Let the buyer beware

Valves supplier HS Pipequipment (HSP) has recently completed a survey of business decision-makers and key industry workers in the UK oil, gas and petrochemical industries to identify the issues that are still causing the most costly delays for process operators.

In the poll, conducted in May 2010, 34% of those surveyed said that valves caused the greatest difficulties.

“When you consider that individual valve types are manufactured to a multitude of different specifications, it is clear that the headaches they cause during the procurement process are vastly disproportionate to their actual value,” said Peter Everett, HSP’s chief executive.

“Add to this mix that any individual plant may have five or six of the same valve type that have been manufactured to different specifications and it’s clear why even more time is spent getting clarification of exactly what part is needed.”

Another consideration is that in older petrochemical plants, a valve can last up to 20 years, making it extremely difficult to track down the original paperwork and specifications that the manufacturer might have archived. And, with a profusion of subtly different variants, each ball, gate or globe valve can have hundreds of different combinations of components and materials.

HSP’s survey showed the effect that this complexity has during the procurement process, with as many as 55% of respondents saying that identifying the correct product/specifications was the most time-consuming part of the procurement process in petrochemical plants. In the oil and gas industry the biggest delays came from the engineering review of quotations, with 37% of respondents saying this held up the process the most.

Shift towards Asia

Another issue raised by the survey included the trend towards the manufacture of valves in eastern Asia. While 45% of respondents said their organisations never procure valves made in the region, 56% believe that valve manufacture is likely to shift to Asia in future.

An unexpected requirement for essential components was the most common problem reported during site shutdowns. An overwhelming 79% of respondents in the survey said it was the most likely factor to cause difficulties, with 26% reporting that a lack of out-of-hours support from the supply chain contributed to the problem.

Cost and quality have always been major influences when selecting an equipment supplier (see graph, left), yet, according to the survey, more users are also looking for a whole range of other qualities. In particular, responsiveness, product availability, consistent reliability, technical expertise and providing the proper documentation were also found to be extremely desirable qualities.

“In the fast-moving oil, gas and petrochemical industries, where needs change according to production priorities and shutdown planning, unexpected requirements arise all the time,” said Everett.

At most plants and assets, operators make every effort to plan ahead, but inevitably priorities change, which means that a significant effort is needed when purchasing materials. This process often includes mandatory documentation and the inspection of valves and their subcomponents.

But, concluded Everett, however complex the process, “it is essential that suppliers can be relied on to attend to all the technical and commercial details, provide the necessary paperwork and keep their promises when fulfilling an order under extreme time pressures”.

Pipeline perspective

James Roper, industrial brand manager for Durapipe UK, offers a different perspective on the specification of valves. Many specifiers, he argues, do not realise how integral the devices are to the efficiency of all process manufacturing activities.

“Valves are often not considered properly at the outset of a project and can sometimes be an afterthought after the pipework system has been specified,” said Roper.

“When maintenance and repair work is required on any valve, it often requires the whole system to shut down, which can result in costly downtime. Plant operators and managers are, therefore, continually looking for products and techniques that can make this process ever quicker and easier.”

Being able to easily identify what is contained within a pipework system is of utmost importance, especially when pipelines are being maintained and repaired

“It is vital that plant managers are aware of what substance they are closing off and what effect this will have on the system,” added Roper. “Closing off the wrong valve could have disastrous consequences; if the conveyance of certain substances is restricted due to it wrongly being shut off, this can result in problems with the manufacturing process.”

This can be a particular problem in chemical-processing applications, said Roper. If a particular substance is absent from the final manufactured product, it will cause quality control issues, resulting in significant delays in orders being fulfilled at a significant cost to the plant operator.

In addition to issues with the delivered output, an unexpected closure of a certain part of the process could also cause failures within the system, incurring costs from both downtime and repair and maintenance.

Clearly identifying the material running through a pipework system can avoid any confusion over which valves to shut off for maintenance and replacement requirements. Often substances are identified by labels being fastened on to pipelines, but these can often fall off or prove illegible, calling for a quicker and more innovative way of identification.

Technology is now available that allows customers to label the valve through specialist software that is provided with the product. This eliminates the need for labels to be fastened to pipelines and avoids any confusion over which valves to shut off.

The physical process of replacing valves during maintenance work can also be a complex and time-consuming process if the valves are hard to access and are difficult to remove for repair and maintenance. It is vital that plant managers are aware of what substance they are closing off and what

effect this will have on the system”Every minute that part of a process system is shut down can cost thousands of pounds, so plant managers are always looking to install products that need minimal maintenance and then that can be quickly and easily removed or replaced as required,” said Roper.

In terms of removing valves for maintenance work, plant managers can specify products that are easier to remove and replace. Some designs incorporate a valve handle that in addition to opening and closing the valve can also be used to tighten the double union nuts during installation.
This, said Roper, is particularly useful where valves are fitted into tight corners, as minimum space is needed to install it; the handle uses the valve stem as a pivot in order to tighten the valve ends.

The design and materials of valve components need to keep up with changing application demands. However, one area that is easily missed is the O-ring seals used in the valve itself.

“Many people overlook the importance of O-rings in the overall performance of a valve and incorrect material specification can affect the minimum working temperature considerably,” reports Clive Gamble, managing director of Econosto UK.

Gamble warns, for instance, that valves using Viton A O-rings should not be operated below minus 16°C, as this would compromise the working life of the valve, and, more importantly, process safety.

Econosto, noted its managing director, has recently worked on the development of a trunnion-mounted ball valve, with O-rings made from a special low-temperature grade of Viton elastomer that is also resistant to explosive decompression.