Needle Felt Filter Bag Installation & Operation Guideline

Storage Of Filter Bags

Carton boxes for storing filter bags should keep away from fire and humid environment and avoid direct sunlight and other strong light;
Carton boxes for storing filter bags should handled gently and prevent deformation under heavy objects pressed down;
Carton boxes for storing filter bags should be put on the wooden partition. The distance from the floor and walls should not be less than 30cm to avoid getting damp.

Checking Filter Cages

Check if filter cages are deformed during transport or handling;
Check if filter cages rust;
Check if filter bags have burrs or rough spots;
Check if filter cages’ joint is available. (refer to filter cages that separated in 2 or more parts)

Warning: If any of above situation arises, it cannot be installed and used. Unqualified filter cages will destroy filter bags or influence its lifetime.

Installation of Filter Bags

Preparation:

Clean the cell plate;
Make sure that the cell plate mouth is smooth and without burr;
Clean the blowpipe;
Make sure the blow pipe is clean and unimpeded;
Put the unopened cartons boxes with filter bags next to the dust collector.

Installation:

Take out the filter bag and slowly feed the filter bag from the bottom of the bag into the cell plate hole;
Pay attention to the direction of hot welding line and three-needle sewing threads to make sure it is not on the windward side of the dust collector;
Insert the snap band(filter bag top mouth) into the cell plate after the filter bag body is naturally vertical;
Put the filter cage vertically and slowly, and finally place the filter cage gently on the cell plate. (If the filter cage cannot be installed in time, after the installation of the filter bag is completed, cell plate should be covered with cardboard or other substitutes to avoid stepping on the bag mouth directly.)
Check if filter bags are installed uniformly and vertically from the Dust Collector Manhole. If the bottom of two filter bags are found near or intersect, then adjust the verticality of the filter cage to adjust the bag.

Fluorescent Leak Detection

Function:

Check if there is any problems of newly installed filter bags;
Check if filter bag mouth and cell plate are sealed under negative pressure;
Clean if old filter bags are damaged;
Check if there is any other leakage points in dust collector, like welding lines and etc.

Detecting Operation:

Shut down Dust Cleaning System

This detection should be carried out under the shutdown state. Injection System cannot work within this detection. Shut down the Dust Cleaning System to make sure that the leaked dust can reach and cover the filter bag without falling into the hopper.
During leak detection, the bypass must be closed strictly to avoid the fluorescent being directly emptied without going through the dust collector. At the same time, pay more attention to whether there is short-circuit problem in the gas duct.
The opening degree of induced draft fan should be controlled at about 60%-80% of normal operation.

Add fluorescent powder

Spray fluorescent powder into the entrance of the dust collector. Those powders will travel in the direction of least resistance. This can determine the location of leakage.
The fluorescent powder should be added in the position where 2-3 meters in front of Dust Collector. Approximately 5 grams of fluorescent powder is used for 1m² of filter area. The farther the distance, the more fluorescent powder needs to be added.
Adding the fluorescent powder directly in a short time.
The induced draft fan must be turned off within 45 to 60 seconds. (The maximum wind speed in the gas duct canreach 10m/s, the fluorescent powder reaches the surface of the bag generally within 10 seconds.

(Note:
The common color of fluorescent powder are in pink and green. These two colors work best when excited by fluorescence; These two colors can also meet some customers’ needs for secondary leak etection.

)

Find the leak point

Shine the fluorescence lamp inside the bag and outside the bag mouth where the fluorescence powder appears. If there is fluorescence, then it indicates that the filter bag is damaged.
Wear the filter lens when using fluorescence lamp in detection.
The darker the light in equipment, the better for leak detection. Workers who added the fluorescence powder would better not enter the net chamber for leak detection for their clothes may stained with fluorescence powder.
Leak point must be handled in time. Secondary leak detection can be carried out when uncertain result of handling.
Fluorescence powder may also appears in another bag installation area. This may caused by leaking in metal parts of Dust Collector.

PRE-SPRAY

Function:

Water condensation and even acid condensation may occur during the start-up process, then pre-spraying can effectively protect the filter bag in this process;
Pre-spraying can prevent the sticky material formed by the combustion-supporting diesel fuel from sticking to the surface of the needle felt;
Due to the high air permeability of the new filter bag, the air-to-cloth ratio will increase when the fan is running at full load, and incompletely combusted hydrocarbons will be directly embedded. The cohesive dust used for pre-spraying forms a continuous powder cake layer on the surface of the filter material, which can effectively protect the filter material；
The pre-sprayed powder cake layer has a good neutralization effect on acid substances.

Pre-spraying powder: Ca(OH)² Approximately 250 grams of pre-spray powder is needed per square meter of filtration area.

Recommended Pre-spraying Procedures

Start the fan;
Turn off the compressed air Dust Cleaning System;
Feed the Ca(OH)²powder from the inlet of dust collector slowly tomake sure that the powder is evenly distributed over the filter bag;
(The result of pre-spraying will increase the pressure difference by 4-5 mbar. In the case of possible settlement, the amount of powder can be appropriately increased to ensure that each filter bag is evenly coated with lime Ca(OH)² powder.)
Start up the Dust Cleaning System when the pressure difference gradually rises by 10-12mbar (the powder cake has been formed already) after ignition.

Recommended Start-Up Procedure

Turn off the Dust Cleaning System before start-up to pre-spray the filter bag; (Gas or light oil is recommended when start-up.)
Electric heating of the hopper and (or) burning fuel with lower sulfur content to preheat the dust collector to the temperature that above the acid dew point; (Heat the dust collector as soon as possible to shorten the dew formation.)
Turn on the partial load of the fan to avoid high air-to-cloth ratio and overload of the filter bag when starting up. Gradually increase the power of the motor;
Start up the Dust Cleaning System when exceeded the acid dew point and the pressure difference reaches approximately 12 mbar. (When the Dust Cleaning System is just started, the dust cleaning pressure must be as low as possible because the filter material still has a high initial air permeability and does not require strong dust cleaning. Power cake is easier to remove under lower cleaning pressure. Too high cleaning pressure at the beginning will cause excessive cleaning and paste bag, especially when there is a strong fluidity of fine dust.)

Note: If the boiler is forced to stop during start-up, and it runs for less than 48 hours before stopping. It needs to be pre-sprayed again before next time’s start-up.

Recommended Shut-Down Procedure

Turn off the boiler;
(Try to adopt the burning fuel with lower sulfur content if possible, to reduce the concentration of acidic gas before shut-down,)
After turning off the boiler, the surrounding air should be immediately introduced to remove the flue gas remaining in the conveying pipe and the dust collector until the filter bag is dry.;
Clean the system for 2 to 3 cycles. For dust with strong cohesiveness, it is recommended to remove the dust through multiple pulses and remove the dust accumulation in the hopper;
Pre-spraying 250g/m²Ca(OH)²powder to protect the filter bag . (The pre-spray layer will protect the filter bag until the next Start-up.)
Shut-down the Dust Collector.

Note: If the dust collector shuts down for a short period of time (for example, it is turned off only on weekends), the dust collector must be heated with electricity to keep the temperature at least above the dew point.