About Chain Bar Screens

Home

Chain Bar Screens and cable bar screens fall under the mechanical bar screen umbrella. Fundamentally, there isn't much difference between these two types of bar screens. Cable bar screen use was more widespread in past wastewater treatment facilities, but today have been replaced with more robust screening devices. Mechanical cable and chain bar screens that utilize tines to dislodge objects from the bar screen are the oldest screening devices. These screens are available in several arrangements: front clean/ front return, front clean/ rear return, and back clean/ rear return. Each set-up offers advantages and disadvantages depending on the application the bar screen is being used for.

Trash Racks

Manual Bar Screens

Mechanical Bar Screens

Chain Bar Screens

The front clean/ front return configuration withholds screenings more efficiently by reducing solids carry-over. The front clean/ front return arrangement is the newer configuration and is largely used in typical municipal wastewater treatment facilities. The front clean/ front return configuration uses a raking mechanism that cleans trapped solids from the face of the bar screen by engaging the screen in an upward moving motion.

Once the raking mechanism reaches the top of the screen, the mechanism is cleaned by a cleaning mechanism. Even though this is the newer and more efficient arrangement, it is not as sturdy as the others and it is vulnerable to jamming from debris trapped at the base of the unit. The front clean/ front return chain bar screen is typically not used in facilities that serve combined sewer systems.

Reciprocating Rake Bar Screens

Catenary Bar Screens

Continuous Belt Bar Screens

Contact

Custom Search

Combined sewer systems receive very large debris that may potentially jam or brake tines, therefore this configuration is typically used in collection systems that serve separate sanitary sewers. For the more heavy-duty applications, the front clean/ rear return arrangement is used. The cleaning sequence is similar to the front clean/ front return, except the raking mechanisms advances to the back of the bar screen after cleaning.

This configuration has one drawback compared to the front clean/ front return. Screenings that are not removed from the tines during cleaning my be put back into screened water.

The bars geometry for both the front clean/ front return and the front clean/ rear return screens should be trapeziodal in cross section. The tapered shape will reduce wedging and clogging from trapped debris between the bars. One drawback that effects both of these configurations is the potential for jamming (especially if trash racks aren't used) by objects caught at the bottom of the bar screen.

Back clean/ rear return chain bar screens are very similar in operation to the front clean configurations. With the back clean/ rear return, the raking mechanism cleans the bar screen from the back by pushing particles away from the bars as it removes debris from the channel. It also reduces the amount of particles that become wedged between the bars. This arrangement has an advantage over the front clean configuration in that the cleaning mechanism is protected by the bar screen from bulky objects that make their way into the sewer system.

Although the tines engage the bar screen from the back, if the tines are too long they are more vulnerable to breakage than the front cleaned arrangement. When wipers on the cleaning mechanism begin to wear, this set-up also becomes susceptible to carryover of screenings downstream. Because this arrangement requires the tines to pass through the top of the bar screen, there are less supports which makes this configurations less rugged. Even though this design is less rugged, it does reduce the potential for jamming.

Post Your Review

The above mentioned arrangements may differ in their operations, but they do have some drawbacks in common. Most of the chain bar screens require frequent attention from operators to maintain successful operation.

For example, the submerged sprockets and chains need to be inspected on a routine schedule. Also, these bar screens have limited a screening capacity and issues related to braking mechanisms may arise. If the chain bar screen does not pivot out of the channel, the entire channel may need to be isolated and dewatered for maintenance.

blog comments powered by Disqus

Always consult with the manufacturer or your local equipment representative if you have specific questions about bar screens. This site is done by a random individual to help get you informed, but is not to substitute for professional opinion. Please read our disclaimer.