Key Questions to Ask When Ordering valve spare parts

For such a small part, the valve guide is pretty important. In fact, I’d say it’s the foundation for the rest of the cylinder head.

Valve guides support the valves and help keep them running cool. If the guides are worn, you’ll have increased oil consumption and decreased cooling of the valves. Remember 25% of a valve’s cooling depends on heat transfer from the stem to the valve guide.

Worn guides will also allow engine oil to be drawn past the valve stem, resulting in excessive oil consumption. Oil drawn past the valve guides can coke on the port side of the valves causing reduced air flow, exhaust or intake, compromising engine performance. Oil build up (coking) can also accumulate in the combustion chamber and on the piston top. Results here could be severe including a definite drop in performance and possibly mechanical damage as a result of pre-ignition. Pre-ignition being the glowing edges of carbon deposits igniting the incoming fuel mixture before the properly timed ignition spark.

Worn guides can also lead to another engine failure. Since the guides support and center the valves, a worn guide will allow the valve to flex as it closes against a now loosely aligned valve seat. After just so long, this can cause the head to break off the valve stem, damaging piston, cylinder head and cylinder block.

A general rule of thumb is that intake guides need guide-to-stem clearance of .001″ to .003″ and exhaust guides need from .002″ to .004″ clearance. The type of engine will make a difference. Air-cooled, water-cooled or diesel, as well as the material of the valve, the valve guide and application. Diesels don’t require quite as tight a clearance and if you have sodium filled valves you’ll need an additional .001″ to take care of the heat that’s conducted out through the stems. Air cooled engines also use a larger clearance. These figures are only general – always check the specification manual for the make and model you are rebuilding for exact figures.

It’s not enough to say the guides are worn. To do a quality job you need to know how much wear you have. Are they serviceable, within specs, or do they need replacing? Service limits are exact, so break out your precision tools, micrometer and split ball gauge (Goodson #SHG-4) at a minimum. You can use the gauge to measure each guide, or speed things up by setting the gauge to the valve guide maximum diameter and use it as a go, no-go gauge. Simply try the split ball gauge in each guide after setting it to size. If it enters the guide it is out of tolerance. NOTE: upon disassembly, keep valves in order. In my book, this is essential. While measuring guides, we might run into a larger I.D. This could reflect previous work, where a replacement valve with a larger stem might have been installed. Right, wrong, it is a method of repair; as long as the stem to guide clearance is correct. If not, replace the guide or repair by means of a false, Bronze Wall or Bronze-Liner guide repair system. All of these are available through Goodson Tools and Supplies.

You can see the importance of an organized tear down? Which valve came from which valve guide? Other valve train components should be organized too. By doing this we can test every thing systematically. Valve springs, stems, keeper grooves, and cam followers to name a few parts. Organizers are available from Goodson under part numbers, SHO-8, DOHC-1, and VTO-80.

It’s just like going to the doctor to see why you are ill. You probably would not like to see the results of your tests thrown around his office, mixed with every one else's. Is that really mine or what? Same thing goes at a quality machine shop. Every thing is tested and organized so the customer can be shown exactly why his or her head is in a hurt and what it will take to repair it.

Now that you’ve got the head torn down and the customer’s go-ahead to do the repair, you have some repair options.  And remember, if you have questions about any of what’s covered here (or just about anything else) contact one of the Goodson Techxperts™ at 1-800-533-8010 or drop us an email.

Many ball valve manufacturers will provide an estimate of the expected lifespan of a ball valve, and proper maintenance can certainly extend this range. However, ball valve lifespan can be influenced by a variety of other factors.

Actuation

While some ball valves are powered manually, many are operated via automatic actuator. Depending on your system’s intended cycle speed, you have your choice between pneumatic (air-powered), electric (motorized) or hydraulic (fluid-powered) actuation. By choosing the appropriate power source for your application, you can reduce maintenance expenses, increase uptime and maximize safety. Pneumatic actuated ball valves are the most durable option in high-pressure environments, provided you have access to compressed air. In most cases, actuators will far outlive the ball valves they control.

Two examples of pneumatic actuated ball valves. The actuator sits on top of the valve body and operates the valve via compressed air.

Design

Ball valves come in one-, two- and three-piece designs, the first two of which do not allow for maintenance and must be replaced when components fail. Three-piece ball valves, however, are designed so that the seats and seals can be removed and replaced quickly and easily without removing the entire valve from the system. Provided the valve is made of durable material, the ability to replace components means that three-piece ball valves can long outlive their one- and two-piece counterparts. For this reason, three-piece ball valves are favored for high-cycle and high-pressure applications that subject the seal components to lots of wear and tear.

Left: A manual two-piece ball valve; Right: A manual three-piece ball valve.

Serviceability

Seals are typically the first component to fail in a ball valve, since they are made of much softer material than the valve body. While one-piece and two-piece ball valves must be replaced when their seals expire, three-piece ball valves allow for easy replacement of seals without removing the valve entirely.

Temperature and pressure rating

Ball valves used in high-pressure or high-cycle settings will need to be serviced or replaced more frequently than those in lower-pressure applications. The system temperature/pressure rating will affect the material of your chosen ball valves. Be aware that the closer the media’s temperature/pressure rating is to the ball valve’s rating, the more frequently the valve will need to be replaced.

The good news is that the actuator (which is typically the more expensive component in an actuated valve assembly) will normally outlast the ball valve. This means that in most cases the valve can be replaced without replacing the existing actuator.

Media

Ball valves are generally intended for the on/off control of fluids and gases without solid particulates. Any particles in the media can abrade the valve seals, leading to repairs, valve failure or actuator failure. Conversely, lubricative medias such as oils can reduce seal wear and extend the life of the valve even further.

Valve materials

Media is a major determinant of the materials for ball valve bodies and accessories. Ball valves can be made of stainless steel, brass, bronze, or plastic (PVC). While PVC offers flexibility and cost savings, metal ball valves are more durable and able to withstand higher temperatures and pressures. Overall, metal ball valves have a longer lifespan than those made with PVC or other synthetic materials. When in doubt regarding the appropriate valve material, use the Cole-Parmer Chemical Compatibility Database to ensure valve materials are compatible with your specific media.

Left: A manual two-piece brass ball valve; Right: A manual two-piece stainless steel ball valve.

Source

If your plant contains processing equipment made in the U.S., you’ll want to source ball valves from domestic manufacturers and suppliers. Some valve retailers source their products from all over the world, but products from overseas carry the risk of incompatibility with products made Stateside. Quality aside, it’s best to buy ball valves from domestic sources to ensure longevity and prevent premature replacements.