4. preventive maintenance
(PM system)
ldentify the System Operating Condition
Equipment Manufacturer’s Maintenance
Requirements
System Component Maintenance Requirements
5.
6.
7.
8.
9.
10.
11.
12. Symptoms:
1. The carriage drive has slowed down in
both directions.
2. The cutting torch traverse cylinder is
operating slowly when extending.
3. The system is running hotter than usual .
13. Hydraulic machines are machinery and tools that use
liquid fluid power to do simple work. Heavy equipment
is a common example.
A fundamental feature of hydraulic systems is the
ability to apply force or torque multiplication in an
easy way, independent of the distance between the
input and output, without the need for mechanical
gears or levers.
14. To obtain a good work from hydraulic
circuits we should be sure from that,
we have suitable safety devises in this
circuits to avoid damage or failure.
17. Legal and code requirements in industry:
In most countries, industries are legally required to protect
pressure vessels and other equipment by using relief valves.
Also, in most countries, equipment design codes such as
those provided by the ASME, API and other organizations like
ISO (ISO 4126) must be complied with and those codes
include design standards for relief valves.
•ASME (American Society of Mechanical Engineers) Boiler & Pressure
Vessel Code.
•API (American Petroleum Institute) Recommended Practice 520 and API
Standard 526, API Standard 2000 (low pressure - Storage tank)
18. Special functions:
To overcome nuisance Velocity fuses work by sensing flow across a control
orifice when the pressure differential exceeds a predetermined amount
(usually 50 psid). A spring-biased poppet closes, shutting flow to the
damaged hydraulic circuit.
trips, a time delay feature in a velocity fuse allows an overshoot above
rated flow for up to 0.2 sec before closing. This prevents nuisance trips
caused by sudden flow surges.
Elevator and lift applications may mandate a maximum deceleration. Other
requirements include safety pressure rating (7to 8 times normal operating
pressure), maximum speed, and performance requirements. To meet these
requirements, a variable orifice incorporated into the velocity fuse limits
the shock load to less than
0.3 Gs and closing time to less than 0.2 sec.
19.
20. A safety control conforming to the above standards is not
required only in the following press applications:
• Forging and other presses where the material cannot be manually
handled.
• Machines running in automatic mode with closed working areas,
although a safety control may still be required for maintenance and machine
set-up.
• Closing speed of the press slower than 0.4 inches/second (10 mm/s).
• Stroke of the ram less than 0.24 inches (6 mm).
