RECOMMENDED MAINTENANCE MODIFICATIONS

Modifications to an existing hydraulic system need to be accomplished professionally. A modification to a hydraulic system in order to improve the maintenance efficiency is important to a company’s goal of maximum equipment reliability and reduced maintenance cost.

First: Filtration Pump with Accessories

Objective: The objective of this pump and modifi- cation is to reduce contamination that is introduced into an existing hydraulic system through the addition of new fluid and the device used to add oil to the system.

Additional information: Hydraulic fluid from the distributor usually is not filtered to the requirements of an operating hydraulic system. Typically, this oil is strained to a mesh rating and not a micron rating. How clean is clean? Typically, hydraulic fluid must be fil- tered to 10 microns absolute or less for most hydraulic

systems; 25 microns is the size of a white blood cell, and 40 microns is the lower limit of visibility with the unaided eye.

Many maintenance organizations add hydraulic fluid to a system through a contaminated funnel and may even, without cleaning it, use a bucket that has had other types of fluids and lubricants in it previously.

Recommended equipment and parts:

● _{Portable filter pump with a filter rating of 3 microns}

absolute.

● _{Quick disconnects that meet or exceed the flow rat-}

ing of the portable filter pump.

● _{A ¾}′′ _{pipe long enough to reach the bottom of the}

hydraulic container your fluids are delivered in from the distributor.

● _{A 2}′′ _{reducer bushing to ¾}′′ _{NPT to fit into the}

55-gallon drum, if you receive your fluid by the drum. Otherwise, mount the filter buggy to the double wall “tote” tank supports if you receive larger quantities.

● _{Reservoir vent screens should be replaced with} 3_⁄ 10

micron filters, and openings around piping entering the reservoir sealed.

Show a double wall tote tank, of about 300 gallons mounted on a frame for fork truck handling, with the pump mounted on the framework. Also show pumping from a drum mounted on a frame for fork truck handling, sitting in a catch pan, for secondary containment, with the filter buggy attached.

Regulations require that you have secondary con- tainment, so make everything “leak” into the pan. See Figure 9.3.

Second: Modify the Hydraulic Reservoir (see Figure 9.4)

Objective: The objective is to eliminate the introduc- tion of contamination through oil being added to the system or contaminants being added through the air

1 0 50 100 150 Particle Count /PPM 200 2 3 4 5 6 7 Month Component Failure Potential Component Failure 8 9 10 11 12

intake of the reservoir. A valve needs to be installed for oil sampling.

Additional information: The air breather strainer should be replaced with a 10-micron filter if the hydraulic reservoir cycles. A quick disconnect should be installed on the bottom of the hydraulic unit and at the three-quarter level point on the reservoir with valves to isolate the quick disconnects in case of fail- ure. This allows the oil to add from a filter pump as previously discussed and would allow for external fil- tering of the hydraulic reservoir oil if needed. Install a petcock valve on the front of the reservoir, which will be used for consistent oil sampling.

Equipment and parts needed:

● _{Quick disconnects that meet or exceed the flow rat-}

ing of the portable filter pump.

● _{Two gate valves with pipe nipples.} ● _{One 10-micron filter breather.}

Warning: Do not weld on a hydraulic reservoir to install the quick disconnects or air filter.

To summarize, maintenance of a hydraulic system is the first line of defense to prevent component fail- ure and thus improve equipment reliability. As dis- cussed earlier, discipline is the key to the success of any proactive maintenance program.

10 Micron Filter

55 Gallon Drum

Portable Filter Pump To Hydraulic

Reservoir

Air Breather

FIGURE 9.3. Filter pumping unit.

Drain Plug Strainer Baffle Plate Mounting Plate for Electric Motors

and Pump Air Breather and Filter Pump Inlet Line Drain Return Return Line Sealed Flange

C H A P T E R

10

Maintenance Welding*

An important use of arc welding is the repair of plant machinery and equipment. In this respect, weld- ing is an indispensable tool without which production operations would soon shut down. Fortunately, weld- ing machines and electrodes have been developed to the point where reliable welding can be accomplished under the most adverse circumstances. Frequently, welding must be done under something less than ideal conditions, and therefore, equipment and operators for maintenance welding should be the best.

Besides making quick, on-the-spot repairs of broken machinery parts, welding offers the maintenance depart- ment a means of making many items needed to meet a particular demand promptly. Broken castings, when new ones are no longer available, can be replaced with steel weldments fashioned out of standard shapes and plates (see Figure 10.1). Special machine tools required by pro- duction for specific operations often can be designed and made for a fraction of the cost of purchasing a standard machine and adapting it to the job. Material-handling devices can be made to fit the plant’s physical dimen- sions. Individual jib cranes can be installed. Conveyors, either rolldown or pallet-type, can be tailor-made for specific applications. Tubs and containers can be made to fit products. Grabs, hooks, and other handling equip- ment can be made for shipping and receiving. Jigs and fixtures, as well as other simple tooling, can be fabricated in the maintenance department as either permanent tool- ing or as temporary tooling for a trial lot.

The almost infinite variety of this type of welding makes it impossible to do more than suggest what can be done. Figures 10.2 through 10.5 provide just a few examples of the imaginative applications of welding technology achieved by some maintenance technicians.

The welding involved should present no particular problems if the operators have the necessary training and background to provide them with a knowledge of the many welding techniques that can be used.

A maintenance crew proficient in welding can fabri- cate and erect many of the structures required by a plant, even to the extent of making structural steel for a major expansion. Welding can be done either in the plant main- tenance department or on the erection site. Structures must, of course, be adequately designed to withstand the loads to which they will be subjected. Such loads will vary from those of wind and snow in simple sheds to dynamic loads of several tons where a crane is involved. Materials and joint designs must be selected with a knowledge of what each can do. Then the design must be executed by properly trained and qualified welders. Structural welding involves out-of-position work, so a welder must be able to make good welds under all con- ditions. Typical joints that are used in welded structures are shown in Figures 10.6 through 10.9.

Standard structural shapes, including pipe, which makes an excellent structural shape, can be used. Elec- trodes such as the E6010-11 types are often the welder’s first choice for this kind of fabrication welding because of their all-position characteristics. These electrodes, which are not low-hydrogen types, may be used pro- viding the weldability of the steel is such that neither weld cracks nor severe porosity is likely to occur.

Scrap materials often can be put to good use. When using scrap, however, it is best to weld with a low- hydrogen E7016-18 type of electrode, since the analysis of the steel is unlikely to be known and some high- carbon steels may be encountered. Low-hydrogen elec- trodes minimize cracking tendencies. Structural scrap frequently comes from dismantled structures such as elevated railroads, which use rivet-quality steel that takes little or no account of the carbon content.

*Source: Ricky Smith and Keith Mobley, Industrial Machinery Repair: Best Maintenance Practices Pocket Guide (Boston: Butterworth– Heinemann, 2003), pp. 460–538.

10.1. SHIELDED METAL ARC WELDING