James Hoare - 23 June 2016
Editor James Hoare attended a valve course recently and wondered how many of us know what we don’t know, and how this applies to valve selection.
There is a lot we all don’t know. For example, you’re sitting in a hire car, and need to fill up with gas. On which side of the car is the gas tank? Most get out of the car or take a guess, but the answer on the arrow on your fuel gauge. It’s one of those things that you wish you’d known a lot earlier. But don’t feel silly if you didn’t know this (most people don’t – I certainly didn’t). Spare a thought for this guy who found out, at the age of 50, he’d been tying his shoelaces incorrectly all his life.
This brings me to a situation a few weeks ago when I sat in on an introductory valve course. Some of the participants were learning how to qualify their customer’s needs during the purchase of a valve. To do this, an inside sales professional needs a good general knowledge of all valve types, uses, advantages and disadvantages. They need to know what questions a customer should be asking to avoid headache later on (and if they don’t ask it, a good service professional should ask it for them). One thing the course participants learnt was that there is never an ideal valve - it’s always relative to an intended use and application. Hence the often heard mantra: “know your customer” and “understand the valve’s intended application” and so on.
So, here are some top 5 tips* for those new sales and service professionals:
- Know your application.
When choosing a valve, you must have certain pieces of information in hand, including the chemical composition of the system media and the full range of pressure and temperatures over the course of the valve’s life. Make sure your valve choice can accommodate these parameters. Don’t go with hunches or approximations. Consult the product data.
- Check for material compatibility.
It is possible to have the right valve but the wrong materials of construction. Valves will often come with a standard set of materials, but there are alter natives. You should always check the product catalogue to identify temperature and pressure ranges, as well as compatibility with different system media (chemicals). When in doubt, consult your manufacturer.
- Know your maintenance schedule.
Different valves have different maintenance schedules, and your system parameters, including the number of times the valve is cycled, will affect this schedule. The valve’s maintenance schedule needs to be manageable for your maintenance team. This seems like an obvious point but it is often overlooked. Are you willing to service that valve once every 20 days when it is 100 feet in the air?
- Understand pressure drops.
Most every valve or other component produces a drop in pressure. You need to be aware of the cumulative pressure drop because otherwise you may end up with too little pressure at a certain point in the line. Every valve is rated with a flow coefficient (Cv), which describes the relationship between the pressure drop across an orifice, valve, or other assembly, and the corresponding flow rate. The higher the Cv, the lower the pressure drop. A ball valve and needle valve of the same size will produce very different pressure drops. A ball valve will produce very little pressure drop, whereas a needle valve (or other globe valve) will produce a significant pressure drop.
- Consider cost of ownership.
The true cost of a valve is not its purchase price. The true cost is the purchase price plus the cost of owning and maintaining or replacing that valve over time. To calculate the cost of ownership, you must know how long a valve will operate in your particular system between maintenance checks. Maintenance costs must be figured not only in replacement parts, but also in labor and downtime. Note that some valves are much easier to service than others. Some can be serviced in place; others must be removed from the process line. Also, given your valve choice, what are the chances of unscheduled maintenance and downtime?
*(Credit to Michael Adkins from Swagelok Company for his article: “Matching valve type
to function: A tutorial in valve selection” – Valve World, November 2012)