GPM Gas Corp., Houston, has begun replacing its catalytic converters on compressor engines with a converter that saves time and effort in inspection and maintenance, especially for converters that are elevated and difficult to access.
The replacement is the Hatchback converter designed and patented by Johnson Matthey Environmental Products Group, Wayne, Pa. Its removable hatch, secured by only eight bolts, eliminates the need to remove the entire converter from the exhaust piping and thereby significantly cuts down time.
Of approximately 285 engines at 75 booster stations and 4 gas processing sites, more than 40 are equipped with catalytic converters, many elevated as much as 20 ft (Fig. 1). GPM has replaced more than half its previous catalytic converters atop the engines with the new design.
GPM, a wholly owned gas gathering and processing subsidiary of Phillips Petroleum Co., is the largest U.S. producer of NGLs.
MAINTENANCE HEADACHES
In most locations, GPM operates 580-hp L7042 Waukeshau and 585-hp 8G825 Whit Superior engines. AR are equipped with speed controllers to adjust the load, as well as air-fuel ratio controllers, and routinely operate between 600 and 750 rpm.
GPM installed its first converters in 1981, according to Jim Herrman, GPM's regional preventive-maintenance planner. In the following decade, he says, servicing time and costs for the converters have risen.
GPM's maintenance schedule calls for a back pressure check of each catalytic converter with a water manometer every 60 days during routine preventive maintenance. All engines are tested by a mechanical technician every 120 days to measure levels of CO, NO,, and combustibles being removed from the exhaust.
In Oklahoma, the state's Department of Health requires that a continuous log be maintained to record all emissions for a 2-year period. If adjustment, cleaning, or correction is required, it is done immediately as specified in the state permit.
Under such a rigid maintenance schedule to ensure compliance with emissions regulations, multi-bolted catalytic converters have posed an increasingly severe problem.
A simple inspection, Herrman says, could involve the time-consuming removal of several bolts just to gain access to the catalyst, not to mention the down time involved on the engines.
One converter, for example, had 96 bolts that had to be loosened or removed before entry to the catalyst could be gained.
This design, says Herrman, was more often the rule than the exception.
Servicing these units required at least two men, a truck, a "cherry picker," and patience in detaching them from the exhaust, lowering them to the ground, and loosening 70-112 bolts just to look at the catalyst.
A routine inspection and cleaning averaged 2 days per converter.
NEW DESIGN
In early 1990, upon a suggestion from Herrman, Johnson Matthey engineers developed a prototype of a converter with a hatch for easier inspection and servicing of the catalyst.
Under Herrman's supervision, the first Hatchback catalytic converter was installed on Mar. 15, 1990, and tested under normal running conditions for 90 days.
During the test period, Herrman checked the Hatchback design with an ultrasound unit to detect any pressure leakage in the converter. Additionally, the unit was checked to ensure it consistently complied with state emissions regulations for CO, NO,, and combustibles.
Careful attention was given to the hatch during the test period to be certain it could be opened and closed easily. Particular observation centered on its resealing capability. The test revealed no problems, nor have any surfaced since.
Following the test run, GPM ordered and installed two more Hatchback units within 30 days and has continued to purchase the unit for new booster stations, on new engines, or on engines that have been relocated. To date, GPM has purchased more than 20 units.
With the new design, maintenance and inspection of a single unit with the new design require the same two employees as before, the truck, and only about 3 hr.
Copyright 1993 Oil & Gas Journal. All Rights Reserved.
