Bob Flitney

As I write this we have just had Easter and it is Spring, which should be a time for looking forward with optimism. This is probably very difficult for a lot of people at present. 

The effects of the current downturn are widely evident and the seal industry is no exception. Jobs are being moved to lower-cost countries, and many others are on short-time because of reduced demand. However, in some sectors of the industry companies are still busy, but this may be partly a phase effect. The decrease in demand will happen at different times, depending on whether one’s customer is a producer of consumer goods or raw materials, for instance. 

There is also the problem that recession breeds recession. In the UK the market for cars is stalled, as the government debates whether to subsidise the replacement of old vehicles with new. No one is likely to buy a new car this week if they think the government will pay them £2000 to get one next week. My wife had a conversation with colleagues at work that a similar trend is true in many areas. With prices reducing, there is a big incentive to delay purchases and see if things are cheaper next week. 

An interesting development that seems to be affecting some sectors of the manufacturing industry is the return of work that had been lost to developing economies, back to traditional manufacturing countries. Factors creating this trend appear to include quality control, delivery times and logistics together with an erosion of cost differentials. I am not sure if this trend is also true of seal manufacturing yet, it will be interesting to see if it happens. We have news items virtually every month of new customer service centres, many of which include some manufacturing capability. In many instances it appears optimum for at least some manufacturing capability to be close to the customer, to provide a rapid response. 

But, it is not all doom and gloom. Wearing my consultancy hat I have recently been involved in some very interesting developments of completely new products, at least one of which has a very large potential market. It will not work without an effective sealing device, will provide a considerable lifestyle benefit to many people, and be reasonably recession-proof. 

Bob Flitney

I have been involved with presenting two courses this month and the discussions helped to emphasise how standards and design codes impact on sealing methods and can potentially lead to design problems. 

While there are plenty of standards that have a significant benefit quite often an industry adherence to a familiar design code can, in my humble opinion, have very questionable consequences on the selection of an appropriate sealing solution. 

Pump seals in the petrochemical industry are specified to the API682/ISO21049 standard. This document has been essentially user driven in an attempt to improve the general reliability and safety of mechanical seals. This has probably been a general benefit to the industry in mandating configurations for known problem areas, even if there is plenty of room for disagreement on the detail. The commitment to this document across the industry is demonstrated by the efforts to ensure that it is published by both API and ISO and reliability improvements over the last two decades must in part be due to the discipline this has created. 

In certain other areas I have my doubts. There is a huge array of pipe and vessel flange and gasket standards that are applied across different industries. They are often applied across the entire plant regardless of the sealing requirements, when at the top and bottom ends of the temperature/pressure spectrum it may well be much more cost effective and reliable to use something else. The automotive industry has long ago given up trying to use a plain flat rubber gasket with obvious benefits. A glance through our patents section will often provide an idea of innovative ways of providing a more reliable solution. But, there is a wide insistence across many industries to use often expensive and cumbersome flanges, that are then only lightly loaded and unreliable. 

At high pressures and temperatures efforts are made to use various metal joint rings often with questionable efficiency when again an alternative approach may prove both more reliable and cost effective. But, something that looks familiar must be used. 

Sometimes when a design code has rather grown like topsy for several generations it must be worth asking the questions, “What are we trying to achieve and what is the most effective solution available? 

Bob Flitney, editor

Extending the life of existing plant and equipment together with an improved prediction of performance appear to be topics that have if anything been given a boost in interest by the current economic situation.

This can be seen by the number of meetings being organised on such topics and a continuing interest in qualifying seals and materials. Critical to the life and reliability of practically any equipment is the performance of the seals. A lot of thought and engineering development has been devoted to this cause across all types of seals. Evidence of this includes the large amount of data generated for gasket materials and the various devices for monitoring mechanical seals. A huge amount of effort has been expended on attempting to predict the performance of elastomers, and some may ask how far has it got us?

Perhaps some of the lack of progress can be attributed to entrenched attitudes and a tendency to stick to old ideas. A good example of this is what appears to be continuing debate on the relative merits of stress relaxation and compression set. Opposing camps seem to argue endlessly about the virtues of one and the relative uselessness of the other. In reality neither gives a complete picture, and I can provide examples of results where one or other if used in isolation can give very misleading results. A further problem with this debate is the method used to measure compression set. The long established standard methods were developed for material processing QA, not for predicting seal performance. The hot release used can give results that are not necessarily particularly useful. Methods using a cold release followed by a re-heat can give a very useful comparison of recoverable and permanent set, also often referred to as physical and chemical set. The use of this method provides a great deal more information about the performance of the material at a range of temperatures and hence much of the information provided by stress relaxation but with rather less expensive equipment. And, with the ever wider application of high fluorine elastomers which can have rather doubtful low temperature properties such an approach can be especially useful.

A more flexible and broad minded approach to some areas of performance prediction could have important benefits.

Bob Flitney, editor

The Donald Julius Groen Prize Lecture at the Institution of Mechanical Engineers in London on 3 December was presented by Ian Taylor from Shell Global Solutions, who spoke about the contribution of lubricants to energy efficiency. 

He reminded us that the Jost Report in the 1960s estimated that 10% of gross national product (GNP) was spent overcoming friction and wear, and that around 1.5% of GNP could be saved by optimal selection of lubricants. 

The majority of the talk demonstrated the significant savings in friction that have proved possible in the automotive industry by the adoption of modern lubricants. These tend to be of much lower viscosity than their predecessors, and also have considerable improved viscosity index. Even apparently very small savings in powertrain friction could translate into significant annual savings for operators of large truck fleets. 

A relatively short section at the end of the talk discussed the contribution of the hydraulic fluid to circuit power consumption. It was suggested, or we were reminded, that the major friction loss in a hydraulic system is pipe friction. Figures presented showed power consumption savings of 25% on a forklift truck used in a cold environment, by changing from conventional straight oil to a high viscosity index oil of the same ISO 32 grade. 

Having made the serious mistake with one test rig I designed, of neglecting the hydraulic pipe pressure drop, this set me thinking. When I first got involved with hydraulic systems, the standard oil seemed to be what would now be an ISO 37 grade. There seems to have been a general trend to adopt ISO 46 fluid. For those not familiar with ISO grading of oils, the number represents the viscosity in cSt at 40°C. 

My fluid mechanics is a bit rusty, but I think that as a first approximation the friction for laminar flow in a pipe will be roughly proportional to viscosity, so changing from a 46 grade oil to 32 would reduce pipe friction losses by 30%. This is very likely to be a massive saving compared with specifying low-friction seals, even though the difference will decrease as temperature increases. But, it may introduce some interesting seal development problems with the reduced viscosity. 

It sounds to me as if it is something that should be looked at seriously with regard to energy saving. 

Bob Flitney, editor

I am writing this just before Christmas in what must be some of the most uncertain times that many of us have experienced, and whatever I write is likely to be out of date before it gets as far as the production team, let alone arrives at you the reader. 

The run up to Christmas which should be a time of happy anticipation is filled with concern for many. I know that a lot of readers in the manufacturing industries will be having an extended Christmas and New Year break brought upon them by the sudden drop in demand for their company’s products. 

The problems of the automotive industry have been the focus of much publicity. Their high volumes and short lead times mean that the suppliers involved also suddenly find they have to reduce production. But many other industries such as building have been in recession for some time in various countries. This knocks on to suppliers such as seal companies involved with earth-moving and mechanical handling. 

Although it does not seem to have hit the headlines, a number of major chemical process companies are closing down a considerable number of their plants, no doubt the reduced demand from automotive soon knocks on to plastics suppliers etc. This may potentially be a short-term benefit to seal companies in the process plant sector, if these shutdowns lead to an increase in maintenance work. 

But, what will happen in the longer term? If the fallout from the current problems is that consumption falls to what we can afford, rather than get on credit, will the overall reduction in global consumption mean that much of the new production capacity in Eastern countries will take over even more rapidly from that in Europe and the US? 

As a highly intelligent and perceptive colleague of mine used to say, ‘I am only a simple engineer.’ But then, how many engineers have been predicting exactly what has happened for some considerable time? 

This comes with my very best wishes for 2009 and I hope that you have had a relaxing and enjoyable break over the holiday period. And if it was longer than originally planned I trust that you managed to make the most of the time. 

Bob Flitney, editor

This is an opportune time to start this blog as in the last month I have attended two meetings at which a major topic of discussion was testing and qualification standards. One was Valve World (www.valve-world.net/vw2008), and the second was the ISO TC 131 meetings in London where a draft standard for testing and qualification of O-ring materials was debated. 

Emission testing of valves, and valve components is obviously a very important topic, but there is the significant problem of proliferation of standards. There is, or I know of; ISO 15848, parts 1 and 2, Shell MESC SPE77/312, API 622, TA Luft/VDI 2440, ISA 93, and ANSI/FCI 91-1. This proliferation causes a significant headache for suppliers, both of sealing products and the valves themselves. The first step is to make sure that we are comparing like with like. The TA Luft/VDI2440 and API 622 are both packing tests in a test rig, they do not qualify a valve. The ISO and Shell tests both test the valve which is surely ultimately important. Some others such as ISA are test methods without specific qualification criteria. 

It would seem to make sense that what is really required is an effective but sensible pragmatic test and qualification of valves. The ISO 15848 standard is becoming due for five yearly review, so now is the time for both suppliers and users to get involved with their national standards and sort out an ISO standard that could be used worldwide. 

Proliferation of standards also appears to be happening with elastomer materials. Having published the ISO 3601 geometric standards the Working Group is turning attention to Part 5, the material guidance. This is now being converted to a material qualification standard. There is already an ISO elastomer compatibility standard, ISO 6072, which is very little used. Why introduce another standard when 6072 could be amended to suit? I also found it rather worrying that some of those involved in this work seemed to have little experience of actually applying elastomer testing to real applications. Hopefully common sense will prevail. 

Bob Flitney, editor