Pyrometric Cone Equivalent (PCE) Test in ORTON or SEGAR to Determine Refractoriness of a Refractory Material

5-Aug-2020

The thermal softening behaviour of a refractory material technically known as ‘Refractoriness’, is determined by Pyrometric Cone Equivalent (PCE) test. In other words, by Pyrometric Cone Equivalent (PCE) of a refractory material we come to know about its ability to withstand exposure to elevated temperature without undergoing appreciable deformation.   

Refractories due to their chemical complexity and phase change undergo fusion (melt progressively) over a range of temperature. This softening behaviour or refractoriness of any refractory material is determined by PCE test which is done in a PCE furnace by comparing ceramic specimen of known softening behaviour (either in ORTON or SEGAR Cones) with the Cone of the refractory material. Value of PCE Cones in ORTON is followed in British standard while SEGAR is in German standard of testing. To view / download PCE Cone numbers with their temperature please click -

Pyrometric Cone Equivalent, PCE in ORTON and SEGAR used to Determine Refractoriness

PCE Cones are small triangular ceramic prisms of definite dimensions that when set at a slight angle bend over in an arc so that the tip reaches the level of the base at a particular temperature if heated at a certain rate (Refer Figures showing PCE Cones set on plaques before and after firing). The bending of the Cones takes place after the formation of a viscous liquid as a result of fusion of the Cone material. PCE is measured by making a Cone of the refractory and firing it until it bends and comparing it with standard Cone(s). Pyrometric Cone Equivalent or PCE test is a must for the quality control purpose for Refractories and Refractory raw materials.

Types of Testing of Refractories | Refractory Industry Guru

The durability of refractories is a matter which vitally concerns all manufacturers and users since it is intimately connected with economics and efficiency of the process in they are employed. Refractories are characteristically anisotropic in nature which makes it all the more difficult to judge exactly the durability while it is in use. The furnace designer has to choose the refractories according to the data from different tests available to him. That means in order to fulfill the users or various application requirements and to achieve long service lives, refractory products must be assessed by testing.

The main functions of refractories testing may be classified into three types: 

1.Evaluation of new materials before use.

2. Quality control by the manufacturer or user.

3. Post-mortem examination of refractory bricks that behaved differently than the normal.

The testing of refractories can be categorized as:

1. Non-destructive type.
2. Destructive type.

A list including both these types of testing is given below:

• Bulk density
• Apparent porosity 
• Apparent specific gravity
• True specific gravity and true density
• Particle size analysis
• Permeability
• Poresize distribution
• Refractoriness or Pyrometric Cone Equivalent (P.C.E)
• Refractoriness Under Load (R.U.L)
• Cold Crushing Stress (C.C.S)
• Modulus of Rupture (M.O.R)
• Modulus of Elasticity (M.O.E)
• Permanent Linear Change (P.L.C)
• Reversible Thermal Expansion (R.T.E)
• Thermal Conductivity
• Differential Thermal Analysis (DTA)
• Thermo-gravimetric Analysis (TGA)
• Spalling Resistance (water quenching and air spalling)
• Hydration Resistance Test
• Creep in Compression Test
• Abrasion Resistance Test
• Resistance to Carbon Monoxide
• Slag Corrosion Test
• Microstructural analysis under Optical Microscope
• Mineral Phase identification by X-ray Diffractometer (XRD pattern)
• Chemical Analysis

There are several Standard Methods to carry out the above testing which have been accepted and performed globally. Here one must remember that the sampling of the refractories specimen for testing become very important because of several reasons. Methods of carrying out all the tests given in the above list will be discussed individually in separate posts at this site.

Standard Methods for Testing of Refractories (Coming up)

Sampling of the Refractory Specimen for Inspection (Coming up)

Manipulating the Test Results of Apparent Porosity (AP) During Testing of Refractory Bricks

Apparent porosity (AP) is the percentage ratio of the void space in the refractory specimen to the total bulk volume of the same. AP is one of the most important physical properties for any type of refractory brick that will be certainly mentioned in its specifications. Hence determination of Apparent Porosity is almost a compulsory part of Inspection / Testing of a Refractory Lot. This property becomes more stringent when the refractory brick is of any complicated shape like, checker bricks or nozzle bricks having tongue - groove etc. In such cases often, it remains a cause of worries for the laboratory person conducting inspection.

The results of AP can be manipulated to show less AP% than what the brick has actually and thus, an inspector may be deceived by a laboratory person. But such actions or manipulation of results are undeniably wrong and liable to be penalized or even the whole Refractory Lot may get rejected, if caught red-handed.

Nevertheless, this article is not to discuss the merits-demerits or right-wrong of the action. That is for you to decide. Here we assume that you have made a conscious decision to learn the trick as how to manipulate the results of Apparent Porosity in order to show a better result of a porous brick. Having so decided, below is a guide (trick) on how you can do it:

=>> Apparent Porosity (%) = {(Soaked Wt - Dry Wt) ÷ (Soaked Wt - Suspended Wt)} x 100

=>> To show less AP% we need to increase Dry wt as much as possible.

=>> Make 30% conc. salt solution (i.e. 30gm salt in 100gm water).

=>> Example: To bring down 75 mm std. Brick having actually AP-25% to AP-18%, soak the brick in approximately 30ml quantity of above salt solution so that its Dry Wt. is increased by approx 9 gm. After applying solution from different sides and its complete soaking put the brick in the drier & properly clean itssurfaces after drying.

Better try to know the actual AP before applying/manipulating.

Pore Size Distribution in Refractories

It is highly essential to measure pore size and its distribution to get the desired optimum properties in any refractory brick. Actually ‘pore size’ and ‘pore size distribution’ are two different things. First, let us discuss the difference between these two terms. The ‘pore size’ is a measure of the diameter of the largest pore whereas; the ‘pore size distribution’ is a measure of the range of pore sizes. The range of pore sizes can be normally distributed, and the spread can be quite narrow (e.g. the ratio of largest to smallest may be less than 2). On the other hand, pore size distribution can be very heterogeneous. In the case of large spreads and heterogeneity, which is not desired, the pore size will be far less predictive.

It is measured by analytical instrument known as Porosimeter based on mercury intrusion and capillary flow methods. The volume of mercury penetrating the pores measured directly as function of applied pressure. Pore Size information is best described graphically, rather than with a single number. An alternative method of describing the distribution curve is to use a collection of values that better describe the distribution curve in more detail, i.e., upper limit, lower limit, mean, standard distribution, etc. This P-V information serves as unique characterization of pore structure. This data together with Microstructural analysis and few other test reports of the refractory sample can be of great help in optimizing the properties as well as for any failure analysis.

Suggested Articles: 

• Permeability of Refractory Bricks and Monolithics
• Effects of Compacting Pressure on Sintering and other Properties of Refractory Bricks
• Bulk Density of Refractory Samples

Apparent Porosity and True Porosity of Refractory Samples

Pores in Refractory Bricks (Porosity)

Porosity is the percentage relationship between the volume of the pore space and the total volume of the refractory sample. Apparent Porosity does not include the volume of the sealed pores. The True Porosity includes the volume of the sealed pores also. The usual difference between the apparent porosity and the true porosity is of the order of 1 to 2 percent unless the proportion of the sealed pores is high. The true porosity figure is the higher than the apparent porosity figure as the true porosity includes the volume of the sealed or closed pores also. The difference between the two values represents the percent volume of closed pores. Porosity can be controlled by the following:

=> By controlling the texture of the brick i.e. by controlling the size distribution of the particles.

=> By the methods of green manufacturing and composition.

=> By controlling the firing temperature, soaking time etc.

=> Quality of raw materials i.e. the inherent grain porosity of the raw materials used.

Higher the porosity, lower will be the strength of the brick. Bricks with lower porosity will have greater resistance to slag attack and more sensitiveness to fluctuations in temperature. Their thermal conductivity will be more.

Suggested Article: Bulk Density of Refractory Samples 

Hence, apparent porosity is the percentage ratio of the void space in the refractory specimen to the total bulk volume of the same. There are two methods used for the determination of apparent porosity of refractory materials which are:

=> Boiling point method, and

=> Evacuation method.

Refractory Samples (Refractory Specimen) measuring 6.5 cm x 6.5 cm x 4 cm is cut from burnt refractory bricks by a cut off wheel from within its core and cleaned any dust or loose particles adhering to its surface and are dried in an oven at 110^OC to a constant weight. For graded materials take 3 to 5 mm size grains and dry at 110^OC. It can be determined by following the steps given in any of the Standard Methods for Refractory Testing like - ASTM, Indian Standards (IS), Ghost, DIN etc.

True Porosity (%) = {1 - (Apparent Sp. Gr. ÷ True Sp. Gr.)} x 100

Apparent Porosity (%) = {(Soaked Wt - Dry Wt) ÷ (Soaked Wt - Suspended Wt)} x 100

 Related Articles 

• How to manipulate test results of Apparent Porosity (AP) during Testing of Refractory Bricks (Refractory Inspection)
• Permeability of Refractory Bricks and Monolithics
• How to check Alkali Resistance (AR) of Refractory Lining - Bricks and Castables

Permeability of Refractory Bricks and Monolithics

5-July-2020

Permeability of any refractory material is defined as the volume of a gas or air which will pass through a cubic centimeter of the material under a pressure of 1 cm of water per second. 

Fig - Refractory Bricks being stacked in stock yard

Permeability is calculated by the following formula:

Permeability = (Vol. of gas/air x thickness) ÷ (Area x Time of flow x Pressure difference)

It is determined by forcing a known volume air or gas through a cube. Time of flow, pressure difference and dimensions of specimens are noted. However, there are ready-made apparatuses and systems available in the market for testing permeability of refractory bricks and monolithics. There is no direct dependence permeability has on porosity however, permeability depends upon the existence of closed pores or channel pores and is a measure of these, whereas porosity measures the total pore volume including closed pores.

Suggested Article: Pore Size Distribution in Refractories 

However, this property permeability for refractory bricks or monolithics become important wherever molten liquid like metal, slag, glass etc. come in contact with the refractory lining i.e. wall of the furnace or container especially, when gas under pressure is present. Due to the anisotropic nature of refractories, the result will depend upon on factors such as the direction of flow and presence or absence of the original skin on the test specimen.

Low permeability is more important than low porosity from the point of view of slag resistance of the refractory. Uniform permeability is an indication of absence of cracks in the refractory.

Related Articles:

• Different tests and procedures to check slag corrosion resistance of refractory products
• How to check Alkali Resistance (AR) of Refractory Lining - Bricks and Castables