The housings of stainless steel membrane housing and PVC membrane housing become hard and brittle due to low temperature, which makes the membrane housing more susceptible to damage and affects the service life of the membrane housing.

Table 3: Rated Operating Temperature of Membrane Housings
TypeFRP Membrane HousingStainless Steel Membrane HousingPVC Membrane Housing
Operating Temperature-10 °C–49 °C0 °C–48 °C2 °C–43 °C

FRP membrane housing is currently the most stable and most widely used membrane housing type on the market. It is suitable for almost all water quality treatment systems. And it can be used in low pressure or high pressure applications. As a professional FRP membrane housing manufacturer, Chengda has supplied high-quality membrane housings for many water treatment projects and has been widely recognized in the industry. If you have any technical problems with your water treatment project or you need some solutions, please contact sales@membranehousing.org.


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