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Anhydrous Ammonia valves will typically be equipped with one of two different styles of packing assemblies. This bulletin is designed to educate the operators on the different types of packing and the suggested maintenance procedures.
Routine inspections of storage tanks, valves and piping systems is an essential part of ensuring a leak free operation; these inspections should be completed at least four times per year.
Tank inspection checklists are provided in our anhydrous ammonia storage and handling booklet which is available hard copy and on our web site at www.tannerind.com. These forms can be copied and utilized for tank and valve inspection documentation.
Always wear proper protective equipment when performing valve inspections and when performing leakage testing.
Litmus paper or Sulfur Tapers may be used during the inspection to check valve stems and threaded connections for leakage. Should you need either of these testing products, please contact Tanner Industries, Inc.
Conventional valve stem packing (adjustable) is obtained by compressing the packing material around the valve stem by means of a packing gland assembly. The cavity of the housing is equipped with a beveled bushing located at the bottom of the cavity, and a second beveled bushing with a sleeve at the top of the cavity with the packing material sandwiched in between. The packing nut is tightened against this upper beveled bushing assembly to compress the packing material around the valve stem to create the seal. Typical packing materials are Teflon, graphite rope seals, or composite (pre-formed) packing. This type of valve is easily identifiable by the large hex nut and threaded outer housing which is threaded into the valve casting.
Prior to operating the valve, the valve stem should be inspected for dirt, debris, rust, etc. These foreign materials should be removed from the valve stem prior to performing any operation of the valve by use of a rag, wire brush or steel wool. A light oil or petroleum jelly applied to the stem periodically will help protect against surface rusting of the stem.
The stem should be lubricated with WD-40 (or equivalent) prior to opening or closing the valve. The packing nut can be loosened slightly prior to operating to allow for the valve stem to move with less restriction; it will also allow for the lubricant to more easily flow into packing gland area. It is not uncommon to experience a slight leakage around the stem during this operation. Once the valve has been opened or closed, the packing nut will need to be re-tightened. This packing nut should not be over tightened as it will crush the packing material and may cause damage. Periodically, the valve should be exercised and lubricated to ensure that the packing material remains pliable.
V- Ring Stem Seal:
The “V-Ring” spring-loaded pressure seal used in REGO style angle and globe valves are not adjustable. The chevron (V- Ring) spring loaded pressure seals are made of Teflon which assures low friction and leak tight performance for an indefinite period of time without having to adjust the packing.
Pressures expand the “V-Shape” of the seal, forcing it against the stem and bonnet surfaces to prevent leakage. The higher the pressure within the valve, the more effective the seal becomes. A spring loaded washer located under the V- Ring keeps them in an expanded position to assure an effective seal in low pressure conditions. A wiper ring is placed above the seal, and keeps the seal free from grit, and/or other foreign material that may hamper operation.
The valve stem should be inspected for dirt, debris, rust or other foreign material prior to operating. The stem should be cleaned prior to operating to ensure that no dirt, rust or debris enter into the valve packing cavity as this foreign material can damage the packing. A light oil or petroleum jelly applied to the stem periodically will help protect against surface rusting of the stem.
Over a period of time, valve packing can dry out and allow slippage of ammonia through the stem assembly. Should leakage be noted, WD-40 or equivalent should be used to lubricate the stem assembly.
Apply a liberal coating of WD-40 to the base of the stem, then open and close the valve (when possible) to help force the material down into the packing cavity. On REGO type valves, there is no adjustment for the packing, this WD-40 will be absorbed into the V-Ring seals and help to soften and expand the Teflon packing and wiper ring to allow for a seal to re-occur. Valves should be left in either the full open or full closed position whenever possible to protect the valve packing cavity against constant pressure.
If lubricating the valve does not repair the leakage, the valve will need to be either rebuilt or replaced. Contact our Manager of Technical Services at Tanner Industries, Inc. 1-800-643-6226 for further assistance.
A well maintained system will insure a continuous, economical and safe source of ammonia. Our drivers are trained to supplement your inspection procedures on each delivery. Upon request, they or our technical personnel will lend assistance in any inspection or maintenance problems you may encounter.
While the information, data, and recommendations set forth herein are believed by us to be accurate. We make no warranties, either expressed or implied, with respect thereto and assume no liability in connection with any use of such information, data, and recommendations. Moreover, please refer to all manufacturer’s instructions, maintenance, and warnings in connection with the installation, use and maintenance of these products.
• Tanner Industries, Inc. Storage and Handling of Anhydrous Ammonia booklet
While the information contained within this bulletin is believed to be true and accurate, a professional engineer should be consulted when designing any tank or piping system and nothing in this informational bulletin should substitute for such professional advice. Moreover, please refer to all manufacturer’s instructions and warnings in connection with the installation, use and replacement of these products. ANSI K61.1 and OSHA1910.111 should also be reviewed for additional information regarding the safe storage and handling of anhydrous ammonia. State and local codes may be more stringent and should also be reviewed.