In today’s lower-for-longer market, operators are looking for ways to best manage costs while maximizing the value of their assets. One way this is accomplished is through the use of products that have demonstrated a low cost of ownership. The Ajax integral engine-compressor product line from Baker Hughes, a GE company (BHGE), is designed to include reliability, ease of maintenance and support for clients in a continually changing emissions compliance environment. The BHGE Ajax packages deliver lower operating cost and less maintenance than high-speed separable packages and operate with higher efficiencies and higher online availability. After 60 years of reliable service, these integral engine-compressors are renowned around the world for their simplicity, making them the user-friendly alternative to high-speed separable packages for customers looking to achieve longterm efficiency.

Low cost of ownership

Ajax packages feature low-speed, low-brake mean effective pressure operation and more robust components. There is less wear on parts and fewer operating cycles than highspeed compression packages, resulting in less downtime and lower maintenance cost. The typical online availability for an Ajax integral is 98% as compared to 96% for a high-speed separable package. This translates to integrals being in service 7.3 days more per year than a high-speed separable package.

The Ajax power cylinder is isolated from the crankcase so that combustion blow-by products cannot enter the crankcase. This means that oil changes are needed only once per year, which could be extended beyond one year with an oil analysis program. In addition, the splash lubrication system for the integral unit means there is no oil pump and no oil filter to maintain.

Additionally, these integrals consume less fuel for any given volume of compressed gas than the high-speed separable packages. Selection of a gas compression package is often based on the brake horsepower (BHP) of the engine. However, the main factor to consider should be the gas compression capacity for the package.

Ajax packages have a substantially lower BHP per cubic meter of compressed gas than a high-speed separable package and have one frame and crankshaft with an overall mechanical efficiency of 95% compared to 90% for high-speed separable packages. Therefore, the compressor horsepower (CHP) available for gas compression is determined by multiplying the engine BHP by 0.95.

Separable packages have two frames and two crankshafts with the associated bearings for two crankshafts. Considering a 95% mechanical efficiency for each frame, the CHP for a separable package equals 0.95 x 0.95 x engine BHP = 0.902 x engine BHP.

Upcoming upgrades

The Ajax integrals were introduced in 1958, and many of the older Ajax units are still in service. The Ajax has fundamentally remained the same since this time, and improvements over the years have only enhanced the strength and simplicity of the original design. Customers also have been able to upgrade their Ajax units with a number of technical and engineered enhancements, available as retrofit kits.

BHGE’s new upgrade kits for the Ajax LE series provide two ways to modernize a fleet. Option one achieves a 1 gram/BHP-hr NOx at full-rated horsepower without derating. For example, the Ajax DPC-2802XLE is rated at 400 BHP at 450 rpm with a NOx level of 1 gram/ BHP-hr at 38 C (100 F), while increasing throughput and revenue by 4.2%, as compared to the DPC-2802LE. Option two includes the benefits of the other option while reducing volatile organic compounds (VOC) by as much as 75%. The resulting engine configuration has been designated the DPC-2800XLE series.

Digital assistance

The Ajax Value Calculator is a digital tool currently planned for a first-quarter 2018 release that will allow a customer to determine the potential savings and cash flow when comparing Ajax to separable high-speed compressor packages. These critical decision- making factors will be determined using operating conditions, maintenance and fuel cost. The calculator will be available on the engageRecip website and can be used in any application where an Ajax is being considered over a separable reciprocating compressor with a high-speed driver. This includes gas gathering, injection, processing, transmission and fuel gas boosting applications.

Case study

As an example of the overall expenses for a compression package, Figure 1 compares an Ajax integral with a high-speed separable package. The packages compared are rated at 400 BHP, and the expenses associated with these packages are based on operating continuously through the year at a production rate of 28.2 Mcm/d with a gas price of $3/Mcf.

In the BHP range of 400 BHP to 600 BHP the first costs for the Ajax integral and a Caterpillar/Ariel package are essentially the same. Outside this BHP range the first cost for the Caterpillar/Ariel packages are generally somewhat lower than those for the Ajax integrals.

However, when the total costs for purchasing and operating these packages are considered, the Ajax integrals have a substantial advantage. As shown, the total costs that need to be considered include the first cost, the operations and maintenance costs (fuel usage plus maintenance), and the online availability for the units. The lost production costs are based on the typical online availabilities, which amount to 7.3 days of downtime per year for the Ajax unit and 14.6 days of downtime per year for the high-speed unit. The resulting total costs for five years show a $210,000 savings for the Ajax integral.

Selection of a BHGE Ajax integral package and a continuous investment in performance and emissions upgrades provide many long-term advantages. Ajax engine/compressor packages have an excellent track record for long-term service and reliability, and recent developments with the Ajax 2800XLE engines have resulted in reductions in NOx and VOC levels at the rated BHPs. The Ajax Value Calculator is designed to be a powerful digital tool, using sophisticated data analysis to determine the payback and benefits over a highspeed package utilizing the user’s own data.