什么時候選拉桿液壓缸，什么時候選焊接液壓缸？兩者的區別是什么？
我們先來看一個液壓油缸分類表：
| 油缸分類 | 產品系列 | 最大使用壓力 |
拉桿 | MOB | 7 Mpa |
HOB | 14 Mpa | |
YG | 21 Mpa | |
焊接 | RO | 14 Mpa |
HRO | 21 Mpa | |
HSG | 21 Mpa | |
Y-HG1 | 25 Mpa | |
其他定制 | 31.5 Mpa |
■ 拉桿液壓缸 Tie rod cylinder
拉桿液壓缸靠螺絲桿連接前后缸蓋，小缸徑時為四根螺絲桿，大缸徑會加多螺絲桿的數量來保證油缸的耐壓性，比如6根、16根，甚至20根。
不同的使用壓力，螺絲桿的材質不同，可能為A3、45號、合金鋼。
Tie rod style hydraulic cylinders use high strength threaded steel rods to hold the two end caps to the cylinder barrel. This method of construction is most often seen in industrial factory applications. Small bore cylinders usually have 4 tie rods, while large borecylinders may require as many as 16 or 20 tie rods in order to retain the endcaps under the tremendous forces produced.
拉桿液壓缸優勢 Advantages：
1）易于拆裝、維修；
2）多為標準系列，半成品或成品有庫存，交期較短。
Tie rod style cylinders can be completely disassembled for service and repair, and they are not always customizable.
■ 焊接液壓缸 Welded cylinder
焊接液壓缸的后蓋焊接在缸筒上，油口焊接在缸筒上，前蓋與缸筒通常使用螺紋或螺栓固定。
Welded body cylinders have no tie rods. The barrel is welded directly to the end caps. The ports are welded to the barrel. The front rod gland is usually threaded into or bolted to the cylinder barrel. This allows the piston rod assembly and the rod seals to be removed for service.
焊接液壓缸的優勢 Advantages：
1）整體的安裝尺寸小于拉桿油缸；
2）比拉桿油缸能夠承受更大的壓力；
3）更容易定制，比如特殊油口、特殊安裝方式、加裝鎖緊閥等
Welded cylinders have a narrower body and often a shorter overall length enabling them to fit better into the tight confines of machinery. Welded cylinders do not suffer from failure due to tie rod stretch at high pressures and long strokes. The welded design also lends itself to customization. Special features are easily added to the cylinder body, including special ports, custom mounts, valve manifolds, and so on.
總結：
1）安裝空間夠，壓力小，行程短，選拉桿液壓缸；
2）安裝空間有限制，壓力大，選焊接液壓缸；
3）使用壓力大，工況比較惡劣，可能需要定期更換密封件，選拉桿液壓缸；
4）油口位置有特殊要求，或需加裝液壓鎖或平衡閥等，選焊接油缸。