Questions and Answers For Filter Press Usage
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1. How to judge that the filter press is full?
(1) The model of the outflow liquid can be judged according to the water output of the tap. When the water flow basically stops, it means that the filter press is full.
(2) Or by observing the working pressure of the ceramic plunger pump, if the pressure reaches about 1.5, it means that the solid in the filter press has formed, so the pressure has increased.
2. How long does it take to replace the hydraulic oil?
(1) Generally, it needs to be replaced once a year, or the working time exceeds hours.
(2) In special circumstances, it is necessary to increase the replacement frequency.
(3) Be careful not to mix water and other impurities in the hydraulic oil, so as not to affect the normal operation of hydraulic components.
3. When do I need to replace or clean the filter cloth?
(1) When it is found that the filter cake starts to become moist, slippery, and not as dry as before. This means that the water permeability of the filter cloth has deteriorated.
(2) You can first try to clean the filter cloth to clean the remaining mud cakes in the pores of the filter cloth.
(3) If the effect is still not good, you should consider replacing the filter cloth.
(4) The service life of the filter cloth depends on the frequency of use, whether it is cleaned and maintained frequently, and the characteristics of the filtered sludge.
(5) Generally speaking, the longest service life of filter cloth is 6 months.
(6) Another thing to pay attention to is the damage of the filter cloth. If the filter cloth is damaged, the sludge will be mixed into the filtrate and the filtrate will be unclear. It can usually be judged by the water outlet of the faucet and needs to be replaced in time. If it is not replaced in time, the mud cake will penetrate the filter cloth and gradually block the backflow groove between the bosses of the filter plate where the filter cloth is located. The fluid will not flow smoothly and the pressure will be uneven or overpressure, which will eventually cause the filter plate to be damaged.
4. Do I need to replace the filter plate?
(1) The normal service life of the filter plate can be several years, but it needs to be maintained and maintained at ordinary times.
(2) If a broken plate is found, it needs to be replaced in time to avoid affecting the remaining filter plates.
5. How long is a cycle?
(1) The cycle time mainly depends on the dewaterability of the sludge. Generally, a cycle is between 2-4 hours.
6. How can I guarantee a drier mud cake?
(1) Ensure that the filter cloth is cleaned and replaced in time
(2) Ensure sufficient cycle time
(3) Some special sludge needs to be pre-treated and then filtered
7. Why is the filtrate unclear?
(1) It is possible that the filter cloth selection is incorrect
(2) It is possible that the filter cloth has been used for too long and needs to be replaced
Contact us to discuss your requirements of sludge filter press. Our experienced sales team can help you identify the options that best suit your needs.
(3) There may be holes in the filter cloth
(4) If it is an embedded filter cloth, the rubber strip may be deformed and fall out of the groove
(5) It is possible that the cloth on the head plate is not installed properly
8. How can I adjust the compression pressure of the cylinder?
(1) Due to the different model and delivery time, please consult my professional staff (Fujian Nanxing Environmental Protection Technology Co., Ltd.).
9. The designed feed pressure of my filter press is 1Mpa. Can I increase the feed pressure?
(1) It is strictly forbidden to feed the material with overpressure, which will cause shotcrete, and it will be destructive to the filter plate and hydraulic system of the filter press.
(2) If you need to use a higher feed pressure, there are other corresponding models, please consult our company (Fujian Nanxing Environmental Protection Technology Co., Ltd.).
10. Why does my filter press leak during the filtration process?
(1) If the filter plate has not been replaced recently, it may be due to residual filter cake sticking to the sealing surface.
(2) Check whether the cylinder pressure is at the recommended value, if not, please adjust it.
(3) It may be because the filter cloth has wrinkles, holes, or the embedded rubber strips are loose.
(4) If the problem still cannot be solved, please consult a professional (Fujian Nanxing Environmental Protection Technology Co., Ltd.).
11. Why is there leakage at the feed of the new machine?
(1) Please check whether the sealing ring is flat and intact, whether the sleeve is tightened, sometimes it may be loose and damaged during transportation
Q: We have recently noticed our plate and frame filter press cake is no longer pressing properly and we are getting soupy and sticky sludge instead of the normal dry hard filter cake we are used to. What could be causing this issue and how can this be corrected?
A: When it comes to dewatering solids from wastewater treatment systems, a plate and frame filter press is reliable and is easily operated. However, changes in water chemistry or a lack of maintenance can quickly turn a filter press into a frustrating issue. The resulting soupy or sticky sludge that has not been properly dewatered will increase cycle time, causing a backup of solids in your system. This issue can even create problems with waste disposal vendors and cause the need for recharacterization if not resolved in a timely manner. A few of the most common causes of this are a lack of filter cloth maintenance, feed pump issues, poorly optimized coagulant use, and proper dosage of flocculants.
Filter Cloth Maintenance: Over time, your filter cloths can build up organic contaminants, precipitated metals, and excess flocculant polymer. Fouling of the cloths causes the efficiency of the press to be reduced and increasing the amount of time for a proper press cycle.
A few methods can be used to clean the filter plates and cloths including washing with a dilute cleaning solution, acid washing with dilute hydrochloric, power washing the cloths or any combination of these methods. Each of these methods has their advantages and drawbacks and should be reviewed to address what is fouling your cloths.
One of the simplest methods is to use a low-pressure spray (with or without a dilute cleaning solution). This type of wash can help remove some oils and organics, but it will not solubilize metals or most flocculants, leading to a secondary dilute acid wash being required.
An acid wash is generally effective in removing most materials from filter cloth pores. A cleaning solution can generally be run through a press (25% HCl) easily with a clean in place (CIP) system. Alternatively, you can set up a tank to soak the filter plates in dilute acid, but this will increase the amount of handling and the overall cleaning time. Plate/cloths are usually soaked overnight in a solution of 4-5% HCl. One will need a method to rinse the plates after soaking and consequently the added handling of spent cleaning solution. It is important to remember that when performing an acid clean, you will need to pay attention to acid compatibility with your filter press pump. If incompatible, use a different pump to move the solution through the filter press. For example, a cast-iron cased air-operated diaphragm pump is commonly found as a feed pump on filter presses and is not compatible with hydrochloric acid.
Power washing with hot or cold-water filter cloths is another option that can be alternated with one of the chemical methods. Care should be taken to prevent damage to the cloths. If too much pressure is applied to a small area the cloth can tear, rendering that filter plate inoperable. Additional personal protective equipment for employees may also be necessary due to the particulate and chemical constituents coming off the filter cloths.
The best solution will likely be a mix of the above methods and should be scheduled on a preventative basis. The proper cleaning of filter cloths will prolong the need for replacement, but eventually, filter cloths will need to be changed due to the wear and tear they experience.
Feed Pump Issues: When experiencing long cycle times, one should look to their feed pump. Air-operated diaphragm feed pumps can become partially blocked by debris and not allow the full feed pressure to the press. This is less common but can be cleared by disassembling the pump and clearing any debris. While disassembling the pump, it is important to check the diaphragms for holes or wear due to debris, as a hole in a diaphragm will cause the same issue, and over longer periods of time, diaphragms are a wearable part that needs to be replaced as needed.
Coagulant Optimization: Coagulant optimization can often be overlooked, especially if your wastewater system discharge water is meeting all permit requirements. If you are not feeding a coagulant, one might be required to condition your water and allow for better flocculant formation. Poor charge neutralization or a failure to treat organic contaminants will yield sludge that will not readily dewater and/or will clog your filter cloths. If you have a sludge that has never really pressed into a good solid cake, this might also be a sign a change to the coagulant dosage or type is needed. Coagulants that are organic in nature can fail to deal with some contaminants and inorganic salt-based coagulants can cause excessive sludge. Blended coagulants help bridge these problems but should be bench tested to determine the proper feed and type to maintain both permit limits and sludge dewatering. Any time a stream feeding the wastewater system changes, a coagulant review will be required for the application. Be especially mindful of production cleaner changes or any influx of oils or grease. In the case of heavy oils, a precoat of diatomaceous earth or lime will be needed for the filter cloths.
Flocculant Optimization: An overdose of flocculant or an improperly made down flocculant can cause the filter cake and filter press cloths to be sticky and slimy. When this happens, the press often needs to be acid washed to break down the flocculant polymer and open the pores in the filter press cloth. It is easy to accidentally overdose your flocculant. This can be caused by a drop in the total suspended solids feeding the system or a change in the flow rate of the system without proper adjustment of the polymer. Another issue commonly witnessed is poor flocculant make-down. For example, if making down your flocculant from a powder into a tank if the polymer is added to quickly or in slugs you can form polymer balls (fisheyes). These will not react with coagulated solids and will ultimately end up in the filter press, sliming up the cloths. This can be fixed by closely monitoring the addition or installing a screen ahead of the polymer feed pump. A simple option is to change to a version that is already made down into a liquid. This will prevent the risk of fisheyes and simplify the system for operators.
No matter what the cause, a poor filter cake can lead to large amounts of time troubleshooting the issue and unnecessary costs in fixing the issue along with disposal costs due to waste vendor issues. With the proper guide or help from an expert, this process can be resolved in a timely manner with little system downtime due to unplanned shutdowns.
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