Installation Of New Cylinder Port Thermocouples

Usage:

ENGINES3500 FAMILY OF DIESEL ENGINES

Problem:

Engine reliability and durability have a direct relationship with the application of ratings and the implementation of proper maintenance practices. When ratings are not used in the correct application or maintenance practices are poor, performance parameters can be exceeded.

Performance parameters and rating criteria are established for optimum operation and should be adhered to for acceptable reliability.

Solution:

Use the following information to monitor performance parameters to prevent engine valve failures and improve engine reliability and service life.

Rating Background

Caterpillar engine ratings provide an opportunity to be competitive in today's world. Ratings are the technical response to meeting customer needs. Ratings must be applied properly to benefit the customer, dealer, and Caterpillar. The consequence of rating applications that are not correct or improper maintenance can be costly.

Certain criteria are evaluated as ratings are developed . Such criteria as structural integrity, thermal stresses, mechanical aspects, life-to-overhaul, environmental aspects, and generator concerns. The development of a rating is a trade-off of these criteria. Technology has made major advancements, yet some questions still require decisions based on judgment and experience.

Ratings are developed and evaluated using the following parameters: exhaust temperatures, cylinder pressures, fuel injection pressure, turbo speed, smoke & emissions, and piston temperatures. These parameters will dictate the limit of the engine rating. It is recommended that close attention be paid to commercial customer rating requirements to improve customer satisfaction, avoid exceeding rating parameters, and increase engine reliability.

Careful consideration should be given to the customer's "worst case" scenario. Installation and components should be selected based on worst case situations. All elements of the rating description should be evaluated.

EPG: Priority should be given to "typical load factor" as specified in the rating guidelines. In most cases ratings should be based on a chronological daily load curve or duration of load curve.

Marine: Priority should be given to maximum time at full throttle combined with total operating time per year. It is understood that many applications are not clearly defined and that extreme requirements may not be economically feasible. However, shortcomings in the rating selection, installation, operation, and maintenance generate significant expense to the customer, dealership, and Caterpillar due to loss of productivity, rework to correct problems, and operation and maintenance costs.

Monitoring Parameters To Improve Engine Reliability And Durability

Caterpillar establishes performance curves and engine information that is based on a bare engine at standard conditions. Technical Marketing Information (TMI) data is based on a bare engine without inlet air restriction, exhaust restriction, altitude compensation (500 ft). Data is corrected to SAE J1349 standard conditions of 100 kPa (29.61 in Hg) and 25 C (77 F). Ratings and TMI data also meet DIN 6271 standard conditions of 100 kPa (29.61 in Hg), and 27 C (81 F), and 60 % relative humidity.

TMI data should be used as a guide since customer installations DO NOT generally operate under these same conditions. The best data for future reference is the performance data gathered at commissioning.

Critical parameter guidelines and limits are outlined below to monitor parameters to improve engine reliability. Caterpillar recommends that these performance parameters be monitored and recorded at least once during daily operation. In some critical applications conditions should be recorded more frequently.

Exhaust temperatures (inlet-to-turbo/exhaust manifold)

Exhaust temperatures measured at the inlet-to-turbo/exhaust manifold is a good indicator of engine performance and valve temperatures. The inlet-to-turbo temperature should be the first choice as performance indicator to monitor and record. Exhaust temperatures measured at the inlet-to-turbo are representative of actual valve temperatures for engines with dry manifolds.

Inlet-to-turbo temperatures should be monitored frequently and as often as hourly for some applications or load conditions. Exhaust stack temperatures for many years have been used to assist in assessing engine performance. This temperature is not a suitable substitute for inlet-to-turbo data. However, exhaust stack temperature along with inlet-to-turbo temperature provides a means of assessing turbocharger performance. It is recommended that inlet-to-turbo temperature ports be installed and customers trained in the proper interpretation of cylinder and inlet-to-turbo temperatures. Refer to section on installing inlet-to-turbo temperature port.

The following table contains normal and extreme operating manifold exhaust temperature limits (inlet-to-turbo). Most engines will operate at, or below, the normal operating temperature range provided the installation, rating application, and maintenance guidelines are followed. If the extreme condition temperature limit is exceeded, severe engine damage may result.

Cylinder Port Temperatures

Cylinder port temperatures are a good indicator of individual cylinder condition. The port thermocouples do not read actual cylinder temperature, but indicate a lesser value than actual cylinder exhaust temperatures due to the lack of constant flow past the sensor.

Cylinder port temperature normally read less than inlet-to-turbo temperature for dry manifolds. Cylinder port temperatures provide a means to determine cylinder condition. They are not to be used as a substitute for inlet-to-turbo temperature data which is a more accurate indicator of engine performance and valve temperature.

Typical problems diagnosed with cylinder port temperatures are bad injectors and valve gutters. The ability to diagnose a valve gutter problem may prevent additional damage to the engine and save significant down time and repair costs.

The following are guidelines for using cylinder port temperatures.

Normal Condition - New engines normally show temperature differences up to 56 C - 70 C (100 - 125 F) from hottest cylinder to coldest cylinder at rated load.

Alert Condition - Cylinders that deviate more than 50 C (90 F) from the average of all cylinder port temperatures.

Corrective Action: Cylinders that deviate more than 100 C (180 F) from the average of all cylinder port temperatures.

Customers should be encouraged to establish baseline load and exhaust temperatures which are recorded at initial commissioning of the engine. This baseline data can be used for accurate comparison as future readings are recorded.

Boost

Boost or manifold pressure is a good indicator of performance if boost criteria has been established at the site. Causes associated with low boost are:

· air leaks.

* plugged filters.

* plugged aftercooler.

* high intake air restriction.

* high exhaust restriction.

* low turbo efficiency.

* poor fuel conditions.

*exhaust leaks.

* poor ventilation.

Intake manifold pressure in TMI DOES NOT account for altitude, air restriction, or exhaust restriction. Therefore, when referring to TMI data use a tolerance of ± 10 percent. For best results establish the boost reference at full load during new engine startup. Then, monitor the boost at the referenced load monthly, at the oil change interval or other established maintenance intervals.

Monitoring boost will ensure the integrity of the air system on the engine. Make sure that inlet-to-turbo exhaust manifold temperature limit is not exceeded when establishing this reference.

Fuel Rate

Refer to TMI Data using a tolerance of ± 5 percent. Fuel rate is a good indicator for commercial engine maintenance schedules.

Inlet Air Conditions

Air filter restriction:

Clean air filter - 10 inches of water maximum. This includes precleaner, secondary air filter and additional air ducts.

Dirty air filter - 25 inches of water maximum. This includes precleaner, secondary air filter and additional air ducts.

Air intake room PRESSURE differential (gauge pressure between outside and room) - less than 0.5 inches of water.

Air intake room TEMPERATURE differential (Temperature increase from outside ambient to room temperature) should not exceed 10°C or 18°F for EPG applications, 17°C or 31°F for marine applications, and 5.6°C or 10°F for petroleum applications.

Maximum air inlet -125°F (temperature measured at the filter inlet).

NOTE: Ventilation air and combustion air flow rate must be increased 10 percent for every 765 m (2500 ft) above sea level.

Intake Air Manifold Temperature

The maximum temperature of the intake air manifold should not exceed 245°F.

Water Temperature

Maximum jacket water temperature all applications (except EPG and machine applications):

Alarm - 96°F (205°F). Shutdown - 101°C (215°F).

Maximum jacket water temperature for EPG and machine engine applications:

Alarm - 101°C (215°F). Shutdown - 107°C (225°F).

Oil Pressure

The normal range for the engine oil pressure is 310 to 420 kPa (45 to 61 psi) at rated engine speed.

The minimum oil pressure at rated engine speed for commercial engines are:

Alarm - 276 kPa (40 psi). Shutdown - 207 kPa (30 psi).

The minimum oil pressure above 1250 rpm for machine engines is:

Low oil pressure warning - 250 kPa (36 psi).

Installation Of Inlet-To-Turbocharger Port

The inlet-to-turbocharger port is located on the exhaust manifold near the turbocharger flange. Many exhaust manifolds have two 8T-6765 Plugs near the turbocharger flange. The purpose of these plugs is to provide access for gathering exhaust manifold data.

Some manifolds have a boss similar to that shown in Illustration 1, or they may have no boss at all. These manifolds without an available hole will require drilling and taping a 1/4 - 18 NPTF hole in the approximate location of the turbocharger flange or provided thermocouple boss.

NOTE: Some plugs are difficult to remove and may require drilling and tapping the hole. A change is planned to provide temperature ports on current production manifolds and all applications.

The following parts are required to install a thermocouple in the inlet-to-turbocharger port. Select only one type of thermocouple.