About the refractory anchor
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About the refractory anchor

What grades of alloy are reinforcing metallic fibers manufactured?

What are the types of Reinforcing Metallic Fibres (RMF) and their application with a refractory cast

ASTM Standard A820 has established three (3) classifications of stainless steel fiber which are as follows:Benefits related to the use of metallic fibers include:Controlled and uniform cracking of the refractory liningStrength retention of the refractory lining,Minimize permanent linear change,Increased lining toughnessImproved thermal shock resistanceIncreased Lining ToughnessThe effectiveness of metal reinforcing fibers related to toughness is based on a comparison of physical properties of the samples fired during one (1) cycle versus the physical properties of specimens taken from the test sample using no MRF and sample using 3% MRF. The strength retention as measured by cold crushing strength was higher for the sample using the MRF as compared the sample not using MRF after ten (10) cycles in the furnace.The PLC for the sample using MRF was half as much as the sample not using MRF. While the abrasion resistance of the samples using MRF increased by 1% versus the 4% increase of the sample not using the MRF. The change in density between the two samples was minimal. The photo of the tow (2) samples shows a significant difference between the two samples after the cold crush test. Sample 7 showed fractures on the sides along with a breaking plane through the mid section of the sample whereas Sample 6 remained in one piece with visible cracking on the sides of the specimen with minimal material loss

What are the length, spacing and pattern required for metallic anchors in a refractory installation?

The typical refractory anchor has the tip of the longest leg of the anchor that is not greater than 1” (25mm) from the surface of the refractory lining. Some specifications require that other  leg of this anchor be ½” (13mm) shorter than the long leg of the anchor which would place the tip of this anchor 1 ½” (38mm) from the surface of the refractory lining.  These offset legs are used to prevent a separation plane at the tip of the refractory anchors from occurring during the dry out or operation of the unit.Typical anchor spacing in a refractory lining will vary depending on the thickness and density of the refractory lining. Other than PIP, there are no stated industry standards spacing of anchors, there are established industry guidelines that can be followed to ensure that there are a sufficient number of anchors to support the monolithic lining.   There are several refractory material manufacturers who have issued guidelines for the use of anchors for their material however these are guidelines and not actual refractory designs.

Is stud welding an acceptable method for the installation of refractory anchors?

The stud welding of anchors has gained acceptance over the past decade. There are numerous applications that utilize stud welding however this installation method should follow the same quality control guidelines (PRQ and WPS) as required for welded metallic anchors.

What anchor material should be used for a refractory installation ?

The material used to fabricate the refractory anchor should be selected based on the operation conditions and service of the lining. Typically, the choice of the anchor material is based on the long term exposure to the operating temperature however other factors such as intermittent operation and corrosion.

Should PMI testing be performed

PMI (Positive Material Identification) should be incorporated to determine the metallic grade of the refractory anchor. This requirement may be waived, if the API method of color coding has been implemented or the material grade has been etched on to the surface of the anchor. Knowledge and verification of the anchor material will assist in the qualification of the weld procedure and personnel qualification.

What type of anchor should be used for an installation ?

here are many different anchors shapes used in the design of refractory lining. The anchor type of anchor chosen for the refractory linings is typically determined by the lining designer and is based on the type material being installed. Refractory anchors can range from simple metallic  “vee” to ceramic  anchors. As shown below anchors come in many different shapes and styles as shown with a few examples below:

What is the refractory anchor ?

All refractories require anchorage systems such as wire formed anchors, formed metal (for example, hexmetal) or ceramic tiles to support the refractory linings. The anchorage used for refractories on roofs and vertical walls are more critical as they must remain able to support the weight of refractories even at the elevated temperatures and operating conditions.The commonly used anchorages have circular or rectangular cross-sections. Circular cross-sections are used for low thickness refractory and they support less weight per unit area; whereas the rectangular cross-section is used for high thickness refractory and can support higher weight of refractory per unit area. The number of anchors depends on operating conditions and the refractory materials. The choice of an anchor's material, shape, quantity, and size has significant impact on the useful life of the refractory.