Selecting the right candle filter element is important for maintaining stable filtration performance and extending filter service life.

Factors such as particle size, flow rate, viscosity, pressure drop, filter media, and operating conditions should be considered before choosing a suitable candle filter element.

This guide explains important selection factors, assembly types, cleaning methods, replacement requirements, and common troubleshooting solutions for candle filter elements.

For more information about the working principle, structure, applications, and key features of candle filter elements, see Candle Filter Element: Working Principle, Applications, and Key Features.

Table of Contents

What Should you Look for When Buying Candle Filter Element?

Below are a few important aspects you should consider when purchasing a candle filter element.

▶ Particle Size andNature

An excellent candle filter filters very fine particles.

However, you need to first evaluate the particle size and characteristics of the filtration liquid for your application.

After that, select a suitable type of candle filter.

▶ Flow Rate/Viscosity

Consider the flow rate and viscosity of your application.

Whether the fluid is highly viscous or low viscosity will affect contaminant absorption and filtration performance.

▶ Pressure Drop

Check whether the candle filter element matches the pressure drop requirements of your application.

A quick rise in pressure drop can lead to filter cake formation, which may affect the filtration process.

▶ Overall Cost of Operation

First, assess the total cost required to purchase and operate different types of candle filters.

Compare these costs with your application requirements and budget.

What is High Differential Pressure Resistance in Candle Filter Element?

High differential pressure resistance refers to the ability of a candle filter element to withstand a large pressure difference during filtration without structural damage.

During operation, fluid enters the candle filter vessel under high pressure to improve filtration efficiency.

When the fluid changes direction and passes through the filter element, the pressure difference across the filter media increases.

If the filter element cannot withstand this pressure difference, it may deform or become damaged.

Therefore, candle filter elements need sufficient mechanical strength to maintain stable filtration performance under high differential pressure conditions.

What Is the Difference Between Screwed and Plugged-in Candle Filter Assembly?

The main difference between screwed and plugged-in candle filter assemblies is the way the candle elements are fixed inside the filter vessel.

Assembly Type	Description
Screwed Candle Filter Assembly	The candle elements are fixed to the base of the filter vessel using screws and bolts, providing a secure connection.
Plugged-in Candle Filter Assembly	The candle elements are attached and removed by rotating them into the base of the vessel, allowing easier installation and replacement from the bottom.

The choice between screwed and plugged-in assembly depends on the filter design, maintenance requirements, and replacement convenience.

How does Simplex and Duplex Candle Filter Elements Compare?

Simplex filter and duplex filter elements are both filtration devices.

Duplex candle filter system

Simplex candle filter system

A simplex filter system has one chamber for operation.

A duplex filter system has two changeover chambers. When one chamber is in process, the other chamber can be on hold.

Simplex filters are preferred where the filter system can be shut down with additional shut-off equipment.

Duplex filters are mainly used where shutting down devices is unnecessary or uneconomical, such as production or marine industries.

Both filter systems can filter liquids and gases.

Their compact design also makes them easy to clean.

Should Candle Filter Elements Have Magnetic Inserts?

A magnetic insert is an optional feature for candle filter elements.

Therefore, it is not necessarily an essential feature in every candle filter assembly.

Magnetic inserts can be selected according to specific application requirements.

How Can You Discharge Cake from Candle Filter Elements?

Formation of cake on candle filters

You can discharge cake from the candle filter element by two methods:

By snap blow – with this technique, the backside of the filtration medium blows, making the trapped cake drops down. This method is only applicable to those cakes, which instantly discharge.
By vibration – for this method, the whole candle filter systems vibrate, shaking off the cakes which are not easily dischargeable.

What is a Spiral Shape Candle Filter?

A spiral shape candle filter is a special type of candle filter with unique helical-shaped candles.

The spiral shape provides additional advantages during filtration, including:

Better cake discharge
Holding loosely attached cakes in position
Extending the service life of the filter cloth

What are the Filtration Modes of Candle Filter Elements?

The filtration mode of the candle filter elements refers to the overall process of obtaining the filtrate from the filtered liquid, for example, slurry.

Inside the filtration vessel, the suspension moves along the direction of candle rotation.

After that, the formation of cakes occurs intermittently around the candle.

Finally, the pure filtrate exits by discharging through the central tube.

It, therefore, means that the filtration mode occurs in the central tube, support tube, and the filter cloth.

How do you Clean Candle Filter Element?

Cleaning candle filter elements is essential to produce uncontaminated filtrate and maintain filtration performance.

Besides normal backwashing, it is also recommended to clean the filter elements manually, especially the filter mesh.

Why?

This helps remove embedded contaminants and restore the functionality of the equipment.

Moreover, you can use some machines and equipment to do the cleaning.

They include:

▶ High-pressure cleaning unit

The unit effectively cleans individual filter elements, filter inserts, and other small components.

The unit uses special detergent for washing.

▶ Cleaning Lances

For better cleaning results, use cleaning lances together with a high-pressure water jet.

Conventional single lances are suitable for general cleaning.

Lances connected with rotary nozzles are more efficient for cleaning heavily contaminated screwed-in and plug-in candles.

▶ Ultrasonic Cleaning

Ultrasonic cleaning uses ultrasonic waves from two sides to remove dirt particles trapped in the filter screen mesh.

The process is simple and effective while restoring the original filtration level of the filter meshes.

When Should you do Candle Filter Element Replacement?

Candle filter elements require regular cleaning and replacement to maintain stable filtration performance.

During continuous operation, particles may accumulate on the filter surface and inside the vessel, which can reduce the flow rate and increase pressure drop.

To maintain filtration efficiency, candle filter elements should be cleaned regularly.

In general, cleaning after about two weeks of operation is recommended, and a soft brush can be used for manual cleaning.

After repeated cleaning cycles, the filter media may wear out and affect particle removal performance.

Although the service life of candle filter elements varies depending on operating conditions, they generally need to be replaced after every 6 to 12 months.

What are the Precautions to Consider when Using Candle Filters?

When using candle filter systems, the following precautions should be considered:

Ensure that you supply the candle filter diesel engine with new fresh oil and not oil the circulating used fuel by the machine.
During cleaning, make sure that both the liquid inlet and the outlet port close first. After that, the compress gas jets into the tank body while the filtration of the hydraulic pressure in the filter tank proceed.
Have a hoisting device and enough headroom above the filter to lift every candle or to move the equipment horizontally to a station next to the filter tank.
Have a unique rig that can hold the candle in position for maintenance.
During the filter column backwashing, ensure that the inflation filter cloth advances at the exit of the filter filtrate.
Try to match the filtering precisions. The standard accuracy is 20 microns, 30 microns, 40 microns, 80 microns, etc.
Ensure there is enough space for removing or hinging the cover of the equipment.
Check the pressure relief valve on top of the tank for emergency functioning.
Check the vent located on top of the head if it allows free withdrawal of air.
Use the right connection technique for the candle filter.
Choose the filter element size per the filter flow.
Select the candle filter, which has top quality, robust, and high accuracy.
Regularly backwashing the candle filter to prolong the service life.

How do You Troubleshoot Candle Filter Element Systems?

Like other filtration equipment, candle filter systems may experience operating issues caused by mechanical problems or incorrect operation.

Common problems include:

Issue	Cause	Solution
Damaged or twisted candles	Excessive infeed Continually operating the filter for long between cleaning cycles.	Regulate the amount of feed. Pause the operation at intervals after cleaning.
newly replaced door gasket leaking	Loosely fitting door due to straight ends.	Replace the door with newly cut angled ends.
Murky Filtrate/ hasty blinding	Use of wrong filter media	Replace the filter media with a suitable one.
Slow filtration	Possible Blockage of the candle. Loose particles or fiber in the filter elements.	Pass water briefly in the reverse direction through the candle. Soak the candles in a pool of water for some hours.

What is the difference between Bag Filter Element and Candle Filter Element?

Bag filter elements and candle filter elements are both used for filtration, but they work differently.

Bag filter systems collects minute solid particles (dust) from a stream of air or gas.

Candle filter elements are mainly used to obtain clean filtrate by separating suspended solids from filtration liquids such as slurry.

Bag filter

Candle filters

Bag Filter Element	Candle Filter Element
Collects dust particles from air or gas	Separates solids from liquids or gases
Often used to collect dust as a final product or prevent harmful particle release	Collects suspended solids as filter cake while producing purified filtrate
Works mainly through vacuum suction	Uses liquid filtration principles

Bag filters are commonly used for gas filtration, while candle filters are widely used for liquid-solid separation applications.

Candle Filter Element Selection, Maintenance, and Troubleshooting Guide