These are very close tolerance and will not withstand misalignment for long if at all. This seal arrangement is commonly used in Submersible wastewater pumps, between the pump and motor, with oil as the barrier liquid. There are many types of mechanical seal, ranging from simple single spring designs to considerably more complex cartridge seal types. The primary disadvantage is the higher cost, plus in some cases they will not fit into existing stuffing box/seal housings. The … This begs for a better understanding of this seal type and its application. The cost of these seals can range from $1000 to $3000 per inch of shaft diameter. The features of this seal arrangement are: The other multiple seal configuration is called a Tandem (dual unpressurized) arrangement, where the two individual seals are positioned in the same direction. Primary seal face wear is typically accommodated by welded metal or elastomeric bellows which move to assist in the compression of the rotary to stationary seal faces. There are many types of mechanical seal, ranging from simple single spring designs to considerably more complex cartridge seal … The seal between the rotating member and shaft or shaft sleeve (4). One component is stationary and the other rotates against it to achieve a seal (Figure 2). After completing a recent training class, I had opportunity to ask our customer what were some of the highest cost failures they experienced. The front side of the seal … To address these situations, the seal industry has developed configurations which incorporate two sets of sealing faces, with a clean barrier fluid injected between these two sets of seal faces. I had always hoped to one day give back some of the knowledge I have been fortunate enough to gain from others in my field. The seal between the stationary member (1) and stuffing box face, i.e. So, lubrication is required which for simplicity, is supplied by the product media. If you have any questions you can contact our inside sales staff at 714-361-1435. They are types of mechanical springs that can be used in valves, suspensions, ball point pens, on shafts, in a round hole or anywhere a pushing or compressing force needs to be applied. Download preview PDF. Potentially five times the life of a single seal in severe environments. Not logged in While researching several mechanical seal manufacturers to gain some insight as to what their tolerances were (they are specific to configuration and are provided with the mechanical seal), I ran across the following very good article on mechanical seal basics. A mechanical seal consists of 2 principle components. Can small deposits of solids form ahead of the secondary sealing member? BACK TO BASICS: MECHANICAL SEALS EXPLAINED. Field applications of dry gas seal designs were completed in 1952. However, because of the delicate components used for this new sealing method, mechanical seal failures are the greatest cause of pump down time. In a non-pusher seal the secondary seal is in a static state at all times, even when the pump is in operation. Best of class pump users give strong consideration to the use of cartridge seals. Mating faces must also resist corrosion and wear. Over time, clogging of the sprin… III. The advantages are that this seal configuration eliminates the requirement for seal setting measurements at installation. This flatness minimizes leakage to a degree where it is essentially negligible. The answer? This is where Mac was first introduced to VibrAlign. insufficient compression will result in leakage. A pusher seal type should not be selected if the secondary seal is likely to hang-up. Pre-assemble the mechanical seal as required. On the back side of the "seal head" (the end which fits towards the "spring"), measure the inside diameter. Mechanical seal failures. “I was so impressed with the people, passion, and products of VibrAlign. Spring-Loaded Rotary Shaft Seals Also known as oil seals, use these to retain oil on rotating shafts in … This primary seal is the basis of a mechanical seal design, and is what makes it work. II. Then fit … Most pump shafts today are sealed by means of mechanical seals. NON-PUSHER OR BELLOWS SEAL does not have a secondary seal that must move along the shaft or sleeve to maintain seal face contact. 8). There is a minor mechanical seal leak (Mechanical seal practically should have zero leak) 2. Thermal degradation of Mechanical Seal … Hardware consisting mainly of spring and retainer. Years ago, most pump shafts were sealed using rings of soft packing, compressed by a packing gland, but this type of shaft seal required a fair amount of leakage just to lubricate the packing and keep it cool. By adjusting the spring groove, spring size, wire diameter and … 1. The first dry gas seal for a compressor was patented by Kaydon Ring & Seal in 1951 when it was known as Koppers Corporation. [Map it! All of our single spring seals are made of stainless steel. distance from the gland gasket to the top of the seal. Mechanical Seal Seal Pressure Angular Misalignment Compression Unit Face Loading These keywords were added by machine and not by the authors. 530-G Southlake Blvd. The more common multiple seal configuration is called a Double (dual pressurized) seal, where the two seal face sets are oriented in opposite directions. The functional categories of a mechanical seal are: 1. Then came the development of the “mechanical seal,” which accomplishes the job of restraining product leakage around the pump shaft with two very flat surfaces (one stationary and one rotating). VibrAlign has given me that opportunity.”, Address The decision to choose between a double or single seal comes down to the initial cost to purchase the seal vs. the cost of operation, maintenance and downtime caused by the seal, plus the environmental and user plant emission standards for leakage from the seal. Remove the centering tabs only when the gland is fully tightened and the seal … A secondary sealing member is not required to make up the travel as the rotary and stationary seal faces wear. 3. These keywords were added by machine and not by the authors. Mechanical seals are leakage control devices, which are found on rotating equipment such as pumps and mixers to prevent the leakage of liquids and gases from escaping into the environment. "Realign America"| Alignment tolerances| mechanical seals. This will determine the seal size diameter - which is either the shaft size or the sleeve size that the seal fits over. The governing rule is: The spring's direction of coiling must concur with the sense of rotation of the shaft when looking at the sliding face of the rotating seal … VibrAlign, Inc. Mechanical seals contain those leak paths with static seals such as … This is generally correct, but there are applications for which mechanical seals represent “too much technology,” and services for which they are not suitable (see the introduction to Chap. 192.185.81.202. Gasket (2). Many early mechanical seal designs placed the spring inside the process fluid. Most products (process fluids) that are sealed are not very clean. Finally, it should be noted that there are special single seal housing designs that greatly minimize the abrasives reaching the seal faces, even without an external water flush, but this is a subject for another column. While mechanical pump seals generally seal along the seal faces, braided packing seals along the shaft sleeve and the stuffing box walls. This is known as the secondary seal and may be an o -ring as shown, a v -ring, a wedge or any similar sealing ring. Measure both seal heads and spring x 0.5 = OP HT * Please note: Do not include seat height measurements. By way of example, a simple mechanical seal design has 7 components (Fig 3): 1. Over compression of the seal face will result in premature wear. The pressure between seals is lower than the seal chamber pressure (typically atmospheric), The external fluid only lubricates the most outside set of faces, Pumped fluid lubricates most inside faces, The outside seal serves as a safety seal or containment device. This field is for validation purposes and should be left unchanged. ... Spring compression (usually) provides initial face pressure. This design provides an ... compression … A mechanical seal has 4 main sealing points: I. Richmond, VA 23236 The advantages of this seal type are the ability to handle high and low temperature applications (metal bellows), and that it does not require a rotating secondary seal, which means it is not prone to secondary seal hang-up or shaft/sleeve fretting. Maintenance crew inserted back the seal setting plate and with the help of filler gauge on both sides increased the spring compression … This process is experimental and the keywords may be updated as the learning algorithm improves. One component is stationary and the other rotates against it to achieve a seal (Figure 2). Characteristics of the Liquid:  Abrasive liquids create excessive wear and shorten seal life. There are multiple designs available for the mechanical seal configuration. Primary sealing ring and mating ring. Elastomeric bellows seals are commonly used for water applications. (For immediate consideration), Spring compression (usually) provides initial face pressure. The rotating component (3) and stationary component (1) are pressed against each other, usually by means of spring force.The mating faces of both components are precision machined (lapped) to be extremely flat within 2 light bands, which is an optical method of measuring flatness). The rotating component (3) and stationary component (1) are pressed against each other, usually by means of spring force… They fit directly over the shaft or shaft sleeve, and are available in single, double, and tandem configurations. The primary disadvantage of this seal type is that it is prone to secondary seal hang-up and fretting of the shaft or sleeve, especially when the seal is exposed to solids. Through a process of elimination, match the types and measurement gathered in steps 1 – 5 to determine mechanical seal … © 2020 Springer Nature Switzerland AG. Secondary seals consisting of O-rings or other suitable gaskets. This improved design allows the seal to be in field repairable. These seals have a metal case that creates a tight seal when mating with smooth surfaces. If the mechanical seal faces rotated against each other without some form of lubrication they would wear out (and the seal would fail) due to face friction and the resultant heat generated. This service is more advanced with JavaScript available, Centrifugal Pumps Figure 1 above shows a typical centrifugal pump, which highlights its constituent parts, including the mechanical seal. Double seals and double gas barrier seals are becoming the seals of choice. Understanding how they work will help the readers select the appropriate type for their application. The typical features of this seal arrangement are: The proper selection of a mechanical seal can be made only if the full operating conditions are known. For best results with double (or tandem) seals handling abrasive, the inboard seal faces should be a hard material, such as silicon carbide vs. silicon carbide, while the outboard seal faces should have maximum lubricity, such as silicon carbide vs. carbon graphite. CARTRIDGE SEALS have the mechanical seal pre-mounted on a sleeve (including the gland). This is a preview of subscription content, https://doi.org/10.1007/978-1-4615-6604-5_9. In stock and ready to ship. Mechanical spring … 5. Temperature: Can determine the use of the sealing members as materials must be selected to handle liquid temperature. Proper spring compression check (‘working height’) – obtain dimension from seal drawing which shows the distance between the back of the seal retainer and the seal chamber face. The metal inner seal parts are never exposed to the liquid product being pumped, which means no need for expensive metallurgy; especially good for viscous, abrasive, or thermosetting liquids.