Flowrox Пресс-центр

Результаты проведения специальной оценки условий труда сотрудников ООО «Флоурокс»:

  Имя Размер
Сводная ведомость рабочих мест 000115 Таблица 70.6 KB

Improving Silo Isolation with Larox Pinch Valves

Julkaisuaika 2011-04-18

Silo isolation can be a challenge if you do not use the correct type of valve for the top of the cement silos. The cost of selecting a wrong valve can be huge: you may end up contaminating a full silo of valuable cement due to a leaking valve.


In many cases companies are stuck with the process equipment that was originally supplied when the plant was built. However, today there are many new and better technologies available. Concerning shut-off and control solutions pinch valves are one of the best technologies for the isolation of pneumatically conveyed cement. For example, many Asian cement plants have recognized the benefits of a pinch valve and have not only replaced old valve technologies with pinch valves, but are also using pinch valve as standard for their new terminal projects across the Asia.

Diverter and Knife Gate Valves in Silo Isolation

Diverter valve is a commonly used valve type. It has been used for many years and it works reasonably well. However this type of valve often has problems over time. The mechanical flapper in these diverter valves over time usually begins to cause problems. The problems typically experienced are 1) increased force required to switch the flapper from one side to another, 2) no longer tight shut-off when switched and finally 3) these types of valve typically need to be repaired every year.

The other type of valve that is widely used for silo isolation is a knife gate valve. These valves are good for pneumatically conveyed materials and they also are one of the least expensive alternatives. Unfortunately, they are the one type of valve that will be replaced more frequently than any other type of valve used in these systems. What will typically happen to a knife gate is that a small pinhole leak occurs in the seating area. The cement and air blow through this tiny hole at high velocity and slowly gouge a larger hole. The entire knife gate and body are typically destroyed in a short time span.


Pinch Valve is the Best Solution

The best available technology today for the silo isolation at cement plants is a pinch valve. A rubber tube or sleeve is pinched by steel bars on the centerline of the valve to close. Self-cleaning pinch valves provide 100% tight shut-off even if solids have built up on the sleeve wall. When compressed, any crystallized particles flake off the sleeve surface and are washed downstream. 

The operating principle of a pinch valve is simple. In the open position, the valve is at full bore with no flow restrictions thus making the valve an integral part of the pipeline. During closing, two pinch bars squeeze the sleeve shut on the centerline.

The core of the pinch valve is the sleeve. It has to be made from three layers: wear resistant inter layer, fiber reinforcement layer, and protecting outer rubber layer as shown in picture below. This construction guarantees long lifetime of the sleeve. There can be found some copies with molded one layer sleeves, but they are gaining only 10% of quality sleeve lifetime.

Pinch valve itself is rather simple to build; however, the sleeve is not. Making quality sleeve demands wide knowledge of elastomer technology to mix right rubber for each application. In today’s markets there are only three pinch valve companies that are manufacturing layered and reinforced sleeves. Buying pinch valves from other than these manufacturers is comparable to assembling bicycle tires under 18 wheel truck. Tires are cheap but you need to stop the vehicle to repair the tires all the time.

Why Elastomers are Better Against Abrasion than Hard Materials?

The actual reason why pinch valve is better for abrasive duties than metal or ceramic valves is behind the following fact. Energy from particle impacts is absorbed to different materials in different ways. Metal, for instance, absorbs the impact energy of particle to itself. Every time when particles hit to metal they take a small piece of metal surface away with the flow. That eventually causes a hole or a sealing leak. Softer materials allow the abrasive particles to bounce off the surface without destroying it. So the energy of the particle impacts is used to maintain the flow instead of wearing the valve.

For this reason, pinch valves are constantly taking more market share from conventional valves in mining and cement applications where very coarse slurries and abrasive pneumatically conveyed materials are handled. A pinch valve also offers protection against clogging and jamming that can occur with other valves in cement service. Many valves such as knife gates or diverter valves with stellite or harder coatings might be able to withstand the abrasiveness of pneumatically conveyed cement. However, they are subject to jamming or clogging because they have cavities that allow for material collection.

In conclusion, many cement companies agree that high quality pinch valves are the best valve solution for silo isolation because they have long service interval, they are easy to operate, are easy to repair and in general they have very low cost of ownership. Finally, even if the pinch valve sleeve is beginning to fail, you will typically still be able to close the valve sleeve and prevent silo contamination.  

Takaisin listaukseen

 Показать больше

Контакт для прессы

Tuija Tiilikainen
e-mail: tuija.tiilikainen @ flowrox.com
mobile: +358 (0)45 878 3528

This website stores cookies on your computer. These cookies are used to improve our website and provide more personalised services to you.


To make this site work properly, we sometimes place small data files called cookies on your device. Most big websites do this too.

1. What are cookies?

A cookie is a small text file that a website saves on your computer or mobile device when you visit the site. It enables the website to remember your actions and preferences (such as login, language, font size and other display preferences) over a period of time, so you don’t have to keep re-entering them whenever you come back to the site or browse from one page to another.

2. How do we use cookies?

A number of our pages use cookies to remember your actions and preferences (such as login, language, font size and other display preferences.)

Also, some videos embedded in our pages use a cookie to anonymously gather statistics on how you got there and what videos you visited.

Enabling these cookies is not strictly necessary for the website to work but it will provide you with a better browsing experience. You can delete or block these cookies, but if you do that some features of this site may not work as intended.

The cookie-related information is not used to identify you personally and the pattern data is fully under our control. These cookies are not used for any purpose other than those described here.

3. How to control cookies

You can control and/or delete cookies as you wish – for details, see aboutcookies.org. You can delete all cookies that are already on your computer and you can set most browsers to prevent them from being placed. If you do this, however, you may have to manually adjust some preferences every time you visit a site and some services and functionalities may not work.