Hydraulic swivels are usually one of the higher dollar purchased component items on a crane/utility truck/log loader…etc. The cost is a function of the design requirements and operating conditions. To get the absolute best bang for the buck, the hydraulic swivel should not be an afterthought or a cylindrical mystery device with hoses attached to it. Some upfront practicality can pay large dividends. Here are some ideas and design considerations to keep the cost down when looking for a hydraulic swivel quote.
1: Multiple drains or returns are usually cheaper to manufacture then one large one. The size of the largest port usually dictates the wall thickness of the housing. The returns or drains tend to be the largest ports in the circuit as most circuits operate more efficiently with little to no back pressure on the return lines. If you can split your -24 into two -16 ports (if the very slight reduction in flow area is acceptable), you can usually save a sizable amount on the weight and cost. In addition, you can add clearance into your rotating assembly.
2: The thru hole size on a hydraulic swivel directly effects the OD. If you can reduce the thru hole size from 2″ to 1″, it is typically a sure bet that we can reduce the OD of the housing by 1″. Usually when customers want a large center thru hole, it’s so the slip ring harness and plug can pass thru the hydraulic swivel. If you can assemble the center harness plug onto the harness after you pass the harness thru the swivel you can save substantial cost, weight and room.
3: When swivels have more than 8 ports, the top of the spool head can become quite full of ports. During the design process we determine if there is enough clearance to spin an open ended wrench one index, or enough to keep spinning the hose end or fitting. With a large number of ports we need to space the ports out a ways to account for the wrench clearance. To save some space we may recommend that half the ports come out the spool head side (every other one). This will allow us to cluster the ports together tighter while still having enough wrench clearance. This can save cost, weight, and room.
4: Our standard seal package involves high pressure cap seals between each high pressure circuit, wearing rings to reduce premature seal wear, single lip/outward facing excluder seals, and inward facing uni-directional seals. The inward facing uni-directional seals keep any low pressure/low temperature weepage from making its way to the outside of the swivel. These seals work very well for keeping weep at bay. They are also very good at handling moderately low pressures. If you can keep the outboard circuits low pressure such as returns or drains, we can refrain from putting high pressure cap seals on the outboard ends of the outboard circuits. Considering the cap seals are the highest cost seal in the swivel, these savings make a difference in the final price.
5: This last idea won’t make as much of a difference as the first 4 in price but it is something to think about. The total length of the swivel is determined in a large part, by the individual thread diameters of the ports in the housing. The two styles of flow grooves are tall and skinny versus short and fat. The tall and skinny style’s flow groove has the same height as the thread diameter, the short and fat’s flow groove has the same height as the min diameter of the port. We usually try and make the largest two ports using the tall and skinny style while all the smaller ports utilizing the short and fat style. We have found this to be the optimal combination between cost and size reduction. However if the diameter is ultra critical or the overall length is ultra critical, we can make the swivel fit your requirements. Roughly speaking a swivel designed completely using the short and fat style is about 1 or 2% less costly than a swivel designed with the tall and skinny style. However other variables can create larger variances depending on the specific application.
These simple ideas can payout in the end especially if production quantities are high. Reducing hydraulic swivel costs is something that the UEA engineering team takes seriously for customers. If you would like to learn more, give us a call.