Seal leaks

The factors that cause mechanical seals to leak are numerous  

A pump seal ought to last about six years. Running a seal dry for a few seconds during start-up can reduce the seal life by six months. For a self-flushed pump that loses suction pressure on start-up, there will be little or no seal flush pressure until a normal pump suction pressure is established. (See section on starting NPSH requirements in Chap. 36.) Also, a pump that cavitates on start-up, due to the loss of suction pressure, will vibrate, which also contributes to the damage to the pump s mechanical seal faces. 

I have read that pump cavitation is typically accompanied by the sound of nuts and bolts ratcheting around in a metal bucket. Much of the time this is not true. I typically cannot identify a large centrifugal pump in hydrocarbon service that is cavitating by the sound of the pump. If the pump discharge pressure is erratically low, this is a more reliable indication of cavitation than sounds omitted from the pump s case. Erratically low motor driver amperage also indicates pump cavitation. 

If the radial support bearings are damaged, the resulting vibrations will be transmitted to the seal and damage the seal faces. Water contamination of lube oil in the bearing house is the most common cause of bearing damage. 

A pump case in hot service should be heated evenly prior to starting or switching the pump. This is usually done by the warm-up valve on the pump discharge. This valve bypasses the discharge check valve, thus permitting the hot liquid being pumped by the primary pump to back into and preheat the spare pump that is being put online. 

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Condensate Polishing. Ion exchange can be used to purify or poHsh returned condensate, removing corrosion products that could cause harmful deposits in boilers. Typically, the contaminants in the condensate system are particulate iron and copper. Low levels of other contaminants may enter the system through condenser and pump seal leaks or carryover of boiler water into the steam. Condensate poHshers filter out the particulates and remove soluble contaminants by ion exchange. 

Steel mills Blast furnaces charging, pouring CO, fumes, smoke, particulates (dust) Good maintenance, seal leaks use of higher ratio of pelletized or sintered ore CO burned in waste-heat boilers, stoves, or coke ovens cyclone, scrubber, and baghouse... 

Include operator emergency response to indications of a seal leak in written operating procedures... 

CRANKSHAFT OIL SEAL LEAKS 1. Faulty seal installation. 2. Clogged drain hole. 

The report presents the findings from the analysis of the RCP failures. Estimates of the annual frequency for the spectrum of leak rates induced by RCP seal failures and their impact on plant safety (contribution to coremelt frequency) are made. The safety impact of smaller RCP seal leaks was assessed qualitatively, whereas for leaks above the normal makeup capacity, formal PRA methodologies were applied. Also included are the life distribution of RCP seals and the conditional leak rate distributions, given a RCP seal failure the contribution of various root causes and estimates for the dependency factors and the failure intensity for the different combinations of pump designers and plant vendors. 

GPSLLK Glycol pump seal leaks undetected... 

During the last year we have built an FTMS instrument specifically designed for laser-induced thermal desorption from single-crystal surfaces. Figure 5 is a perspective drawing of the Instrument. The chamber is pumped by a 150 1/s ion pump and has a base pressure of 2.0 X 10- torr. Gases are Introduced through sapphire-sealed leak valves from a diffusion pumped gas manifold. 

At this point, the system was tested with catalyst for activation and FTS, in the hopes that the seal leak rates would be impeded by the presence of small catalyst particles. The FTFE 20-B catalyst (L-3950) (Fe, 50.2% Cu, 4.2% K, 1.5% and Si, 2.4%) was utilized. This is part of the batch used for LaPorte FTS run II.20 The catalyst was activated at 543 K with CO at a space velocity (SV) of 9 sl/h/g catalyst for 48 h. A total of 1,100 g of catalyst was taken and 7.9 L of C30 oil was used as the start-up solvent. At the end of the activation period, an attempt was made for Fischer-Tropsch synthesis at 503 K, 175 psig, syngas SV = 9 sl/h/g catalyst, and H2/CO = 0.7. However, the catalyst was found to be completely inactive for Fischer-Tropsch synthesis. Potential reasons for catalyst poisoning under present experimental conditions were investigated. Sulfur and fluorine are known to poison iron-based Fischer-Tropsch catalysts.21,22 Since the stator of the pump is... 

The above equations were used to compute the seal leak rate through all four sides of a 10 x 10 cm cell having a 1-cm seal margin and a seal height of 50 jitm (0.002"). An average seal differential pressure of 750 Pa (3" HzO column) was assumed. The computed unsealed, or open gap, leak rate was 1.8 standard cm3/min per cell unit... 

The contractor should place any material that is removed and any debris from the work in sealed, leak-proof, properly labeled, plastic bags (6 mm thick) and should dispose of them in a proper land-fill. The contractor should comply with Health Department instructions about how to dispose of asbestos-containing material. 

Figures 17.10 and 17.11 illustrate the color and severity of ABS formation and fouling. This is an SCR on a refinery heater. The ABS precipitated on the edge of the access door probably due to cooler temperatures created because of a seal leak. The interior side and top edges of the door showed ABS corrosion once the maintenance personnel performed their inspection. If the seal problem went uncorrected, eventually ABS would have destroyed the door requiring it to be replaced.

Often, centrifugal pumps develop seal leaks. If the suction of a centrifugal pump is under a vacuum, air will be drawn into the pump through the leaking seal. The pump s capacity will be severely reduced. To stop the suspected air leak, I sprayed water from a hose over the pump s seal. Now, instead of sucking air, the leaking seal drew in cold water. As a result... 

When correctly selected and used, the methods for seal, leak, and burst testing are the essential tools available to the manufacturer to assist in providing... 

This guideline covers only nonroutine or accidental events. Many hazardous events start with the discharge or loss of containment of a flammable and/or toxic material from a vessel or pipe. These discharges, which may take the form of vapor, liquid, solid, or multiphase vapor-liquid-solid mixtures, may be released into a confined area, such as a dike, building, or an equipment array, or into an open, unconfined area. The sources of these releases could be holes in vessels or pipelines, open pressure-relief devices, pipe ruptures, flange and seal leaks, or catastrophic vessel mptures. The range of releases is illustrated in Figure 2.1. 

Steel mills Blast furnaces charging, pouring CO, fumes, smoke, particulates (dust) Good maintenance, seal leaks use of... 

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 seal leaks, which can include product loss, flammability, waste disposal, and exposure of personnel to hazardous vapors. 

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