Is the most popular choice of cheap seals

2022-08-15
  • Detail

Are cheap seals used

Mr. Rick page, marketing director of John Crane seal manufacturer, said: "Companies that use seals should give up the thinking of 'the cheaper the better'. Now, many factory construction projects are 'dirty and messy'. In order to reduce costs, factories regard liquid pumps and seals as some of the worst culprits. However, they also have the characteristics of wide measurement range, high precision, fast response, etc. from a long-term operation perspective, if they buy cheap seals because of this pressure, it will give the public The operation of the Division has had the opposite effect, resulting in their loss of competitiveness in today's world market. "

according to different application fields, the sales price of mechanical seals produced by prestigious companies such as John Crane can range from $2 to $50000, or even higher. Mr. Page explained: "Especially when participating in the bidding of new construction projects, due to the great pressure on costs, there is insufficient attention to reliability and improving energy efficiency. What makes things worse is that some seal suppliers encourage the idea of 'purchasing cheap' products and pursue the lowest price strategy at the expense of equipment reliability, so as to achieve the purpose of reducing the total price of end-user contract assets."

in the current atmosphere of blindly pursuing cost savings, such a low price is not good news for the reliability and overall life cost of the factory. Mr. Page said, "20 years ago, engineers and factory managers purchased the best technical solutions in order to maximize the reliability, effectiveness and safety of the factory. But this is not the case now."

we can be sure that we have better economic conditions now, so we don't have to buy the cheapest products. Mr. Page tried to prove this. He said the key is that the managers and Accountants of the factory must agree. He got an inspiration from industry expert Paul Barringer. For a long time, this expert has insisted that in order to make a case change, engineers must speak with figures and net present value (NPV). Mr. Page said, "using the traditional engineering debate, even the payback period theory, has a certain encouraging effect on short-term behavior, but now many decisions about this kind of behavior need to be approved by the above." NPV is a favorite term used by accountants. It is calculated based on the overall service life of the liquid pump, such as 20 years. It can reveal that the cost of using different seal options will vary greatly

from liquid pump to seal

with the support of two industrial associations, liquid seal Association and European seal Association, Mr. Page began to create a calculation guidance model to determine the life cycle cost of seals

first of all, he created a calculation model for the life cycle cost of liquid pumps - LCC Analysis Guide for liquid pump systems, which was published by the European Institute of liquid pumps and hydraulics. Although the book gives a good description of the cost calculation principle of the life cycle, the FSA soon decided that engineers engaged in practical work must master more practical knowledge and more detailed information. Mr. Page said, "the calculation of the life cycle cost of seals is actually more complex than that of liquid pumps. We need a tool suitable for beginners and experts. We also need a standard that has a certain degree of credibility and is recognized and accepted by the industry." In addition to books, the FSA decided to produce a computer-based computing tool that can be used online or offline. Jason gondron, an engineer of John Crane Company, was hired to prepare Microsoft Excel tables, and finally completed the life cycle cost evaluation table. Although it can never be said that this is the first tool to calculate the cost of seals, Mr. page is convinced that using this tool is the easiest, the most complete and accurate. He said, "the cost calculation tool used in our own room is a little clumsy and difficult to use. I believe that the situation of other seal suppliers must be the same. The life cycle cost estimation table of FSA has been greatly improved. Our sales personnel of electronic servo universal experimental machine have used this estimation table to help customers and make suggestions for them."

the extended form can be downloaded from the computer and then put on the desktop for use. For easier access, there is also a special network interface. Through this interface, three kinds of seals can be compared and checked at the same time, which is simple and flexible. Mr. Page explained that the cost of seals involved dozens of parameters, which experts could review and propose modifications if they were willing. He said: "Engineers' initial expertise is not in the cost calculation of seals, but they can accept most defective values, which makes the use of the tool very easy. This tool currently adopts British units, but soon ESA can provide a metric version of the tool. After the table itself is updated in the future, all hidden calculation values on the table can be explained directly on the station.

figure note: life cycle cost The cost evaluation table can be used on the Internet or offline

benefits of simplicity

from the life cycle cost evaluation table, we can mainly learn such experience and knowledge: in order to obtain higher reliability, higher energy efficiency and better working environment, or all these, it is worth paying more in the early stage. Mr. Page said: "There used to be a saying in the industry that if you have enough secondary equipment to support you -- such as coolers, filters, separators, etc. -- you can almost use really cheap seals. However, by using accurate life cycle cost calculation, users can find effective sealing solutions. Maybe the cost is high at the beginning, but only a few external support systems are needed in the operation process."

there is a typical example of not using expensive sealing system: This is an ordinary single seal with direct isolation of liquid, which will dilute the liquid pumped. When a new dual gas seal is used to replace this seal, the sealing liquid is eliminated, so the cost in the early stage increases, but the reliability of the process flow is often improved, and the maintenance cost is reduced. No costing tool can provide all the answers, Mr. Page pointed out: "If you compare three different seal options, you will find that their life cycle costs are related to their prices, such as $30000, $40000 and $150000 respectively. Maybe you have good reasons to choose the seal with a value of $40000 instead of the cheapest one, but at least you understand that giving up the seal with a value of $150000 may be a good idea."

If a device needs frequent maintenance for some reason rather than seal failure, then selecting short-life seals may be an effective option. However, Mr. Page said, "if the service life of the seal is taken as the limiting factor, then the seal with higher reliability may be selected, and of course, the price may also be relatively high. At the end of the experiment"

however, there is another option with higher investment, which does not need to spend a high cost in long-term operation, that is, the use of non sealing liquid pump. Such problems are also involved in the life cycle cost estimation table. Mr. Page said that sealless pumps will cause transmission losses, so the energy efficiency is significantly lower than that of ordinary liquid pumps. And like ordinary liquid pumps, they need to be sent to the manufacturer for repair frequently, so the maintenance cost and inventory cost are always relatively high

finally, it should be noted that the calculation of life cycle cost can be accurate only when the seal reaches its expected performance, that is, the seal must be installed correctly and operated correctly. Mr. Page said that modern barrel type mechanical seals are easy to install and accurate in place, but improper operation will still cause damage. For example, he said, "a large double head liquid pump, especially its hot runner, needs several hours of preheating before starting. If the company cuts off its fillet, it will inevitably shorten the service life of the seal."

process Journal of process industry (end)

Copyright © 2011 JIN SHI