Supply Pressure And Return Circuit; Description - Manitowoc Grove TMS800E Service And Maintenance Manual

Table of Contents

TMS800E SERVICE MANUAL

properly adjusted, and the component is not at fault, check

the valve for scored or worn parts. Scoring is a sign of the

number one problem in hydraulics - contamination (external

contamination by dust or internal contamination by debris

from deteriorating components or oxidized hydraulic oil).

Scored or severely worn valve components must be

replaced.

Check valves in the control valves are designed to permit a

flow of hydraulic oil in one direction only. If a piece of dirt or

rust has worked its way into the check valve and lodges

between the poppet and seat, it will keep the valve open and

allow a return flow of hydraulic oil. The remedy is to clean the

valve, but it is also a good idea to follow through and ensure

the hydraulic system filter is still serviceable.

Binding Spools

Some of the most common causes for stiff spool movement

or jammed spool action are system overheating, excessive

pressure, contaminated or deteriorated hydraulic oil, or

warped mountings. When scorched or deteriorated hydraulic

oil or contamination is the cause, flushing the system and

replenishing with clean hydraulic oil may solve the problem.

If the spool bores are badly scored or galled, the valve must

be removed for servicing.

Warping occurs when mounting plates are not level or they

become distorted from machine damage. As mentioned

previously, the valve can be shimmed level.

Also, check the valve for rust. Rust or dirt collecting on the

valves can prevent free movement of the spool, and keep it

from the true center position. Excessive system pressure

can create both internal and external leaks in valves that are

otherwise sound. Only qualified technicians using the correct

equipment should make pressure adjustments when

pressure adjustments are needed.

Visual Inspection of Hoses and Fittings

Visually inspect hoses and fittings once a month or

every 250 hours for the following:

Leaks at hose fitting or in hose

Damaged, cut or abraded cover

Exposed reinforcement

Kinked, crushed, flattened, or twisted hose

Hard, stiff, heat cracked, or charred hose

Blistered, soft, degraded, or loose cover

Cracked, damaged, or badly corroded fittings

Fitting slippage on hose

Other signs of significant deterioration

If any of the above conditions exist, evaluate hose

assemblies for correction or replacement. For replacement

GROVE

of hose assemblies, refer to your Manitowoc Crane Care

Parts Manual.

At the same service interval, visually inspect all other

hydraulic components and valves for the following:

Leaking Ports

Leaking valve sections or manifolds and valves

installed into cylinders or onto motors.

Damaged or missing hose clamps, guard, or

shields.

Excessive dirt and debris around the hose

assemblies.

If any of these conditions exist, address them appropriately.

Hydraulic hose assemblies operating in climate zone "C"

are recommended to be replaced after 8000 hours of

service life.

Hydraulic hose assemblies operating in climate zones

"A" or "B" with high ambient temperatures, could see

hose service life reduced by 40% - 50%. Therefore, it is

recommended to replace these hoses after 4000 - 5000

hours of service life.

Hydraulic hose assemblies operating in climate zones

"D" and "E" cold climates should expect a degrade of

mechanical properties such as elasticity. Therefore it is

recommended that these hoses be inspected and

addressed correctly.

Zone

Classification

Tropical Moist: All months average above 18°C.

Latitude: 15° - 25 ° North & South

Dry or Arid: deficient precipitation most of the

year. Latitude: 20° - 35° North & South

Most Mid-Latitude: Temperate with mild winters.

Latitude: 30° - 50° North & South

Moist Mid-Latitude: Cold Winters. Latitude: 50° -

70° North & South

Polar: Extremely cold winters and summers.

Latitude: 60° - 75° North and South