How to stop fluid system leakage, save energy and run plant effectively.?
FACTORS RESPONSIBLE FOR LEAKAGE :
The main factors, which are responsible for leakage, are pulsation, system vibration and thermal cycling. Irrespective of the kind of fitting, leakage is present to some extend and sometimes unavoidable. The situation worsens by factors like stress due to side load and improper installation.
The problems arising due to stress and weariness is on larger scale compared to problems due to other factors. Hence using a "stress curve" the stress factor can be reduced to a greater degree because the stress curve shows number of cycles generated and affect of stress on specimen. It also brings up the cause of failure related to depth of the groove or notch made in the pipe or tubing line by the fitting as it is tightened.
HOW TO AVOID LEAKAGE
Leakage is mostly occurs due to poor selection and implementation of components. Although foolproof idea for avoiding leakage does not exist but it is possible to reduce leakage by evaluating the various fitting connections types available. Also, proper and effective system energy management must be at a higher priority, which may ensure effective fluid-handling systems.
KINDS OF PIPEFITTING
1. WELDED FITTING : Welded type pipefitting is resistant to both vibration and fatigue. But welding equipment and specialized training needed to make the connection can be costly. In addition to that time required for installation of pipe butt weld fitting into a system is greater compared to other fitting installation options.
2. THREADED PIPEFITTING : Threaded pipefitting is the one of the most commonly adopted type of fitting. The various kinds of threaded fittings are :
NATIONAL PIE FITTING(NPT) FITTING
SOCIETY AUTOMOTIVE ENGINEERS(SAE) STRAIGHT THREAD FITTING
INTERNATIONAL STANDARDS ORGANIZATION (ISO) PARALLEL AND TAPERED THREAD FITTING.
NPTF NATIONAL PIPE TAPERED DRYSEAL FITTING
37-DEGREE AN FLARE FITTING
NPT FITTING :
NPT has cone-shaped thread on both the male and female ends. While joining NPT threaded connections, it is necessary to apply lubricant agent or a sealant with a lubricating agent on the male threads to avoid damage. A commonly used thread sealant is polytetrafluooethlene(PTFE) tape. While applying tape to lubricate or fill voids in the thread crest, root and flanks, plant personal must take following precautionary measures:
Restrict tape application to two to three wraps of the male threads.
Never wrap tape over the end of the first thread, because the tape is bound to Breakaway partly and enter into the fluid-handling system and may damage the internals of system components.
Cut and Remove excess tape and draw the free end of the tape around the threads tightly to conform to the thread. After doing this, press on the tape firmly with thumb and index finger at the overlay point. If the crest of the threads protrude through the tape, galling might occur, so extra tape may be required. It is also very necessary to remove all excess tape and apply new tape before reassembling the threaded connections if the threads are disassembled for maintenance.
NOTE : IF THE TAPE IS NOT REMOVED FROM INITIAL INSTALLATION IT MAY LEAD TO LEAKAGE, WHICH MAY CAUSE MORE PROBLEMS.
SAE STRAIGHT THREAD FITTING :
The SAE straight threads are mechanical types, made to hold only the fitting in place but do not provide a seal. The function of sealing is provided by an elastomer, usually located at the bottom of the male thread. The elastomer compresses against a flat surface near the entrance to the female port.
ISO PARALLEL AND TAPERED THREAD FITTING :
ISO thread fitting is same as to NPT tapered thread fittings i.e., it depends on threads to perform the sealing characteristic. SAE thread fittings uses elastomer, bonded metal washer or gasket as its backup seal.
NPTF NATIONAL PIPE TAPERED DRYSEAL FITTING :
Roots of dryseals are more truncated than the crests. The working behind this thread is that when the crest, root, and flank of the threads are engaged, mating contact always is achieved, producing a seal without lubrication. It has its own problem with metals like carbon steel and stainless steel which causes galling to occur without lubrication, giving problems during initial installation.
37-DEGREE AN FLARE FITTING :
A 37-degree male flared end is usually machined on the end of the fitting, mates with a female flared surface at the bottom of the female threaded port. Connections of this type are found in hydraulic applications.
ADOPTING ENERGY MANAGEMENT PLAN
Energy consumption and operating cost are two big factors, which is matters the most for proper functioning of a plant because problems like leakage of air, choked filters, and warm air which gets inside compressor leads to energy wastage. So it is very important that proper arrangement is made so that leakage of any form gets a right escape route. This can be done by identifying areas where leakage is occurring and by maintaining statistics to make the required improvement.
Example working from as many as 1,000 checkpoints in a typical system, plants can identify leakage problem approximately up to 24 percent to 30 percent and applying this statistics to companys cost per kwh, losses can be calculated. A performance contract can be established to bring down the leakage to less than 3 percent. Hence, a proper analysis of energy supply, consumption, and detailed information of past years energy bills will ensure efficient running of plant.
CONCLUSION: THE ABOVE-MENTIONED METHODS WILL NOT ONLY HELP TO CHOOSE RIGHT METHODS REQUIRED TO PREVENT LEAKAGES AND TO SAVE ENERGY, BUT WILL ALSO INCREASE EFFIENCY AND REDUCE OPERATIONAL PROBLEMS IN A PLANT, IF PROPERLY APPLIED.
|Posted : 9/13/2005|