Sealless pumps

Due to the stringent enviranmental laws, sometimes it is required that zero leakage at pump. In the late 19SQ s, advanced sealless pumps are developed to achieve this goal. Another incentive to develop sealless piunp is to eliminate the maintenance cost from using the mechanical seals. 

The disadvantage of sealless pumps are (1) less efficient bearingiS have to be used for the impeller shaft, (2) more heat is geTLerated in the metal containment shdl, (3) pumping efficiency is lower, and (4) limited by allowable pumping liquid temperature and viscosity, 

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Pumps for Leakage Prevention. When leakage to atmosphere must be contained to essentially 2ero, magnetically coupled or canned motor sealless pumps can be used. These pumps do not have rotating seals between the pumped Hquid and the atmosphere. 

It should not be assumed that just because there is no seal, sealless pumps are always safer than pumps with seals, even with the advanced technology now available in sealless pumps. Use sealless pumps with considerable caution when handling hazardous or flammable liquids. 

Sealless pumps rely on the process fluid to lubricate the bearings. If the wear rate of the bearings in the fluid being handled is not known, the bearings can wear unexpec tedly, causing rupture of the can. 

For many plants handling monomers and other hazardous materials, sealless pumps are the first choice. They can practically eliminate the pump problems that can occur due to se leaks, which can include product loss, flammabihty, waste disposal, and exposure of personnel to hazardous vapors. 

It is veiy important that sealless pumps be flooded with hquid before starting, to avoid damage to bearings from imbalance or overheating. Entrained gases in the suction can cause immediate imbalance problems and lead to internal bearing damage. Some type of liquia sensor is recommended. Sealless pumps must not be operated deadheaded (pump hquid full with inlet and/or outlet valves closed). 

Properly installed and maintained, sealless pumps, both canned and magnetic-drive, offer an economical and safe way to minimize hazards and leaks of hazardous hquids. 

Can safer chemicals be used (Nontoxic or nonvolatile reactant.) Can quantities be reduced (Careful look at intermediates storage.) Can potential releases be reduced via lower temperatures or pressures, elimination of equipment or by using sealless pumps Can waste be reduced (Regenerable catalyst or recycle.)... 

Eierman, R. G. (1995). Improving Inherent Safety with Sealless Pumps. Proceedings of the 29th Annual Loss Prevention Symposium, July 31-August 2,1995, Boston, MA, ed. E. D. Wixom and R. P. Benedetti, Paper le. New York American Institute of Chemical Engineers. 

The standard bearing monitor solves the most basic problem common to all sealless pumps—detecting normal bearing wear so that routine maintenance can be accomplished before serious motor damage occurs. It responds to bearing wear in both the axial and radial directions and is over 98% effective on 70,000 operational units. 

The instrumentation recommended for sealless pumps may seem somewhat excessive. However, sealless pumps are expensive, and they... 

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