OCR Text |
Show abrasion marks were observed on the stator, but no wear was apparent after months of operation with COM. The connecting rod and pins between the drive shaft and the pump rotor showed significant wear after 500 hours of COM operation. The pump manufacturer has changed the connecting rod design to a sealed gear, universal-joint design for new pumps, thereby eliminating the direct contact between the moving parts and fluids being pumped. The four valves in the original fuel train of the 700-hp boiler had to be replaced after they became clogged with coal particles during the first trial runs with COM. The fuel-oil safety shutoff solenoid valve and the oil-return solenoid valve were replaced with pneumatically actuated stainless steel full-ported ball valves. The oil pressure differential regulator and the oil flow control valve were removed, and the fuel flow control function was provided by the progressing cavity feed pump driven by an adjustable-speed DC motor. The COM flow rate was measured by a Micro-Motion mass flowmeter. A slurry preheater was required in the fuel train to bring the COM's to the desired viscosity for effective atomization. The fuel train for CWM and CMM firing in the 100-hp boiler is nearly identical to that just described except that the fuel safety shutoff solenoid valve and fuel-return solenoid valve are incorporated in one pneumatically actuated, full-ported, three-way ball valve. Binding of this valve has been experienced over a period of time; fine coal particles penetrate into the ball seats, causing sluggish operation. A three-way valve currently used in the CWM fuel train in the 700-hp CWM facility is a pneumatically actuated pinch valve. An elastomer lining within the valve housing is pinched shut by an air-driven piston, effecting positive shutoff. This type of valve has proven to be very reliable and could be used on all coal-slurry fuel trains. In all CWM and CMM tests conducted to date, the fuel has not been preheated. During earlier COM tests with high coal concentrations, occasional fuel-line plugging with agglomerated coal particles was 14-7 |