Oregon State University, Department of Chemistry
Standard Operating Procedure (SOP): Hydraulic Pellet Press in Gilbert 202 (ver. 1.0)
Author: Mas Subramanian (
Safety Web Inception Date: 2/18/2010
Revised: N/A

Chemistry Department Safety Office: Gilbert Hall Room 153
Emergency Medical Services: 911
Campus Student Health Center: 7-9355
Poison Control: 9-1-800-222-1222
OSU Environmental Health and Safety: 7-2273
Campus Security: 7-7000


A. Introduction

Preparation of solid pellets requires a hydraulic press. Together with a die, a stable pellet can be produced with a fine surface. The hydraulic press has numerous uses, from the compression of soft materials such as waste paper and cotton into compact bales to the shaping of motor-car bodies and the forging of steel armour plate. In its simplest form the hydraulic press consists of a cylinder and piston of large diameter, connected by a pipe to a force pump of much smaller diameter. Oil from a supply tank is pumped into the cylinder and the piston (or ram) moves out, exerting considerable force. A valve is provided to release the pressure and allow the oil to return to the tank, after the press has done its work.

This SOP should be read and understood prior to the commencement of relevant work and used to complement supervised practical familiarization with the various techniques described.


B. Hazard identification and PPE

B1. Hazards: Crushing, eye and body injury.

B2. Personnal protective equipment (PPE): Appropriate eye protection and/or a face shield must be worn during all stages of operation of the pellet press.


C. Procedures for use of the pellet press

(a) The user must be properly trained before using the pellet press.

(b) Always check for damage or broken parts and oil leak before using the press.

(c) Press the prepared die into the pellet press. If the platform is too high, loosen the knob (i.e. turn it counterclockwise) located on the front of the press. Do not loosen this all the way or it will fall out and spill a quart of hydraulic oil on the bench. CAUTION Align the apparatus in the exact middle of the press, with the top of the dies centered under the metal knob that projects downward from the top plate of the press.

(d) Double check that the die assembly is centered and that the knob on the front of the press is firmly closed (do not overtighten). Pump the handle to raise the lower platform. There is a movable black line on the pressure dial -- this is a high pressure cutout. Pump the press and let your pellet sit at that pressure for a minute or two. Use extreme caution when pressing pellets. If the die is misaligned, it could shoot across the room with enough force to injure someone.

(e) When you are done, loosen the front knob to release the pressure and lower the platform. If it doesn't move on its own then press down on the platform gently. Retighten the knob.

(f) Remove the die containing your pellet and the piston. Turn it upside down. Find the cylindrical aluminum piece and place this on top. Put the whole assembly back into the press and pump the handle to force the pellet out (this should not generate appreciable pressure on the die). Be sure to hold onto the body of the die as you do this or your pellet could fall out unexpectedly.

(g) Use cotton-tipped applicators and/or KimWipes to clean all residues from the die components. Do not use acid. Avoid scraping and scratching which could damage the die walls or faces.


D. Further reading

1. Wikipedia entry on hydraulic press:

2. For guidelines on the use of related pneumatic press devices (from the University of Kentucky), see:

3. Analysco presses:

This chemical safety advisory document was prepared solely for the use of researchers affiliated to Oregon State University. As stated above (Section A), the content is designed to inform on good working practices and it is not intended to replace hands-on practical training in the techniques described. It is the responsibility of the Principal Investigator to see to it that his/her co-workers are properly trained and informed on hazard management, including the possibility of customization of the information herein as appropriate to meet specific needs. Neither Oregon State University, nor any of its employees (including the author), makes any warranty, express of implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, or represents that its use would not infringe privately owned rights. Reference herein to any specific commerical product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by Oregon State University.