![]() ![]() In some projects it has happened that MAST value calculated by valve vendor was higher than actual, even than it resulted in failure of stem. If it happens stem may be subjected to mechanical failure. Engineering unit Nm OR lb-inĭuring valve operation, torque delivered by actuator (Pneumatic or electric) at any stage, should not exceed MAST value. It is maximum allowable torque a stem of a quarter turn valve can be subjected to without mechanical failure. ![]() It will not close when there is a close command and this may lead to disastrous situation … MAST: Definition & its importance If stem key of an ESDV is failed OR damaged in open position……. “Stem design is sufficient enough to withstand actuator torque”. However as far as stem components are concerned we either give little attention to mechanical integrity of stem or sometimes we leave it to valve vendor and assume Archive issues are available at know ball valves (rotary valves) are used as ESDVs/BDVs in critical services like shutdown, isolation and blow down application.Īs an engineer we always ensure reliability and integrity of actuator and its components. Reprinted with permission from PSI Commercial Fleet Tire Digest, a newsletter from Pressure Systems International, the manufacturer of the Meritor Tire Inflation System by PSI. The major tire supply companies sell a valve stem torque wrench which is highly recommended. These allow tires to be pressure checked, inflated, and deflated without removing the valve cap.Īlways buy good quality valve stems that adhere to SAE standards and have a TR number. Gaining in popularity are double seal or inflate-thru valve caps that provide two seals. A metal sealing, high temperature valve cap or inflate-thru cap must be used on every valve stem. Valve caps are the primary seal to the valve stem assembly and prevent contamination of the valve core. Truck valve cores typically have a red seal with a temperature range up to 250 degrees. The valve core must be in good working order with no debris within it since debris will not allow the core to seal properly. If there is no valve cap, then it is also exposed to ice and dirt. Valve cores are the secondary seal of the valve assembly and are exposed to heat. Recommended torque is 100 - 125 inch-pounds. These are all bent valves with various lengths. If the valve hole is 0.625" then you must use either the TR509, 510, or 511 valves. O-ring seal type TR540 series is used on 15 degree drop center wheels with a 0.380" valve hole. For aluminum wheels, there are several different types of truck valves depending on wheel type. If your application sees excessive heat, there are special rubber grommets that are rated at 400 degrees and higher. Truck valves come furnished with standard rubber grommets that are normally rated to about 300 degrees. Recommended torque is 35 - 55 inch-pounds for the TR500, 501, 570-573 series. The valves with various bend angles are the TR571C, TR572C, and the TR573C. There are various bends available depending on your specific application. These clamp-in style valves are not straight like the TR500/501 series. The other common valve stem for steel wheels is the TR570C. The TR500 valve is 2.00" long compared to the TR501 which has a length of 1.50". ![]() There are valve stems designed for steel wheels and other valve stems designed for aluminum wheels.įor the most common tubeless radial truck tires with a 5 degree drop center steel wheel and 0.625" diameter valve hole, valve stems TR500 and TR501 are typically spec'ed. Truck tire valves are typically rated at 200 psi. Truck valve stems are high-pressure valves that can handle the maximum tire pressure molded into the tire sidewall of commercial truck tires. Tire & Rim Association publishes industry recommended dimensions (specifications) for producing tires, wheels, and valves. A TR number is the official Tire & Rim Association designation. Valves for aluminum wheels are brass with chrome plating.Ĭompanies that produce tire valves should have a TR number stamped on the valve stem. Most of today's valves are made out of brass because it is corrosion resistant and can easily be bent to facilitate servicing. The selection of valve hardware is based on wheel type, wheel size, and tire air pressure specification. Most fleets consider tire valve stems and valve hardware as an afterthought, but there are many issues associated with valve stem hardware that fleets need to be aware of. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |